Online ISSN
1751-8636
Print ISSN
1751-8628
IET Communications
Volume 3, Issue 1, January 2009
Volumes & issues:
Volume 3, Issue 1
January 2009
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- Author(s): W.-K. Kuo and S.-Y. Lien
- Source: IET Communications, Volume 3, Issue 1, p. 1 –9
- DOI: 10.1049/iet-com:20080015
- Type: Article
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The IEEE 802.15.3 medium access control (MAC) protocol is an emerging standard for high-rate wireless personal area networks (WPANs), especially for supporting high-quality real-time multimedia applications. Despite defining quality of service (QoS) signalling mechanisms for interoperability between devices, IEEE 802.15.3 does not specify resource allocation algorithms that are left to manufacturers. To guarantee the QoS of real-time variable bit rate (VBR) videos and utilise the radio resource efficiently, the authors propose a dynamic resource allocation algorithm. The proposed bandwidth allocation algorithm is based on a novel traffic predictor. Recently, the variable step-size normalised least mean square (VSSNLMS) algorithm was employed for on-line traffic prediction of VBR videos. However, the performance of the VSSNLMS algorithm significantly degrades due to the abrupt traffic variation occurring at the scene boundary. To tackle this problem, the authors design a novel traffic predictor based on a simple scene detection algorithm and the VSSNLMS algorithm. Analyses using real-life MPEG video traces indicate that the proposed traffic predictor significantly outperforms the VSSNLMS algorithm with respect to the prediction error. The performance of the proposed bandwidth allocation algorithm is also investigated by comparing several existing algorithms. Simulation results demonstrate that the proposed bandwidth allocation algorithm surpasses other mechanisms in terms of channel utilisation, buffer usage and packet loss rate. - Author(s): H.A. Abou Saleh and W. Hamouda
- Source: IET Communications, Volume 3, Issue 1, p. 10 –16
- DOI: 10.1049/iet-com:20080110
- Type: Article
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The bit error rate (BER) performance of the zero-forcing (ZF) receiver over transmit-correlated flat Ricean fading channels is investigated. In particular, for a multiple-input multiple-output (MIMO) channel with M transmit and N receive antennas, an approximation for the average BER of each substream is derived. Then the system performance in receive-correlated flat Ricean fading channels is addressed. In this case, it is shown that the performance, when N=M, is the same as that of transmit-correlated flat Ricean fading channels. A closed-form expression for the optimum transmit correlation coefficient, which achieves the maximum capacity (i.e. uncorrelated case), is also derived. As a result, a significant capacity gain is achieved by exploiting the knowledge of the Ricean channel. Extensive simulations are presented to validate and demonstrate the performance gain with different system parameters. - Author(s): X.-W. Chang ; X. Yang ; T. Le-Ngoc ; P. Wang
- Source: IET Communications, Volume 3, Issue 1, p. 17 –24
- DOI: 10.1049/iet-com:20080210
- Type: Article
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The maximum likelihood detection problem in many underdetermined linear communications systems can be described as an underdetermined integer least squares (ILS) problem. To solve it efficiently, a partial regularisation approach is proposed. The original underdetermined ILS problem is first transformed to an equivalent overdetermined ILS problem by using part of the transmit vector to do the regularisation. Then the overdetermined ILS problem is solved by conventional sphere decoding algorithms. Simulation results indicate that this approach can be much more efficient than other approaches for any square constellation higher than 4QAM. - Author(s): E.A. Jammeh ; M. Fleury ; M. Ghanbari
- Source: IET Communications, Volume 3, Issue 1, p. 25 –37
- DOI: 10.1049/iet-com:20080047
- Type: Article
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The anticipated growth of IPTV makes selection of suitable congestion controllers for video-stream traffic of vital concern. Measurements of packet dispersion at the receiver provide a graded way of estimating congestion, which is particularly suited to video as it does not rely on packet loss. A closed-loop congestion controller, which dynamically adapts the bitstream output of a transcoder or video encoder to a rate less likely to lead to packet loss, is presented. The video congestion controller is based on fuzzy logic with packet dispersion and its rate of change forming the inputs. Compared with TCP emulators such as TCP-friendly rate control (TFRC) and rate adaptation protocol (RAP), which rely on packet loss for real-time congestion control, the fuzzy-logic trained system's sending rate is significantly smoother when multiple video-bearing sources share a tight link. Using a packet dispersion method similarly results in a fairer allocation of bandwidth than TFRC and RAP. These gains for video traffic are primarily because of better estimation of network congestion through packet dispersion but also result from accurate interpretation by the fuzzy-logic controller. - Author(s): C.M. Vithanage ; Y. Wang ; J.P. Coon
