ALBERT

Description: In cognitive radio networks, the secondary users (SUs) switch the data transmission to another empty spectrum band to give priority to primary users (PUs). In this paper, channel switching in cognitive radio mobile ad hoc networks (CR-MANETs) through an established route is modeled. The probability of channel availability in this route is calculated based on the PU's activity, SU's mobility, and channel heterogeneity. Based on the proposed model, the channel and link availability time are predicted. These predictions are used for channel assignment in the proposed channel allocation scheme. A handoff threshold as well as a life time threshold is used in order to reduce the handoff delay and the number of channel handoffs originating from the short channel usage time. When the channel handoff cannot be done due to the SU's mobility, the local flow handoff is performed to find an appropriate node in the vicinity of a potential link breakage and transfer the current data flow to it. The local flow handoff is performed to avoid possible flow disruption and also to reduce the delay caused by the link breakage. The study reveals that the channel heterogeneity and SU's mobility must be considered as important factors, which affect the performance of the handoff management in the CR-MANETs. The results emphasize on the improvement of the route maintenance probability after using the local flow handoff. It is also stated that the amounts of handoff requirement and handoff delay are decreased after using the predicted channel usage life time and handoff threshold time.

Description: The water quality of the River Rhine has improved and might again suit the critically endangered European sturgeon A. sturio L, which was extirpated from the river by 1950. This study describes the tracking of 43 juvenile hatchery-reared A. sturio, in the Dutch part of the Lower Rhine and Delta, originating from an ex situ measure of the River Gironde population. Observing in situ juvenile downstream migration could help to identify essential habitats and potential threats, before actual stocking. Fish were implanted with transponders of the NEDAP Trail® system and released in two batches, in May ( n  = 13) and June 2012 ( n  = 30). Detections collected ( n  = 26) exhibited no upstream movement. Test-fish moved downstream with the flow. Because the historic estuary is disconnected from the North Sea by a sea lock “Haringvlietdam”, the migration of the fish followed the re-directed river discharge into the Port of Rotterdam (161 km). 96 % ( n  = 19) of the detections was collected from the harbor in brackish water, where fish presumably acclimatized to higher salinities. 14 % ( n  = 6) of the sturgeons were recaptured in coastal waters by beam trawlers, five within 1 month after release. It is concluded that sustainable coastal fisheries is a key-condition for rehabilitation of the European sturgeon. Adapted management of the sea lock will reconnect the estuary to the North Sea and create more favorable conditions for the species in the Lower Rhine and Delta.

Description: Rapidly eroding soft rock cliffs typically retreat at rates in excess of several metres per year, thus allowing the resolution of linkages between cliff dynamics and a range of climatic and marine forcing factors. New evidence from UK coastline of East Anglian coastline, southern North Sea shows that unprotected soft rock cliffs at three widely-spaced locations all show similar variability in retreat behaviour on decadal timescales, which we attribute to changing patterns of storminess in these decades. The 1990s were characterized by frequent months in which the North Atlantic Oscillation (NAO; a well-established measure of inter-annual climatic variability in North-West Europe) was extremely positive (more positive than +3) or extremely negative (more negative than −3), while the 2000s showed few occurrences of such extreme values. Depression tracks in positive NAO phases make the East Anglian coast prone to storm surges in which raised water levels result from deeply developed low pressure systems, generally associated with westerly air streams. In negative NAO phases the region is prone to easterly airflow which results in periods of strong onshore wind. Both phases are associated with high energetics in the forcing factors. Decadal-scale variability in cliffline retreat rates has implications for the practice of coastal management and policy making and suggests that cliff system responses to global environmental change are not simply driven by secular sea level rise.

Description: Due to interference between co-located wireless networks, obtaining accurate channel assessment becomesincreasingly important for wireless network configuration. This information is used, amongothers, for cognitive radio solutions and for intelligent channel selection in wireless networks. Solutionssuch as spectrum analyzers are capable of scanning a wide spectrum range, but are not dedicatedfor channel occupation assessment because they are extremely costly and not able to perform continuousrecording for a time period longer than a few seconds. On the other hand, low-cost solutionslack the flexibility and required performance in terms of configuration and sensing efficiency. To remedythe situation, this paper presents an alternative for channel assessment on top of a commercialsoftware-defined radio platform. Although there exist software solutions for performing spectrumsensing on such platforms, to the best of our knowledge, continuous spectrum sensing and long-termrecording remain challenging. We propose a pioneering solution that is capable of seamless spectrumsensing over a wide spectrum band and guarantees sufficient flexibility in terms of configurations. Theproposed solution is validated experimentally. We demonstrate two advantages of seamless spectrumsensing: the capability of accurate channel occupancy measurement and detecting transient signalssuch as Bluetooth.

Description: Long-term monitoring of an environment is a fundamental requirement for most wireless sensornetworks. Owing to the fact that the sensor nodes have limited energy budget, prolonging theirlifetime is essential in order to permit long-term monitoring. Furthermore, many applications requiresensor nodes to obtain an accurate estimation of a point-source signal (for example, an animal call orseismic activity). Commonly, multiple sensor nodes simultaneously sample and then cooperate toestimate the event signal. The selection of cooperation nodes is important to reduce the estimationerror while conserving the network's energy. In this paper, we present a novel method for sensor dataacquisition and signal estimation, which considers estimation accuracy, energy conservation, andenergy balance. The method, using a concept of 'virtual clusters,' forms groups of sensor nodes withthe same spatial and temporal properties. Two algorithms are used to provide functionality. The'distributed formation' algorithm automatically forms and classifies the virtual clusters. The 'roundrobin sample scheme' schedules the virtual clusters to sample the event signals in turn. Theestimation error and the energy consumption of the method, when used with a generalized sensingmodel, are evaluated through analysis and simulation. The results show that this method can achievean improved signal estimation while reducing and balancing energy consumption.

Description: We study the problem of achieving maximum network throughput with fairness among the flows at the nodes in a wireless mesh network, given their location and the number of their half-duplex radio interfaces. Our goal is to find the minimum number of non-overlapping frequency channels required to achieve interference-free communication. We use our existing Select x for less than x topology control algorithm (TCA) to build the connectivity graph (CG), which enhances spatial channel reuse to help minimize the number of channels required. We show that the TCA-based CG approach requires fewer channels than the classical approach of building the CG based on the maximum power. We use multi-path routing to achieve the maximum network throughput and show that it provides better network throughput than the classical minimum power-based shortest path routing. We also develop an effective heuristic method to determine the minimum number of channels required for interference-free channel assignment.

Description: Radio frequency identification (RFID) is a promising wireless technology for using tiny, remotely powered chips as identifiers. The number of RFID applications is rapidly increasing because RFID technology is convenient, fast, and contactless. However, collisions occur when multiple tags simultaneously transmit their IDs. Therefore, an efficient anti-collision algorithm is needed to accelerate tag identification. In some applications, the reader may repeatedly identify staying tags, which constantly exist in the reader's range. The adaptive query splitting algorithm (AQS) was proposed for reserving information obtained from the last identification process to enable rapid re-identification of staying tags. However, since AQS is a non-blocking algorithm that allows newly arriving tags to use the slots reserved for staying tags, collisions among them are problematic. Thus, semi-blocking AQS (SBA) proposed in this study is designed to reduce the collisions between arriving tags and staying tags by applying a semi-blocking technique in which only a minority of arriving tags use the slots reserved for staying tags. By counting the number of minor arriving tags, SBA estimates the number of unrecognized arriving tags and generates proper queries to minimize their collisions. The identification delay of SBA is analyzed, and simulation results show that SBA significantly outperforms AQS.

Description: Using the impulse responses of these multipath channels, the bit error rate (BER) performance for binary pulse amplitude modulation impulse radio ultra-wideband communication system is calculated. The optimization location of receiving antenna is investigated by dynamic differential evolution (DDE) and genetic algorithm (GA) to minimize the outage probability. Numerical results show that the performance for reducing BER and outage probability by DDE algorithm is better than that by GA.

Description: Coastal ecosystems generate diverse services, such as protection, production of food, climate regulation and recreation across the globe. These services are vital for extremely vulnerable coastal areas for enhancing present and future adaptation capacity under changing climate. Bangladesh has long coastline which provides opportunities to large population for multiple resource uses; and threats from extreme natural disasters. The CBACC-Coastal Afforestation is the priority initiative of Bangladesh NAPA that has come in actions under first LDCF adaptation project. The project has focused to reduce climatic vulnerability through enhancing resilience of coastal forests and adaptive capacity of communities. With a total of 6,100 ha of new mangrove plantation and introducing 10 important mangrove species in existing monoculture areas, the project increased protective and carbon rich forest coverage, and also functional capacity of coastal vegetation to adapt to current and future climatic shocks. Concurrently, the project developed co-benefit regime for community based adaptation through innovating integrated land uses for livelihoods of adjacent households. A new land use model (Forest, Fish and Fruit-Triple F) has been implemented to restore fallow coastal lands into community based livelihood adaptation practices. The Triple F practice has reduced inundation and salinity risks and freshwater scarcity in cultivation of agricultural crops and fish. The rational land uses improved household adaptation capacity of landless households through short-, mid- and long-term income generation. The project lesson has further focus to justify the land use innovation for harnessing potential opportunities of ecosystem based adaptation in coastal Bangladesh.

Description: In the winter of 2006/2007 approximately 200,000 m 3 of high quality sand from the dredging of the local marina were placed at the ocean-side beaches in the vicinity of a tourism development in Tróia, Portugal. The beach-quality sediment provided a source of “sand of opportunity” which was used to increase the dry-beach width of the highly used coastal stretch. The sediment was placed along approximately 600 m of shoreline and a monitoring program has since being carried out twice a year. High-resolution topographic surveys and sediment analysis are being conducted to evaluate the performance and response of the fill to the local forcing factors and ultimately to evaluate the effectiveness of the fill project. Two years after the nourishment, the sediment has been distributed both cross-shore and alongshore. The pre-nourishment beach slope was attained and the new shoreline has acquired a natural shape. Berm width increased by a maximum of 100 m, and a set of new dune ridges has developed, due to sand accumulation promoted by the settlement of vegetation. In conclusion, 2 years after its completion, the beach nourishment in Tróia can be viewed as a successful project in which the beneficial use of dredged material resulted in: 1) area for increased dune field growth and development, 2) enhancement of potential shorebird nesting areas and habitat, and 3) increased area for recreation purposes.

Description: Community complexity and abiotic conditions are key components of environmental heterogeneity that affect the abundance and distribution of species. In this study we evaluated how environmental conditions affect abundances of supralittoral amphipods (Talitridae) in four habitats (sandy beach, rivermouth, wrack and lakeshore), along the Italian peninsula in the Mediterranean Sea. All samplings covered a 12 month period, and used the same sampling methodology thereby enabling comparison of abundances and species composition and richness. Four species ( Talitrus saltator (Montagu, 1808), Orchestia gammarellus (Pallas, 1766), O. montagui Audouin 1826, O. cf. cavimana Heller 1865) were collected in the different habitats, but most species were found or were abundant in only one of the four habitats. Abundances of talitrids (numbers per sampling hour) differed significantly among the habitats with highest abundances found in the wrack and on the riverbank in proximity to an estuary, and lowest abundances observed on four sandy beach sites. Environmental conditions (temperature, moisture, substrate penetrability) differed among the habitats and were associated with some of the among-site variability in abundances. Our findings demonstrate that talitrids thrive better in some supralittoral habitats than others, and that some habitats could be considered to be “hotspots” of talitrid ecology and biodiversity.

