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Communications, IEEE Transactions on

Issue 12 • Date Dec. 1999

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Displaying Results 1 - 24 of 24
  • Author index

    Publication Year: 1999 , Page(s): 1 - 5
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    Freely Available from IEEE
  • Subject index

    Publication Year: 1999 , Page(s): 5 - 19
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    Freely Available from IEEE
  • A hybrid interleaving scheme that enables packet switching on multiple-access radio communication channels

    Publication Year: 1999 , Page(s): 1777 - 1780
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (80 KB)  

    An interleaving technique is proposed that is memory, delay, and packet efficient for demand assignment multiple-access, packet-switched transmission with frequency-hopped survivability interleaved signals over jammed or scintillated radio channels. This hybrid interleaving scheme concatenates the convolutional interleaver and the block interleaver View full abstract»

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  • Performance of BFSK FHMA systems with RTT side information over fading channels

    Publication Year: 1999 , Page(s): 1785 - 1787
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (104 KB)  

    The performance of frequency-hopping multiple-access systems with side information and binary frequency-shift keying signaling is evaluated. The side information is generated by Viterbi's ratio threshold test (RTT). Both synchronous and asynchronous hopping systems over fading channels are examined. The system with RTT side information performs significantly better than that with perfect side information or hard decision. Compared with hard decision, the RTT side information provides more than 20% improvement in capacity for Eb/N0 =10 dB over Rayleigh channels. Also, we find that the optimum threshold in the RTT scheme should be dynamically adjusted with the number of simultaneous users in the system View full abstract»

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  • Theory of the performance of a DECT receiver in a static channel

    Publication Year: 1999 , Page(s): 1849 - 1855
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (148 KB)  

    The performance of a digital enhanced cordless telecommunications (DECT) receiver in a static channel is studied. The theoretical results are then compared with computer-based simulations. The following issues were investigated: bit-error-rate performance of the differentially coherent detector with and without decision feedback, performance of both the frequency offset estimation from the DECT preamble, and the signal-to-noise ratio obtained from both the DECT preamble and the data field View full abstract»

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  • A high-performance two-stage packet switch architecture

    Publication Year: 1999 , Page(s): 1792 - 1795
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (84 KB)  

    This paper contributes a distributed packet controller which reduces queueing to a single stage in two-stage packet switches. Software and neural network based controllers are described. Simulations under a range of traffic conditions for a 1024×1024 switch size shows the simplest architecture has the best performance View full abstract»

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  • Outage evaluation for slow frequency-hopping mobile radio systems

    Publication Year: 1999 , Page(s): 1865 - 1874
    Cited by:  Papers (23)  |  Patents (28)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    In a shadowing-free environment, the improvement introduced by slow frequency-hopping (SFH) on a time-division multiple-access based mobile radio system can be taken into account by redefining the minimum carrier-to-interference ratio. This protection ratio, with SFH, is dependent on the transmission system, channel model, traffic, and frequency reuse parameters. In this paper, the above-mentioned analysis is used in order to investigate the capacity of a SFH mobile radio system, with reference to both the uplink and downlink, by taking into account a complete scenario, i.e., shadowing, fast fading, power control, antenna diversity, discontinuous transmission, and forward error correction with nonideal interleaving and sectorization. Outage probability is evaluated by a completely analytical methodology for the uplink, whereas the downlink requires a semianalytical approach to take users' positions into account. Comparison with a pure simulative approach is used to validate the results View full abstract»

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  • Analysis of quasi-ML multiuser detection of DS/CDMA systems in asynchronous channels

    Publication Year: 1999 , Page(s): 1875 - 1883
    Cited by:  Papers (9)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (324 KB)  

    We consider the quasi-maximum-likelihood (quasi-ML) detectors of the reverse link system that uses antenna arrays in asynchronous channels when the channel vector is time-invariant and time-varying. A channel vector estimation method based on eigendecomposition for time-invariant channels and its adaptive version suitable for the time-varying channels are also proposed. It is shown that the proposed quasi-ML detector can be regarded as a beamformer followed by a decorrelating filter and that the proposed system performs better than the conventional decorrelator scheme. It is also observed that the performance gain of the proposed scheme over the conventional decorrelator system increases as the numbers of active users and antenna arrays increase View full abstract»

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  • Antijamming performance of a multicarrier direct-sequence spread-spectrum system

    Publication Year: 1999 , Page(s): 1781 - 1784
    Cited by:  Papers (9)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (112 KB)  

