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Communications, IEEE Transactions on

Issue 8 • Date Aug 1997

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Displaying Results 1 - 19 of 19
  • A bandwidth-optimized reduced-complexity equalized multicarrier transceiver

    Publication Year: 1997 , Page(s): 948 - 956
    Cited by:  Papers (17)  |  Patents (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    A bandwidth-optimized and equalized multicarrier transceiver that achieves near-optimum performance at a practical complexity level is described. The equalizer used is a relatively short FIR filter whose taps and delay are set to optimize the performance of the multicarrier transceiver. Simulation results on a set of carrier-serving-area digital subscriber loops are also presented to demonstrate the separate and joint effects of bandwidth optimization and equalization on performance. Finally, the intriguing idea of using a pole-zero equalizer to achieve the high performance of long FIR equalizers at a much lower implementation cost is investigated View full abstract»

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  • Performance comparison of frequency-diversity and frequency-hopping spread-spectrum systems

    Publication Year: 1997 , Page(s): 910 - 912
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (104 KB)  

    In the presence of partial-band Gaussian interference, the frequency-hopping spread-spectrum system, without and with optimum diversity, performs worse than the frequency-diversity spread-spectrum system proposed by Kaleh (see ibid., p.886-93, vol.44, no.7, 1996) The latter offers the advantage of coherent reception with coherent diversity combining View full abstract»

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  • Fair packet discarding for controlling ABR traffic in ATM networks

    Publication Year: 1997 , Page(s): 913 - 916
    Cited by:  Papers (8)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (64 KB)  

    The asynchronous transfer mode (ATM) Forum has chosen rate-based control as the flow control scheme for the available bit-rate (ABR) service. However, rate-based schemes can achieve congestion control only if all users act in a cooperative manner. Even a limited number of uncooperative users can cause congestion collapse. We propose a mechanism called fair packet discarding to provide incentives to users to participate in network congestion control so that the network can operate in a more efficient manner View full abstract»

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  • Compensating frequency drift in DPSK systems via baseband signal processing

    Publication Year: 1997 , Page(s): 921 - 924
    Cited by:  Papers (2)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (164 KB)  

    A new baseband signal processing method for compensating frequency shift in differential phase-shift keying (DPSK) systems is introduced. This method consists of a signal processor for the initial acquisition of frequency shift and a simple adaptive equalizer for tracking. The former is based on the observation that the effect of frequency shift can be eliminated by using boundary values of the received baseband signal between symbol periods. The latter is a single tap equalizer employing the least mean-square (LMS) adaptation algorithm. Computer simulation results demonstrate that the proposed frequency shift compensation technique outperforms existing methods, and works well for a wide range of frequency shift View full abstract»

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  • Symbol-rate timing recovery comprising the optimum signal-to-noise ratio in a digital subscriber loop

    Publication Year: 1997 , Page(s): 925 - 936
    Cited by:  Papers (2)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    The paper investigates a symbol-rate timing recovery algorithm that is based on the correlation between an error from the decision feedback equalizer and the arriving signal samples. The mean-square error due to uncancelled precursor intersymbol interference is applied as a criterion to choose optimal timing instants. Various signal and error combinations may be used to approximate its minimum as a function of the steady-state location of the sampling instants. The timing function is selected on the premise that the estimated correlation function passes through zero only once, at the desired sampling phase. We propose a semianalytical framework for analyzing the relationship among the timing estimate variance, the acceptable noise level, and the dead-zone thresholds. It allows us to achieve a compromise between, on the one hand, the ability to track and compensate for frequency drift and for changes in the transmission media, and on the other hand, immunity against unnecessary phase corrections. The performance of the postulated timing function is examined by means of simulations View full abstract»

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  • Mean power consumption of artificial power capture in wireless networks

    Publication Year: 1997 , Page(s): 957 - 964
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    In wireless networks, portable terminals are usually powered by battery, and they communicate through the free-space spectrum. Therefore, both the transmission power and bandwidth are scarce resources. Artificial power capture is a simple and effective method to exploit the transmission bandwidth to give a higher throughput, but it may consume a larger mean transmission power because some packets are transmitted at higher power. In this paper, we analyze the mean power consumption of artificial power capture, and formulate two capture control problems which regulate the mean power consumption and the throughput. The analysis reveals that, although some packets are transmitted at higher power, artificial power capture has a smaller mean power consumption than the case without capture when the traffic is sufficiently heavy. This is because artificial power capture can significantly increase the probability of successful transmission at heavy traffic, and hence the mean power consumed for successfully transmitting a packet is smaller View full abstract»