Description: The purpose of this study is to experimentally determine the differences between four grazing treatments on the trampling of nests. Additionally, we examine to what extent the trampling probability of nests is higher close to a source of fresh water. We compare the trampling of artificial nests in five different grazing treatments in an experimental design. We use buried clay pigeon targets as artificial mimics of bird nests to obtain reliable estimates of trampling risk and compare these with real nests. We find that horses trample significantly more artificial nests than cattle resulting in lower survival rates of artificial nests under horse grazing than under cattle grazing. For both horses and cattle, we find a clear trend, approaching significance, towards more trampling at higher numbers of livestock. We found that more artificial nests are trampled closer to a freshwater tank. The survival probability of artificial nests in cattle grazed treatments in this study is found to be in the same range as real nests in the study area and very close to the survival probability of Northern Lapwing ( Vanellus vanellus ) nests under cattle grazing in a different system. We recommend that horses should not be used as grazers for management purposes in areas with high densities of birds’ nests in order to minimize the risk of nests being trampled. Additionally, we confirm that the location of freshwater tanks has an important effect on the distribution of livestock and hence on trampling of nests.

Description: Geomorphologic information, topographic maps (dated 1967), aerial photographs (dated 1999 and 2008), and spatial analysis procedures were used to investigate a 90 km long coastal sector in South Sicily (Italy). Information was obtained on coastal erosion/accretion areas, general sediment circulation pattern and littoral cell distribution. Human-made structures and natural headlands constituted important artificial limits dividing littoral in morphological cells. Ports and harbours were observed at Scoglitti, Punta Secca, Marina di Ragusa, Donnalucata and Pozzallo. Most of them worked as “transit” limits which interrupted predominant, eastward directed sedimentary transport, this way generating accretion in updrift (west) side of mentioned structures and erosion in downdrift (east) side. During the 1967–2008 period, about 62,000 m 2 and 42,000 m 2 of beach surface were respectively formed updrift of Scoglitti and Donnalucata ports. The construction of Pozzallo port gave rise to the formation of a “convergent” limit which favoured large accretion (94,000 m 2 ) east of port structure. Most important natural structures were observed at Punta Zafaglione, P. Braccetto and Cava d’Aliga. The knowledge of littoral cell distribution acquires a great importance for appropriate management of coastal erosion processes which may be mitigated installing by-passing systems in ports and harbours and carrying out nourishment works in eroding areas, often located downdrift of ports and harbours (when these structures work as transit limits) and in central part of littoral cells (when these structures work as convergent limits).

Description: The coastal stretch of north-eastern Mediterranean Morocco holds vitally important ecological, social, and economic functions. The implementation of large-scale luxury tourism resorts shall push socio-economic development and facilitate the shift from a mainly agrarian to a service economy. Sufficient water availability and intact beaches are among the key requirements for the successful realization of regional development plans. The water situation is already critical, additional water-intense sectors could overstrain the capacity of water resources. Further, coastal erosion caused by sea-level rise is projected. Regional climate change is observable, and must be included in regional water management. Long-term climate trends are assessed for the larger region (Moulouya basin) and for the near-coastal zone at Saidia. The amount of additional water demand is assessed for the large-dimensioned Saidia resort; including the monthly, seasonal and annual tourist per capita water need under inclusion of irrigated golf courses and garden areas. A shift of climate patterns is observed, a lengthening of the dry summer season, and as well a significant decline of annual precipitation. Thus, current water scarcity is mainly human-induced; however, climate change will aggravate the situation. As a consequence, severe environmental damage due to water scarcity is likely and could impinge on the quality of local tourism. The re-adjustment of current management routines is therefore essential. Possible adjustments are discussed and the analysis concludes with management recommendations for innovative regional water management of tourism facilities.

Description: According to the ongoing IEEE 802.11ac amendment, the wireless network is about to embrace the gigabit-per-second raw data rate. Compared with previous IEEE standards, this significant performance improvement can be attributed to the novel physical and medium access control (MAC) features, such as multi-user multiple-input multiple-output transmissions, the frame aggregation, and the channel bonding. In this paper, we first briefly survey the main features of IEEE 802.11ac, and then, we evaluate these new features in a fully connected wireless mesh network using an analytic model and simulations. More specifically, the performance of the MAC scheme defined by IEEE 802.11ac, which employs the explicit compressed feedback (ECFB) mechanism for the channel sounding, is evaluated. In addition, we propose an extended request-to-send/clear-to-send scheme that integrates the ECFB operation to compare with the IEEE 802.11ac-defined one in saturated conditions. The comparison of the two MAC schemes is conducted through three spatial stream allocation algorithms. A simple but accurate analytical model is derived for the two MAC schemes, the results of which are validated with simulations. The observations of the results not only reveal the importance of spatial stream allocations but also provide insight into how the newly introduced features could affect the performance of IEEE 802.11ac-based wireless mesh networks.

Description: In this paper, we derive a performance comparison between two training-based schemes for multipleinputmultiple-output systems. The two schemes are the time-division multiplexing scheme and therecently proposed data-dependent superimposed pilot scheme. For both schemes, a closed-form expressionfor the bit error rate (BER) is provided. We also determine, for both schemes, the optimalallocation of power between the pilot and data that minimizes the BER.

Description: Per-cell codebook-based limited feedback is highly desirable in coordinated multi-point (CoMP) systems owing to flexibility and compatibility. Except for the per-cell codeword indices, each user should feed back other information for the central unit to reconstruct global channel direction information (CDI) and estimate channel quality information (CQI) for downlink transmission. In this paper, we analyze the essential feedback information for per-cell codebook-based coherent CoMP systems. To show what should be fed back to estimate the CQI, we first derive a conservative CQI estimation to avoid the outage in transmission, which depends on the quantization accuracy and the norm of the global channel. We then analyze whether the per-cell small-scale fading channel norms are necessary to feed back in obtaining the global channel norm and reconstructing the global CDI. Next, we analyze whether the feedback of phase ambiguity (PA) is necessary. Both the analysis and simulation results show that the global channel norm should be fed back instead of the per-cell channel norms. The benefit of the PA feedback is evident only when the number of base stations is large and the number of antennas at each base station is small.

Description: As the geostationary orbit (GEO) is congested in the commercial Ku band, the adjacent satellites willreceive the interference from small aperture terminals which have a wide field of view. To reducethe interference toward the adjacent satellites, code division multiple access (CDMA) with spreadspectrum needs to be adopted in the satellite communications on-the-move system. However, themutual interference between CDMA users leads to the performance loss, which is not acceptable forthe power-sensitive small aperture terminals, and the computation complexity is still an intractableproblem when the conventional iterative minimum mean square error (MMSE) scheme is employedto suppress the multiple access interference (MAI) in satellite systems especially that is coded bylow-density parity-check (LDPC) code. Moreover, the long transmission delays of different userscaused by the long transmission distance require the robustness of the interference suppression forthe asynchronous case. In this paper, a joint chip-level algorithm for CDMA multiuser detectionand LDPC decoding with a new and simple iterative structure based on belief propagation (BP)for satellite systems is developed, which integrates the iterations of multiuser detection and theiterations of LDPC decoding with factor graphs. Through analysis and simulations, it is verified thatthe proposed algorithm is robust to the asynchronous CDMA satellite system, and with the similariterative complexity, the performance of the proposed algorithm outperforms that of the conventionaliterative MMSE scheme in the asynchronous CDMA satellite system.

Description: In this paper, we propose the use of bit-interleaved coded modulation in alternate-relaying decode-and-forward cooperative communication systems. At the destination, we exploit the interference signal, which results from the simultaneous transmission of data streams through both direct and one of the relay channels to develop an optimal detector. It is shown that the proposed detector can be implemented by parallel concatenating maximum \textit{a posteriori} (MAP) algorithms and demappers to the decoders. The detector exchanges soft information between the decoders and the MAP algorithms in an iterative way for performance improvement. The proposed optimal detector requires a long delay as the destination has to receive and store the entire frame before performing data detection. To avoid this, a sub-optimal detector is also proposed. Unlike the optimal detector, the sub-optimal one exploits two consecutive received packets to decode one packet. It turns out that the sub-optimal detector has less reduced delay, complexity, memory size, and bandwidth loss with a slight increase of the bit-error-rate. Extensive simulation results are presented to demonstrate the effectiveness of the proposed detectors.

Description: Opportunistic routing (OR) protocols for ad hoc networks basically consist of selecting a few forwardersbetween the source and destination and prioritizing their transmission. The performance ofOR protocols depends on how these two steps are performed. The aim was to reduce the numberof transmissions to deliver packets to the destination. In this paper, we first present a mathematicalmodel to compute the total number of packets including duplicate packets generated by OR protocols.We use the model to analyse well-known OR protocols and understand the reason behind theirincrease in number of transmissions. Next, we propose an OR scheme transmission-aware opportunisticad hoc routing (TOAR) protocol, which attempts to minimize retransmissions. Our proposedOR protocol uses tree structures to select forwarders and prioritize them. The use of tree structureshelps in identifying primary forwarders which carry packets farthest to the destination during eachtransmission round. TOAR also helps in choosing secondary forwarders which will transmit packetsmissed out by the forwarder. The optimized selection of forwarders results in significant reduction inretransmissions, a smaller forwarder list set, and improvement in goodput.

Description: Coastal vulnerability assessments to climate change impacts have been conducted in the past. However, few if any account for the highly variable risk associated with tidal stage in macro-tidal environments. The purpose of this research was to develop a geomatics tool which interactively determines the biophysical vulnerability of a macro-tidal estuary in the Bay of Fundy to varying levels of storm surge and tide state. A conceptual framework was designed to illustrate the relative interrelationships between exposure conditions (surge height, tidal stage), biophysical state (freeboard, exposure, width of foreshore, intertidal slope, observed erodibility, shore protection) and morphological resilience condition. This conceptual framework was then used to develop a dynamic, custom Python programming script within ArcGIS 9.3 to calculate coastal vulnerability for user determined combinations of surge height and tide state. The analysis was conducted for four coastlines, backshore, upper foreshore, middle foreshore and lower foreshore, to reflect varying biophysical states with varying tide levels. The results of the tool were compared with known areas of concern (high erosion, dyke overtopping), as determined by historical records, local expert knowledge and GIS analysis of aerial photography. The number of known locations of concern is lower than that of the results produced by the tool. This is most likely due to the results being analyzed at extreme water levels, greater than higher high water large tide. However, this estimation of vulnerability may limit negative impacts of climate change by highlighting vulnerable areas prior to an event, allowing coastal managers and planners to install measures to reduce the vulnerability and enhance the adaptive capacity of local communities.

Description: A new protocol, called fully distributed space-time coded (FDSTC) protocol having information exchange between relays, is proposed and compared with the conventional distributed space-time coded (DSTC) protocol using non-regenerative relays (NR-relays) and regenerative relays (R-relays). Closed-form error probabilities are derived to verify the simulations. In terms of error performance, the FDSTC protocol gets significant average signal-to-noise ratio (SNR) gains (3.7 dB for NR-relays and 18.1 dB for R-relays). In addition, the impact of the relative distance of relays on the required SNR is reduced up to 70\%. The system diversity order using the FDSTC protocol is higher than that using the DSTC protocol (especially, the FDSTC protocol obtains full diversity with NR-relays). As a result, at the same spectral efficiency, FDSTC has better performance in terms of outage probability in high SNR regions. In terms of energy efficiency, the FDSTC protocol is shown to outperform DSTC for long-range transmissions.

Description: The global change currently observed is deemed to generate accelerated coastal erosion and an increase in frequency and intensity of extreme weather events. Populated tropical island coasts are particularly vulnerable. Awareness of this vulnerability has prompted recourse to the construction of operational observatories on the coastal dynamics of several French tropical islands, including Mayotte. The aims of this initiative are to characterise the coastal morphology of tropical islands and to monitor their rhythms and mechanisms of evolution, adaptation and resilience in the face of extreme climate and wave events (cyclones, storms, surges, strong swells…). Based on this, appropriate defence and/or adaptation strategies can be developed and implemented. Mayotte Island is a fine example of the implementation and utility of such an observatory. The island, in the southwest Indian Ocean, is characterised by a highly diversified coral reef-lagoon complex comprising pocket beaches and mangroves subject to increasing pressure from strong island demographic growth. The operational observatory set up on the island incorporates a Geographical Information System (GIS) based on a network sourced by various field measurements and observations conducted on the coastal forms on the basis of a predefined protocol and methodology. Field experiments include hydrodynamic measurements, topographic surveys, and observations, and these are coupled with the analysis of aerial photographs and regional meteorological data in order to gain a better understanding of the coastal morphology and of the evolution of the reef-lagoon complex. The results fed into the observatory and analysed through the GIS provide interactive maps of the coastal landforms and their evolution and dynamics over various timescales. Within a local framework of strong socio-economic and demographic pressures, and a more global context of environmental change, this observatory should lead to a better understanding and prediction of the morphodynamics of the coast of Mayotte, while providing data to the public at large, to researchers, and to stakeholders involved in decision-making in the face of the major and rapid environmental and socio-economic changes liable to affect the fragile reef-mangrove systems and pocket beaches.