    Uncoded antijamming capability of the multicarrier direct-sequence spread-spectrum system proposed by Kondo and Milstein (see ibid. vol.44, p.238-46, 1996 ) is analyzed. Joint pulse/partial-band noise jamming is considered with various subcarrier demodulator output combining schemes. We find that full-band pulse jamming maximizes the error probability for all cases considered. With Rayleigh fading and maximal-ratio combining, the multicarrier system achieves performance very close to that of the single-carrier system without fading even with a very small number of subcarriers View full abstract»

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  • Comparison of multicarrier DS-CDMA broadcast systems in a multipath fading channel

    Publication Year: 1999 , Page(s): 1897 - 1904
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (204 KB)  

    The performance of a multicarrier direct sequence code-division multiple-access (CDMA) system employed in the forward link of a cellular system operating over a Rayleigh fading channel is analyzed and compared to the performance of both single-carrier CDMA and hybrid multicarrier CDMA/frequency division multiplexing systems. A RAKE receiver is provided for each subcarrier. We compare the performance of all three systems for various multipath intensity profiles. It is found that for a service requiring high quality and a small number of users, the multicarrier system is the best, but for a service requiring low quality and a large number of users, the hybrid system can support more users than the others. Also, for the case when nonorthogonal codes are used, the multiple-access interference in different resolvable paths are correlated. In that case, to maximize the signal-to-noise ratio in a correlated interference environment; maximal-ratio combining (MRC) is not optimal. However, we found that there is not much difference between the optimum combining and the conventional MRC View full abstract»

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  • Analysis of a dynamic reservation protocol for interactive data services on TDMA-based wireless networks

    Publication Year: 1999 , Page(s): 1796 - 1801
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (112 KB)  

    This paper presents the dynamic reservation protocol for supporting variable-rate data services on time-division multiple-access based wireless networks. It allows a large number of data terminals to access data applications by sharing a reserved data-carrier. Through dynamic reservation data terminals can get their needed radio channels for uplink transmission without contention. The protocol performance is evaluated by queuing analysis and verified by computer simulation View full abstract»

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  • A DS-CDMA system using despreading sequences weighted by adjustable chip waveforms

    Publication Year: 1999 , Page(s): 1884 - 1896
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    This paper evaluates the performance of a direct-sequence code-division multiple-access system using coherent receivers in which the despreading sequences are weighted by adjustable chip waveforms. The chip weighting waveforms under consideration are designed for multiple-access interference (MAI) rejection. Assuming that the received chip waveforms are rectangular, new expressions for the signal-to-interference-plus-noise ratio (SINR) of the decision variable are derived when different weighted despreading sequences (WDSs) are used in the receiver. The novelty of the derived expressions is that each of the expressions, when the system parameters are given, is determined only by one parameter of the adjustable chip waveforms employed. As a result, we can simply tune the parameter to its optimal value in real-time for MAI rejection without knowing the other users' spreading codes, timing, and phase. The criterion for tuning the parameter is to maximize the SINR of the decision variable based on the relative strength between the additive Gaussian white noise and the MAI. Numerical results show that when the multiple-access interference is significant, the receivers using WDSs outperform significantly the conventional receiver using a rectangular despreading sequence. Brief analysis for bandlimited spreading signals is also provided to reveal the practical implications of the proposed technique View full abstract»

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  • Performance evaluation of a modified PRMA protocol for joint voice and data packet wireless networks

    Publication Year: 1999 , Page(s): 1837 - 1848
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (332 KB)  

    In this paper, a modified version of the packet reservation multiple-access (PRMA) protocol is proposed to provide spatially dispersed voice and data user terminals wireless access to a base station over a common short-range radio channel. An analytical approach is presented in order to derive system performance in terms of mean data message delay and voice packet dropping probability. A suitable permission probability design is also proposed to enhance system performance. Performance comparisons with an extension of the PRMA protocol to voice data systems previously reported in literature are shown to highlight the better behavior of this approach View full abstract»

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  • Bit-error probability analysis of linear receivers for CDMA systems in frequency-selective fading channels

    Publication Year: 1999 , Page(s): 1788 - 1791
    Cited by:  Papers (19)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (128 KB)  

    The bit-error probability of a linear receiver for code-division multiple-access communications is analyzed. The analysis is presented for the additive white Gaussian noise and fading multipath channels also with data-aided channel estimation. Two ways to approximate the averaging over the interfering data symbol combinations are considered and compared. Numerical examples are presented to demonstrate the usefulness of the analysis methods View full abstract»

