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Communications, IEEE Transactions on

Issue 6 • Date Jun 1993

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Displaying Results 1 - 23 of 23
  • Detection and source location of weak cyclostationary signals: simplifications of the maximum-likelihood receiver

    Publication Year: 1993 , Page(s): 905 - 916
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (948 KB)  

    The problem of dual-receiver interception of low-SNR signals, which includes detection of the presence of a particular signal type and location of its source, is considered. In particular, source-location based on time-difference-of-arrival (TDOA) measurements is examined, and the low-SNR maximum-likelihood receiver for joint detection and TDOA estimation is taken as a starting point. By explicitly revealing the way in which this receiver exploits the spectral correlation properties of the cyclostationary signal, several partial implementations with optimality properties of their own are proposed. These greatly simplified implementations, which require only a one-dimensional search over the TDOA parameter, are shown by simulation to perform competitively with the relatively complicated maximum-likelihood receiver which requires a two- or three-dimensional search for phase-shift keyed (PSK) signals View full abstract»

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  • Implication of dropping packets from the front of a queue

    Publication Year: 1993 , Page(s): 846 - 851
    Cited by:  Papers (17)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (444 KB)  

    When congestion occurs in a packet queuing system, packets can be dropped from the rear or the front of the queue. It is demonstrated that the probability of a packet being dropped is the same in systems with rear and front packet dropping. It is shown that the probability of a packet being delayed longer than a given value in a system with front dropping is less than or equal to that in a system with rear dropping. It is further illustrated that front dropping not only improves the delay performance on an internodal link, but also provides the overall loss performance for time constrained traffic such as packet voice View full abstract»

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  • New ternary line codes based on trellis structure

    Publication Year: 1993 , Page(s): 864 - 873
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (708 KB)  

    The trellis coding technique is applied to line-coded baseband digital transmission systems. For R=n/n+1(n=1,2,3) coding rates, a new codeword assignment model is proposed to accomplish basic requirements for line coding in which each length n binary data sequence is encoded into a length n+1 ternary (+,0,-) line codeword chosen among the code alphabet with 2n+2 elements. Assuming Viterbi decoding, the system error performance is improved by increasing the free Euclidean distance between coded sequences. A new algorithm is given for the calculation of the free distance between line-coded sequences so obtained. For R=1/2 and R=3/4 rates, the analytical error performance upper bounds are derived. The power spectral densities of the new line codes are also calculated and compared with those of known line codes View full abstract»

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  • On orthogonal signaling over the slow nonselective Rician fading channel with unknown specular component

    Publication Year: 1993 , Page(s): 817 - 819
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    Orthogonal signaling over the slow nonselective Rician fading channel is considered. Previous receiver designs have all assumed the amplitude and phase of the specular component of the received carrier to be known completely, but this assumption is entirely unrealistic. The problem is reformulated with unknown random amplitude and phase of the specular component. The optimum maximum likelihood receiver is obtained for equally likely equal-energy orthogonal signals and is shown to be identical to the quadratic receiver for the purely unknown phase channel and the pure Rayleigh fading channel. The error probability performance is analyzed for a fixed known specular amplitude. When specialized to the binary signaling case this error probability result exhibits a performance that is very close to and asymptotically approaches that of the conventional coherent-specular-component case for high SNR. Thus, knowledge of the specular component phase is not important to the optimum receiver View full abstract»

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  • A modified design of trellis-coded MPSK for the fading channel

    Publication Year: 1993 , Page(s): 874 - 882
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (776 KB)  

    It is shown that the classical additive white Gaussian noise (AWGN) channel design can be retained for the fading channel with any degree of fading, if carried out with the appropriate signal set size M=Mmin. The size of the signal set M min is shown to depend upon the number of parallel transitions between a given pair of states and the throughput rate. In the proposed multiple trellis-coded modulation (MTCM) scheme with a modified design (MTCM (MD)), the output bits from a rate m/m+1 trellis encoder are assigned multiple signals from an Mmin-PSK signal set. Compared to the MTCM with set partitioning proposed for the fading channel (SPF) design, the MTCM (MD) scheme provides the same signal diversity and the same or increased values of the branch distance product, and always leads to increased value of d2(free). As a result, the performance is always improved on the Rician fading channel due to the increased d2(free), and is improved on any fading channel when an increase in branch distance produce P takes place. When compared to the MTCM with the set partitioning optimum for the AWGN channel (SPA) design, the MTCM (MD) scheme, under certain conditions, provides the same value of d2(free) as the MTCM (SPA) design, and is then asymptotically optimum for both the AWGN channel and the fading channels View full abstract»

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  • Reliability polynomial for a ring network

    Publication Year: 1993 , Page(s): 825 - 827
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (188 KB)  