Description: 4G cellular systems envisions a comprehensive all-IP-based solution, including voice, data, and streamed multimedia at much higher data rates and spectral efficiency. Emerging standards and technologies like LTE and M-WiMAX are actually leading towards this vision. The objective of this special issue is to address specific research research issues and solutions on different aspects of 4G wireless systems and beyond. The total six papers included in this special issue demonstrates research outcomes in different aspects of 4G wireless, like scheduling, resource allocation, cognitive and cooperative communications, multicast services and coverage and planning of small cells. We hope that the research results included in this special issue will serve as an important step for further research and development in 4G wireless communication systems.

Description: The modern society evolves into a sensorial network environment where individual sensor data can be transformed into cumulative and comprehensive representation for human. In a real time, it is independent of current location or behavior. The only limits to increase productivity and to create a smarter surrounding environment are personal habits and technology progress. The paper describes sensorial framework, which is dealing with the current aspects of technology, sociology, and usability in daily life usage of ubiquitous mobile devices with sensors, and arising computed and energy power. Nowadays, most of the common tasks of our lives are mainly influenced by network and social connectivity where infrastructural speed limits are provided by the information flow.

Description: Cognitive radio (CR) enriches wireless technology systems by harnessing spectrum white spaces. Such systems require continuous and reliable sensing to provide high-quality service to their users and to minimize the interference they may cause to legacy networks. As the simplicity of implementation of energy detectors and their incoherent requirements make them an ideal candidate for this type of application, this work provides a further mathematical analysis to the probability of detection over different fading channels. We derive a tight closed-form expression for the probability of detection over Nakagami channels. In addition, we introduce an accurate recursive algorithm to compute the probability of detection for an odd degree of freedom over additive white Gaussian noise channels, which has been overlooked in the literature so far. Finally, we present the simulation results which concur with the numerical results and which are also a perfect match with the mathematical expressions derived.

Description: We investigate the estimation of the time of arrival (ToA) of a radio signal transmitted over a flat-fading channel. The path attenuation is assumed to depend only on the transmitter-receiver distance and the path loss exponent (PLE) which, in turn, depends on the physical environment. All previous approaches to the problem either assume that the PLE is perfectly known or rely on estimators of the ToA which do not depend on the PLE. In this paper, we introduce a novel analysis of the performance of the maximum likelihood (ML) estimator of the ToA under an imperfect knowledge of the PLE. Specifically, we carry out a Taylor series expansion that approximates the bias and the root mean square error of the ML estimator in closed form as a function of the PLE error. The analysis is first carried out for a path loss model in which the received signal gain depends only on the PLE and the transmitter-receiver distance. Then, we extend the obtained results to account also for shadow fading scenarios. Our computer simulations show that this approximate analysis is accurate when the signal-to-noise ratio (SNR) of the received signal is medium to high. A simple Monte Carlo method based on the analysis is also proposed. This technique is computationally efficient and yields a better approximation of the ML estimator in the low SNR region. The obtained analytical (and Monte Carlo) approximations can be useful at the design stage of wireless communication and localization systems.

Description: In this paper, efficient power allocation strategies for multi-hop multi-branch amplify-and-forward networks are developed in generalized fading environments. In particular, we consider the following power optimization schemes: \emph{i)} minimizing of the all transmission powers subject to an outage constraint; and \emph{ii)} minimizing the outage probability subject to constraint on total transmit powers. In this work, we first derive asymptotically tight approximations for the statistics of the received SNR in the system under study with maximal ratio combining (MRC) and selection combining (SC) combiners. With the statistical characterization of the received SNR, we then carryout a thorough performance analysis of the system. Finally, the asymptotic expression of the outage probability is used to formulate the original optimization problems using geometric programming. The geometric programming can be readily transformed into nonlinear convex optimization problem and therefore solved efficiently and globally using the interior-point methods. Numerical results are provided to substantiate the analytical results and to demonstrate the considerable performance improvement achieved by the power allocation.

Description: Barrier islands and coastal beach systems provide nesting habitat for marine and estuarine turtles. Densely settled coastal areas may subsidize nest predators. Our purpose was to inform conservation by providing a greater understanding of habitat-based risk factors for nest predation, for an estuarine turtle. We expected that habitat conditions at predated nests would differ from random locations at two spatial extents. We developed and validated an island-wide model for the distribution of predated Diamondback terrapin nests using locations of 198 predated nests collected during exhaustive searches at Fisherman Island National Wildlife Refuge, USA. We used aerial photographs to identify all areas of possible nesting habitat and searched each and surrounding environments for nests, collecting location and random-point microhabitat data. We built models for the probability of finding a predated nest using an equal number of random points and validated them with a reserve set ( N  = 67). Five variables in 9 a priori models were used and the best selected model (AIC weight 0.98) reflected positive associations with sand patches near marshes and roadways. Model validation had an average capture rate of predated nests of 84.14 % (26.17–97.38 %, Q1 77.53 %, median 88.07 %, Q3 95.08 %). Microhabitat selection results suggest that nests placed at the edges of sand patches adjacent to upland shrub/forest and marsh systems are vulnerable to predation. Forests and marshes provide cover and alternative resources for predators and roadways provide access; a suggestion is to focus nest protection efforts on the edges of dunes, near dense vegetation and roads.

Description: The technology for through-wall human detection with ultra-wideband (UWB) radar was discussed. Due to the large amount of UWB radar data, compressive sensing theory was introduced and compressed UWB radar data can be collected. The singular value decomposition algorithm was used to acquire the singular values of compressed radar data. The compressed UWB radar data were collected at two statuses of human being for gypsum wall. The experimental results showed that the singular values with a human target were increased compared with those without a target.

Description: The theory of compressive sensing is briefly introduced, and some construction methods for measurement matrix are deduced. A measurement matrix based on Kronecker product is devised, and it has been proved in mathematical proof. Numerical simulations on 2-D image verify that the proposed measurement matrix has better performance in storage space, construction time, and image reconstruction effect when compared with commonly used matrices in compressive sensing. This novel measurement matrix offers great potential for hardware implementation of compressive sensing in image and high-dimensional signal.

Description: The refraction of the 2004 Indian Ocean tsunami waves caused drastic devastation along East coast of India, mainly in the area of investigation. Here, we appraise and integrate the sedimentary characteristics and microfossil studies of the area. The gigantic tsunami waves caused the landward fining of sediments that were carried as suspended load. Tsunami sediments have distinctive characteristics, like fine-to-medium grained sand, moderately to poorly sorted sediments which indicating sudden winnowing followed by tranquil flood. Positively skewed grain size distribution indicating unidirectional transport, and mesokurtic to platykurtic character implying poorly sorted single source origin. The species of benthonic foraminifers and ostracods reside in marine environment indicating shallow water origin of sediments. The onshore deposits are vertically divided into three depositional units interpreted from Ground Penetrating Radar (GPR) signatures—Unit 1 is a relatively continuous parallel layer indicative of calm environment; Unit 2 has paleochannels and burial scarps, seen as oblique reflections that might be indicative of an intense erosional environment; Unit 3 is interpreted as 2004 tsunami layer, has three subunits. Each main units have been separated by Heavy Mineral Concentrated (HMC) layers, deposited by continuous wave action (~ 20 cm) and by the tsunami (〉 30 cm) activity, evidenced by low magnetic susceptibility values at the bottom compared to the top of the HMC layers. GPR has been effectively utilized in this paper as subsurface imaging tool for the interpretation and reconstruction of stratigraphy, and also helped to unearth the erosional and depositional environments.

Description: Coastal lagoons have long been subjected to anthropogenic disturbances due to the increasingly urbanization pressure along the margins. As a result, the composition, structure and distribution of macrozoobenthic communities are strongly affected by environmental gradients and harsh ecological conditions. This study address the first signs changes in the Piratininga-Itaipu lagoon system, located in the southeastern Brazilian coastline, state of Rio de Janeiro, after the opening of a tidal channel in the most deteriorated area of Piratininga lagoon in April 2008, as part of restoration measures concerning the severe eutrophication of this system. In order to observe changes in environmental conditions and community structure before and after the channel opening, sampling of the benthic macrofauna and abiotic variables were conducted in seven sites, from August 2007 to March 2009. According to statistical tools, no significant differences were shown in both environmental characteristics and community structure before and after the channel at the distinct locations. Nevertheless, local changes in the abundance and composition of species were detected particularly in Piratininga, in the site where the tidal channel was constructed. A remarkable loss in abundance of most opportunistic species and the appearance of six new taxa in Piratininga after the opening of the channel was related to habitat regeneration in virtue of the intrusion of marine waters into the lagoon. However, marine inflow seems to be restricted since no clear evidence of the channel influence was felt in the remaining sites of Piratininga and in Itaipu. Macrobenthic communities were heterogeneous between both lagoons throughout the sampling period, characterized by low diversity and evenness indices. A general increase in salinity and redox potential were observed in Piratininga. Both variables allied to dissolved oxygen appeared to play a major role in structuring the benthic communities. This study is the first contribution to knowledge of taxonomic biodiversity of macrozoobenthic assemblages of Piratininga-Itaipu lagoon system and pioneer in describing apparent ecosystem ameliorations after the channel opening. Therefore, continuous monitoring ought to be carried out in order to evaluate the effectiveness of the tidal channel and follow further recovery of this ecosystem. Macrobenthos were quite heterogeneous between both lagoons throughout the sampling period, with biological attributes showing a remarkable loss in species abundance, mostly opportunistic. The appearance of new taxa, Polydora cornuta, after the opening of the channel was related to improvement of better oxygenation of water and sediments, causing regeneration of habitat. Other resilient taxa with persistant bioturbation activities, such as Allita, Streblospio, Capitella and oligochaetes, dominated the early stages of recovery. This study is the first contribution to knowledge of taxonomic biodiversity of macrozoobenthic assemblages of Piratining-Itaipu lagoon system and pioneer in describing apparent ecosystem ameliorations after the channel opening. Therefore, continuous monitoring ought to be carried out in order to follow further recovery of this ecosystem.

Description: Coastal erosion results in loss of land, which impacts the economy, coastal residents and settlement plans, especially in the context of rising sea levels caused by climate change. Studying soil particle-size fractions in mangrove forests will help provide a better understanding of the relationship between soil proportions and coastal processes as well as the role of mangrove forests to support coastal planning and management. Soil samples were collected at 26 sampling plots at depths of 10 cm and 40 cm in the Cu Lao Dung (CLD), Long Phu (LP) and Vinh Chau (VC) mangrove forests in Viet Nam’s Soc Trang Province. The soil proportions based on six different particle-sizes (〈0.074 mm, 0.074–0.1 mm, 0.1–0.25 mm, 0.25–0.5 mm, 0.5–1.0 mm, and 〉1.0 mm) were measured using a dry sieving method. Analysis showed that soil particle-sizes ranging between 0.074 and 0.5 mm made up 75–95 % of the soil sample weight at both depths. The high standard deviation values of soil proportions of each given particle-size among sampling plots indicated the soil proportions by particle-size varied widely across the sampling plots. Cluster analysis found similar pattern of soil particle-size proportions for samples collected in CLD and VC, and different pattern of soil particle-size proportions in samples collected at LP, which is more impacted by the Mekong River flow and has a thin mangrove forest belt. Non-metric dimension scaling (NMDS) analysis showed that sampling plots across the landward sites of the three mangrove forest areas were distributed in the nearby locations ( Stress  = 0.11). This indicated that soil proportions of particle-sizes of samples collected from areas of the natural forest composed of different species were more similar. Such similarities were not found, however, in samples collected from middle and seaward plots dominated by single-species plantations.

