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Communications, IEEE Transactions on

Issue 5 • Date May 1993

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Displaying Results 1 - 20 of 20
  • Analysis of packet switches with input and output queuing

    Publication Year: 1993 , Page(s): 731 - 740
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (926 KB)  

    A single-stage nonblocking N*N packet switch with both output and input queuing is considered. The limited queuing at the output ports resolves output port contention partially. Overflow at the output queues is prevented by a backpressure mechanism and additional queuing at the input ports. The impact of the backpressure effect on the switch performance for arbitrary output buffer sizes and for N to infinity is studied. Two different switch models are considered: an asynchronous model with Poisson arrivals and a synchronous model with Bernoulli arrivals. The investigation is based on the average delay and the maximum throughput of the switch. Closed-form expressions for these performance measures are derived for operation with fixed size packets. The results demonstrate that a modest amount of output queuing, in conjunction with appropriate switch speedup, provides significant delay and throughput improvements over pure input queuing. The maximum throughput is the same for the synchronous and the asynchronous switch model, although the delay is different.<> View full abstract»

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  • Effect of signal transition variation on bit synchronizer performance

    Publication Year: 1993 , Page(s): 673 - 677
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    The effect of the signal transition variation, due to the signal transition density, data asymmetry, and sinusoidal modulation, on the performance of the data transition tracking loop (DTTL) symbol synchronizer is addressed. These factors will affect the DTTL performance, such as the clock jitter and the cycle slippage rate, and unnecessary system loss may result if the system parameters are not well selected. Given the background of C. S. Tsang and W. C. Lindsey (1986), this result can serve as an engineering design guideline for the DTTL in the context of the signal transition variation View full abstract»

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  • Markov characterization of channels with soft decision outputs

    Publication Year: 1993 , Page(s): 678 - 682
    Cited by:  Papers (29)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB)  

    It is shown that a methodology based on hidden Markov models is applicable to the modeling of slowly varying Rayleigh fading channels with additive Gaussian noise and soft decision outputs. The fading is considered to be frequency nonselective, and ideal demodulation is considered throughout. To prove the validity of robustness of the modeling technique, various results that show good agreement between the simulated channels and the models found are presented. Two soft decision statistical distributions, namely, the soft burst and soft burst interval distributions, are defined and compared. To illustrate the accuracy of the models obtained, the simulation and model outputs are compared for a convolutional encoder with Viterbi decoding and various degrees of interleaving View full abstract»

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  • On the performance of an ATM switch with multichannel transmission groups

    Publication Year: 1993 , Page(s): 760 - 770
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (876 KB)  

    A routing architecture applying the concept of multichannel transmission groups (MCTGs) for ATM systems is proposed. A queuing analysis of an internally nonblocking ATM switch employing this MCTG concept with partially shared output buffers is presented. The analysis is based on the discrete-time DA///D/c /B queuing model. Both bulk input traffic bulk-size distribution (A) and deterministic traffic (D1 +. . .+DN) are considered. The impact of switch speedup on the performance is also taken into account. It is shown that the MCTG architecture yields better performance in terms of delay and cell loss probability than its single channel counterpart. It is also found that the switch speedup required to closely approximate the optimal performance obtained by having the switch fabric run N times as fast as the input and output channels, where N is the size of the switch, is rather small compared to N. This makes the practical realization of the proposed switch architecture feasible View full abstract»

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  • Analysis of modified Erlangian input single-server model, Ek/G/1

    Publication Year: 1993 , Page(s): 667 - 669
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (116 KB)  

    The single-server general queuing model G1/G/1 is studied for a modified Erlangian input that covers a wide range of bursty and nonbursty input processes. The Ek/G/1 model is analyzed using spectral factorization, and explicit form performance is evaluated in terms of the mean and variance of the waiting time. View full abstract»

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  • Bounds on the delay distribution of window random-access algorithms

    Publication Year: 1993 , Page(s): 683 - 693
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (780 KB)  

    A method for analyzing the delay distribution of window random-access algorithms is presented. The window size is allowed to vary during the operation of the algorithm. It is shown that the quantities of interest in the computation of the delay distribution can be related to the solution of appropriate infinite systems of linear equations. Once the constants and the coefficients of the unknowns of the system are determined, bounds on the solution can be developed by applying previously developed methodologies. The method is applied to the delay distribution analysis of the Capetanakis window random-access algorithm and the part-and-try algorithm, both under binary feedback View full abstract»

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  • An adaptive link assignment algorithm for dynamically changing topologies

    Publication Year: 1993 , Page(s): 694 - 706
    Cited by:  Papers (12)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1256 KB)  

    An adaptive link assignment algorithm for the distributed optimization of dynamically changing network topologies is presented. The algorithm is responsible for determining the network connectivity by controlling the selection of links to be established and disconnected. This algorithm is designed to recover from predictable link outages as well as massive unpredictable failures. To minimize computational time complexity as well as to improve transient response. Some known graph-theoretic algorithms are utilized View full abstract»

