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Communications, IEEE Transactions on

Issue 2 • Date Feb. 1988

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Displaying Results 1 - 18 of 18
  • Comments on "Performance of single access classes on the IEEE 802.4 token bus" by M.A. Colvin and A.C. Weaver

    Page(s): 224 - 225
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (244 KB)  

    In the above correspondence (ibid., vol.COM-34, no.12, p.1253-6, Dec. 1986), throughput bounds are derived for the IEEE 802-4 token passing scheme, in the presence of a single class of messages. It does not consider the fact that even after the token holdtimer expires, a node is allowed to complete its message transmission. Here, the fact is considered, and the upper bounds on throughput are modified.<> View full abstract»

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  • Design and analysis of a contention-based lookahead reservation protocol on a multichannel local area network

    Page(s): 234 - 238
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    The contention-based lookahead reservation (CLAR) protocol can provide fast circuit-switching services that are particularly advantageous for networks supporting integrated services. The delay and throughput performance for message transmission are obtained, and they agree closely with that obtained by simulation. The delay performance of CLAR is similar to that of the M-CSMA protocol for an M-channel network, but only CLAR can give a stable maximum throughput of (M-1)/M independent of the cable length. Moreover, CLAR requires only two sets of transceivers, while M-CSMA requires M. The lookahead reservation technique can provide 9% throughput increase for fixed-size messages and 19% for geometrically distributed messages View full abstract»

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  • Performance analysis of interconnected metropolitan area circuit-switched telecommunications networks

    Page(s): 171 - 185
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1040 KB)  

    A circuit-switched telecommunications network is considered that consists of two metropolitan area networks (MANs) interconnectd by a multiaccess communications channel, such as a satellite or multiaccess multichannel terrestrial trunk. The blocking probability performance of this network is computed, using a finite-source-traffic model, by setting up a Markov chain model and applying results based on the reversibility of this chain to compute the underlying state probabilities. Local and long-distance blocking probabilities are calculated. each in terms of its two components: circuit-blocking and destination-busy probabilities. Both dedicated and shared circuit allocation policies are used in allocating the circuits of a MAN between its local and long-distance calls. Explicit performance equations are presented. Illustrative results and performance curves are given, indicating the various underlying system performance characteristics and tradeoffs View full abstract»

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  • A method to dramatically improve subcarrier tracking

    Page(s): 238 - 243
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (364 KB)  

    A method is presented for achieving a considerable improvement in phase tracking of square-wave subcarriers or other square waves. The amplitude of the phase quadrature reference signal is set to zero, except near the zero crossings of the input signal. Without changing the loop bandwidth, the variance of the phase error can be reduced by approximately Wσ02 where σ 02 is the phase error variance without windowing and W is the fraction of cycle in which the reference signal has a nonzero value. Simulation results confirm the results of the analysis and establish minimum W versus SNR (signal-to-noise ratio). Typically, the window can be made so narrow as to achieve a phase error variance of 1.5 σ04 View full abstract»

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  • Integrated voice/data multiplexers with slotted and nongated packet services

    Page(s): 228 - 231
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    Integrated voice/data multiplexers that provide packet services for both voice and data traffic are discussed. A slotted service is assumed, so that packet transmissions are synchronized to slot boundaries. Nongated service, in which packets are transmitted as soon as the transmission capacity becomes available, is also assumed. The performance of nongated and slotted multiplexers is obtained by analytic and simulation approaches. In particular, a PRIO (head-of-the-line priority to voice packets) and a BVFD (busy-voice, fixed-data) multiplexer are shown to be suitable for such a nongated environment View full abstract»

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  • Asymptotic results for partial concentrators

    Page(s): 214 - 217
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (412 KB)  

    Various switching network construction advantageously use modules known as partial concentrators. A partial concentrator is an n-input, m-output, single-stage switching device in which each input has access to some but not all of the outputs. A partial concentrator is said to have capacity c, if, for any kc inputs, there exist k disjoint paths from the k inputs to some set of k outputs. Here, capacity values achievable for large n when each input has access to exactly M outputs, are considered. For a partial concentrator in which each input has access to exactly M outputs, it is shown that the cost ratio can be made arbitrarily small for any fixed M⩾2. In addition, it is shown that the rate of decrease of the cost ratio with increasing n is logarithmic for M=2, and polynomial for M⩾3 View full abstract»