Description: A comparison of 4 x 4 multiple-input multiple-output wireless local area network wireless communication characteristics for six different geometrical shapes is investigated. These six shapes include the straight shape corridor with rectangular cross section, the straight shape corridor with arched cross section, the curved shape corridor with rectangular cross section, the curved shape corridor with arched cross section, the L-shape corridor, and the T-shape corridor. The impulse responses of these corridors are computed by applying shooting and bouncing ray/image (SBR/Image) techniques along with inverse Fourier transform. By using the impulse response of these multipath channels, the mean excess delay, root mean square (RMS) delay spread for these six corridors can be obtained. Numerical results show that the capacity for the rectangular cross section corridors is smaller than those for the arched cross section corridors regardless of the shapes. And the RMS delay spreads for the T-and the L-shape corridors are greater than the other corridors.

Description: In this article, we study the medium access control (MAC) problem inunderwater wireless acoustic networks. We explore the random accessand handshaking (i.e., RTS/CTS) techniques in both single-channeland multi-channel network scenarios. We model and analyze these twoapproaches, and conduct extensive simulations to study theirperformance in various network conditions. Based on our results, weobserve that the performance of both approaches are affected by manyfactors such as data rate, propagation delay and packet size. Ourresults show that the RTS/CTS approach is more suitable for densenetworks with high date rate, whereas the random access approach ispreferred in sparse networks with low data rate. Our results alsodemonstrate that multi-channel techniques can potentially help uscombat the long delay feature of underwater acoustic channels.However, uncoordinated random channel access cannot fully exploitthe advantages of the multi-channel network settings and it performseven worse than the single-channel random access protocol. Only withcareful design and coordination such as multi-channel access withRTS/CTS handshaking process, can multi-channel MAC protocols greatlyimprove the system performance. We believe that this study willprovide useful guidelines for efficient MAC design in underwaterwireless acoustic networks.

Description: In order to mitigate the mutual interference between ultra-wideband (UWB) impulse radio and other existing wireless systems, a novel adaptive interference-avoiding UWB pulse, in the context of the appealing cognitive radio, is presented based on the radial basis function neural networks. Theoretical and implementation architecture for UWB pulse generator is addressed. Transmission performance in the presence of narrowband interference including tone interference is comprehensively analyzed. The presented generator can adaptively change the spectrum shape of UWB signals according to the authorized users' working states, and hence the mutual interference between UWB and other systems sharing the frequency bands can efficiently be avoided. The critical performance indication parameters, such as the SNR, SIR, and BER of UWB communication links, are also derived. Performance evaluations and comparisons between the proposed scheme and other pulse optimization methods have been provided based on the extensive numerical simulations. It is demonstrated that the presented pulse can indeed achieve much superior performance in terms of either single-link BER or anti-jamming capability.

Description: The risk associated with a given hazard (natural or technological) generally results from the interaction between the hazard potential and the vulnerability. This paper is centred on the assessment of the vulnerability variable. A quantitative vulnerability assessment and mapping methodology is proposed, with two main specificities: (1) it is hazard- and spatially-centred (respectively, oil spills and coastal areas) and; (2) the spatial segregation level used is the municipality. Due to the geographic context of the Portuguese mainland coast, the proposed methodology was applied in an attempt to illustrate the spatial distribution and the degree of the vulnerability associated to oil spills for mainland Portugal coastal municipalities. A final map is presented together with other informative elements. Analysis and discussion of the results allows for the understanding that: (1) there is a very heterogeneous and differential distribution of the degree of vulnerability to oil spills along the Portuguese coastline; (2) the application of specific hazard-centred and spatially-centred vulnerability assessment methodologies, comprising multi-dimensional indicators (e.g., geographic, ecological, demographic, social and economic), produces more robust and realistic results, highlighted by a thorough and spatially detailed analysis; and (3) future research is required on vulnerability assessment in Portugal; along side, hazard potential assessment methodologies must also be developed in order to create a final risk profile, which can be an extremely useful tool in spatial planning and management.

Description: Coral reefs around the world are facing serious threats. These fragile ecosystems are in need for conservation. The coastal state of Bahia hosts the most extensive and richest area of coral reefs in the South Atlantic Ocean. Assessment, planning and management of coral reef ecosystems are particularly challenging tasks. This work shows how the creation of a GIS improves the process of management, monitoring and conservation of the Bahian reef environments The initial data input started by the vectorization of 1) bathymetric data from the Bureau of Hydrography and Navigation (DHN), 2) shoreline and mangrove areas from Landsat 7 ETM + images, 3) near surface reefs from Quickbird images, and 4) coastal and marine protected areas of federal, state and local administrations. Geological, physical, biological and social information was then included in order to create a suitable marine GIS for conservation aims. The data includes information on sediment granulometry and transport patterns, rocky substrate outcrops, sea surface temperature, wave direction, rain precipitation, major contributing river discharge, artisanal fishery, benthic cover and bleaching data. ReefBahia GIS has provided essential information for a better understanding of coral reefs of the state of Bahia geological and ecological characteristics such as mapping, representation, connectivity and biodiversity of coral reefs, geological facies, Quaternary sedimentation, numeric modeling of wave refraction and monitoring of bleaching events.

Description: The Wairoa River, a barrier enclosed estuary situated in Hawke’s Bay, New Zealand was modelled using a one-dimensional hydrodynamic model. Water level data obtained during a flood and a bathymetric survey were available but the entrance cross-section had not been surveyed. This paper describes the calibration of the model to jointly optimise the selection of the Manning coefficient and the depth of the estuary entrance.

Description: Recent sea-level rise has mostly been attributed to global warming and this process is expected to continue for centuries. The extent of the impact of sea level rise on tourism in Ghana is unknown though there are predictions that some prominent tourism facilities are at risk. This paper assessed the potential impact of enhanced sea level rise (ESLR) for different IPCC scenarios on tourism facilities along the coast of Accra. Shorelines for 1974 and 2005 were extracted from orthophotos and topographic maps, and vulnerability for tourism facilities estimated. Mean sea level measurements indicated an average rise of 3.3 mm/year, while the shoreline eroded by as much as 0.86 m/year. Predictions for Ghana showed 10 cm, 23.4 cm and 36.4 cm sea level rise for 2020, 2060 and 2100 respectively with 1990 as base year. Modelled predictions for the years 2020, 2060 and 2100 based on A2 (enhanced regional economic growth) and B2 (more environmentally focused) IPCC scenarios indicated that 13 tourism facilities are at risk to sea level rise. Out of the total number of tourism facilities at risk, 31 % cannot physically withstand the event of sea level rise hazard. In terms of socio-economic vulnerability, accommodation facilities are the most susceptible. Salinization and sanitation problems along the coast will adversely affect tourism.

Description: Purpose Ammophila arenaria (marram grass) may invade remote beach-dune systems by the marine dispersal of rhizomes. In New Zealand, and elsewhere, the conservation of the remaining dune systems of high conservation value would be advanced by predicting where this species might successfully establish and undertaking appropriate surveillance. This paper examines the ability of A. arenaria to sustain growth in the stressful back-beach environment. Methods Shoots developed from rhizomes were subjected to burial, depth, salt spray and desiccation treatments in the glasshouse. Plants were also subjected to salt water inundation. Two field populations of A. arenaria were surveyed for a period of almost 3 years, following rhizome stranding in July 2007. Results Shoots were able to emerge from depths of up to 40 cm. Rhizomes failed to produce shoots when the moisture content of rhizomes was less than 18.25 %, which occurred after 3 days of drought. The survival of buried plants was significantly reduced compared to non-buried plants when burial exceeded 80 % of the plant height. No plants survived when burial exceeded 100 % of the plant height. No tillers survived without water for more than 3 weeks. Exposure to salt spray had no effect on shoot survival. Immersion in seawater significantly reduced survival—exposure to seawater, equivalent to only one high tide immersion event, was sufficient to reduce plant survival in the glasshouse. Conclusions Burial, desiccation and salt-spray may, on occasion, be responsible for either preventing the regeneration of A. arenaria rhizomes or limiting the survival of the resultant plants, but exposure to wave activity determines the viability of a population.

Description: The interface between the sea and land is a very dynamic system that is always migrating landward or seaward. The landward migration results in the shoreline threatening coastal infrastructure and destroying the coastal environment. Coastal erosion has resulted in both social and economic problems. Coastal cities have also experienced increasing infrastructure development and population growth. This has resulted in a land “squeeze situation” in which both the shoreline and the “humanline” are competing for space along the coast. This struggle for space could result in serious environmental disaster as a result of the dynamics of the oceanic system, which could impact the immediate environs severely. The aim of this study was to determine if the rate of human encroachment of coastal lands for development exceed the rate at which the shoreline is moving inland as part of its natural cyclic behaviour. This study used 1985 aerial photographs and 2005 orthophoto map of the Accra western coast. Major land cover was identified, classified and overlayed in GIS environment. This enabled changes to be estimated. The shorelines were also digitised and the rate of change computed using the DSAS software. The results indicate that the estimated total area of land lost by human encroachment on the coastal land within the period under study is about 242,139.7 m2. However, the rate of land lost to human development is about 8,349.64 m2/year, which is relatively high. The historic rate of erosion computed for the period under study is about 1.92 m/year. Comparing the two rates indicates that human activities are moving closer to the shoreline as compared to the rate at which the shoreline is moving inland. This study recommends that setback lines should be put in place to protect lands for the shoreline’s cyclic activities.

Description: Land-use suitability is the ability of a given type of land to support a defined use. GIS is known as a powerful tool for handling spatial data in land-use analysis. Application of this tool alone cannot overcome the lack of consistency in opinions given by experts when trying to assign relative importance to each of the several criteria considered in a suitability analysis. The combination of GIS and Multi-Criteria Decision Analysis (MCDA) is a powerful approach used to assess land suitability. To address this issue, the Analytical Hierarchy Process method is used in combination with the GIS tool. The aim of this study is to demonstrate how GIS tools and AHP model can be used for integrated coastal resource planning and management. Based on the information from final map/suitability map, we can define the best area. The findings indicate that the area 1 (2111 m) from class 3 is the most appropriate one because it has good facilities and wide open areas. This study indicates how the integrated tool is handled effectively in a land use suitability analysis for building hotels in the coastal areas of Terengganu in Malaysia. This research develops a framework for integrating GIS and AHP to incorporate the decision maker’s preferences on a range of factors in finding land areas suitable for coastal development.

Description: Sicily is the largest island in the Mediterranean, and tourism represents the most important income in the regional budget. This is due to a mild climate, to its considerable archaeological and cultural heritage, but above all to the beaches, which host visitors for most of the year. Nevertheless, Sicily has no official Integrated Coastal Zone Management (ICZM) policy and also lacks an overall plan for coastal protection. In 2000, however, driven by the EU, a process of selection of projects based on objective parameters was initiated. Not all of these projects have had the expected results and some are yet to be completed. One of these is Giardini Naxos, Taormina beach, one of the main tourist resorts in Sicily. There, due both to the incorrect position of the port structure and to the rapidly increasing coastal urbanization (second homes, hotels and waterfront), a process of coastal erosion has started, the beach has disappeared, and the promenade has been damaged. To rebuild the shore in order to protect the structures behind it and to restore the coast for beach goers, a submerged barrier (like a reef) was designed to protect an artificial beach replenishment using local and remote sands, mined from the continental platform bottom and compatible both in terms of composition and grain size. Even though the results were excellent during the first stages of the project, towards the end, financial support disappeared and the funds were allocated to other projects. This experience in Giardini Naxos illustrates the ineffectiveness of defensive action in the absence of coastal planning that takes into account the sustainability of interventions on a regional basis both from a structural and an economic standpoint.

