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Electrical and Computer Engineering, Canadian Journal of

Issue 1/2 • Date Jan.-April 2004

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Displaying Results 1 - 23 of 23
  • Canadian Journal of Electrical and Computer Engineering

    Page(s): 1 - 4
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    Freely Available from IEEE
  • Table of contents

    Page(s): i - ii
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    Freely Available from IEEE
  • Message from the editors

    Page(s): iii
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    Freely Available from IEEE
  • Guest editorial: advances in wireless communications and networking

    Page(s): iv - vi
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    Freely Available from IEEE
  • Contributors

    Page(s): vii
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    Freely Available from IEEE
  • Unified performance bounds for generalized selection diversity combining in independent generalized fading channels

    Page(s): 7 - 14
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    The cumulative distribution function (cdf) and the moment generating function (mgf) of a linear sum of ordered random variables (RVs) are needed for characterizing the performance of a generalized selection combining (GSC) receiver. Unfortunately, in all but a few cases, the mgf and the cdf either are not in closed form or exist only as multidimensional integrals. Consequently, analyzing the GSC performance in a generalized fading environment is difficult and time-consuming, especially when the number of diversity branches, L, is large. This paper therefore derives new upper and lower bounds for the cdf of the GSC output signal-to-noise ratio (SNR) in generalized fading channels. These bounds are either closed-form or single finite integral expressions. New bounds are also derived for the average symbol error rates (SERs) for a multitude of binary and M-ary digital modulations in a variety of fading channel models that heretofore had resisted simple solutions. View full abstract»

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  • Maximal-ratio eigen-combining: a performance analysis

    Page(s): 15 - 22
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    Maximal-ratio eigen-combining (MREC) for wireless communications channels, also known as eigen-beamforming for receivers equipped with antenna arrays, integrates conventional maximum average signal-to-noise-ratio beamforming (Max-ASNR BF) and maximal-ratio combining (MRC) to provide both high average SNR in high fading correlation as well as diversity in low fading correlation. Previous studies of MREC were based on simulation or limited analysis and suggested that MREC can outperform Max-ASNR BF and MRC in terms of average error probability (AEP). A comprehensive analysis of MREC is provided for BPSK signals and Rayleigh fading, including computable AEP and outage probability (OP) expressions for perfectly known, correlated channel gains. Particular cases of these expressions apply to Max-ASNR BF and MRC. For imperfectly known channels the analysis yields a new and general AEP expression for MREC, which is specialized to estimation based on pilot-symbol-aidedmodulation (PSAM) and interpolation. In particular, this AEP expression applies to Max-ASNR BF and, for PSAM and data-independent interpolation filters, to MRC. Numerical results for antenna arrays receiving signals with angle-of-arrival dispersion and imperfectly known channel gains confirm the potential advantage of MREC over Max-ASNR BF and MRC. View full abstract»

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  • Performance of multicarrier DS-CDMA systems with time-limited chip waveforms

    Page(s): 23 - 29
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    This paper studies the effect of time-limited chip waveform shaping on the performance of multicarrier direct-sequence code division multiple access (MC-DS-CDMA) systems. The performance criterion is the average multiple access interference (MAI) at the output of a correlation receiver. Comparison among different chip waveforms is made based on a fixed bit rate and a fixed total bandwidth, where the fractional out-of-bandpower (FOBP) definition is used. It is demonstrated that, compared to the performance of single-carrier DS-CDMA (SC-DS-CDMA) systems, the performance of MC-DS-CDMA systems is less sensitive to the chip waveform shaping. Moreover, the relative performance of MC-DS-CDMA systems using different time-limited chip waveforms depends heavily on the bandwidth definition and is also very different compared to that of SC-DS-CDMA systems. View full abstract»

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  • Multilevel code design for multistage and parallel decoding schemes for rayleigh fading channels

    Page(s): 31 - 34
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    The objective is to design efficient coded modulation systems with sub-optimum but practical decoding schemes for Rayleigh fading channels. The well-known rate design rule is conventionally used for additive white Gaussian noise (AWGN) channels. In this paper its application is extended to the Rayleigh fading case by modelling the channel as a time-invariant additive non-Gaussian noise channel, and the equivalent channel capacity equations are evaluated. The sub-optimumbut practical decoding schemes of multistage decoding and parallel decoding on levels are considered. The fading channel is modelled as a time-invariant additive non-Gaussian noise channel by assuming that the channel state information is available at the receiver. The equivalent channel capacity equations for both decoding schemes and a code design example are presented. It is demonstrated that very good coding gains can be achieved if code rates are selected correctly. View full abstract»

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  • Linear-complexity detection with iterative processing for space-time coded systems