- Source: IET Communications, Volume 3, Issue 1, p. 38 –47
- DOI: 10.1049/iet-com:20080175
- Type: Article
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A novel methodology of transmit beamforming for systems subjected to equivalent isotropic radiated power restrictions is presented in this paper. Based on the properties of the radiation due to the optimal beamforming method compared with that due to the eigen-beamforming, beamforming vectors are designed by perturbing the scaled eigen-beamforming vector such that the peak-to-average power ratio of the spatial radiation is reduced. Two algorithms incorporating this general methodology are presented. With a computational complexity less than the optimal method, both are shown to outperform conventional sub-optimal beamforming methods. For example, in an investigated system with four transmit and one receive antennas, performance is improved by more than 1 dB at a packet-error-rate of 10−3. - Author(s): K. Mammasis ; R.W. Stewart ; E. Pfann ; G. Freeland
- Source: IET Communications, Volume 3, Issue 1, p. 48 –56
- DOI: 10.1049/iet-com:20070518
- Type: Article
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Recently, the third generation partnership standards bodies (3GPP/3GPP2) have defined a two-dimensional channel model for multiple-input multiple-output (MIMO) systems, where the propagating plane waves are assumed to arrive only from the azimuthal direction and therefore not include the elevation domain. As a result of this assumption, the derived angle-of-arrival (AoA) distribution is characterised only by the azimuth direction of these waves. The AoA distribution of multipaths is implemented with a novel three-dimensional approach. The von Mises-Fisher (VMF) probability density function is used to describe their distribution within the propagation environment in both azimuth and co-latitude. More specifically, the proposed model uses a mixture of VMF distributions. A mixture can be composed of any number of clusters and this is clutter specific. The parameters of the individual cluster of scatterers within the mixture are derived and an estimation of those parameters is achieved using the spherical K-means algorithm and also the expectation maximisation algorithm. Statistical tests are provided to measure the goodness of fit of the proposed model. The results indicate that the proposed model fits well with MIMO experimental data obtained from a measurement campaign in Germany. - Author(s): R.M. Radaydeh
- Source: IET Communications, Volume 3, Issue 1, p. 57 –66
- DOI: 10.1049/iet-com:20070582
- Type: Article
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The performance of selection combining (SC) diversity in the presence of additive white Gaussian noise as well as multiple co-channel interfering signals over fading channels is analysed. The analysis considers two SC algorithms, namely, the signal-to-noise ratio-(SNR) based SC algorithm and the signal-to-interference-plus-noise ratio (SINR)-based SC algorithm. Closed-form expressions for the distribution of the resulting SINR and the outage probability performance are derived for both SC algorithms. The derived expressions are valid for arbitrary number of interfering signals, and when the desired signal replicas experience independent Rayleigh fading with generalised statistics. In addition, they are applicable for the general case when the interfering signals are subject to arbitrary fading models, which include the cases of identical, non-identical, correlated and mixed-mode fading scenarios. Numerical results are presented to examine the impact of different fading conditions and system parameters on the outage performance for both SC algorithms under consideration. - Author(s): R.A. Farrugia and C.J. Debono
- Source: IET Communications, Volume 3, Issue 1, p. 67 –74
- DOI: 10.1049/iet-com:20070602
- Type: Article