Description: Coastal barrier environments are heavily influenced by human activities yet there are few examples of landscape ecological work investigating human dimensions of settlement disturbance patterns and processes. We investigated the impacts of residential development on vegetation cover for a remote roadless coastal barrier in Carova, North Carolina that is subject to policies from the federal to local levels and addressed three research questions: How has the region’s the policy history influenced patterns of residential parcel development? What are the spatial and temporal patterns of parcel development? How has development impacted patterns of barrier vegetation cover? We traced the influences of the federal 1982 Coastal Barrier Resources Act (CBRA) designed to discourage development in risky coastal areas as well as state/local coastal policies and employed remote sensing change detection, NDVI analysis and spatial analysis and regression techniques. Results showed an acceleration of new housing structures since 1990, contrary to the intended effects of CBRA. An estimated vegetation cover loss of 437 m 2 was associated with each newly developed parcel. NDVI varied along spatial and temporal gradients with more recent development having lower NDVI than older development. Recently developed parcels were larger in area, closer to the beach, and contained houses with larger footprints compared to older developed parcels. Our approach represents a place-based analytical framework for coastal barrier landscapes. Beyond the Carova case study, adopting such an approach coupling natural and human systems for the entire eastern US barrier system requires defining a comprehensive set of coastal barrier spatial units to enable typological classification and subsequent systematic investigation to inform debates regarding coastal ecosystem services and sustainability.

Description: The conservation of wild fisheries resources in the face of an ever-increasing world demand for seafood requires the use of a number of management tools, including no-take zones, and gear, species, and temporal restrictions. One way of enforcing some of these regulations is through the use of Vessel Monitoring System (VMS) data that provides enforcement officers with the position of fishing vessels in the management area. The increasing volume of movement data collected using VMS calls for new methods that could help analysts extract useful knowledge from these large data sets. Various approaches have been proposed for visualizing and exploring movement data and detecting patterns within these data, but those approaches have generally not been tested in a real-world context or compared together, making their actual usability and utility unclear. This paper describes, compares, and assesses three such approaches in the context of fisheries enforcement: an existing system used for fisheries enforcement operations in Canada (VUE), a novel Hybrid Spatio-temporal Filtering (HSF) system developed by the authors, and an automated Behavioural Change Point Analysis (BCPA) system. A field trial was conducted with experienced fisheries enforcement officers to compare and contrast the benefits and drawbacks of the three approaches. While all three presented advantages and disadvantages, the interactivity of VUE and HSF were identified as desirable features, as they provide analysts with more control over the data, while allowing flexible data exploration. BCPA, while providing an automated approach to the data analysis, was pointed out as being too much of a “black box”, causing unease among the experts who require a level of transparency similar to that of legally admissible evidence. In the end, the experts suggested that the best approach would be to merge the analytical power of their existing VUE system with the exploratory power of the HSF system. This study provides insight into the value of using interactive mapping and filtering approaches in support of data analysis in the context of fisheries enforcement.

Description: The aim of the present work is to unveil the potential of some of the unexplored remote sensing techniques for mangrove studies. The paper deals with the classification of an Earth Observing–1 Hyperion image of the mangrove area of Bhitarkanika National Park, Odisha, India into mangrove floristic composition classes. Out of 196 calibrated bands of the image, 56 were found to be highly uncorrelated and contained maximum information; therefore, these 56 bands were used for classification. Amongst the three full–pixel classifiers tested in the investigation, Support Vector Machine produced the best results in terms of training pixel accuracy with overall precision of 96.85 %, in comparison to about 70–72.0 % for the other two classifiers. A total of five mangrove classes were obtained – pure or dominant class of Heritiera fomes , mixed class of H. fomes , mixed Excoecaria agallocha with Avicennia officinalis , mixed class of fringing Sonneratia apetala and class comprising of mangrove associates with salt resistant grasses. Post–classification field data also established the same. Pure or dominant classes of H. fomes occupied more than 50 % of the total mangrove vegetation in the forest blocks of the National Park. Spectral profile matching of image pixels with that of in – situ collected canopy reflectance profile revealed good match for H. fomes (pure or dominant stands). Red–edge index, which was a preferred criterion for matching was notably correlated in case of H. fomes and E. agallocha . The outcomes indicated the efficacy of hyperspectral canopy reflectance library for such kind of work. It is hoped that the methodology presented in this paper will prove to be useful and may be followed for producing mangrove floristic maps at finer levels.

Description: The Ada peninsular in Ghana has suffered rapid coastal erosion and inundation for over half a century, accompanied by loss of property and livelihoods, economic stagnation and salt water intrusion. Government intervened to respond to these threats by implementing a sea defence project. A preliminary assessment indicates the project will deal with some urgent needs of property loss reduction and invigorate livelihood and economic opportunities. However, it will have minimal beneficial impacts on groundwater salinization, and may actually intensify salinity of surface water in the Volta River and adjoining water points by shifting salinity intrusion further upstream to affect hitherto salinity-free areas. The spatial reach of the salinity shift is uncertain. The potential for further sea level rise will aggravate and accentuate the region’s water scarcity dilemma if a coherent water management strategy is not sort sooner. The project demonstrates the limitations of employing static, narrow objectively designed sea defence project as a response to coastal erosion and inundation, because it lacks the capacity to deal with dynamism, complexity and multi-dimensional impacts associated with climate change related sea level rise.

Description: Non-line-of-sight (NLOS) error is a bottleneck problem influencing positioning accuracy. However, a large number of scatterers distribute randomly in the surrounding of the mobile station (MS) in the dense multipath environment, such as urban. In most cases, there is no obstacle between scatterer and MS. So, the geographic information of scatterers around MS can be used to restraint NLOS errors and improve the positioning accuracy. If scatterer can be regarded as the virtual base station (BS), the precondition of the positioning algorithm is easier to satisfy than the traditional positioning algorithm, such as circle positioning algorithm. The algorithm proposed in this article selects suitable scatterers with linear constraints by analyzing the Doppler frequency shift of received signals which reflected by scatterers. Thereby, the selected scatterers and only two real BSs form a complete positioning system. In addition, because MS is motionless in most scenarios, BS must be moving to acquire the Doppler frequency shift. The algorithm proposed in this article is adjusted for the scenarios. And the scatterers with linear constraint can also be utilize fully. Simulation results show the algorithm proposed in this article in two different scenarios, not only simplifies the traditional algorithm, but also achieves the higher positioning accuracy.

Description: This article explores the effects of quantization offeedback information on energy consumption in multiuser wirelesscommunication systems. In order to optimize the energy consumptionof the system, the article concentrates on the amount of transmitenergy, the additional energy due to quantization and theprobability of power outage. Closed form expressions for suchparameters are obtained, where the impact of the number ofquantization bits is explicitly outlined. An optimization problem isthen formulated to find the optimum number of quantization bits ableto minimize the consumption in the energy resources. Simulationsdemonstrate the good results obtainable with the presentedoptimization strategy, and provide effective validation of theanalytic solution presented in the article.

Description: Firewalls are network devices dedicated to analysing and filtering the traffic in order to separate network segments with different levels of trust. Generally theyare placed on the network perimeter and are used to separate the Intranet fromthe Internet. Firewalls are used to forbid some protocols, to shape thebandwidth resources, and to perform deep packet inspection in order to spotmalicious or unauthorized contents passing through the network. In a wirelessmulti-hop network the concept of perimeter is hard to identify and the firewallfunction must be implemented on every node together with routing. But whenthe network size grows, the rule-set used to configure the firewall may growaccordingly and introduce latencies and instabilities for the low-power meshnodes.We propose a novel concept of firewall in which every node filters the trafficonly with a portion of the whole rule-set in order to reduce its computationalburden. Even if at each hop we commit some errors, we show that the filteringefficiency measured for the whole network can achieve the desired precision, with a positive effect on the available network resources. This approach is different from the protection of a space behind a wall: We use the term waterwall to indicate a more distributed and homogeneous filtering function spreadamong all the nodes in the network.

Description: We propose a relaying scheme based on superposition coding (SC) with discrete adaptive modulation and coding (AMC) for a three-node wireless relay system, based on half duplex transmission, where each node decodes messages by successive interference cancelation (SIC). Unlike the previous works where the transmission rate of each link is assumed to achieve Gaussian channel capacity, we design a practical superposition-coded relaying scheme with discrete AMC while taking into account the effect of decoding errors at each stage of the SIC process at each node. In our scheme, hierarchical modulation (HM) is used to create an SC message composed of one basic and one superposed message with optimized power allocation. We firstly introduce the proposed scheme without forward error correction (FEC) for high signal-to-noise ratio (SNR) region and provide the optimal power allocation between the superimposed messages. Next, we extend the uncoded scheme to incorporate FEC to overcome bad channel conditions. The power allocation in this case is based on an approximated expression of the bit error rate (BER). Numerical results show the performance gains of the proposed SC relaying scheme with HM compared to conventional schemes, over a large range of SNRs.

Description: In this paper, a reduced complexity Log-MAP algorithm based on a non-recursive approximation of the max* operator is presented and studied for turbo trellis-coded modulation (TTCM) systems. In the algorithm, denoted as AvN Log-MAP, the max* operation is generalized and performed on n ¿ 2 arguments. The approximation is derived from the Jensen inequality. The non-recursive form of the max* calculations allows to achieve significant reduction in the decoding effort in comparison to the conventional Log-MAP algorithm. Bit-error rate performance simulation results for serial and parallel TTCM schemes in the additive white Gaussian noise and uncorrelated Rayleigh fading channels show that the AvN Log-MAP algorithm performs close to the Log-MAP. Performance and complexity comparisons of the AvN Log-MAP algorithm against the Log-MAP and several relevant reduced complexity turbo decoding algorithms proposed in the literature reveal, that it offers favorable low computational effort for the price of small performance degradation.

Description: In this article, we investigate the information-theoretical performance of a cooperative orthogonalfrequency division multiplexing (OFDM) system with imperfect channel estimation. Assuming thedeployment of training-aided channel estimators, we derive a lower bound on the achievable rate forthe cooperative OFDM system with amplify-and-forward relaying over frequency-selective Rayleighfading channels. The bound is later utilized to allocate power among the training and datatransmission phases. Numerical results demonstrate that the proposed power allocation schemebrings between 5 and 19% improvement depending on the level of signal-to-noise ratio and relaylocations.

Description: The article provides an infrared and visible image fusion algorithm based on directionlets transform. The registered original images were decomposed into the low-frequency and high-frequency coefficients by directionlets transform. Getting the mean of the low-frequency coefficients, applying the local variance maximum principle to the high-frequency coefficients, thereby the fusion coefficients of the fused image can be acquired. Finally, the fused image was obtained using inverse directionlets transform. The experiment indicates that the fusion algorithm can extract the original image features better. Compared with the traditional fusion algorithms, the fusion algorithm presented in this article provides better subjective visual effect, and the standard deviation and entropy value would be somewhat increased.

Description: In this article, we propose a closed-loop precoding method for the Generalized Space Shift Keying (GSSK) modulation scheme, suitable for Multiple-Input-Single-Output (MISO) systems and denoted as adaptive GSSK (AGSSK), which achieves transmit-diversity gains in contrast to GSSK. For the case of a perfect feedback channel, we analytically show that for three and four antennas at the transmitter and rates 1 and 2 bits per channel use (bpcu), respectively, a full transmit-diversity can be achieved without reducing the achievable rate. For higher number of transmit antennas and rates, the performance of the proposed scheme degrades due to the smaller average minimum Euclidean distance as the rate increases. Due to this, we, furthermore, propose an enhancing method for AGSSK which relies on the use of time-orthogonal shaping filters for the different constellation points. For the enhanced method, named as AGSSK with time-orthogonal signal design (AGSSK-TOSD), we analytically prove that it offers transmit-diversity gains which are greater than the number of active transmit antennas for any number of transmit antennas and supported rate. This is attained without any antenna subset selection technique, which alleviates the processing burden on the terminal side. Monte Carlo simulations show that AGSSK significantly outperforms GSSK in terms of average bit error probability (ABEP) and, moreover, for medium to high rates and practical signal-to-noise ratio (SNR) regions AGSSK-TOSD outperforms well-known feedback-based multiple-antenna schemes. This advantage of AGSSK-TOSD is further substantiated with an energy effficiency comparison over the conventional schemes for a target (uncoded) ABEP.