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  • Analysis of bandwidth allocation strategies with access restrictions in broadband ISDN

    Publication Year: 1993 , Page(s): 771 - 781
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (768 KB)  

    Bandwidth allocation strategies with access restrictions for the integration of wideband (WB) and narrowband (NB) traffic in a broadband integrated services digital network (BISDN) are studied. Access restrictions are placed on both types of traffic to meet the grade of service required for each. The WB traffic is assumed nonqueuable, whereas the NB traffic may be queued. As an improved strategy, an access strategy which allows each type of traffic to use its bandwidth in the access-restricted region with the risk of being preempted by an arriving call for which the overflowed region is reserved is considered. Under this strategy, the preempted NB calls are queued at the head of a waiting room, and preempted WB calls are queued in another finite waiting room. The performance of these strategies is analyzed in terms of access delay for NB traffic and blocking probability for WB traffic by the matrix-geometric solution method. It is shown numerically that these strategies can easily be adapted to varying traffic loads by changing the restriction levels View full abstract»

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  • Progressive refinement using local variance estimators

    Publication Year: 1993 , Page(s): 749 - 759
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1184 KB)  

    When transmitting an image over a slow communications link, it is desired to provide the best display possible in early stages of the transmission. Progressive refinement attempts to continuously minimize the deviation between the image and its displayed approximation. It is shown that this minimization is accomplished by transmitting average values of regions of the image at increasingly fine levels of resolution. The optimal refinement strategy is to subdivide the region which maximizes the product of area and pixel variance. Typically, the receiving process cannot determine the pixel variance. Estimators of the variance can be computed from information already received are developed. They are applied to refinement over the spatial distribution of values and simultaneously to refinement over their gray-scale quantization. The estimators are shown to apply equally well to monochrome and full-color image. These techniques are implemented with no transmission overhead and are shown to generate qualitatively and quantitatively superior displays View full abstract»

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  • On the performance of a hybrid frequency and phase shift keying modulation technique

    Publication Year: 1993 , Page(s): 655 - 659
    Cited by:  Papers (8)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (300 KB)  

    The performance of a hybrid modulation technique derived from binary frequency shift keying is presented. In the hybrid scheme, each frequency is allowed to be phase modulated with any of p discrete, equally spaced phase shifts. The spectral separation between frequencies is chosen to make the carriers orthogonal, thus generating a multidimensional modulation scheme. The performance of complete and expurgated phase codes is examined for the Gaussian and Rayleigh fading channels, and their spectral characteristics are determined View full abstract»

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  • A comparison of three switching schemes in isotropic networks with noisy channels

    Publication Year: 1993 , Page(s): 782 - 792
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (808 KB)  

    Previous work on analyzing three switching schemes for isotropic networks, namely single hop and two cut-through communication schemes (with and without error checking by intermediate nodes), is extended. Each scheme is modeled by a discrete Markov chain. It is shown how the performance of the communication schemes depends on path length (n ), load on the network (λ), and the error rate (p). As expected, the cut-through schemes perform much better than the single hop when the communication load is light, but as the load increases, the cut-through schemes deteriorate more rapidly, until they are comparable. In fact, when the load approaches saturation (λ is close to 1-p), the cut-through schemes are actually worse than the single-hop schemes. The schemes with checking always outperform those without, but each node must perform more work in checking the correctness of the packets passing through. The time delay becomes infinite when the throughput approaches 1-p. The solutions are expressed as simple formulas and/or algorithms for each scheme View full abstract»

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  • Near-end crosstalk is almost Gaussian

    Publication Year: 1993 , Page(s): 670 - 672
    Cited by:  Papers (29)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (228 KB)  

    Crosstalk from digital subscriber lines, high rate digital subscriber lines, and asymmetric digital subscriber lines is analyzed. The probability density of crosstalk is estimated. From this estimate the entropy power and chi-squared statistics of crosstalk are computed and compared with that of a Gaussian density View full abstract»

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  • Transformations on channel graphs

    Publication Year: 1993 , Page(s): 664 - 666
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    A channel graph is a directed acyclic graph with a unique source vertex and a unique sink vertex, in which all edges are partitioned into stages according to their distance from the source. The blocking probability of a channel graph is the probability that every source to sink path is blocked. A general transformation that never decreases the blocking probability is developed. This transformation leads to a short proof of a generalization of a theorem of K. Takagi (1971) and a theorem of F. R. K. Chung and F. K. Hwang (1978) in the case of the binomial model View full abstract»

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  • Area-efficient architectures for the Viterbi algorithm II. Applications

