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Selected Areas in Communications, IEEE Journal on

Issue 6 • Date July 1987

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Displaying Results 1 - 15 of 15
  • [Back cover]

    Page(s): 0
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    Freely Available from IEEE
  • [Front cover and table of contents]

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  • Random Signal Levels for Channel Access in Packet Broadcast Networks

    Page(s): 1026 - 1034
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    In this paper, it is proposed to employ random multiple signal levels for channel access in packet broadcast networks. We present priority-free random access protocols that possess the advantage of capture effect. The presented schemes are applied to the slotted ALOHA, and the performance is analyzed based on a conservative capture model. Closed-form expressions for the system throughput are derived for a general two-signal level system and a generalm-signallevel system. It is shown that the maximum throughput for the twolevel system increases from 0.47 to 0.52 as the separation between the two levels increases. For them-level system, the maximum throughput increases from 0.52 to 0.66 asmincreases from three to infinity. Then a rotary-priority sure-capture random access scheme is presented, which can achieve perfect channel utilization. The time-delay characteristic and the throughput-delay tradeoff are analyzed for the simplest two-level system for which the higher level is double the lower level. The results compare favorably to those of the conventional slotted ALOHA system which employs a single signal level for packet transmission. A number of open problems are addressed. View full abstract»

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  • An Algorithm for Evaluation of Throughput in Multihop Packet Radio Networks with Complex Topologies

    Page(s): 1003 - 1012
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    The problem of analyzing the thoughput of packet radio networks with realistic topologies is considered. We present an algorithm for the solution of this problem and show that both the memory requirements and running time of this algorithm in practice grow polynomially with the size of the problem. Although in theory both can grow exponentially in the worst case, we offer computational experience with the procedure and show that for realistic topologies where connectivity is related to distance, the rate of growth is quadratic in the number of links. Even for regular grids, which are pathological in their symmetry, the rate of growth is only cubic in the number of links. We thus conclude that the procedure is effective for realistic topologies with up to several hundred nodes. View full abstract»

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  • Buzz-Net: A Hybrid Token/Random Access LAN

    Page(s): 977 - 988
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    Buzz-net is a local network supported by a pair of unidirectional buses to which stations are connected via passive interfaces. The access protocol is a hybrid which combines random access and virtual token features. More precisely, the network operates in random access mode at light load and virtual token mode at heavy load. Because of the virtual token implementation, Buzz-net retains high efficiency even at very high bus speeds. Efficiency at high speeds and bus unidirectionality make Buzz-net particularly suitable for fiber optics media. This paper describes the protocol, develops approximate analytic models for performance evaluation, and compares Buzz-net performance results to those of other unidirectional bus schemes. View full abstract»

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  • Performance of a CSMA/CD Protocol for Local Area Networks

    Page(s): 948 - 955
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    In this paper we present a performance analysis of a CSMA/CD protocol designed to effectively resolve collisions in a local area network such as Ethernet. We give expressions for the average time required to resolve a collision involvingkstations and the average time for a particular station involved in ak-way collision to send its packet successfully. We also consider the efficiency of this protocol and give a lower bound for the maximum efficiency. The above analysis is independent of any particular packet arrival distribution other than the assumptions that in a successful transmission each station is equally likely to be the one transmitting, that in a collision each station is equally likely to be a participant, and that the probability of the simultaneous arrival of packets is zero. View full abstract»

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  • Discrete-Time Priority Queues with Partial Interference

    Page(s): 1041 - 1050
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    A class of discrete-time priority queueing systems with partial interference is considered. In these systems,Nnodes share a common channel to transmit their packets. One node uses a random access scheme, while other nodes access the channel according to preassigned priorities. Packet arrivals are modeled as discrete-time batch processes, and packets are forwarded through the network according to fixed prescribed probabilities. Steady-state analysis of the class of systems under consideration is provided. In particular, we present a recursive method for the derivation of the joint generating function of the queue lengths distribution at the nodes in steady state. The condition for steady state is also derived. A simple example' demonstrates the general analysis and provides some insights into the behavior of systems with partial interference such as multihop packet radio systems. View full abstract»

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  • Evaluation of the Random Token Protocol for High-Speed and Radio Networks

    Page(s): 969 - 976
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    In high-speed communication networks, the ratio between the end-to-end propagation delay to packet transmission time is large, causing increased scheduling overhead in demand assignment protocols and increased collision probabilities in random access schemes. These lead to rapid degradation of the channel utilization in both channel access control approaches. In this paper, we present a "random token" oriented protocol where channel access is scheduled by random, implicit token passing leading to lower channel access control penalty. By optimally balancing the collision and scheduling penalties, the protocol allows the network to reach better performance than that obtained from random access schemes in networks with and without collision detection, without imposing additional system operational assumptions. Specifically, the random token protocol does not require knowledge of the number of stations, their identities, or synchronization in periods of silence. Therefore, the protocol is also suitable for high-speed networks with frequent reconfiguration and for mobile radio networks. View full abstract»

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  • Architectures and Performance of Multichannel Multihop Packet Radio Networks