Description: Future wireless networks are designed to cope with drastically increasing user demands. However, network resources reach the limits of their capacity to user requirements. Recently, femtocell networks have attracted much attention to enhance the efficiency of wireless resource usage. In this article, a new adaptive power control scheme is developed for the femtocell network system. By using the concept of the weighted voting game, the proposed scheme adaptively adjusts a transmit power level while ensuring relevant tradeoff between system efficiency and fairness. This power control paradigm can provide the ability to practically respond to current communication conditions and suitable for real network operations. Simulation results are presented to verify the effectiveness of the proposed voting game-based scheme in comparison with the existing schemes.

Description: IEEE 802.16j multi-hop relay network systems provide the mobile wireless communication environment. In such network systems, the handover scanning procedure allows a mobile station (MS) to obtain the information about the handover target base stations (BSs) or relay stations (RSs). The network systems need more time to negotiate the association parameters and to handle scanning the BSs and the RSs when the number of BS and RS increases. It results in more overhead for the handover scanning procedure. In order to accelerate the handover process and reduce the transmission interruption, efficient handover scanning procedure schemes and corresponding algorithms must be developed and designed. A novel relative angle computing algorithm is proposed in this article to accelerate the handover process by taking into account the moving behavior of the MS, and the distances among the MS, the RS, and the BS. The main idea of this algorithm is to reduce the management information overhead and to estimate the potential moving path of the MS in the wireless mobile communication networks. By using the proposed scheme, we eliminate the unnecessary associations and scanning intervals, and reduce the handover scanning procedure efficiently. Simulation result demonstrate the superior performance of our proposed scheme and its ability to strike the appropriate performance in the handover overhead and the message delay for IEEE 802.16j multi-hop relay network systems.

Description: This article addresses the spectrum efficiency study of nested sparse sampling and coprime samplingin the estimation of power spectral density for QPSK signal. The authors proposed nested samplingand coprime sampling only showed that these new sub-Nyquist sampling algorithm could achieveenhanced degrees of freedom, but did not consider its spectrum efficiency performance. Spectralefficiency describes the ability of a communication system to accommodate data within a limitedbandwidth. In this article, we give the procedures of using nested and coprime sampling structure toestimate the QPSK signal's autocorrelation and power spectral density (PSD) using a set of sparsesamples. We also provide detailed theoretical analysis of the PSD of these two sampling algorithmswith the increase of sampling intervals. Our results prove that the mainlobe of PSD becomesnarrower as the sampling intervals increase for both nested and coprime sampling. Our simulationresults also show that by making the sampling intervals, i.e., N1 and N2 for nested sampling, and Pand Q for coprime sampling, large enough, the main lobe of PSD obtained from these twosub-Nyquist samplings are much narrower than the original QPSK signal. That is, the bandwidth Boccupancy of the sampled signal is smaller, which improves the spectrum efficiency. Besides thesmaller average rate, the enhanced spectrum efficiency is a new advantage of both nested sparsesampling and coprime sampling.

Description: This article examines how an entrepreneur's strategic choice influences corporate development leading to the initial public offering. The data come from Korean startups in information technology industry. We consider the dynamic interplay between an entrepreneur's attributes and government's institutional support as key factors. An empirical analysis of 615 listed companies shows that an entrepreneur's attributes play a significant role in market entry especially in information technology industry which tends to have shorter lead time to the initial public offering. Government certification and venture capital investment also facilitated corporate growth toward the public company status.

Description: The coexistence of heterogeneous networks within the same spectrum for enhancing the spectrum efficiency has attracted large interest lately in the research community. Furthermore, the research interest towards the deployment of small cells and multibeam satellites is increasing due to high capacity, easier deployment and higher energy efficiency. However, due to the scarcity of available spectrum and the requirement of additional spectrum for these systems, small cells need to coexist with macrocells and multibeam satellites need to coexist with monobeam satellites within the same spectrum. In this context, this contribution investigates an underlay spectral coexistence mechanism which exploits an interference alignment (IA) technique in order to mitigate the interference of cognitive transmitters towards the primary receivers in a normal uplink mode. More specifically, three types of IA techniques, namely static, uncoordinated and coordinated are investigated. The performance of the IA technique is evaluated and compared with primary only, resource division and no-mitigation techniques in terms of sum-rate capacity, primary to secondary rate ratio and primary rate protection ratio. It is shown that the coordinated IA technique perfectly protects the primary rate in both terrestrial and satellite coexistence scenarios.

Description: We address the problem of analyzing the performances of interference-limited cellular networks inlarge-scale shadowing environments. Focusing on the fractional frequency reuse (FFR) framework,we examine how to optimally assign mobile users in a cell either to the full frequency reuse part or tothe orthogonal part of the FFR band. Instead of using traditional Monte Carlo simulations, which donot provide sufficiently accurate results under important shadowing, we propose a fast and accuratenumerical method. We consider a fast-fading environment and we use the ergodic capacity as theperformance measure. Applying a distributed power control and scheduling strategy, we examineboth cases where access points have knowledge of partial- or full-channel state information (CSI); forthe latter, we also propose an approximated waterfilling strategy. The interest of our method lies inthe fact that it allows for a fast and accurate analysis of the performances of FFR. In addition, it takesinto account a broad range of shadowing environments.

Description: We consider multi-antenna base stations using orthogonalfrequency-division multiple access and space division multipleaccess techniques to serve single-antenna users. Some users, calledreal-time users, have minimum rate requirements and must be servedin the current time slot while others, called non real-time users,do not have strict timing constraints and are served on abest-effort basis. The resource allocation (RA) problem is to findthe assignment of users to subcarriers and the transmit beamformingvectors that maximize the total user rates subject to power andminimum rate constraints. In general, this is a nonlinear andnon-convex program and the zero-forcing technique used here makes itinteger as well, exact optimal solutions cannot be computed inreasonable time for realistic cases. For this reason, we present atechnique to compute both upper and lower bounds and show that theseare quite close for some realistic cases. First, we formulate thedual problem whose optimum provides an upper bound to all feasiblesolutions. We then use a simple method to get a primal-feasiblepoint starting from the dual optimal solution, which is a lowerbound on the primal optimal solution. Numerical results for severalcases show that the two bounds are close so that the dual method canbe used to benchmark any heuristic used to solve this problem. As anexample, we provide numerical results showing the performance gap ofthe well-known weight adjustment method and show that there isconsiderable room for improvement.

Description: Lately, wireless sensor network applications have emerged for provision of commercial services to end users. This results in commercial deployment of sensor networks which is as an important research area due to a number of design and quality of service challenges. An important technical challenge for sensor service provision to end users is managing dynamic network conditions such as unreliability of sensor nodes and network links which results in frequent service outages. This research is aimed at addressing this challenge. It presents a novel architecture which utilizes the availability of multiple sensor networks under different administrative domains, deployed in an area such that maximum network connectivity and high service availability are ensured. The architecture incorporates modifications and enhancements at the medium access control and the routing layers of sensor nodes for the collaborative operation of sensor networks. The design is based on IEEE 802.15.4 standard and ad hoc on demand distance vector routing protocol. The proposed architecture is mathematically analyzed with regards to overheads associated with the design such as routing and communication, and techniques to minimize these overheads are recommended. Through simulations using OMNET++, we show that the proposed architecture effectively provides connectivity for disconnected nodes achieving an overall increase in throughput for all the cooperating networks.

Description: Cell range expansion (CRE) is a technique to expand a pico cellrange virtually by adding a bias value to the pico received power,instead of increasing transmit power of pico base station (PBS), sothat coverage, cell-edge throughput, and overall network throughputare improved. Many studies have focused on inter-cell interferencecoordination (ICIC) in CRE, because macro base station's (MBS's)strong transmit power harms the expanded region (ER) user equipments(UEs) that select PBSs by bias value. Optimal bias value thatminimizes the number of outage UEs depends on several factors suchas the dividing ratio of radio resources between MBSs and PBSs. Inaddition it varies from UE to another. Thus, most articles use thecommon bias value among all UEs determined by trial-and-errorMethodIn this article, we propose a scheme to determine the biasvalue of each UE by using Q-learning algorithm where each UElearns its bias value that minimizes the number of outage UEs fromits past experience independently. Simulation results show that,compared to the scheme using optimal common bias value, the proposedscheme reduces the number of outage UEs and improves networkthroughput.

Description: In today's heterogeneous networking (HetNet) environments, where end users are provided with universal connectivity opportunities, femtocell deployments can become key players in the enhancement of critical performance indicators such as capacity, coverage, QoS, etc. In order to confront the up-to-date LTE femtocell challenges, we propose a context-aware framework that provides a controlled environment from the femtocell point of view, which is required for applicable functionality. More specifically, we aim to (a) control the local environment where the femtocell is placed within, by efficiently managing the total incoming traffic load and by continuously adjusting the distribution of the backhaul capacity among the coexisting networks and (b) control the macro--femto interference caused by macrocell users transmitting close to the femtocell by investigating the "femtocell as a relay" concept. Finally, the performance of the proposed framework is evaluated via simulation results showing that the overall performance of a HetNet environment can be leveraged in terms of QoS requirements, energy saving and data rate enhancement.

Description: This paper presents a variational model based segmentation approach for polarimetric synthetic aperture radar (PolSAR) images. The formulation for PolSAR image segmentation is based on a scaled Wishart distribution based continuous Potts model, which can partition the image domain into distinct regions with respect to the statistical property of PolSAR data. To make the segmentation efficient, a duality based optimization approach is utilized to minimize the energy functional. Moreover, an automatic initialization approach which takes the unsupervised H--a classification result of the polarimetric data as input is used to initialize the segmentation process. This approach can estimate the appropriate number of clusters and the corresponding classification map for the PolSAR data, which are used as the input of the following variational segmentation approach. In such a way, the proposed approach is carried out in a fully unsupervised way. Both of the polarimetric decomposition features and the statistical characteristics are used to get the final segmentation result, which helps to increase the accuracy. Experimental results demonstrate the effectiveness of the proposed approach. Without any artificial supervision, the proposed approach can produce superior segmentation results than results obtained with random initialized variational approach and Wishart--H--a classification approach.

Description: In this study, we propose an indoor navigation system that utilizes visible light communication technology, which employs LED lights and a geomagnetic correction method, aimed at supporting visually impaired people who travel indoors. To verify the effectiveness of this system, we conducted an experiment targeting visually impaired people. Although acquiring accurate positional information and detecting directions indoors is difficult, we confirmed that using this system, accurate positional information and travel direction can be obtained utilizing visible light communication technology, which employs LED lights, and correcting the values of the geomagnetic sensor integrated in a smartphone.

Description: A two-dimensional correlation interferometer algorithm based on dimension separation is proposed for wideband direction finding. The original two-dimensional angle searching is divided into 2 one-dimensional searching processes in the proposed algorithm. Therefore, the computational complexity is reduced. Meanwhile the introduced interpolation process ensures the direction finding precision. Simulation results demonstrate that compared with conventional correlation interferometer algorithm, the proposed one can offer higher direction finding speed.

Description: In the 60GHz millimeter-wave radar communication systems, the nonlinear power amplifier is inevitable. In order to combat this problem, a promising estimation algorithm based on the particle filtering (PF) is presented here. By employing the conception of Bayesian approximation and sequential importance sampling, this appealing Monte Carlo random sampling method can address this complicated statistic estimation problem. In sharp contrast to the classical linear equalization problem, nevertheless, in the considered situation the PF-based method may become invalid due to the hardware nonlinearity and the resulting non-analytical importance function. To remedy this difficulty, based on the linearization technique a novel PF framework is suggested, and we show in particular how to linearize the involved nonlinearity transform in the formulated discrete dynamic state-space modeling (DSM). The merit of this method is that it can efficiently deal with discrete DSMs that are practically nonlinear and non-Gaussian. Experimental simulations verify the superior performance of our presented PF-based detection scheme, which may properly be applied to 60GHz millimeter-wave radar communication systems.