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Ka-band satellite multimedia communication networks play important roles because of their capability to provide the required bandwidth in remote places of the globe. However, because of design complexity, in practice they suffer from poor design and performance degradation because of being practically forced to guarantee acceptable end-user satisfaction in conditions of extremely low bit error rates, which is emphasised with the vulnerability of compressed video content to transmission errors, often impossible to be applied during the service development phase. A novel discrete event simulation model is presented, which provides performance estimation for such systems based on subjective measurement and a better quality of experience. The authors show that the proposed model reduces implementation cost and is flexible to be used for different network topologies around the globe. - Author(s): F.S. Tabataba and M. Nasiri-Kenari
- Source: IET Communications, Volume 3, Issue 1, p. 75 –82
- DOI: 10.1049/iet-com:20080128
- Type: Article
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The internally coded time-hopping coherent ultra-short light pulse code division multiple access (CULP CDMA) scheme (recently introduced) with an optical amplifier is described and its performance in fibre-optic communication systems is analysed. In accordance with the important role of optical amplifiers in optical communication systems, a preamplifier at the input of the receiver is used in order to compensate the losses because of the spectral encoder, spectral decoder and optical fibre path. The authors evaluate the bit error rate of the system considering the effects of the multiple access interference, noise because of the optical amplifier and thermal noise using saddle point approximation, and compare the results with those of the conventional CULP CDMA system with and without an amplifier. The numerical results indicate a substantial improvement in the performance of the coded system in comparison with the uncoded one. In addition, the negative effect of amplifier noise in the proposed scheme is much less than that of the conventional CULP CDMA system. - Author(s): T. Quazi ; H.J. Xu ; F. Takawira
- Source: IET Communications, Volume 3, Issue 1, p. 83 –90
- DOI: 10.1049/iet-com:20070285
- Type: Article
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Quality-of-service (QoS) guarantees are critical for the transmission of multimedia traffic over mobile wireless networks. Currently, wireless networks provide QoS guarantees using the legacy layered protocol architecture where each layer provides a separate, independent solution, with its own optimised adaptation and protection mechanisms. Cross-layer design has been proposed as a methodology to extend that paradigm in wireless links where there is interdependence between the layers and hence opportunity for information sharing. Recently, cross-layer adaptation mechanisms have been proposed which attempt to solve the QoS provisioning problem. However, most of these mechanisms only use the lower (physical and data link) layers and the possibility of using higher protocol layers remains unexplored. As a result, restrictions are placed on the system which introduces functional and efficiency limitations. Here, one such limitation is highlighted, namely the inability to insert more than one class of traffic in a physical layer frame. A physical and application layer cross-layer adaptation mechanism is then proposed, which overcomes this limitation. The performance results of the scheme show that the cross-layer mechanism can be efficiently applied for the purpose of providing QoS guarantees for multimedia traffic. - Author(s): G. Li and G. Feng
- Source: IET Communications, Volume 3, Issue 1, p. 91 –99
- DOI: 10.1049/iet-com:20070632
- Type: Article
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Aiming at seeking a low-complexity decoder with fast decoding convergence speed for short or medium low-density parity-check (LDPC) codes, an improved parallel weighted bit-flipping (IPWBF) algorithm, which is applied flexibly for two classes of codes is presented here. For LDPC codes with low column weight in their parity check matrix, both bootstrapping and loop detection procedures, described in the existing literature, are included in IPWBF. Furthermore, a novel delay-handling procedure is introduced to prevent the codeword bits of high reliability from being flipped too hastily. For large column weight finite geometry LDPC codes, only the delay-handling procedure is included in IPWBF to show its effectiveness. Extensive simulation results demonstrate that the proposed algorithm achieves a good tradeoff between performance and complexity. - Author(s): S.-C. Lin
- Source: IET Communications, Volume 3, Issue 1, p. 100 –114
- DOI: 10.1049/iet-com:20070545
- Type: Article