    A mathematical model is developed for the reliability of a system made up of m unreliable nodes arranged in a ring. The model can be used to calculate the reliability of single-ring networks in which the network recovery mechanism depends on bypassing failed stations, but link signal power margins are inadequate to overcome losses due to more than n bypass switches in series. Computational complexity is 0(n2m+nm2/2) in time, and 0(m2/2) in memory requirements View full abstract»

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  • Bit error rate performance for edge-detected CMI data transmission

    Publication Year: 1993 , Page(s): 813 - 816
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB)  

    A single edge detector for coded mark inversion, data transmission is proposed. Its detection performance depends mainly on the false transition probability if the bandwidth of the receiver low-pass filter is reasonably large, say equal to twice the data rate. An approximate expression for the bit error rate (BER) performance of this detector operating in white Gaussian noise is derived by considering the level crossing probability of the noise process. Measurements show that this approximation is closer to the actual BER performance than results obtained from a previously established theoretical approach in some cases View full abstract»

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  • The tone sense multiaccess protocols with partial collision detections (TSMA/PCD) for packet satellite communications

    Publication Year: 1993 , Page(s): 820 - 824
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (352 KB)  

    The tone sense multiaccess with partial collision detection (TSMA/PCD) protocol is particularly suitable for a packet satellite system serving an area with a dense population of earth stations. By incorporating a narrowband ground radio channel for broadcasting busy ones, the earth stations are able to avoid packet collisions by sensing for the absence of busy tones before transmitting packets. Partial collision detection capability can also be achieved. Single-tone TSMA/PCD gives 97% of the carrier-sense multiaccess with collision detection (CSMA/CD) throughput when N=10 tones are used, while for multitone and slot-by-slot announcement TSMA/PCD protocols only N=8 and N=2, respectively, are sufficient to drive the system to the CSMA/CD performance View full abstract»

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  • A note on the conservation law for queues with batch arrivals

    Publication Year: 1993 , Page(s): 832 - 835
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (324 KB)  

    The conservation law formula for work-conserving queues with batch arrivals is derived for when the arrival instants of customers are assumed to constitute an arrivals see time averages (ASTA) process. The derivation is based on the analysis of the corresponding first-in first-out (FIFO) multiclass queue and its steady state. Hence, the mean work load in the queue at an arbitrary time instant can be equated with the mean time that an arbitrary customer has to wait in the FIFO queue View full abstract»

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  • Interpolation in digital modems. II. Implementation and performance

    Publication Year: 1993 , Page(s): 998 - 1008
    Cited by:  Papers (244)  |  Patents (88)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (848 KB)  

    For pt.I, see ibid., vol.41, no.3, p.502-208 (1993). Properties of a specific class of interpolators that are based upon polynomials are discussed. Several implementations are described, one of which is particularly convenient in practical hardware. Simulations demonstrate that simple interpolators give excellent performance. In many cases, two-point, linear interpolation is adequate. If better performance is needed, classical four-point, third-order polynomials could be used. Better yet, a novel four-point interpolating filter with piecewise-parabolic impulse response can have performance superior to that of the standard cubic interpolator and still be implemented much more simply. The NCO-based control method presented in Part I is shown to be equivalent to a conventional phase locked loop and its operation is verified by simulation View full abstract»

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  • Repeated convolutional codes for high-error-rate channels

    Publication Year: 1993 , Page(s): 852 - 863
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1132 KB)  

    An error-correction scheme for an M-ary symmetric channel (MSC) characterized by a large error probability pe is considered. The value of pe can be near, but smaller than, 1-1/M, for which the channel capacity is zero, such as may occur in a jamming environment. The coding scheme consists of an outer convolutional code and an inner repetition code of length m that is used for each convolutional code symbol. At the receiving end, the m inner code symbols are used to form a soft-decision metric, which is passed to a soft-decision decoder for the convolutional code. The effect of finite quantization and methods to generate binary metrics for M>2 are investigated. Monte Carlo simulation results are presented. For the binary symmetric channel (BSC), it is shown that the overall code rate is larger than 0.6R0, where R0 is the cutoff rate of the channel. New union bounds on the bit error probability for systems with a binary convolutional code on 4-ary and 8-ary orthogonal channels are presented. For a BSC and a large m, a method is presented for BER approximation based on the central limit theorem View full abstract»

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  • Base station networking in personal communications

    Publication Year: 1993 , Page(s): 932 - 939
    Cited by:  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (660 KB)  