    Page(s): 35 - 41
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    This paper considers wireless data transmission over multi-input, multi-output (MIMO) channels when only the receiver has perfect channel state information. A linear-complexity space-time detector is derived in the context of a turbo-code-based space-time transmitter and iterative processing (turbo detection, demodulation and decoding). Simulation results illustrate that the proposed receivers, suitable for uplink transmission, perform at a level within 2 to 3 dB of the ergodic channel capacity on MIMO channels affected by uncorrelated and correlated Rayleigh flat fading. View full abstract»

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  • A new CDMA/SDMA structure with transmit diversity

    Page(s): 43 - 49
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    Space division multiple access (SDMA) is a technique which can be used to increase the capacity of mobile communication systems by exploiting the spatial separation between different users. Space-time block codes can provide good performance in wireless fading channels through spatial diversity. Here these two techniques are combined to produce a new cooperative diversity architecture for code division multiple access (CDMA)/SDMA cellular systems using a space-time block code. An analysis of the system performance is given for a Rayleigh fading channel. This analysis can easily be generalized to similar systems. The bit error rate performance for this architecture with the Universal Mobile Telecommunications System, UMTS Terrestrial Radio Access, time-division duplex (UMTS UTRA TDD) and time-division synchronous CDMA (TD-SCDMA) systems is presented. View full abstract»

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  • Multiple-antenna communication systems: an emerging technology

    Page(s): 51 - 59
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    A recent development in wireless communications is the application of multiple-input multiple-output (MIMO) systems to radio communications via use of multiple antennas. In order to investigate the technologys potential, an experimental MIMO system containing two four-element antenna arrays (4x4) has been developed at the University of Alberta. The system is used to obtain MIMO channel measurements in a typical indoor office environment in the ISM band (902-928 MHz). Measurement campaigns have been performed using different antenna spacings and two different types of antenna: half-wavelength (lambda/2) centre-fed dipoles and dual-polarized patches. The measurements are used to calculate channel capacities for an indoor 4x4 MIMO system. The measurements confirm the high capacity potential of a MIMO channel, with ergodic capacity of approximately 21 bits per channel use available with either antenna type at a signal-to-noise ratio of 20 dB if the antenna element separation is lambda/2 or larger. An introduction to basic MIMO theory, a discussion of the University of Alberta wireless MIMO testbed, and observations regarding the measured indoor MIMO channel are presented in the paper. View full abstract»

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  • Integrated rate, power and cell control in cellular CDMA systems: an interference-balancing approach

    Page(s): 61 - 67
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    In this paper, a novel combined rate, power and cell control scheme that minimizes transmit bit energy while gracefully implementing the congestion control is proposed and studied. The reverse link in a code division multiple access (CDMA) system with a high degree of traffic fluctuation temporally as well as spatially is considered. The proposed radio resource management scheme attempts to reduce the interference power variation among base station antennas that can exist in a real radio network. Transmission rates of those users in the congested (non-congested) cells are decreased (increased); hence, the proposed scheme is appropriate for delay-insensitive variable-bit-rate applications. Minimization of average transmit bit energy is achieved, subject to maintenance of individual target Eb/I0 for each user. Two algorithms, one directly minimizing the transmit bit energy, and the other doing so indirectly using the measured pilot power, are presented. It can be shown that both algorithms select the optimal base station if forward- and reverse-link gains are reciprocal; however, the latter gain is decentralized and uses only the local measurements and is amenable for practical implementation. View full abstract»

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  • Source-based network-balanced receive power control with fixed base station assignment in cellular multimedia CDMA systems

    Page(s): 69 - 75
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    In this paper, the receive power control (RPC) problem for users with different data rate and service requirements in a cellular code division multiple access (CDMA) system with fixed assignment of mobiles to base stations is analyzed. It is shown that the problem of RPC in a multi-cell multimedia system can be split into two optimization problems: source-based RPC (SBRPC) and network-balanced RPC (NBRPC). SBRPC determines the relative receive power levels (RPLs) between different classes in each cell irrespective of the intercell interference and is locally implemented. NBRPC determines the relative RPLs between cells, can be achieved by solving an eigenvalue problem with system-wide class-wise SIR balancing, and is globally implemented. It can be seen that minimizing the total mobile transmit power via interference balancing among base station receivers sets the reference RPLs for each class of users equally in each cell. An equivalent-bandwidth-based call admission control is also derived based on the solution to the RPC problem. Numerical results are presented to demonstrate the effectiveness of the RPC in a cellular multimedia CDMA system. View full abstract»

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  • An adaptive resource reservation strategy for handoff in wireless CDMA cellular networks

