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  • 1
    Electronic Resource
    Electronic Resource
    Floor control for multimedia conferencing and collaboration (1997)
    Springer
    Multimedia systems 5 (1997), S. 23-38 
    Details
    ISSN: 1432-1882
    Keywords: Key words:Multimedia collaboration – Distributed application sharing – CSCW – Middleware for session orchestration – Floor control for shared multimedia objects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract. Floor control allows users of networked multimedia applications to utilize and share resources such as remote devices, distributed data sets, telepointers, or continuous media such as video and audio without access conflicts. Floors are temporary permissions granted dynamically to collaborating users in order to mitigate race conditions and guarantee mutually exclusive resource usage. A general framework for floor control is presented. Collaborative environments are characterized and the requirements for realization of floor control will be identified. The differences to session control, as well as concurrency control and access control are elicited. Based upon a brief taxonomy of collaboration-relevant parameters, system design issues for floor control are discussed. Floor control mechanisms are discerned from service policies and principal architectures of collaborative systems are compared. The structure of control packets and an application programmer's interface are proposed and further implementation aspects are elaborated. User-related aspects such as floor presentation, assignment, and the timely stages of floor-controlled interaction in relation to user-interface design are also presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005300050040
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A comparison of reliable multicast protocols (1998)
    Springer
    Multimedia systems 6 (1998), S. 334-348 
    Details
    ISSN: 1432-1882
    Keywords: Key words:Reliable multicast – Multicast transport protocols –ack implosion – Tree-based protocols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract. We analyze the maximum throughput that known classes of reliable multicast transport protocols can attain. A new taxonomy of reliable multicast transport protocols is introduced based on the premise that the mechanisms used to release data at the source after correct delivery should be decoupled from the mechanisms used to pace the transmission of data and to effect error recovery. Receiver-initiated protocols, which are based entirely on negative acknowledgments (naks) sent from the receivers to the sender, have been proposed to avoid the implosion of acknowledgements (acks) to the source. However, these protocols are shown to require infinite buffers in order to prevent deadlocks. Two other solutions to the ack-implosion problem are tree-based protocols and ring-based protocols. The first organize the receivers in a tree and send acks along the tree; the latter send acks to the sender along a ring of receivers. These two classes of protocols are shown to operate correctly with finite buffers. It is shown that tree-based protocols constitute the most scalable class of all reliable multicast protocols proposed to date.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005300050097
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Collision avoidance and resolution multiple access (CARMA) (1998)
    Springer
    Cluster computing 1 (1998), S. 197-212 
    Details
    ISSN: 1573-7543
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The collision avoidance and resolution multiple access (CARMA) protocol is presented and analyzed. CARMA uses a collision avoidance handshake in which the sender and receiver exchange a request to send (RTS) and a clear to send (CTS) before the sender transmits any data. CARMA is based on carrier sensing, together with collision resolution based on a deterministic tree-splitting algorithm. For analytical purposes, an upper bound is derived for the average number of steps required to resolve collisions of RTSs using the tree-splitting algorithm. This bound is then applied to the computation of the average channel utilization in a fully connected network with a large number of stations. Under light-load conditions, CARMA achieves the same average throughput as multiple access protocols based on RTS/CTS exchange and carrier sensing. It is also shown that, as the arrival rate of RTSs increases, the throughput achieved by CARMA is close to the maximum throughput that any protocol based on collision avoidance (i.e., RTS/CTS exchange) can achieve if the control packets used to acquire the floor are much smaller than the data packet trains sent by the stations. Simulation results validate the simplifying approximations made in the analytical model. Our analysis results indicate that collision resolution makes floor acquisition multiple access much more effective.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019089616850
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  • 4
    Electronic Resource
    Electronic Resource
    Efficacy of floor control protocols in distributed multimedia collaboration (1999)
    Springer
    Cluster computing 2 (1999), S. 17-33 
    Details
    ISSN: 1573-7543
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Distributed multipoint applications for group interaction across wide-area networks, such as for simulation and telecollaboration, are becoming increasingly popular. While reliable multicasting has made significant advances in recent years, effective mechanisms to synchronize and coordinate work within large multicast groups and across long distances are still lacking. Synchronous sharing of resources, whose operational semantics prohibits parallel usage, typically creates race conditions among users, which can be resolved through an access discipline called floor control. Existing solutions on floor control, implemented either at the session or application layer, are mostly proprietary, limited in scope and not scalable. Furthermore, no performance comparison of floor control protocols has been attempted to date. We present a novel taxonomy and comparative performance analysis of known classes of floor control protocols, ranging from socially mediated control to protocols operating on ring and tree topologies. We find that aggregation and selective transmission of control information in a tree structure is the most promising solution with regard to scalability, efficacy, and robustness. The principal operation of such a tree protocol is outlined, which dynamically organizes participants in a multi-level control tree and aggregates resource sharing directives on the paths between interacting stations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019010221393
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  • 5
    Electronic Resource
    Electronic Resource
    Collision avoidance and resolution multiple access with transmission queues (1999)
    Springer
    Wireless networks 5 (1999), S. 95-109 
    Details