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The error probability of minimum-mean-square-error decision-feedback equalisation (MMSE-DFE) is evaluated for digital cellular mobile radio systems in the presence of cochannel interference (CCI) and is compared with linear equalisation (LE). The main contribution of the paper is that this analysis accounts for pulse waveform, modulation and fading of the signal of interest, as well as the CCI. Quadrature-amplitude modulation (QAM) signalling in frequency-selective and quasi-static channels is considered. The CCI is treated as a stationary process, when caused by random phase and symbol-timing offsets relative to the signal of interest. Analysis includes techniques combining antenna diversity. The performance improvement as a function of taps in both feedforward and feedback filters is quantified. Owing to residual intersymbol interference (ISI) and CCI, the evaluation of the error probability is extremely complicated and time consuming in simulation. To overcome this issue, an efficient method based upon Gauss quadrature rules (GQR) is presented to compute the error probability. The method is not limited due to interference statistics and it yields remarkable advantages compared with other methods. The convergence of finite-length results to their infinite-length counterparts is also provided. Unlike the case of white noise, the simulations reveal that with the same finite length the DFE is unable to outperform the linear equaliser in a CCI-dominated channel if the feedback filter is of insufficient length. - Author(s): A.K. Yousafzai and M.R. Nakhai
- Source: IET Communications, Volume 3, Issue 1, p. 115 –122
- DOI: 10.1049/iet-com:20080415
- Type: Article
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The combination of vertical Bell Labs layered space time (V-BLAST) and space time block coding (STBC), known as a Layered STBC (LSTBC) system, offers high spectral efficiency with a higher order of diversity. The system structure, computational complexity and error performance of the V-BLAST and LSTBC multiple-input multiple-output orthogonal frequency division multiplexing systems are analysed and compared. It is shown that, compared with V-BLAST, the overall diversity order of LSTBC increases two fold. This diversity gain is achieved at the expense of a four–fold increase in the computational complexity of the QR decomposition (QRD) algorithm, required at the receiver of both LSTBC and V-BLAST. The authors propose a modified QRD algorithm which reduces this four-fold complexity to two fold. - Author(s): S.A. Paredes ; S. Taebi ; T.J. Hall
- Source: IET Communications, Volume 3, Issue 1, p. 123 –134
- DOI: 10.1049/iet-com:20070099
- Type: Article
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A packet switch architecture and a method for load-balancing are described, which involve no centralised schedulers. The method is implemented by distributing extended cross-point queues (a three-dimensional structure) over all elements of the switch and deploying pollers to append packets and to select the queues to be served, together with simple local work-conserving schedulers. The queue structure is such that it renders the proof that no packet will be mis-sequenced trivial. The architecture is practical and shows enhanced performance compared with other state-of-the-art load-balancing architectures, not only for the average delay but also for the distribution of individual delays, the latter being measured by a custom tool that compares the performance of the architecture to the ideal operation of an output queued switch. The queue structure permits the fair penalisation of only the offending input–output flows within the switch in the case of buffer overflow. The basic scheme is enhanced to avoid improper operation in the presence of packet drops, a problem that reintroduces mis-sequencing and that has not been properly addressed in the class of architectures that use pollers to distribute packets. - Author(s): S. Khalesehosseini and J. Nielsen
- Source: IET Communications, Volume 3, Issue 1, p. 135 –142
- DOI: 10.1049/iet-com:20080021
- Type: Article
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The Cramér–Rao lower bound (CRLB) for the data-aided (DA) and non-data-aided (NDA) estimation of ultra-wideband (UWB) multipath channel parameters has been previously derived in the literature based on the assumption of a perfectly synchronised clock frequency between the transmitter and the receiver. These results are extended by considering the practical case where there is an initial unknown clock frequency offset that needs to be jointly estimated as part of a successful acquisition of the UWB signal. Intuitively, the additional uncertainty of the clock offset should inflate the CRLB for the estimation of the UWB channel parameters. However, as shown here, this is only valid for a small number of multipath components. As the number of multipath components is increased, the inflation of the CRLB of the channel parameter estimation because of the unknown clock offset becomes negligible. This is of practical significance for UWB propagation channels as they are typically characterised by a large number of multipath components. - Author(s): D.-F. Tseng and Z.-C. Lin