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  • Prioritized demand assignment protocols and their evaluation

    Page(s): 133 - 143
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (932 KB)  

    A class of message-based or station-based priority protocols for demand-assignment-based local area networks (LANs), such as Token Bus, HYPERbus, LCN, etc., is defined. It is shown how existing priority protocols can be represented within this class and how they can be extended for a more efficient realization with regard to both delay and capacity of prioritized channel access in LANs. An analytic approach for analyzing multiple-access systems operating under prioritized demand assignment protocols is introduced. The approach permits the modeling of station-dependent and priority-dependent arrival rates and generally distributed transmission times. The introduced finite-population model is especially appropriate for prioritized systems where the number of users per priority class is typically small and users place different service demands on the system. For modeling systems with large populations of users, an approximate model, which is shown to be significantly more computationally efficient than the exact model without imposing additional modeling restrictions, is introduced View full abstract»

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  • System design for optical PPM communications with diode combining

    Page(s): 186 - 190
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    The most efficient way to encode laser diodes for maximum data rate is studied. Three different system architectures are considered, with combining achieved by dichroic mirrors operating in conjunction with a pulse-position-modulated (PPM) format. The basic criterion is to maximize the data rate with increasing number of diodes, while maintaining diode power constraints and decoding bit error probability. The three systems are: power combining into a single pulse, followed by PPM encoding; parallel channels, in which each diode is separately PPM encoded; and color coding, in which diodes are encoded over a common wavelength-time slot alphabet. Data rate equations are presented as a function of the number of diodes, mirror combining losses, PPM alphabet size, and the operating optical signal-to-noise ratio View full abstract»

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  • On saving decoder states for some trellis codes and partial response channels

    Page(s): 222 - 224
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    It is shown that under certain conditions, when convolutional codes with precoding are used in conjunction with a partial response channel, the number of decoder states in a maximum-likelihood decoder matched to both the code and channel is 1/2 of that predicted by J.K. Wolf and G. Ungerboeck (ibid., vol.COM-34, no.7, p.751-72, 1986) View full abstract»

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  • Queueing-blocking system with two arrival streams and guard channels

    Page(s): 153 - 163
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (800 KB)  

    An approach to the study of a multichannel cutoff priority system for two Poisson arrival streams with distinct arrival rates and the same potential service time distribution is proposed. This approach makes it possible to obtain the state probabilities in simple closed-form expressions. These expressions provide a straightforward way to derive the distribution of the number of busy servers, the queue length distributions, and, above all, a very simple criterion for the stability of the system. The computations can still be carried out for large systems (e.g. 100 servers). The method can easily be extended from the infinite-queue-length case to a system with finite capacity. As applied to cellular radio, the method offers a means of increasing the total carried traffic while improving the perceived service quality View full abstract»

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  • Video transmission in optical fiber communication systems using pulse frequency modulation

    Page(s): 191 - 194
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    A design procedure has been developed to determine the required operating conditions for a pulse-frequency modulation (PFM) system (modulation index, required system bandwidth, and receiver carrier-to-noise ratio (CNR) for a specified receiver SNR (signal-to-noise ratio) and number of clicks per second. The PFM processing gain (=SNR/CNR) was measured to be 40 dB for a modulation index of β=2.5, which agrees closely with the theory. The theoretical processing gain advantage of PFM over FM is 15.9 dB for a modulation index of β=2.5 with receiver bandwidth Brx =50 MHz View full abstract»

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  • The throughput efficiency of the go-back-N ARQ scheme under Markov and related error structures

