IEE Proceedings - Communications
Volume 151, Issue 6, December 2004
Volumes & issues:
Volume 151, Issue 6
December 2004
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- Author(s): D. Wei and N. Ansari
- Source: IEE Proceedings - Communications, Volume 151, Issue 6, p. 521 –528
- DOI: 10.1049/ip-com:20040840
- Type: Article
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p.
521
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The virtual private network (VPN) provides customers with predictable and secure network connections over a shared network infrastructure. The recently proposed hose model for VPNs has desirable properties in terms of greater flexibility and better multiplexing gain. However, the ‘classic’ fair bandwidth allocation scheme introduces the issue of low overall utilisation in this model; furthermore, when the VPN links are established, the VPN customers cannot manage their VPN resources by themselves dynamically. The authors propose a fluid hose-modelled VPN, and based on this model they develop an idealised fluid fair bandwidth allocation scheme to improve the performance of the VPN. With the proposed scheme, they achieve two goals: maximising the overall throughput of the VPN; and providing a mechanism that enables the VPN customers to allocate the bandwidth according to their own requirements, thus achieving the predictable QoS performance. Based on deficit round robin (DRR), a transmission scheduling scheme for output buffer switches, a novel scheme, two-dimensional deficit round robin (2-D DRR), is developed to approximate/realise the idealised fluid fair bandwidth allocation scheme for the hose-modelled VPN. The simulation results also show that the 2-D DRR can improve the overall throughput without compromising fairness and implementation complexity. - Author(s): B. Friedlander and E. Pasternak
- Source: IEE Proceedings - Communications, Volume 151, Issue 6, p. 529 –534
- DOI: 10.1049/ip-com:20040705
- Type: Article
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529
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The authors analyse the performance of a mixed analogue–digital modulation technique called signal code modulation (SCM). The technique is based on the idea of representing the analogue signal by a digital (i.e. quantised) component, and an analogue component consisting of the quantisation error. The combination of these digital and analogue components provides an exact representation of the original signal. Both components are transmitted by the communication system and used to reconstruct an estimate of the signal at the receiver. The presence of the analogue residual allows system performance to improve when excess channel SNR is available. The digital component provides an SNR gain and makes it possible to employ coding to achieve near-error-free transmission. The performance of the SCM method is analysed in some detail. - Author(s): O. Lee ; M. Anshel ; I. Chung
- Source: IEE Proceedings - Communications, Volume 151, Issue 6, p. 535 –538
- DOI: 10.1049/ip-com:20040704
- Type: Article
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To maintain load balancing in a distributed system, it is necessary to obtain workload information from all the nodes in the network. This processing requires O(v2) communication complexity, where v is the number of nodes. The authors present a new synchronous dynamic distributed load balancing algorithm on a (v, k+1, 1)-configured network applying a symmetric balanced incomplete block design, where v=k2+k+1. The algorithm needs only O (v√v) communication complexity and each node receives workload information from all the nodes without redundancy. Therefore, load balancing is maintained since every link has the same amount of traffic for transferring workload information. - Author(s): J. Li and C. Manikopoulos
- Source: IEE Proceedings - Communications, Volume 151, Issue 6, p. 539 –548
- DOI: 10.1049/ip-com:20040522
- Type: Article
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A novel statistical model, the one-dimensional hyperbolic distribution, is proposed for network traffic activity. This includes the modelling of network traffic performance and descriptive parameters, organised as probability distribution functions of activity monitored during an observation window. This model promises accurate representation in a compact manner, of particular interest in statistical anomaly intrusion detection systems. The hyperbolic distribution has been tested in modelling several performance parameters in data traces of IP traffic collected from various actual network environments, including the campus LANs of the New Jersey Institute of Technology and the WAN of the Bergen County Cooperative Library Network System (BCCLNS), as well as simulated client–server LANs. By fitting the model parameters to the experimental data, it is shown that this analytic model performs significantly better than the models currently in common use, such as the Weibull, Pareto, normal and lognormal distributions. - Author(s): Hui Wang ; J.S. Li ; P.L. Hong