    Page(s): 1013 - 1025
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    Packet radio networks that employ several parallel multiple-access channels are considered. An architecture for such a network dictates the selection of channels for packet transmission. We propose and analyze two multichannel architectures. In the first, each node employs a single radio and is assigned a channel on which it listens when it does not transmit. To transmit a packet, the node tunes its radio to the channel of the intended receiver for that transmission only. The second architecture requires each radio to use a single channel for both transmission and reception, but provides some of the nodes with more than one radio each, allowing them to serve as bridges between channels. Within these architectures, one can further select the amount of routing information held by each node and the channel-access protocol, both of which greatly affect the network performance. To ascertain the effects of the various parameters, we calculate the throughput in both architectures. The channel-access protocols we consider are slotted ALOHA and CSMA with and without capture. We also evaluate the effect of increasing the amount of routing information held by the nodes. View full abstract»

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  • Slotted Random Access Spread-Spectrum Networks: An Analytical Framework

    Page(s): 989 - 1002
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    An analytic framework is proposed for the study of singlehop spread-spectrum networks using random access and packet switching under various network topologies and channel conditions. The key feature of the theory is the identification of a set of probabilistic parameters, which, based on a symmetry argument, serve to efficiently summarize the effect on performance of various network considerations such as transmitter-receiver configuration, spreadspectrum code allocation, error correction and detection mechanisms, spreading format, jamming conditions, etc. Examples investigating capture effects, coding tradeoffs, and scheduling optimizations are presented. Various previously known results are shown to be special cases of the framework that we describe. View full abstract»

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  • A Method for the Delay Analysis of Random Multiple-Access Algorithms Whose Delay Process is Regenerative

    Page(s): 1051 - 1062
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    Random multiple-access algorithms are used to control the accessing of a common communication channel by a large population of bursty channel users. For such algorithms, the induced transmission delay is a key performance measure. A systematic method for finding the delay characteristics of random multiple-access algorithms, whose delay process is regenerative, is presented. The method uses a powerful result from the theory of regenerative processes, in effect, to reduce the problem of determining the delay moments to the problem of solving denumerable dimensional systems of linear equations. Techniques for finding tight bounds on the solutions of such systems are presented. The "0.487" algorithm is used to exemplify the method. View full abstract»

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  • Collision Detection and Multitone Tree Search for Multiple-Access Protocols on Radio Channels

    Page(s): 1035 - 1040
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    The carrier sense multiple access with collision detection (CSMA-CD) protocol cannot be applied directly to radio channels because of the difficulty in sensing remote carrier in the presence of local transmission. Only recently, a new protocol called the CSMA with timesplit collision detection (CSMA-TCD) was introduced to overcome this problem on radio channels. This paper presents an extension of the CSMA-TCD protocol, called CSMA-TCD with multitone tree search (CSMA-TCD-MTTS). In CSMA-TCD, a preamble is transmitted before data transmission. For CSMA-TCD-MTTS, the preamble is modulated with one out ofNtones. In case of a collision, a resolution algorithm splits the terminals involved into anN-degree tree according to the tone chosen. This paper presents the throughput and approximate delay analysis of the CSMA-TCD-MTTS protocol. View full abstract»

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  • A Channel Access Protocol for Integrated Voice/Data Applications

    Page(s): 939 - 947
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    A new multiaccess protocol is proposed for an integrated voice/data application. The protocol, which is a variation of virtual time CSMA (VT-CSMA), takes advantage of the periodicity of voice packets and possesses a number of important features. With this protocol, voice stations appear to have a dedicated time-division multiplexed (TDM) slot, and the delay of a voice packet is bounded by the length of a frame (defined to be the period between two consecutive voice packets from a voice station). Also, the amount of data added to the channel has little effect on the voice traffic. When silence detection is used, many more voice conversations can be supported without losing the dedicated-slot characteristic. This is in contrast to a movingboundary TDM system where the excessive bandwidth saved by silence detection can only be used for data. The protocol requires no global synchronization and is easy to implement. Simulation results are presented to evaluate its performance. View full abstract»

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  • Space-Time Models of Asynchronous CSMA Protocols for Local Area Networks

    Page(s): 956 - 968
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    Carrier sense multiple-access (CSMA) protocols are widely used in local area networks (LAN's) to control access to a shared communications channel such as a coaxial cable or radio frequency band. CSMA protocols are designed to exploit the property that the signal propagation time across the LAN is much smaller than the packet transmission time. Consequently, their performance depends on the exact timing of a sequence of asynchronous events originating at different points in the network. Previous models of CSMA protocols have not captured this essential space-time characteristic. Instead, the system has been reduced to a 1-dimensional model (i.e., a sequence of events on a single time line) by assuming either that events are synchronous (i.e., "slotted" operation of the protocol) or that all stations are mutually equidistant (so it can be assumed that each station's time line is identical). The novelty in our work is to describe the system state in terms of an (N + 1)-dimensional "ribbon" of space-time, allowing us to faithfully model the exact timings of events for LAN's where the stations are distributed over a fully connected region inN-space. For example, an Ethernet-like "bus" network can be viewed as a 1-dimensional LAN, a terrestrial packet radio network can be viewed as a 2dimensional LAN, and so on. First we highlight some of the key properties exhibited by such a model in the general case, including the notion of an embedded Markovian sequence of "idle points," and the decomposition of the space-time ribbon into cycles (each of which can be further decomposed into a number of "regions"). Then we present extensive results for the interesting special case of a 1-dimensional LAN, i.e., an Ethernet-like "bus" network. Our results show that previous models of bus LAN's can significantly underestimate their performance. View full abstract»

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Aims & Scope

IEEE Journal on Selected Areas in Communications focuses on all telecommunications, including telephone, telegraphy, facsimile, and point-to-point television, by electromagnetic propagation.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Muriel Médard
MIT