    Base stations in personal communications serve as the interface between portable terminals and their central offices. For many reasons, such as cost-effectiveness, higher reliability, simpler handover, and simple clock distribution, it is desirable to use a network instead of point-to-point links to connect base stations to their central offices. The author considers a base station network that has a regular rectangular mesh topology and an access protocol that is based on the slotted ring. The mesh topology provides clock distribution which can synchronize the timing for time-division multiple access (TDMA) or frequency-division multiaccess (FDMA) radio access when the network is physically regular. The slotted-ring protocol provides simple medium access, simple interface with TDMA or FDMA radio channels and simpler handover processing. The author also discusses how base station networks in different central office zones can be interconnected to form a metropolitan area network for both voice and data traffic View full abstract»

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  • Adaptive entropy-coded subband coding of image sequences

    Publication Year: 1993 , Page(s): 975 - 987
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1304 KB)  

    A new approach to image sequence coding based on variable-rate entropy-constrained subband coding (ECSBC) is described. The corresponding practical implementation of the ECSBC scheme for fixed-rate channels is developed by extending recent adaptive entropy-coded (AEC) quantization techniques. Although the entropy-constrained design of subband coding systems provides improve coding efficiency compared to level-constrained design approaches, the resulting coding system generates variable-rate outputs which must be buffered before fixed-rate transmissions. In this case, the finite buffer, however large, that interfaces the encoder and the channel will eventually overflow or underflow, resulting in a catastrophic loss of encoder-decoder synchronism with an associated large amount of distortion. A buffer-adaptive arithmetic-coded implementation of the ECSBC scheme, called adaptive entropy-coded subband coding (ECSBC/AEC), is described to completely eliminate the associated encoder buffer overflow/underflow problems, even with a very small encoder buffer View full abstract»

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  • An approximate model of a switching network carrying mixture of different multichannel traffic streams

    Publication Year: 1993 , Page(s): 836 - 840
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    An approximate model of a multistage switching network carrying a mixture of different multichannel traffic streams is proposed. In the model the multistage switching network is reduced to a single-channel system, that is, to an Erlang ideal grading to which a mixture of different multichannel traffic is offered. An approximate method for recurrence determination of the distribution of being busy in such grading is presented. The determined distribution enables calculation of blocking probabilities for traffic streams of various classes. The derived formula is a generalization of Kaufman (1981) and Robert's (1981) recurrence formula covering a full-availability trunk group with various multichannel traffic streams, and it can be useful for the analysis of ISDN systems View full abstract»

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  • Performance of the prioritized random token protocol for high-speed and ratio networks

    Publication Year: 1993 , Page(s): 917 - 931
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (928 KB)  

    A random token protocol that incorporates priority functions is presented. In this prioritized random token protocol, the access right to a channel is given to the user of the highest priority by giving the earliest scheduling time. The protocol is suitable for high-speed networks with frequency reconfiguration, and also for mobile networks. It can be used with and without the collision detection feature. The prioritized random token protocol is analyzed with two priority classes and the delay-throughput characteristics for each priority class are determined. It is shown that the proposed protocol yields better throughput-delay performance than the p-persistent protocol of prioritized carrier sense multiple access. In addition, numerical results obtained for various system parameters are discussed and verified by simulation View full abstract»

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  • Probing techniques and estimation processes for fine-time synchronization of FH systems

    Publication Year: 1993 , Page(s): 962 - 974
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (904 KB)  

    Five methods for estimating the time error in a frequency-hopped spread-spectrum (FHSS) system are analyzed and compared. These methods are based upon estimation of the second-order moments of the envelope-detected, match-filtered, received signal. The performance of these estimators is determined as a function of the Gaussian noise level and of the number of samples L used to form the estimate. The estimator mean and standard deviation are approximated by means of the central limit theorem. Solutions compare favorably with simulation results. Results for signal-to-noise ratios of 0, 5, and 10 dB and with L between 1 and 512 show that these estimators are superior to previously known methods View full abstract»

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  • Fast initialization of data-driven Nyquist in-band echo cancellers

    Publication Year: 1993 , Page(s): 893 - 904
    Cited by:  Papers (8)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (964 KB)  

    A echo canceller fast training scheme for data-driven Nyquist in-band echo cancellers is presented. This scheme simultaneously estimates the desired near and far echo canceller coefficients by sending a special periodic training sequence and correlating a segment of the sequence with the real echo samples. The requirements and the generation of the training sequence are discussed. It is shown that the fast training method can also provide the parameters for the fast initialization of the phase roll compensator in the echo canceller, and thus complete the fast training of the entire echo canceller. Compared to the conventional LMS training and other training methods, this scheme provides accurate estimates of the echo canceller coefficients in a significantly reduced training time View full abstract»

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  • Design of quadricorrelators for automatic frequency control systems

    Publication Year: 1993 , Page(s): 988 - 997
    Cited by:  Papers (11)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (716 KB)  