    Page(s): 231 - 234
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    A formula for the go-back-N ARQ (automatic repeat request) scheme applicable to Markov error patterns is derived. It is a generalization of the well-known efficiency formula p/[p +m(1-p)] (where m is the round trip delay in number of block durations and p is the block transmission success probability), and it has been successfully validated against simulation measurements. It is found that for a given error rate, error patterns having zero correlation between successive transmission generally fare better than those with negative correlation, and that error patterns with positive correlation fare better still. It is shown that the present analysis can be extended in a straightforward manner to cope with error patterns of a more complex nature. Simple procedures for numerical evaluation of efficiency under quite general error structures are presented View full abstract»

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  • On constructing embedded multilevel trellis codes

    Page(s): 218 - 221
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    A design technique to reduce the search time for trellis codes with multilevel phase modulation is presented. Codes are constructed by connecting trellis diagrams for codes with fewer states in parallel. For example, an N-state code can be constructed by connecting two N/2-state codes. The way in which the embedded codes are connected increases the upper limit on minimum free distance otherwise imposed by parallel transitions between states. In some cases, this technique can reduce the number of codes in a code search by a factor of approximately 2ν, the number of coder states. A computer search incorporating this technique for eight-level amplitude modulation (8-AM) codes having 211 and 212 states produced codes with greater minimum free distance than reported previously (i.e. greater than 6 dB coding gain). New eight-level phase-shift-keying (8-PSK) codes, which have a different structure from previously reported codes, are also presented View full abstract»

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  • A circulating loop experimental technique to simulate the jitter accumulation of a chain of fiber-optic regenerators

    Page(s): 205 - 213
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (704 KB)  

    A circulating-loop experimental technique to simulate the jitter accumulation of a chain of fiber-optic regenerators is described. This technique allows system designer to establish the jitter accumulation characteristics of systems without the need for many test regenerators. An analytic description of how well the loop technique simulates a china of identical fiber-optic regenerators is presented along with a comparison of calculated and simulated jitter accumulation View full abstract»

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  • Reliable link initialization procedures

    Page(s): 144 - 152
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1024 KB)  

    It is known that HDLC (high-level data link control) and other bit-oriented DLC procedures ensure data transmission reliability across noisy transmission media, provided that all frame errors are detected and the link processes are synchronized at initialization. It is shown that the HDLC initialization procedure does not ensure synchronization and allows inadvertent loss of data. Several link initialization procedures are proposed and it is proved that they do ensure synchronization View full abstract»

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  • Waiting times in discrete-time cyclic-service systems

    Page(s): 164 - 170
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    Single-served, multiqueue systems with cyclic service in discrete time are considered. Nonzero switchover times between consecutive queues are assumed; the service strategies at the various queues may differ. A decomposition for the amount of work in such systems is obtained, leading to an exact expression for a weighted sum of the mean waiting times at the various queues View full abstract»

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  • Rejection of multiple narrow-band interference in both BPSK and QPSK DS spread-spectrum systems

    Page(s): 195 - 204
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (568 KB)  

    The performance of direct-sequence spread-spectrum systems using a suppression filter in the presence of multiple narrow band interference with rational spectral densities is analyzed. Both BPSK and QPSK systems are considered, and analytical expressions for both the means-square error of the filter output and the performance improvement are established. When the bandwidths of the narrow band components of the interference are all small, approximate expressions are obtained and used to provide further insight into the behavior of the system. Results are presented for the limiting case when the bandwidths approach aero (i.e. when multiple narrow band interference becomes multiple sinusoidal interference) View full abstract»

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  • A hybrid contention-based TDMA technique for data transmissions

    Page(s): 225 - 228
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    A hybrid contention-based time-division multiaccess (TDMA) protocol is proposed and studied. Channel time is organized into frames, each consisting of reservation, fixed, and variable subframes. Users are divided into groups. Each group is given a data slot in the fixed subframe that is open to users in that group on the basis of contention. Each user can also place his demand in the reservation subframe. The number of slots assigned to a particular user is based on the information gathered from the other two subframes. Performance analyses, both transient and steady-state, are successfully carried out. Computer simulations verify the analyses View full abstract»

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Aims & Scope

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

 

 

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Editor-in-Chief
Robert Schober
University of British Columbia