    Page(s): 77 - 83
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    A threshold-based adaptive resource reservation scheme for soft handoff calls in wireless code division multiple access (CDMA) cellular networks is proposed. The scheme gives handoff calls a higher admission priority than new calls, and is designed to adaptively adjust the reservation-request time threshold according to the varying traffic load. The individual reservation requests form a common reservation pool, and handoff calls are served on a first-come, first-served basis. With the proposed scheme, a minimum grade of service (GoS) in terms of new call blocking and handoff call dropping probabilities can be achieved. Simulation results are given to demonstrate the improvement in the GoS performance in comparison with other schemes. View full abstract»

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  • An efficient wireless resource management scheme to support handoff data recovery in packet-switched cellular multicast networks

    Page(s): 85 - 92
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    To support data transfer reliability similar to that of a fixed multicast network, migrating terminals in a packet-switched cellular wireless multicast network supporting reliable multicast data transfer need to recover lost data during handoffs before they can merge into the respective multicast groups in the new cells. The multicast groups in packet-switched wireless networks typically share resources on a statistical multiplexed basis. To minimize impact on other terminals, this paper proposes to allow part of a multicast group's assigned bandwidth to be shared by the handoff terminals for transient data recovery using the proposed Weighted Fair Share (WFS) method with optimal weight selection. Handoff terminals are admitted into the new cell using the proposed Multicast Connection Admission Control (MCAC) scheme. These methods together constitute the Fair and Efficient Wireless Multicast resource management Scheme (FEWMS) presented in this paper. Under FEWMS, a migrating terminal can quickly recover lost data and merge into the existing multicast group during a handoff. Simulations using self-similar traffic sources show that the proposed method reduces the handoff failure probability of migrating terminals and the average packet delay of the multicast group, and increases the overall system throughput, compared with an existing proposal. Evaluations of different performance measures show that the system throughput does not give a complete picture of the system performance, as different resource management schemes may have substantial impact on other performance measures such as average delay and handoff failure probability. View full abstract»

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  • User mobility support in an urban CDMA-based wireless network

    Page(s): 93 - 100
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    A salient feature of wireless networks is the ability to support user roaming. However, user mobility has a profound effect on grade of service (GoS) and quality of service (QoS) provisioning. Code division multiple access (CDMA) is the multiple access technology for the third-generation wireless standard (3G) and is envisioned to be the multiple access technology beyond 3G. CDMA is interference-limited. The signal-to-interference (SIR) ratio, expressible in the form of Eb/I0, is an important parameter in CDMA systems and has a profound effect on the system capacity. The system capacity in turn affects the call-level GoS of the network layer in terms of new call blocking probability and forced termination probability. The effect of user mobility on (i) degradation in utilization and (ii) excess capacity needed to satisfy the QoS/GoS requirements, in an urban environment, is examined and quantified. A relationship between the link-layer Eb/I0 specification and the call-level GoS parameters in the presence of user mobility is also established. Numerical results which display the linkages between the link-layer QoS and call-level GoS parameters are presented and discussed. This coupling gives a quantification of the link-layer requirement to provision the call-level GoS, in the presence of user mobility. View full abstract»

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  • Adaptive bandwidth framework for provisioning connection-level QoS for next-generation wireless cellular networks

    Page(s): 101 - 108
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    The next generation of wireless cellular networks is expected to support real-time multimedia services with different classes of traffic and diverse bandwidth requirements. Bandwidth is a scarce resource in wireless networking that needs to be carefully allocated amid competing connections with different quality of service (QoS) requirements. In this paper, an adaptive framework for supporting multiple classes of multimedia services with different QoS requirements in wireless cellular networks is proposed. The framework combines the following components: (1) a threshold-based bandwidth allocation policy that gives priority to handoff calls over new calls and prioritizes among different classes of handoff calls by assigning a threshold to each class; (2) an efficient threshold-type call admission control (CAC) algorithm; and (3) a bandwidth adaptation algorithm (BAA) that dynamically adjusts the bandwidth of ongoing multimedia calls to minimize the number of calls receiving lower bandwidth than they had requested. Numerical results show that the proposed adaptive multimedia framework outperforms existing non-adaptive schemes in terms of the handoff call dropping probability and effective utilization. View full abstract»

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  • Comparisons of link-adaptation-based scheduling algorithms for the WCDMA system with high-speed downlink packet access