    Publication Year: 1993 , Page(s): 802 - 807
    Cited by:  Papers (17)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    In part I the theoretical foundations of a new class of area-efficient architectures for the Viterbi algorithm were established. Area-efficient architectures for practical codes are presented here to illustrate the design procedures and demonstrate the favourable area-time tradeoff results. Three examples from convolutional codes, matched-spectral-null (MSN) trellis codes, and Ungerboeck codes are presented. The application of the area-efficient techniques to codes with a very large number of states, codes with time-varying trellises, and a programmable Viterbi decoder is discussed View full abstract»

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  • Error and flow control performance of a high speed protocol

    Publication Year: 1993 , Page(s): 707 - 720
    Cited by:  Papers (14)  |  Patents (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1332 KB)  

    The performance of the SNR protocol of A. N. Netravali et al. (1990) is studied when it is implemented for end-to-end flow and error control. Using a combination of analysis and simulation, the efficiency with which this protocol uses the network bandwidth and its achievable throughput is evaluated as a function of certain network and protocol parameters. The protocol is enhanced by introducing two windows to decouple the two functions of receiver flow control and network congestion control. This enhancement and the original protocol are compared with go-back-N (GBN) and one-at-a-time-selective-repeat (OSR) retransmission procedures, are shown to have significantly higher throughput for a wide range of network conditions. As an example, for a virtual circuit with 60-ms roundtrip delay and 10-8 bit error rate, in order to deliver 500 Mb/s throughput, both the GBN and OSR require a raw transmission bandwidth of approximately 800 Mb/s, whereas SNR with two windows needs slightly higher than 500 Mb/s raw bandwidth. Periodic exchange of state can also provide a variety of measures for congestion control in a timely and accurate fashion View full abstract»

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  • Performance of ARQ protocols in nonindependent channel errors

    Publication Year: 1993 , Page(s): 721 - 730
    Cited by:  Papers (38)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (664 KB)  

    The performance of automatic-repeat-request (ARQ) protocols which are affected by nonindependent channel errors is studied. The protocols are the three basic ARQ protocols: stop-and-wait, go-back-N, and selective-repeat. Two types of nonindependent channel errors are considered: the kth-order Markovian errors and the gap errors. Both throughput efficiency and packet delay are obtained. The validity of analysis is verified by computer simulations. One key discovery is that when channel errors are dependent, selective-repeat ARQ achieves the same throughput efficiency as that in independent channel errors View full abstract»

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  • Multiple hops/symbol FFH-SSMA with MFSK modulation and Reed-Solomon coding for indoor radio

    Publication Year: 1993 , Page(s): 793 - 801
    Cited by:  Papers (37)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (752 KB)  

    A multiple-hopes-per-symbol fast-frequency-hopped spread-spectrum multiple-access (FFH-SSMA) system for indoor radio communication is treated. The data are Reed-Solomon (RS) encoded and then modulate a carrier by means of M-ary frequency-shift-keying (MFSK) The indoor radio channel is described as a multipath (Rayleigh or Rician) slowly fading channel. The receiver uses predetection diversity by linearly combining the squared enveloped of the different hops of the same MFSK symbol. The bit error rate (BER) performane is evaluated, and how the performance is influenced by various parameters, such as the number of hops per symbol, the size of the symbol alphabet, the ratio of specular power to fading power, and the ratio of nonreference user power to reference user power, is investigated View full abstract»

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  • Performance of the go-back-∞ protocol under correlated packet loses

    Publication Year: 1993 , Page(s): 660 - 663
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB)  

    The go-back-∞ protocol is studied under a two-state Markov chain packet-loss model, where the delay for packet acknowledgements is random. Expressions are presented for the z transform, mean, and variance of the time τ taken to successfully transmit N packets. In addition, the authors discuss how the probability distribution of the delay for packet acknowledgements can affect E |τ| View full abstract»

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  • Algorithmic construction of trellis codes

    Publication Year: 1993 , Page(s): 649 - 654
    Cited by:  Papers (13)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (396 KB)  

    An algorithmic approach is proposed whereby long convolutional codes of rate rc=k/n can easily be constructed for any chosen signal constellation in signal space. These algorithms are iterative, and in each step a number of candidate codes are found which locally maximize the distance (Hamming or Euclidean) between the codewords. The result is not necessarily a free-distance-optimizing code. However, since the construction complexity can be chosen, optimal codes are quite frequently found. The codes ae constructed such that a rapid growth of the column distance is achieved. A method of combining two codes into a single code of twice the constraint length is also presented View full abstract»

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  • Adaptive quantization: solution via nonadaptive linear control

    Publication Year: 1993 , Page(s): 741 - 748
    Cited by:  Papers (5)  |  Patents (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    A common nonlinear adaptive quantization problem is posed as a corresponding linear quadratic control problem. Adaptive quantizer algorithms are generated using methods of disturbance rejection in linear systems. Simulation with speech data shows that these algorithms can outperform a previous well-known method. The new approach subsumes and extends previous algorithms in a logical fashion 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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Meet Our Editors

Editor-in-Chief
Robert Schober
University of British Columbia