Description: The impact of outdated channel state information (CSI) on the capacity of amplify-and-forward (AF) partial relay selection systems is studied in this paper. The closed-form expressions for the distribution of received signal-to-noise ratio (SNR) in a multi-relay cooperative communications system is first derived, with independent and identically distributed (i.i.d.) Rayleigh fading channels being assumed in each wireless link. After that, the theoretical closed-form expressions for both outage probability and channel capacity of partial relay selection are derived, with four classical adaptive transmission techniques, including the constant power with optimal rate adaption (ORA), the optimal power and rate adaption (OPRA), the channel inversion with fixed rate (CIFR) and truncated channel inversion with fixed rate (TIFR), being considered. Numerical analysis proves that the channel capacity of partial relay selection is impacted considerably by some critical parameters, including the number of relays, the channel correlation coefficient and the end-to-end SNR, etc. It's also exhibited in the numerical results that among the four adaptive transmission techniques, the diversity order of OPRA is larger than that of TIFR, and the OPRA outperforms TIFR with about 0.15 bits/s/Hz in terms of average channel capacity.

Description: Editorial Article

Description: We present the delay tolerant firework routing (DTFR) protocol, a protocol designed for use in disconnected delay tolerant networks that consist of a very large number of location-aware, highly mobile nodes. Networks with these properties appear frequently in many settings, notably in vehicular networks. Under DTFR, each data packet travels from the source to the estimated location of the destination using high-priority transmissions and a delay-tolerant variant of geographic forwarding. Once there, a number of packet replicas are created, and the replicas proceed to travel through the area where the destination is expected to be. Using simulations in an urban setting, we compare DTFR with two baseline protocols (Flooding and Spray andWait), one recently proposed state-of-the-art protocol (GeoDTN+Nav), and an idealistic protocol of our design which we term Bethlehem Routing (BR). For a wide range of environmental parameters, DTFR performs significantly better than the other realistic protocols, in terms of throughput and delay, and close to the upper performance bounds of BR. We also develop an analytical framework based on stochastic geometry tools, a number of simplifying assumptions, and a small number of judiciously chosen approximations. Using this framework, we develop approximate closed form expressions for the average end-to-end throughput and delivery delay of DTFR and BR.

Description: In vehicular ad hoc networks (VANETs), essentially the information of one-hop neighbors is important for data delivery. In a general way, each node broadcasts short packets, i.e., hello packets, to indicate its appearance and establishes a neighbor table for storing neighbor information through receiving others' hello packets. As a popular approach, it is named as a hello scheme. Determining the validity of the neighbor table, a hello scheme is vital to routing protocols in VANETs. However, a hello scheme with high accuracy and low overhead is severely challenged due to the highly dynamic topology and restricted vehicle mobility in VANETs. To address the issue, it is crucial to optimally configure two key parameters, called as hello interval (HI) and timeout interval (TI), respectively. In this article, a probability model of the hello scheme for VANETs is proposed. It is used to analyze factors affecting the two key parameters. Depending on derivation results, an effective local information-based adaptive hello scheme (LAH) is proposed subsequently. It utilizes the local information, i.e., the variation of neighbor table and received hello packets, to adjust HI and TI adaptively. According to different TI adjustment algorithms, four variants of LAH are designed as LAH-I, LAH-L, LAH-1, and LAH-2. In the end, a comparison between LAH schemes and existing three solutions is conducted to evaluate the performance. Results verify that the proposed LAH schemes are capable of obtaining higher accuracy of neighbor table and lower overhead.

Description: Coordination between base stations (BSs) is a promising solution for cellular wireless systems to mitigate intercell interference, improving system fairness, and increasing capacity in the years to come. The aim of this manuscript is to propose a new distributed power allocation scheme for the downlink of distributed precoded multicell MISO-OFDM systems. By treating the multicell system as a superposition of single cell systems we define the average virtual bit error rate (BER) of one single-cell system, allowing us to compute the power allocation in a distributed manner at each BS. The precoders are designed in two phases: first the precoder vectors are computed in a distributed manner at each BS considering two criteria, distributed zero-forcing and virtual signal-to-interference noise ratio; then the system is optimized through distributed power allocation with per-BS power constraint. The proposed power allocation scheme minimizes the average virtual BER over all user terminals and the available subcarriers. Both the precoder vectors and the power allocation are computed by assuming that the BSs have only knowledge of local channel state information. The performance of the proposed scheme is compared against other power allocation schemes that have recently been proposed for precoded multicell systems based on LTE specifications. The results also show that although our power allocation scheme is based on the minimization of the virtual uncoded BER, it also has significant gains in coded systems.

Description: Relay-assisted Automatic Repeat reQuest (ARQ), which allows the relays instead of the source tocarry out retransmissions of packets erroneously received at the destination, is an efficient coopera-tive transmission technique to improve link reliability with high spectrum efficiency in wireless net-works. In cognitive radio (CR) systems, however, this relay-assisted ARQ could induce large latency,since a successful transmission of a packet may consume two idle timeslot or temporal spectrumholes. To overcome this limitation, an active interference cancellation (IC)-aided distributed relay-assisted ARQ method is proposed in this article to serve heterogeneous elastic traffics with diversequality of service (QoS) demands in CR systems. Specifically, by applying our recently proposeddistributed beamforming-based IC method in the physical layer, cognitive relays can exploit spatialspectrum holes (SSHs) to retransmit while keeping the interference to primary users at a tolerablelevel. Meanwhile, at the MAC layer, two scheduling policies, namely probabilistic and queue-length-based scheduling, are proposed to obtain an efficient allocation of temporal and SSHs to direct trans-missions and retransmissions. The performance of the proposed schemes are analyzed and optimizedby adjusting the scheduling parameters. As a result, the secondary users can obtain significant QoSgains, as validated by theoretical and simulation results.

Description: Track-before-detect (TBD) based on the particle filter (PF) algorithm is known for its outstanding performance in detecting and tracking of weak targets. However, large amount of calculation leads to difficulty in real-time applications. To solve this problem, effective implementation of the PF-based TBD on the graphics processing units (GPU) is proposed in this article. By recasting the particles propagation process and weights calculating process on the parallel structure of GPU, the running time of this algorithm can greatly be reduced. Simulation results in the infrared scenario and the radar scenario are demonstrated to compare the implementation on two types of the GPU card with the CPU-only implementation.

Description: In this article, we propose a resource allocation algorithm for orthogonal frequency division multiplexing-based cellular system that serves users each of which requests a regular service or a multimedia broadcast multicast service (MBMS). We assume that the MBMSs are considered for video services such as mobile TV. In order to efficiently serve the users with heterogeneous channel conditions, we employed channel-adaptive video streams by using scalable video coding (SVC), where a realistic multicast configuration is considered for multicasting the SVC streams. Therefore, we designed the cellular system to serve constant and flexible bit rates for the regular services and the MBMSs, respectively. Thus, we consider three objectives when allocating the bandwidth resources, where total transmit power is regulated. First, the bit rate of each regular service has to be guaranteed. Second, the minimum bit rate of each MBMS for achieving the minimum video quality has to be guaranteed. Third, the average video quality of the users requesting MBMSs has to be maximized. In order to achieve the objectives, we propose to quantify the service quality of each service, and then find the resource allocation that maximizes the total service quality. By using the computer simulation results, we could verify that the three objectives can efficiently be achieved. Also, we could verify that the performance of the proposed algorithm is superior to that of the previous algorithm designed to maximize the total bit rate while guaranteeing the minimum bit rates.

Description: Inspired by recent advances in compressive sensing (CS), we introduce CS to the radar sensor network(RSN) using pulse compression technique. Our idea is to employ a set of stepped-frequency(SF) waveforms as pulse compression codes for transmit sensors, and to use the same SF waveformsas the sparse matrix to compress the signal in the receiving sensor. We obtain that the signal samplesalong the time domain could be largely compressed so that they could be recovered by a small numberof measurements. A diversity gain could also be obtained at the output of the matched filters. In addition,we also develop a maximum likelihood (ML) algorithm for radar cross section (RCS) parameterestimation and provide the Cramer-Rao lower bound (CRLB) to validate the theoretical result. Simulationresults show that the signal could be perfectly reconstructed if the number of measurementsis equal to or larger than the number of transmit sensors. Even if the signal could not be completelyrecovered, the probability of miss detection of target could be kept zero. It is also illustrated that theactual variance of the RCS parameter estimationb \theta satisfies the CRLB and our ML estimator is anaccurate estimator on the target RCS parameter.

Description: Synthetic aperture radar (SAR) automatic target recognition (ATR) is playing a very important role in military and civil field. Much work has been done to improve the performance of SAR ATR systems. It is well-known that ensemble methods can be used for improving prediction performance. Thus recognition using multiple classifiers fusion (MCF) has become a research hotspot in SAR ATR. Most current researchers focus on the fusion methods by parallel structure. However, such parallel structure has some disadvantages, such as large time consumption, features attribution conflict and low capability on confuser recognition. A hierarchical propelled strategy for multi-classifier fusion (HPSMCF) is proposed in this paper. The proposed HPSMCF has the characters both of series and parallel structure. Features can be used more effective and the recognition efficiency can be improved by extracting features and fusing the probabilistic outputs in a hierarchical propelled way. Meanwhile, the confuser recognition can be achieved by setting thresholds for the confidence in each level. Experiments on MSTAR public data demonstrate that the proposed HPSMCF is robust for variant recognition conditions. Compared with the parallel structure, HPSMCF has better performance both on time consumption and recognition rate.

Description: Reliable spectrum sensing is one of the most crucial aspects for the successful deployment of cog-nitive radio (CR) technology. For CR, it is not possible to transmit on a licensed band and sense itsimultaneously, therefore sensing must be interleaved with transmission. Spectrum sensing in CR ischallenged by a number of uncertainties, which degrade the sensing performance and in turn requiremuch more time to achieve the targeted sensing efficiency. Hence, the authors propose a spectrumsensing scheme which obtains reliable results with less mean detection time. First, the scheme deter-mines a better matched filter, or a combination of energy and cyclostationary detectors based on thepower and band of interest. In the combined energy and cyclostationary detector, an energy detectorwith a bi-threshold is used, and the cyclostationary detector is applied only if the energy of the signallies between two thresholds. Second, sensing is performed by the selection choice resulting from thefirst step. To evaluate the scheme's performance, the results are compared with those where only anenergy detector, matched filter, or cyclostationary detector are performed. The performance metricsare the probability of detection, probability of false alarm, and mean detection time.

Description: Femtocell is a promising solution for enhancing the indoor coverage and capacity in wireless net-works. However, for the small size of femtocell and potentially frequent power on/off, existing han-dover schemes may not be reliable enough for femtocell networks. Moreover, improper handoverparameters settings may lead to handover failures and unnecessary handovers, which make it neces-sary to enhance the mobility robustness for femtocells. In this article, we propose a gradient methodand cost function-based mobility robustness optimization scheme for long term evolution (LTE) fem-tocell self-organizing networks. Moreover, signalling overhead of the scheme is analyzed. Simulationresults show that the proposed scheme has a better performance than the fixed parameters method interms of reduced the number of handover failures and unnecessary handovers with limited signallingmodifications.

Description: We consider resource allocation for semi-elastic applications such as video conferencing. We proposeto model user utility as a sigmoid function of the average bit rate over multiple time slots. Thegoal is to maximize the total expected user utility over time through allocation of downlink powerand subcarriers in each time slot. We propose resource allocation that considers both the average rateachieved so far and the future expected rate, and show how the future expected rate can be estimated bymodeling the probability that a user will be allocated a subcarrier in a future time slot. The algorithmcan be implemented in a distributed fashion by an exchange of price and demand amongst users, thenetwork, and an intermediate power allocation module. To reduce the complexity, we also proposea greedy algorithm to maximize incremental utility in the current time slot. The performance isillustrated using numerical results.