    Page(s): 109 - 116
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    The wideband code division multiple access (WCDMA) system with high-speed downlink packet access (HSDPA) is an important next-generation wireless system. By adopting adaptive modulation, efficient scheduling, and hybrid automatic repeat request technologies, it can support data rates of up to 10 Mb/s in the mobile cellular environment. Among these techniques, the scheduling algorithm plays a key role in realizing the HSDPA concept. A good scheduling algorithm should consider all the important factors, including channel impact, delay issues, and fairness. In this paper, a fairness index is adopted to examine the fairness performance of current link-adaptation-based scheduling algorithms, including the maximum carrier-to-interference (C/I), round-robin, proportional fair, and exponential rule schedulers. It is found that when multi-type services are supported, the fairness performance of current scheduling algorithms, including the round-robin scheduler, can be further improved even though the round-robin scheduler is viewed as the scheduler of the greatest fairness. Thus, a new scheduling algorithm, namely the queue-based exponential rule scheduler, is developed. Through simulations, it is shown that in the context of multi-type services the fairness performance of the queue-based exponential rule scheduler can surpass that of all the other schedulers in the time-multiplexing fashion, while maintaining good throughput and delay performance. View full abstract»

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  • Scheduling algorithms for high-throughput packet data service in cellular radio systems

    Page(s): 117 - 127
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    This paper examines the performance of a number of scheduling algorithms for the wireless packet data access evolution of third-generation cellular systems. The algorithms are analyzed using three different wireless channel models (two pedestrian, one vehicular). For each channel model, a comparison of the performance of the algorithms using outdated channel state information plus margins tuned to provide an average 1% packet error rate, as well as using perfect channel prediction in order to determine the supportable bit rate and transmission format for each user, has been carried out. The performance of the algorithms is evaluated in terms of the average throughput per sector as a function of the number of users. The average delay per packet and per user versus the number of users per sector and the distributions of allocated slots per user are also determined as a measure of the fairness of each algorithm. It is also shown that the use of outdated information and margins can be an effective substitute for prediction, provided that the outdated measurements are reasonably accurate. View full abstract»

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  • TCP performance over mobile ad hoc networks

    Page(s): 129 - 134
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    TCP is a transport protocol that guarantees reliable ordered delivery of data packets over wired networks. Although it is well tuned for wired networks, TCP performs poorly in mobile ad hoc networks (MANETs). This is because TCP's implicit assumption that any packet loss is due to congestion is invalid in mobile ad hoc networks where wireless channel errors, link contention, mobility and multipath routing may significantly corrupt or disorder packet delivery. If TCP misinterprets such losses as congestion and consequently invokes congestion control procedures, it will suffer from performance degradation and unfairness. To understand TCP behaviour and improve the TCP performance over multi-hop ad hoc networks, considerable research has been carried out. As the research in this area is still active and many problems are still wide open, an in-depth and timely survey is needed. In this paper, the challenges imposed on the standard TCP in the wireless ad hoc network environment are first identified. Then some existing solutions are discussed according to their design philosophy. Finally, some suggestions regarding future research issues are presented. View full abstract»

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  • Fixed cycles and adaptive bandwidth allocation can coexist in bluetooth

    Page(s): 135 - 147
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    A novel polling scheme for intra-piconet scheduling in Bluetooth piconets is described. The scheme allocates time to each slave according to its current traffic, while trying to limit the maximum piconet cycle time. This approach makes scheduling of mixed asynchronous and constant-bit-rate (CBR) traffic much easier than do other known schemes. In this manner, the scheme is able to provide low delay and high throughput for asynchronous data traffic, guaranteed delay for CBR traffic, and inherent fairness among slaves with asymmetric traffic; in addition it has low complexity. A detailed queueing model of this policy is presented and simulations are conducted to confirm the analytical results. Simulations confirm that the new scheme performs as well as, or in some cases even better than, other common polling schemes. View full abstract»

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  • Perfor mance of a QoS-based multiple-route ad hoc on-demand distance vector protocol for mobile ad hoc networks

    Page(s): 149 - 155
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    This paper proposes a quality of service based multiple-route ad hoc on-demand distance vector (QoS-MRAODV) routing protocol for achieving and maintaining QoS in mobile ad hoc networks (MANETs). The QoS-MRAODV protocol supports one active QoS-based primary route and several backup routes to provide hot standby redundancy against frequent route failures that are prevalent in MANETs. Results from extensive performance simulation of the QoS-MRAODV protocol demonstrate that it is indeed a viable protocol for achieving and maintaining QoS support in MANETs, providing the additional benefits of fast route discovery time and low routing overhead without a significant increase in end-to-end packet delay. View full abstract»

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Aims & Scope

The role of the Canadian Journal of Electrical and Computer Engineering is to provide scientific and professional activity for its members in Canada, the CJECE complements international journals and will be of particular interest to anyone involved in research and development activities in the field of electrical and computer engineering.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Dr. Shahram Yousefi
Dept. of Electrical and Computer
     Engineering
Queen's University