    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract We introduce a stable multiple access protocol for broadcast channels shared by bursty stations, which we call CARMA-NTQ (for collision avoidance and resolution multiple access with non-persistence and transmission queues). Like previous efficient MAC protocols based on tree-splitting algorithms (e.g., DQRAP), CARMA-NTQ maintains a distributed queue for the transmission of data packets and a stack for the transmission of control packets used in collision resolution. However, CARMA-NTQ does not require the mini-slots commonly used in protocols based on collision resolution. CARMA-NTQ dynamically divides the channel into cycles of variable length; each cycle consists of a contention period and a queue-transmission period. The queue-transmission period is a variable-length train of packets, which are transmitted by stations that have been added to the distributed transmission queue by successfully completing a collision-resolution round in a previous contention period. During the contention period, stations with packets to send compete for the right to be added to the data-transmission queue using a deterministic first-success tree-splitting algorithm, so that a new station is added to the transmission queue. A lower bound is derived for the average throughput achieved with CARMA-NTQ as a function of the size of the transmission queue and the number of queue-addition requests that need to be resolved. This bound is based on the upper bound on the average number of collision resolution steps needed to resolve a given number of queue-add requests.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019178423020
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  • 6
    Electronic Resource
    Electronic Resource
    An efficient packet sensing MAC protocol for wireless networks (1998)
    Springer
    Mobile networks and applications 3 (1998), S. 221-234 
    Details
    ISSN: 1572-8153
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The Group Allocation Multiple Access with Packet-Sensing (GAMA-PS) protocol for scheduling real-time and datagram traffic in a wireless LAN is specified and analyzed. By maintaining a dynamically-sized cycle that changes in length depending on the amount of network traffic, GAMA-PS is able to efficiently control channel access while ensuring that there are no collisions of data packets. Each cycle contains a contention period and a group-transmission period; a station with data to send competes for membership in the “transmission group” by using packet sensing to successfully complete an RTS/CTS message exchange during the contention period. Once a station is a member of the transmission group, it is able to transmit a collision-free data packet during each cycle; as long as a station has data to send, it maintains its position in the group.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019176816001
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  • 7
    Electronic Resource
    Electronic Resource
    Floor acquisition multiple access (FAMA) in single‐channel wireless networks (1999)
    Springer
    Mobile networks and applications 4 (1999), S. 157-174 
    Details
    ISSN: 1572-8153
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The FAMA‐NCS protocol is introduced for wireless LANs and ad‐hoc networks that are based on a single channel and asynchronous transmissions (i.e., no time slotting). FAMA‐NCS (for floor acquisition multiple access with non‐persistent carrier sensing) guarantees that a single sender is able to send data packets free of collisions to a given receiver at any given time. FAMA‐NCS is based on a three‐way handshake between sender and receiver in which the sender uses non‐persistent carrier sensing to transmit a request‐to‐send (RTS) and the receiver sends a clear‐to‐send (CTS) that lasts much longer than the RTS to serve as a “busy tone” that forces all hidden nodes to back off long enough to allow a collision‐free data packet to arrive at the receiver. It is shown that carrier sensing is needed to support collision‐free transmissions in the presence of hidden terminals when nodes transmit RTSs asynchronously. The throughput of FAMA‐NCS is analyzed for single‐channel networks with and without hidden terminals; the analysis shows that FAMA‐NCS performs better than ALOHA, CSMA, and all prior proposals based on collision avoidance dialogues (e.g., MACA, MACAW, and IEEE 802.11 DFWMAC) in the presence of hidden terminals. Simulation experiments are used to confirm the analytical results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019146831447
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  • 8
    Electronic Resource
    Electronic Resource
    A routing architecture for mobile integrated services networks (1998)
    Springer
    Mobile networks and applications 3 (1998), S. 391-407 
    Details
    ISSN: 1572-8153
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A drawback of the conventional Internet routing architecture is that its route computation and packet forwarding mechanisms are poorly integrated with congestion control mechanisms. Any datagram offered to the network is accepted; routers forward packets on a best-effort basis and react to congestion only after the network resources have already been wasted. A number of proposals improve on this to support multimedia applications; a promising example is the Integrated Services Packet Network (ISPN) architecture. However, these proposals are oriented to networks with fairly static topologies and rely on the same conventional Internet routing protocols to operate. This paper presents a routing architecture for mobile integrated services networks in which network nodes (routers) can move constantly while providing end-to-end performance guarantees. In the proposed connectionless routing architecture, packets are individually routed towards their destinations on a hop by hop basis. A packet intended for a given destination is allowed to enter the network if and only if there is at least one path of routers with enough resources to ensure its delivery within a finite time. Once a packet is accepted into the network, it is delivered to its destination, unless resource failures prevent it. Each router reserves resources for each active destination, rather than for each source–destination session, and forwards a received packet along one of multiple loop-free paths towards the destination. The resources and available paths for each destination are updated to adapt to congestion and topology changes. This mechanism could be extended to aggregate dissimilar flows as well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019105622361
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  • 9
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    A new distributed cooperative MIMO scheme for mobile ad hoc networks (2013)
    Elsevier
    Details
    Publication Date: 2013-05-01
    Print ISSN: 0020-0255
    Electronic ISSN: 1872-6291
    Topics: Computer Science
    Published by Elsevier
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