- Source: IET Communications, Volume 3, Issue 1, p. 143 –150
- DOI: 10.1049/iet-com:20070524
- Type: Article
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It is well known that an anti-collision protocol plays an essential role in the overall tag read time in radio-frequency identification systems because of the obstruction caused by tag collision. With an aim at speeding up the tag identification process, the authors propose an anti-collision algorithm, the spread partial-Q slot count (SPSC) algorithm, based on a slotted ALOHA code division multiple access technique along with tag set partitioning. A new packet structure is introduced preceded by a description of the mechanism of partition-wise identification process. In fact, according to received power levels, tags are partitioned into a certain number of groups. In the partition-wise identification process, tags belonging to two subsets are regrouped as a partition with a guarantee of having a uniformly largest received power level difference in a tag set so as to be interrogated by the reader simultaneously. The identification process for each partition is then operated sequentially. Indeed, tag set partitioning in conjunction with spread spectrum techniques could enable a simple multi-tag access detection scheme and improve system throughput as well. Simulations demonstrated that the SPSC algorithm outperforms some existing anti-collision algorithms in terms of throughput. - Author(s): L. Ghabeli and M.R. Aref
- Source: IET Communications, Volume 3, Issue 1, p. 151 –159
- DOI: 10.1049/iet-com:20080373
- Type: Article
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Symmetric relaying is a method of relaying in which the relays can decode the message of other relays in the network in addition to the source message. In this paper an achievable rate is presented for a symmetric two-relay network based on partial decoding. The strategy make use of familiar techniques such as product binning, regular encoding/sliding window decoding and regular encoding/backward decoding. The proposed rate is shown to subsume the previously proposed rate for feed-forward relay network based on decode-and-forward. This rate is also used to establish the capacity of a generalisation of Aref network called ‘semi-deterministic relay network with no interference at the relays’ and independent relay inputs.
Dynamic resource allocation for supporting real-time multimedia applications in IEEE 802.15.3 WPANs
Performance of zero-forcing detectors over MIMO flat-correlated Ricean fading channels
Partial regularisation approach for detection problems in underdetermined linear systems
Rate-adaptive video streaming through packet dispersion feedback
Transmit beamforming methods for improved received signal-to-noise ratio in equivalent isotropic radiated power-constrained systems
Three-dimensional channel modelling using spherical statistics for multiple-input multiple-output systems
SNR and SINR-based selection combining algorithms in the presence of arbitrarily distributed co-channel interferers
Accurate modelling of Ka-band videoconferencing systems based on the quality of experience
Internally coded time-hopping coherent ultra-short light pulse code division multiple access scheme with optical amplifier and its performance analysis using additive noise model
Quality of service for multimedia traffic using cross-layer design
Improved parallel weighted bit-flipping decoding algorithm for LDPC codes
Performance analysis of decision-feedback equalisation for cellular mobile radio with cochannel interference and fading
Reduced complexity detection technique for layered space time block coded multiple-input multiple-output orthogonal frequency division multiplexing
Packet-loss-robust load-balancing switch with distributed extended cross-point queues
Cramér–Rao lower bound for data-aided and non-data-aided synchronisation of ultra-wideband signals with clock offset
Anti-collision algorithm with the aid of interference cancellation and tag set partitioning in radio-frequency identification systems
Symmetric relaying based on partial decoding and the capacity of a class of relay networks
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