Description: The combination of MIMO--OFDM is a very attractive solution for broadband wireless services. Thus, the two prominent fourth-generation (4G) cellular systems, WiMAX and LTE-advanced, have both adopted MIMO--OFDM transmission at the physical layer. OFDM signal however suffers from nonlinear distortions when passed through high-power amplifier (HPA) at the RF stage. This nonlinear distortion introduces out-of-band spectral broadening and in-band distortions on the transmitted signals. 4G cellular standards have placed strict limits on the allowable spectral broadening in their spectrum mask specifications, to insure that data transmission on a given channel is not interfering significantly with an adjacent channel user. In this article, we characterize the out-of-band spectral broadening introduced by HPA when MIMO--OFDM signals are transmitted over multiple relaying channels. Expressions for the power spectral density of MIMO--OFDM signals are derived over multiple relay channels, and the cumulative effects of HPA on the spectrum of the transmitted signals are estimated. It is shown that depending on the number of relays and the relaying configuration employed, it may happen that a transmitted MIMO--OFDM signal with the transmit spectrum mask initially within the allowable set limit at the source node arrives at the destination violating this limit due to the cumulative effects of the multiple HPA's in a multihop relaying channel

Description: An underwater acoustic sensing array was presented in this article. With the high-precision sampling clock generation and transmission system, the array can acquire signals synchronously in sub-microsecond level, which is important in offshore environment. Meanwhile, real-time data transmission and storage system was established. All of the data received in host computer can be saved and displayed immediately. Data acquisition experiment was implemented in freshwater reservoir near Tianjin city,China, and the results of the signal wave show that the acquisition and transmission system of hydrophone array can be used to get the underwater information by acoustic exploration.

Description: This article presents a hybrid adaptive multi-carrier architecture that, according to the channel condition, wisely switches between orthogonal frequency division multiplexing (OFDM) and orthogonal filtered multitone (FMT) modulations. This new scheme is referred to as hybrid-FMT (H-FMT). For H-FMT, the problem of jointly allocating the sub-channels powers, the overhead duration, and the modulation scheme, to the channel condition to (a) maximize the achievable rate, or (b) minimize the total transmitted power, is considered. Furthermore, we present an efficient implementation that requires minimal increased complexity w.r.t. baseline OFDM. The potential benefits given by the adoption of H-FMT are shown through extensive numerical results over typical WLAN channels.

Description: This paper studies the bit error rate (BER) performance of an adaptive decode-and-forward (DF) relaying scheme for a cooperative wireless network operating on independent and identically distributed (i.i.d.) or independent and non-identically distributed (i.n.d.) Rayleigh fading channels. The considered network is with one source, $K$ relays, and one destination in which binary frequency-shift keying modulation is employed to facilitate noncoherent communications. A relay decodes and retransmits the received signal to the destination only if its decision variable is larger than the corresponding threshold. Depending on the availability of the information of whether a particular relay retransmits or remains silent, the destination combines the received signals from all the relays and the received signal from the source or only the received signals from the retransmitting relays and the received signal from the source to detect the transmitted information. The average end-to-end BERs are determined in closed-form expressions. The thresholds employed at the relays are investigated to minimize the end-to-end BERs. Analytical and simulation results are provided to validate our theoretical analysis. The obtained results show that the studied scheme improves the BER performance significantly compared to the previous proposed piecewise-linear (PL) scheme. In addition, the information of whether a particular relay retransmits or remains silent at the destination does not really improve the BER performance of the network.

Description: In this paper, we present a comprehensive performance analysis of dual-hop multiple antenna channel state information (CSI) assisted amplify-and-forward (AF) relaying systems over Rayleigh fading channels employing arbitrary transmit antenna selection (TAS) and receiver maximum ratio combining (MRC) with feedback delay in the presence of co-channel interference (CCI) at both the relay and destination. Specifically, an upper bound on the cumulative distribution function (CDF) of the end-to-end signal-to-interference ratio (SIR) is proposed, based on which closed-form expressions for the outage probability and the average symbol error rate (SER) are derived. To gain further insights, simple and high informative expressions for the outage probability and the average SER are obtained at the high SIR regime, which readily enable us to characterize the achievable diversity order and coding gain of the system. Moreover, we present new analytical upper and lower bounds for the ergodic capacity of the system, which apply to the system with arbitrary number of antennas, CCI and feedback delay at any SIRs. Finally, to minimize the outage probability of the system, an optimum power allocation scheme is devised under the total transmission power constraint between the source and the relay. The findings suggest that the feedback delay limits the diversity order to one, while the CCI degrades the outage performance by affecting the coding gain of the system.

Description: This paper investigates mobile video delivery in a heterogeneous wireless network from a video server to a multi-homed client. Joint source-channel coding (JSCC) has proven to be an effective solution for video transmission over bandwidth-limited, error-prone wireless networks. However, one major problem with the existing JSCC approaches is that they consider the network between the server and the client as a single transport link. The situation becomes more complicated in the context of multiple available links because involving a low-bandwidth, highly lossy, or long-delay wireless network in the transmission will only degrade the video quality. To address the critical problem, we propose a novel flow rate allocation-based JSCC (FRA-JSCC) approach that includes three key phases: (1) forward error correction redundancy estimation under loss requirement, (2) source rate adaption under delay constraint, and (3) dynamic rate allocation to minimize end-to-end video distortion. We present a mathematical formulation of JSCC to optimize video quality over multiple wireless channels and provide comprehensive analysis for channel distortion. We evaluate the performance of FRA-JSCC through emulations in Exata and compare it with the existing schemes. Experimental results show that FRA-JSCC outperforms the competing models in improving the video peak signal-to-noise ratio as well as in reducing the end-to-end delay.

Description: Recently, the fingerprint-based wireless local area network (WLAN) positioning has gained significant interest. A probability distribution-aided indoor positioning algorithm based on the affinity propagation clustering is proposed. Different from the conventional fingerprint-based WLAN positioning algorithms, the paper first utilizes the affinity propagation clustering to minimize the searching space of reference points (RPs). Then, we introduce the probability distribution-aided positioning algorithm to obtain the target's refined position. Furthermore, because the affinity clustering can effectively lead to a reduction of the computational cost for the RP searching which is involved in the probability distribution-aided positioning algorithm, the proposed algorithm can lower the difficulty and minimize the power consumption when estimating the user's position. Experimental results conducted in the real environments show that our proposed algorithm will significantly improve the performance of the probability distribution-aided positioning algorithm in both the positioning accuracy and real-time ability.

Description: Two blind adaptive receivers, based on constrained constant modulus (CM) algorithms, are investigated for the detection of the multicarrier code division multiple access (MC-CDMA) system in the multiuser and multipath channels. As the data rate of the information bit is getting high enough, the transmitted signal of the MC-CDMA system becomes more sensitive to the frequency-selective fading. To mitigate this drawback, the parallel transmissions of multiple data symbols within one OFDM block are employed in the proposed systems to ensure that the length of the cyclic prefix (CP) is longer than the delay spread of the multipath channel. The first receiver is called a full-tap receiver (TDes receiver), which can carry out the interference suppression in the frequency-domain. Alternatively, a reduced-tap receiver (TRTap) is proposed on the basis of the derived cyclically shifting matrix. According to the derived matrix representation of the received signal, the analytical steady-state mean square errors (MSEs) for both receivers are also derived and compared. Simulation results are provided to illustrate the effectiveness of the proposed receivers and validate the accuracy of the theoretical analysis. As expected, the symbol error rate (SER) performance of the full-tap receiver is better than that of the reduced-tap receiver in severe interference environments. In contrast, the reduced-tap receiver can provide the satisfied SER performance just like the full-tap receiver in low-interference scenarios, even though the former one adopts only one-tap equalization.

Description: In most applications, wireless sensor networks are supposed to operate in an unattended manner fora long period after sensor nodes' deployment. However, in such networks, sensor nodes frequentlybecome faulty and unreliable because of the harsh environment of the observed area. Therefore,protocols used in wireless sensor networks must be designed to be robust. Moreover, because thebattery capacity of a node is limited, energy savings are crucial in wireless sensor networks. Tomeet the requirements of future diverse wireless sensor networks, a sophisticated any-to-any routingprotocol is thus required. As well as meeting the typical demands of wireless sensor networks, anany-to-any routing protocol needs to achieve low energy consumption, high scalability, robustness,and reliability. In this paper, we realize a potential-based any-to-any routing protocol (PBAR) bymerging potential-based upstream and downstream routing. In PBAR, sensor nodes can send data toa certain sensor node by routing the data via a sink node. In simulation experiments, we show that,given a suitable node density, PBAR attains a data delivery ratio greater than 99.7%. We also showthat the data delivery ratio recovers immediately after failure of 30% of sensor nodes or failure of asink node.

Description: Reliability analysis is an important issue in wireless sensor networks (WSNs). This paper aims to study the reliability of a data flow in event-driven wireless sensor networks with multiple sending transmission approach without acknowledgments. Initially, an event-driven wireless sensor network model is described in terms of limited node battery energy and shadowed fading channels. Then, in order to analyze the network reliability, the wireless link reliability and the node energy availability are investigated, respectively. Furthermore, the analytical expressions of the instantaneous network reliability and the mean time to failure (MTTF) are derived. Finally, the simulation results validate the correctness and accuracy of the analytical results.

Description: The ability to determine in real-time the geographic location of client nodes is an important tool inwireless networks, allowing instantaneous mobile tracking, implementation of location-awareservices and also efficient channel and power allocation planning. Among existing classicalcooperative localization techniques for wireless networks, the maximum likelihood estimator (MLE)is theoretically the best. However, the gradient-based algorithms that are commonly used formaximum likelihood estimation are quite sensitive to the initial values and cannot achieve thetheoretical optimal performance. In this paper, we propose a new iterative positioning algorithmbased on received signal strength information that employs a location ordering strategy and anumerical nonlinear optimization method. The algorithm performance is evaluated throughsimulation for different network scenarios. A real wireless network scenario is also implemented inorder to demonstrate the algorithm effectiveness. The proposed algorithm, while presenting asimplified implementation, can achieve better positioning estimates than the classical MLE approachbased on the conjugated gradient.

Description: In this paper, an efficient sphere detection (SD) scheme for multiple-input multiple-output (MIMO) systems is presented. The proposed SD scheme can substantially reduce computational complexity by introducing a pre-processing scheme and an adaptive threshold. In particular, our proposed pre- processing scheme is based on an iterative successive interference cancelation (SIC). The proposed adaptive threshold is used to judge whether a traversed path is correct or not and obtained by analyzing the distributions of the correct and erroneous estimates which have the minimum error pattern among all the SD searching paths. Simulation results show that our proposed scheme offers a substantial complexity reduction in terms of the number of visited nodes while keeping a significantly small performance degradation compared to conventional approaches.

Description: One of the most important objectives of wireless network service providers is to make the traffic as uniform as possible in different sectors of the network. In this paper, we analyze the uniformity of the traffic in a WiMAX network with the aid of a forecasting methodology. Taking into account the high volume of data transferred in a wireless network and the requirement of real time, we propose a forecasting methodology based on data mining. The theoretical basis of the proposed method is explained in detail. Its implementation is highlighted by diagrams, which explain each step of the algorithm. The method is applied on real data and the obtained results are discussed.

Description: This paper investigates the sparse channel estimation issue of multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. Beginning with the formulation of least squares (LS) solution to sparse MIMO-OFDM channel estimation, a compressed channel sensing (CCS) framework based on the new smoothed l0-norm-regularized least squares (l2-Sl0) algorithm is proposed. Three methods, namely quasi-Newton, conjugate gradient, and optimization in the null and complement spaces of the measurement matrix, are then proposed to solve the l2-Sl0 unconstrained optimization problem. Moreover, the two former are also applied to solve the l2-Sl0 channel estimation. A number of computer simulation-based experiments are conducted showing a better reconstruction accuracy of the l2-Sl0 algorithm as compared with the smoothed l0-norm (Sl0) algorithm in the presence of noise. The proposed CCS approach can save nearly 25% pilot signals to maintain the same mean square error (MSE) and bit error rate (BER) performances as given by the conventional LS method.