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  • Network architecture for optical path transport networks

    Publication Year: 1997 , Page(s): 968 - 977
    Cited by:  Papers (6)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    This paper proposes a new layered transport network architecture on which the WDM optical path network can be effectively created. The optical path network will play a key role in the development of the transport network that will realize the bandwidth-abundant B-ISDN. This paper extends the layered transport network architecture described in ITU-T Recommendation G.803 which is applied in existing SDH networks. First, we elucidate an application example of WDM optical path networks. Next, we propose a new layered architecture for WDM-based transport networks that retains maximum commonality with the layered architectures developed for existing B-ISDN networks. The proposed architecture is composed of circuit layer networks, electrical path layer networks, optical layer networks, and physical media (fiber) networks. The optical layer is divided into an optical path layer and an optical section layer. The optical path layer accommodates electrical paths. Optical section layer networks are divided into optical multiplex section (OMS) layer networks and optical repeater section (ORS) layer networks. The OMS layer network is concerned with the end-to-end transfer of information between locations transferring or terminating optical paths, whereas the ORS layer is concerned with the transfer of information between individual optical repeaters. Finally, a detailed functional block model of WDM optical path networks, the function allocation of each layer, and an optical transport module (OTM) are developed View full abstract»

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  • Parallel acquisition of spread-spectrum signals with antenna diversity

    Publication Year: 1997 , Page(s): 903 - 905
    Cited by:  Papers (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (112 KB)  

    The use of antenna diversity is investigated for improving the parallel acquisition performance of a direct-sequence spread-spectrum signal in both flat and frequency-selective fading channels. Noncoherent combining techniques are analyzed because coherent diversity techniques, such as maximal ratio combining, cannot be employed prior to initial acquisition. A major application of this work is to cellular communications View full abstract»

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  • Coaxial cable passive mesh networks

    Publication Year: 1997 , Page(s): 937 - 947
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    This paper presents a new type of fault-tolerant access network: an all-passive coaxial cable mesh network. The passive mesh network could have any topology, with cycles allowed. A technique for calculating the multipath response of the passive mesh network is presented. Both the delay and attenuation of a coaxial cable are represented by a single transform variable. The mesh network is modeled as a linear system with a state space that represents signal propagation. The channel responses of the individual sections of cable define the entries of a state-transition matrix. Using this theory, expressions are given for the overall mesh-network channel response. These expressions are manipulated to derive equalizer structures. The equalizers are zero-forcing and use decision feedback. It is shown that signals transmitted on any mesh network can be equalized. An example mesh topology, and equalizers for it, are presented. Signal and interference attenuation, and opposite-phase received carrier cancellation, are also discussed. The passive mesh network could be an inexpensive fault-tolerant architecture for residential access to telephony, cable TV, and future services View full abstract»

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  • Presence of residual echo and impulsive noise

    Publication Year: 1997 , Page(s): 917 - 920
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (164 KB)  

    A general analysis is presented for the jitter performance of a common type of symbol timing recovery (STR) system employed in a digital subscriber loop (DSL) transceiver for high-speed digital data transmission over twisted copper pair cables in the presence of residual echo and impulsive noise (IN). Numerical results, obtained for an experimental study of a timing recovery system, show that the presence of these disturbing signals can substantially degrade the STR performance View full abstract»

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  • Multitrellis Viterbi algorithm for indoor systems using narrowbeam antennas

    Publication Year: 1997 , Page(s): 900 - 902
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (120 KB)  

    In earlier work, the performance (in terms of data eye closure) of a threshold detector in 2- and 4-PSK modulation schemes has been analyzed for wireless indoor systems using narrowbeam antennas. Here, assuming the channel is known, a very efficient implementation of the Viterbi algorithm (VA) is included in the receiver, and a bit-error rate (BER) criterion is used to evaluate the receiver robustness to channel conditions. In contrast to the earlier work, it is seen that 4-PSK signals with VA detectors are indeed more robust than 2-PSK signals to channel conditions View full abstract»

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  • Optical duobinary modulation with alleviated phase constraints

    Publication Year: 1997 , Page(s): 965 - 967
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (136 KB)  

    Spectral compression is a necessary function for applications in optical communication such as noise reduction, use of bandwidth-limited devices, etc. Ideal duobinary modulation, which allows the reduction of the spectrum bandwidth, requires a π (rad) phase shift between the “-1” and the “+1” logical levels. We show that with a reasonable finite extinction ratio of 10 dB, a phase shift as low as 0.18 π can be used, with a resulting spectrum compression ratio of nearly 2 View full abstract»