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  • Analysis and optimization of the performance of OFDM on frequency-selective time-selective fading channels

    Publication Year: 1999 , Page(s): 1811 - 1819
    Cited by:  Papers (56)  |  Patents (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    In mobile radio communication, the fading channels generally exhibit both time-selectivity and frequency-selectivity. Orthogonal frequency-division multiplexing has been proposed to combat the frequency-selectivity, but its performance is also affected by the time-selectivity. We investigate how various parameters, such as the number of carriers, the guard time length, and the sampling offset between receiver and transmitter, affect the system performance. Further, we determine the optimum values of the above parameters, which minimize the degradation of the signal to-noise ratio at the input of the decision device View full abstract»

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  • Complexity of Verdu optimum multiuser detection algorithm in multichannel CDMA systems

    Publication Year: 1999 , Page(s): 1913 - 1920
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB)  

    A statistical characterization of the complexity function of the Verdu optimum multiuser detection (VOMD) algorithm is presented for a communication system employing a finite number of randomly accessed orthogonal channels and a finite number of simultaneous users. Multichannel code-division multiple-access (CDMA) systems are proposed. It is proved that the probability, in which the individual channel complexity is greater than Ar(1+α), approaches zero exponentially fast as the average number of simultaneous users in each channel increases, where A is the modulation alphabet size and α>0. When the number of simultaneous users is large, the complexity of applying the VOMD algorithm to each individual channel is negligible when compared with the complexity of applying the same algorithm directly to the traditional single-channel CDMA system supporting the same number of simultaneous users. The probability distribution of the joint complexity function of the aggregate system is found. It is shown that when the number of simultaneous users is large, the joint complexity function is negligible compared with applying the VOMD algorithm directly to the traditional single-channel CDMA system supporting the same number of simultaneous users. Therefore, a multichannel CDMA communication system can support a comparable population of simultaneous users to the traditional single-channel CDMA system of comparable bandwidth, while reducing the complexity of optimum multiuser detection to a practical level View full abstract»

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  • Analysis of hybrid selection/maximal-ratio combining in Rayleigh fading

    Publication Year: 1999 , Page(s): 1773 - 1776
    Cited by:  Papers (128)  |  Patents (1)
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    We use a novel virtual branch technique to succinctly derive the mean and variance of the combiner output signal-to-noise ratio for hybrid selection/maximal-ratio combining in a multipath-fading environment View full abstract»

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  • Effect of channel estimation error on M-QAM BER performance in Rayleigh fading

    Publication Year: 1999 , Page(s): 1856 - 1864
    Cited by:  Papers (119)  |  Patents (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    We determine the bit-error rate (BER) of multilevel quadrature amplitude modulation (M-QAM) in flat Rayleigh fading with imperfect channel estimates, Despite its high spectral efficiency, M-QAM is not commonly used over fading channels because of the channel amplitude and phase variation. Since the decision regions of the demodulator depend on the channel fading, estimation error of the channel variation can severely degrade the demodulator performance. Among the various fading estimation techniques, pilot symbol assisted modulation (PSAM) proves to be an effective choice. We first characterize the distribution of the amplitude and phase estimates using PSAM. We then use this distribution to obtain the BER of M-QAM as a function of the PSAM and channel parameters. By using a change of variables, our exact BER expression has a particularly simple form that involves just a few finite-range integrals. This approach can be used to compute the BER for any value of M. We compute the BER for 16-QAM and 64-QAM numerically and verify our analytical results by computer simulation. We show that for these modulations, amplitude estimation error leads to a 1-dB degradation in average signal-to-noise ratio and combined amplitude-phase estimation error leads to 2.5-dB degradation for the parameters we consider View full abstract»

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  • Soft-decision phase detection with Viterbi decoding for CPM signals

    Publication Year: 1999 , Page(s): 1802 - 1810
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (212 KB)  

    It is known that continuous phase modulation (CPM) signals can be optimally detected by using coherent demodulation followed by Viterbi decoding. However, such a receiver is generally complicated, particularly at higher numbers of states, as it requires many correlators and many reference signals in the demodulator. In this study, a much simpler receiver, which employs a soft-decision phase detector followed by a Viterbi decoder, is proposed for the detection of CPM signals. The phase detector makes a decision in favor of one of the preselected phase subregions at the end of every interval, which is then used to calculate metrics for decoding. As in optimal detection, the Viterbi decoder decodes according to the trellis structure of CPM signals. The proposed receiver is analyzed in a narrow-band Gaussian channel with 2REC, 2-h, and trellis-coded continuous-phase frequency-shift keying signals. Numerical results show that the proposed receiver performs close to optimal detection with all types of signals considered in this study. The effect of the number of subregions in the phase detector is examined View full abstract»