    The authors investigate the performance of an automatic frequency control loop operating in a receiver for linearly modulated digital signals. The loop uses a balanced quadricorrelator as a frequency detector. The design of such a detector for optimum loop tracing performance is considered. This problem involves the analysis of the disturbances generated in the quadricorrelator, which are conveniently divided into self-noise and thermal-noise-induced components. It is shown that the quadricorrelator can be designed to make self-noise negligible in the steady state, both with staggered and nonstaggered modulations. This leaves the thermal-noise-induced components as the sole obstacle to loop operation in the tracking mode. The level of such components is then minimized by further selection of the quadricorrelator filters. Numerical examples are worked out to assess the advantages of optimized quadricorrelators over more conventional schemes. It is found that tracking errors can be substantially reduced with no penalty for frequency acquisition times of the loop View full abstract»

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  • Performance evaluation of input-buffered replicated banyan networks

    Publication Year: 1993 , Page(s): 841 - 845
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB)  

    Input-buffered replicated networks are considered for broadband switching applications. They are characterized by many design parameters such as the replication factor, the traffic management policy, and input buffer location and length. To show the influence of these parameters on switching performance, an analytical model is defined based on a Markov chain representation of the input buffer. This model is suitable for application to input buffered architecture having different routing network choices. The results, expressed in terms of throughput, packet delay, and packet loss probability, outline the performance improvements with respect to other well-known networks with input buffers, such as banyan and crossbar, reached through the flexibility offered by this architectural solution View full abstract»

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  • A parallel algorithm for broadcast scheduling problems in packet radio networks

    Publication Year: 1993 , Page(s): 828 - 831
    Cited by:  Papers (28)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (260 KB)  

    A parallel algorithm based on an artificial neural network model for broadcast scheduling problems in packet radio networks is presented. The algorithm requires n×m processing elements for an n-mode-m-slot radio network problem. The algorithm is verified by simulating 13 different networks View full abstract»

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  • Optimization of cyclic redundancy-check codes with 24 and 32 parity bits

    Publication Year: 1993 , Page(s): 883 - 892
    Cited by:  Papers (19)  |  Patents (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (800 KB)  

    The method developed by T. Fujiwara et al. (1985) for efficiently computing the minimum distance of shortened Hamming codes using the weight distribution of their dual codes is extended to treat arbitrary shortened cyclic codes. Using this method implemented on a high-speed special-purpose processor, several classes of cyclic redundancy-check (CRC) codes with 24 and 32 parity bits are investigated. The CRC codes of each class are known to have the same minimum distance dmin.L in a certain range L of block lengths n, and within each class that CRC code has been determined the minimum distance of which exceeds dmin.L up to the largest block length. The dmin profiles of the resulting codes are presented and compared with the dmin profiles of recent suggestions of P. Merkey and E. C. Posner (1984), as well as with the dmin profile of the widely used 32 parity-bit standard code recommended in IEEE-802 View full abstract»

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  • Analysis of a rate-based access control mechanism for high-speed networks

    Publication Year: 1993 , Page(s): 940 - 950
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (888 KB)  

    The authors present an analysis of a rate-based access control mechanism for high-speed networks that is based on the buffered leaky bucket scheme. The analysis assumes a discrete time environment representative of asynchronous transfer mode (ATM) networks and a batch arrival process that captures cell arrivals generated by segmentation of large user packets or superposition of a number of arrival streams. The solution method is based on matrix analytic techniques, but the particular structure of the system allowed for a number of important improvements. It is shown that the problem can be partitioned and that the matrix G, central to the matrix analytic technique, can be computed using exact recursive procedures instead of the traditional iterative approach. These improvements not only extend the range of systems that can be handled, but also eliminate computational issues such as convergence rate and stopping criterion View full abstract»

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  • Resequencing control for a queueing system with two heterogeneous servers

    Publication Year: 1993 , Page(s): 951 - 961
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (752 KB)  

    A heterogeneous M/M/2/L queueing system in which two servers may work at different rates is considered. A class of threshold type scheduling policies, called fixed position policies (FPPs), is introduced. If first-in first-out (FIFO) delivery is required, departures must wait at the receiving node to be put back into proper sequence. Therefore, they incur resequencing delay in addition to whatever previous delays they experienced. A new approach, based on an imbedded Markov chain model for obtaining the resequencing delay characteristics of FPPs is developed. Closed-form expressions for the distribution and the mean of the resequencing delay are derived. For a given threshold value, the choice of the preferred FPP depends on which optimization criterion issued, such as the mean resequencing delay or the expected resequence buffer occupancy. It is shown that the selection rule for the preferred policy depends only on the ratio of the service rates. However, the optimal policy which minimizes the total delay also depends on the threshold. Application examples of these optimization procedures are presented 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