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  • Fractionally spaced decision feedback joint detection for multitone CDMA systems

    Publication Year: 1997 , Page(s): 906 - 909
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (204 KB)  

    We consider a fractionally spaced decision feedback joint detector (FS-DFJD) for multitone code division multiple access (CDMA) systems. We first derive the structure of the receiver for an minimum mean-squared error (MMSE) criterion. Then we investigate the bit-error rate (BER) performance achieved by this detector for binary phase-shift keying (BPSK) modulation in steady-state conditions. We consider an asynchronous scenario where the signal of each user propagates over a two-path channel. The resistance of the detector against timing errors is studied, and the resistance against a near-far scenario is also demonstrated View full abstract»

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  • Physical performance limits for shared buffer ATM switches

    Publication Year: 1997 , Page(s): 997 - 1007
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (244 KB)  

    Performance studies, linking ATM switch capabilities to physical limitations imposed by integrated circuit technology, have been scarce. This paper explores trends in circuit capabilities, and makes projections toward the 0.25-μm technologies that will be available to all switch designers in the year 2000. The limits imposed by circuit technology are applied to shared buffer ATM switches. We determine requirements and physical limits for buffer capacity, buffer throughput, chip I/O throughput, and power dissipation. As a result, we are able to project chip counts, aggregate switch throughputs, and switch dimensions. As well, performance capabilities of single-chip shared buffer switches are estimated. A single-chip shared buffer switch implemented in 0.25-μm technology will be capable of an aggregate throughput of 1.3 Tb/s, will accomplish almost arbitrarily low cell loss rates for bursty traffic, and may be integrated together with translation tables supporting hundreds of connections per port View full abstract»

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  • Variable dimension VQ encoding and codebook design

    Publication Year: 1997 , Page(s): 897 - 899
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (84 KB)  

    A variable dimension vector quantizer (VDVQ) has codewords of unequal dimensions. Here, a trellis-based sequential optimal VDVQ encoding algorithm is proposed. Also, a VDVQ codebook design algorithm based on splitting a node with equal or reduced dimensions is proposed that does not require any codebook parameter to be prespecified unlike known schemes. The VDVQ system is shown to outperform a few known VQ systems for AR(1) sources View full abstract»

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  • A note on windowing in the simulation of continuous-time communication systems

    Publication Year: 1997 , Page(s): 889 - 892
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (140 KB)  

    Simulations of continuous-time systems are frequently used by designers of signal processing and communication systems. Windowed finite-impulse response models are often used in these simulations to model continuous-time linear filters. We investigate the performance of some common windows with respect to waveform fidelity, which is a primary goal in waveform simulation, and we also obtain the form of optimum windows for this criterion. Our results indicate that the rectangular window is generally a practical and reasonably good choice for waveform simulation View full abstract»

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  • Design of a low-orbit-to-geostationary satellite link for maximal throughput

    Publication Year: 1997 , Page(s): 988 - 996
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    We examine the design of a communication link involving the data transfer from a small, low-orbit satellite to a ground station, but through a geostationary satellite. The advantage of this approach is that a single ground station, which tracks only the geostationary satellite, may be shared by a multiplicity of small satellites. Our goal is to select certain small satellite parameters-signaling rate, small satellite antenna beamwidth, modulation scheme and coding scheme-which maximize the data throughput in bits/day. Our approach uses orbital simulations of this scenario together with theoretical analysis based on the channel capacity and cutoff rate. The throughput achievable by several practical coding schemes is also examined View full abstract»

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  • Antiwhistle codes

    Publication Year: 1997 , Page(s): 893 - 896
    Cited by:  Papers (1)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (136 KB)  

    Besides timing recovery and automatic gain control, data receivers often perform adaptive slope or bandwidth control. This note presents a set of maximum run-length constraints that facilitates the joint accomplishment of these three tasks. Simple polarity-bit codes that introduce these constraints are described. The study is of particular interest in digital magnetic recording View full abstract»

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  • Performance analysis of unslotted fiber-optic code-division multiple-access (CDMA) packet networks

    Publication Year: 1997 , Page(s): 978 - 987
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (316 KB)  

    This paper examines code-division multiple-access (CDMA) techniques used in unslotted fiber-optic packet networks. Since the inherent properties and signal processing of the conventional communication channels are different from those of the fiber-optic channels, new code sequences must be constructed for fiber-optic applications. In unslotted systems, the exact solution is very difficult to obtain. Therefore, two approximation methods are presented to analyze the performance of such systems. Simulation is performed to verify the accuracy of the results 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