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  • Fade statistics in Nakagami-lognormal channels

    Publication Year: 1999 , Page(s): 1769 - 1772
    Cited by:  Papers (29)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (124 KB)  

    New expressions for the average level crossing rate (LCR) and average time fade duration (AFD) of the signal envelope in microcellular mobile radio channels, characterized by Nakagami (1960) fading and lognormal shadowing, so called Nakagami-lognormal (NLN) channels, are derived. New LCR and AFD are computed, and the effects of the Nakagami m factor and shadowing spread σs on these fade statistics are discussed. The generality of the NLN model is demonstrated by matching some LCR curves with previously reported measurement for the land mobile satellite channel, commonly described as the Rice-lognormal channels View full abstract»

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  • Reverse link capacity and interference statistics of a fixed-step power-controlled DS/CDMA system under slow multipath fading

    Publication Year: 1999 , Page(s): 1905 - 1912
    Cited by:  Papers (32)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    Power control (PC) on the reverse link of a direct-sequence code-division multiple-access system is essential to increase system capacity. Perfect PC eliminates fluctuations in the received signal level and hence reduces the required signal-to-interference ratio. However, a perfect PC algorithm tracks multipath fading accurately, which results in increasing the intercell interference level. A fixed step PC algorithm becomes almost perfect when the power command rate is too fast compared to the Doppler rate, which is the case for low-mobility users. We investigate the statistics of the intercell interference assuming users are moving slowly. These statistics are then used to find the system capacity. Three parameters that can affect the capacity are considered: the number of the fading process resolvable paths, the maximum transmitted power, and soft handoff View full abstract»

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  • RPA: a flexible scheduling algorithm for input buffered switches

    Publication Year: 1999 , Page(s): 1921 - 1933
    Cited by:  Papers (30)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB)  

    This paper presents and evaluates a quasi-optimal scheduling algorithm for input buffered cell-based switches, named reservation with preemption and acknowledgment (RPA). RPA is based on reservation rounds where the switch input ports indicate their most urgent data transfer needs, possibly overwriting less urgent requests by other input ports, and an acknowledgment round to allow input ports to determine what data they can actually transfer toward the desired switch output port. RPA must be executed during every cell time to determine which cells can be transferred during the following cell time. RPA is shown to be as simple as the simplest proposals of input queuing scheduling, efficient in the sense that no admissible traffic pattern was found under which RPA shows throughput limitations, and flexible, allowing the support of packet-mode operations and different traffic classes with either strict priority discipline or bandwidth guarantee requirements. The effectiveness of RPA is assessed with detailed simulations in uniform as well as unbalanced traffic conditions and its performance is compared with output queuing switches and the optimal maximum weighted matching (MWM) algorithm for input-buffered switches. A bound on the performance difference between the heuristic weight matching adopted in RPA and MWM is analytically computed View full abstract»

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  • Differential detection algorithms for MSK signals over AWGN and frequency-flat Rayleigh fading channels

    Publication Year: 1999 , Page(s): 1820 - 1827
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    Novel symbol-by-symbol differential detection algorithms are proposed for minimum-shift keying signals transmitted over additive white Gaussian noise and frequency-flat Rayleigh fading channels. They are derived as approximations to the maximum likelihood noncoherent detection strategy. Their error performance is assessed by computer simulation and is compared with that of other noncoherent detectors. It is shown that, with fading channels, the new algorithms outperform the traditional methods View full abstract»

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  • Optimal diversity allocation in multiuser communication systems. I. System model

    Publication Year: 1999 , Page(s): 1828 - 1836
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB)  

    A class of multiuser multicarrier communication systems is introduced to study the influence of resource allocation on the performance of multiuser communication systems operating over fading channels. This class of systems includes both systems that employ exclusive allocation schemes, where users are allotted time-bandwidth slots without interference from other users, and systems that employ shared allocation schemes, where users are allotted time-bandwidth slots that are also employed by other users. The optimal weighting factors used in the combining of the received signals from the slots of a single user for the conventional receiver is derived, and the performance of systems in the class is characterized. For each of a number of popular multiuser architectures, it is shown that there exists a system in the class with nearly identical performance. Based on these relations, it is concluded that a class of systems has been introduced that allows the study of the merits of different types of time-bandwidth allocation under a single framework 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