- Source: IEE Proceedings - Communications, Volume 151, Issue 6, p. 549 –551
- DOI: 10.1049/ip-com:20040575
- Type: Article
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The selection of key parameters in ROHC is crucial to its performance. The optimisation of ROHC U-mode key parameters for voice over IPv6 through NS2 simulation is analysed and some possible optimal values of such parameters are presented. - Author(s): H. Zhao ; N. Ansari ; Y.Q. Shi
- Source: IEE Proceedings - Communications, Volume 151, Issue 6, p. 553 –558
- DOI: 10.1049/ip-com:20040550
- Type: Article
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Variable bit rate (VBR) video traffic exhibits high burstiness and long range dependence properties, which, in conjunction with the stringent quality of service (QoS) requirements, pose a great challenge in transporting video traffic over a communication network. The authors propose a QoS guaranteed bandwidth allocation for a given resource utilisation. Simulation and analytical results demonstrate that this scheme provides guaranteed delay and achieves high bandwidth utilisation. - Author(s): C.R.N. Athaudage and A.D.S. Jayalath
- Source: IEE Proceedings - Communications, Volume 151, Issue 6, p. 559 –566
- DOI: 10.1049/ip-com:20040551
- Type: Article
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559
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A novel cyclic-prefix based delay-spread estimation technique for wireless OFDM systems is proposed. In particular, the authors propose a technique for estimating the delays and powers of multipath components when the channel is sparse, i.e. a few strong multipaths distantly spaced in time, and a technique for estimating the RMS delay-spread when the channel has a large number of sample-spaced multipath components. The proposed techniques are based on a multiple-argument correlation function which exhibits change of gradient according to the delay path arrival pattern, i.e delay times and powers. Numerical results demonstrate the accuracy of the proposed techniques in estimating the relative timing and the power of delay paths for a sparse multipath channel, and the RMS delay-spread for a sample-spaced multipath channel. Moreover, the RMS delay-spread estimation can be used adaptively to operate the MMSE channel estimation process in the OFDM receiver at near optimum. - Author(s): M.J. Syed ; J.P. Cances ; V. Meghdadi ; J.M. Dumas
- Source: IEE Proceedings - Communications, Volume 151, Issue 6, p. 567 –573
- DOI: 10.1049/ip-com:20040568
- Type: Article
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p.
567
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The authors consider a space–time coded (STC) orthogonal frequency-division multiplexing (OFDM) system with multiple transmitter and receiver antennas over correlated frequency- and time-selective fading channels. They propose first a maximum-likelihood (ML) receiver for space–time block code OFDM systems based on the expectation–maximisation (EM) algorithm. They then propose a low-density parity-check (LDPC)-code-based STC-OFDM system to interface with the EM algorithm. When comparing the proposed scheme with the conventional space–time trellis code, the LDPC-based STC significantly improves the system performance by exploiting both spatial and selective-fading diversity in wireless channels. Compared with the recently proposed turbo-code-based STC scheme, LDPC-based STC exhibits a lower complexity and more flexible scalability. - Author(s): C.-T. Chiang
- Source: IEE Proceedings - Communications, Volume 151, Issue 6, p. 574 –580
- DOI: 10.1049/ip-com:20040523
- Type: Article
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p.
574
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The system performance of an M-ary DS-CDMA system is investigated for a coherent reception of uplink signals. In addition, the effect of imperfect power control resulting in a lognormal distribution of signal power on the system performance is also considered. A theoretical expression for the bit error rate (BER) performance of M-ary DS-CDMA systems with imperfect power control is achieved. The results show that the M-ary orthogonal modulation can offer performance improvement in terms of BER and capacity, even under imperfect power control. However, the advantage of M-ary technology is almost lost due to bad power control, even increasing the M value. For a specified performance, the derived results can be used as guides in evaluating the required quality of power control for an M-ary DS-CDMA system. Simulation results verify the theoretical derivations. - Author(s): V. Friderikos ; L. Wang ; A.H. Aghvami
- Source: IEE Proceedings - Communications, Volume 151, Issue 6, p. 581 –588
- DOI: 10.1049/ip-com:20040466
- Type: Article
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p.
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A novel joint power and rate adaptation scheme for DS/CDMA networks is proposed using information from the TCP state machine. The impetus behind this cross-layer optimisation approach is to satisfy the varying transmission rates of TCP flows which depend on the congestion window and round-trip time. Initially, a new family of objective functions is defined that encompasses TCP based information. Then by solving the proposed bi-objective optimisation problem using the ɛ-constraint method the Pareto front is calculated, which gives insight into the trade-off between the desired transmission rate and the corresponding transmitted power. Using a polynomial description of the Pareto front, the solution with the minimum L2-norm from a defined utopia point is selected as the optimum trade-off between power consumption and required rate transmission, even though different heuristics can be used. Although the Pareto frontier has been calculated using derivative based optimisation techniques, prominent paradigms of knowledge-based techniques can increase the computational efficiency. Previously proposed schemes allocate resources based on lower-layer information, such as channel conditions and link-layer buffer occupancy. The novelty and prerogative of this cross-layer optimisation approach is that critical transport layer information is integrated into the design of a power and rate adaptation algorithm for DS/CDMA networks. - Author(s): R. Martínez-Rodríguez-Osorio ; L. de-Haro-Ariet ; M. Calvo-Ramón ; M.G. Sánchez
- Source: IEE Proceedings - Communications, Volume 151, Issue 6, p. 589 –594
- DOI: 10.1049/ip-com:20040625
- Type: Article
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p.
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It is well known that impulsive noise may significantly degrade wireless digital communication performance. The authors quantify the BER degradation of W-CDMA signals in the presence of measured impulsive noise interference, and evaluate the performance improvement obtained using adaptive antennas in cellular base stations. The scope of this contribution is two-fold. First, the BER under actual impulsive noise conditions in a single-user situation is estimated by means of Monte Carlo simulations. Then, performance evaluation is made in the presence of MAI in actual impulsive interference scenarios. Shot noise has been modelled as a train of pulses, whose parameters have been obtained from actual data of measurement campaigns in the UMTS band carried out in a typical urban environment. The antenna array has been modelled according to the specifications of a smart antenna prototype under development. Results show that adaptive antennas with beamforming based on the MMSE criteria provide a significant interference energy reduction factor at the array output with respect to a conventional sectored antenna when impulsive noise is present, which straightforwardly implies link quality improvement and system capacity enhancement. - Author(s): H.-P. Lin ; R.-T. Juang ; D.-B. Lin ; C.-Y. Ke ; Y. Wang
- Source: IEE Proceedings - Communications, Volume 151, Issue 6, p. 595 –600
- DOI: 10.1049/ip-com:20040577
- Type: Article
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p.
595
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WCDMA is an interference-limited system and its coverage and data throughput are sensitive to background noise. The results of background noise measurements in urban Taipei city for the licence bands of 3G systems issued in Taiwan are presented. The measurements involve FDD mode uplink and downlink frequency bands measured on building tops and at street level, respectively. The severeness of spectrum pollution of these bands is evaluated by extracting three statistical parameters from the measurement data, and the impact of the background noise on coverage and throughput is analysed for WCDMA systems. Also, based on measurement results, a better solution using a genetic algorithm with the help of a propagation model and digitised building information is proposed for the deployment of the base stations of WCDMA systems, by which the required coverage can be met with a suitable number of base stations, locations, antenna heights and transmitting power. A system is obtained that suffers less impact from background noise and achieves a higher data throughput with minimum cost. - Author(s): A.M. Bravo ; L. Woodhead ; V.K. Bhargava
- Source: IEE Proceedings - Communications, Volume 151, Issue 6, p. 601 –604
- DOI: 10.1049/ip-com:20040579
- Type: Article
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The authors present a new procedure for the generation of non-binary sequences having superior aperiodic crosscorrelation properties to Gold sequences. The proposed procedure randomly extracts points from the surface of a multidimensional sphere, with a posterior selection technique similar to those used in genetic algorithms. A theoretical model is provided, describing the behaviour of these sequences, and several numerical experiments are performed comparing these sequences with those from the literature. It is demonstrated that these sequences outperform both Gold and chaotic generated sequences and approximate the performance of 4-phase sequences in aperiodic crosscorrelation. The sequences have the additional advantages of inherent privacy, due to their random nature and the unlimited number of sequences per set. - Author(s): H.-H. Chen and J.-S. Lee
- Source: IEE Proceedings - Communications, Volume 151, Issue 6, p. 605 –612
- DOI: 10.1049/ip-com:20040578
- Type: Article
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The combination of antenna array beamforming with multiuser detection can effectively improve the detection efficiency for wireless communications under multipath interference, especially for the applications in a fast fading channel. The authors study the performance of an adaptive beamformer incorporated with a B-MMSE detector, which works on a unique signal frame characterised by training sequence preamble and data blocks segmented by zero-bits. Both the beamformer weight updating and B-MMSE detection are carried out by either LMS or RLS algorithms. The comparison of the two adaptive algorithms applied to both the beamformer and the B-MMSE detector is made in terms of convergence behaviour and estimation mean-square error. The final performance in error probability is also given. Various multipath patterns are considered to test the rapidity of the receiver's response to changing multipath interference. The performance of the adaptive B-MMSE detector is also compared with that of the non-adaptive version, i.e. through matrix inversion. The results obtained suggest that the adaptive beamformer should use an RLS algorithm for its fast and robust convergence property; whereas the B-MMSE filter can choose either LMS or RLS algorithms depending on the antenna array size, multipath severity and complexity. - Author(s): J. Bakus and A.K. Khandani
- Source: IEE Proceedings - Communications, Volume 151, Issue 6, p. 613 –618
- DOI: 10.1049/ip-com:20040548
- Type: Article
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A new method of combined source-channel coding for the scalar quantisation of a discrete memoryless source is presented that takes advantage of the channel soft output values produced by the demodulator. The case of transmitting a memoryless Gaussian source using binary phase shift keying (BPSK) modulation over over an additive white Gaussian noise (AWGN) channel with and without Rayleigh fading is studied. Numerical results using some closed form expressions are presented, showing up to 1 dB improvement in the end-to-end distortion with respect to a traditional channel optimised scalar quantiser. - Author(s): A. E. El-Mahdy
- Source: IEE Proceedings - Communications, Volume 151, Issue 6, p. 619 –626
- DOI: 10.1049/ip-com:20040913
- Type: Article
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A classifier for MFSK signals contaminated with Middleton's class-A impulsive noise and transmitted over a time-varying flat correlated fading channel is developed. The correlated fading process of the channel is expanded using the Karhunen–Loeve expansion. The classifier is derived for both synchronous and asynchronous waveforms. Asymptotic theoretical performance evaluation of the classifier is derived. Computer simulations are illustrated to validate the theoretical developments. The performance of the developed classifier is compared with the performance of the conventional classifier (designed for AWGN). It is shown that the conventional classifier has severe performance degradation if it is subject to impulsive noise. A greater performance improvement is obtained when using the developed classifier, especially for smaller impulsive indexes of the noise. It is also shown that the performance of the developed classifier is sensitive to the impulsive index (A) of the noise. Increasing A enhances the performance of the classifier. - Author(s): K. Takeda ; T. Itagaki ; F. Adachi
- Source: IEE Proceedings - Communications, Volume 151, Issue 6, p. 627 –632
- DOI: 10.1049/ip-com:20040624
- Type: Article
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In a frequency-selective fading channel, the performance of non-spread-spectrum single-carrier (SC) transmission degrades significantly due to severe intersymbol interference (ISI). The joint use of space–time transmit diversity (STTD), receive antenna diversity and frequency-domain minimum mean square error (MMSE) equalisation in non-spread SC transmission is studied. Space–time encoding and decoding for frequency-domain MMSE equalisation and receive antenna diversity is presented. The achievable bit error rate (BER) performance of non-spread SC transmission is evaluated by computer simulation. It is found that joint use of STTD, receive antenna diversity and frequency-domain MMSE equalisation can significantly improve the BER performance in a severe frequency-selective fading channel.
Implementing fair bandwidth allocation schemes in hose-modelled VPN
Performance analysis of the signal-code-modulation technique
Design of an efficient load balancing algorithm on distributed networks by employing symmetric balanced incomplete block design
Novel statistical network model: the hyperbolic distribution
Performance analysis of ROHC U-mode in wireless links
Delay guaranteed bandwidth allocation for real-time video delivery
Delay-spread estimation using cyclic-prefix in wireless OFDM systems
LDPC-based space –time coded OFDM systems with channel estimation
Performance analysis of M-ary DS-CDMA systems with imperfect power control
TCP-aware power and rate adaptation in DS/CDMA networks
Performance evaluation of W-CDMA in actual impulsive noise scenarios using adaptive antennas
Cell planning scheme for WCDMA systems using genetic algorithm and measured background noise floor
Spherical sequences with low aperiodic crosscorrelation
Adaptive joint beamforming and B-MMSE detection under multipath interference
Quantiser design for AWGN and Rayleigh fading BPSK channels with soft output decoding
Classification of MFSK signals over time-varying flat correlated fading channels under class-A impulsive noise environment
Application of space–time transmit diversity to single-carrier transmission with frequency-domain equalisation and receive antenna diversity in a frequency-selective fading channel
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