Online ISSN
1751-8636
Print ISSN
1751-8628
IET Communications
Volume 6, Issue 6, 19 April 2012
Volumes & issues:
Volume 6, Issue 6
19 April 2012
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- Author(s): H.T. Nguyen ; T.A. Ramstad ; I. Balasingham
- Source: IET Communications, Volume 6, Issue 6, p. 577 –586
- DOI: 10.1049/iet-com.2010.0978
- Type: Article
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A communication system based on the joint source-channel coding principle is proposed, where a fixed-rate source encoder is used to avoid the error propagation effect as experienced when variable length coding is used and thus gain system robustness. An explicit expression of the mean square error (MSE) distortion of the system for a uniform source is derived. We provide an algorithm to achieve the optimal solution by investigating the Karush–Kuhn–Tucker (KKT) condition. The numerical results show that the overall performance of the proposed system is close to the performance of the entropy coded scalar quantiser (ECSQ) system established by A. György and T. Under for almost all rate region. A 0.176-bits-per-sample performance loss is found for the worst case by comparing our considered system and ECSQ system. An observation resembling the finding by V. Goya1 et al. is that in the low rate region, there exist certain regimes in which the proposed system outperforms the ECSQ system. Finally, the proposed system outperforms the equal rate system with a large margin. - Author(s): H.-Y. Lu
- Source: IET Communications, Volume 6, Issue 6, p. 587 –598
- DOI: 10.1049/iet-com.2011.0609
- Type: Article
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This study presents a family of multiuser detectors (MUDs) for the uplink of spatial-frequency-time-domain (SFT-domain) spread, multi-carrier, direct sequence code division multiple access systems. More specifically, the family is comprised of a joint SFT MUD and six separate MUDs. The proposed joint SFT MUD achieves a significant performance gain because it is based on minimum mean square error (MMSE) decision criteria. For practical realisation, the main contribution of the study is that the authors further reduce the computational complexity by decomposing the complete received signal into several low-dimension signal components and implementing the corresponding separate MMSE MUDs to facilitate symbol detection. The authors also analyse the computational complexity and mean square error bound of the proposed MUDs. The results of simulations demonstrate that the joint SFT MMSE MUD outperforms the other proposed schemes; however, it requires the largest amount of computation. Meanwhile, the performance of the separate MMSE MUDs is effective and close to that of the joint SFT MMSE MUD, but the computational overhead is modest. - Author(s): V.K. Dwivedi and G. Singh
- Source: IET Communications, Volume 6, Issue 6, p. 599 –603
- DOI: 10.1049/iet-com.2010.0870
- Type: Article
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In this study, a repeated correlative coding scheme is proposed to combat the inter-carrier interference (ICI) caused by the frequency offset in orthogonal frequency division multiplexing (OFDM) communication systems. This proposed scheme combine two ideas of the well-known methods, which are the coding of adjacent subcarriers with antipodal of the same data symbol (ICI self-cancellation) and correlative coding. A mathematical expression for the carrier-to-interference ratio (CIR) by using this proposed repeated correlative coding scheme is derived. The simulated result of CIR for the proposed scheme is significantly improved compared to the correlative coding as well as a self-cancellation scheme. The bit-error-rate (BER) of the proposed scheme is also compared with the ICI self-cancellation scheme and correlative coding scheme, which is comparable to that of the ICI self-cancellation scheme and better than the correlative coding scheme. - Author(s): Q. Ibrahim and N. Abdulghani
- Source: IET Communications, Volume 6, Issue 6, p. 604 –612
- DOI: 10.1049/iet-com.2010.1122
- Type: Article
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Speaker recognition (SR) technique has proven to be an effective tool in many applications. In this study, SR was used to enhance the security of voice over Internet protocol system. This work focused on authentication issues and user identification detection depending on the voice signature of the incoming call. The authors suggest the use of SR concepts to support user identification process. First, a complete SR system based on linear prediction coefficients (LPC) feature extraction and decision based on artificial neural network was described and built using MATLAB package. Then, MATLAB package was used to develop a prototype version of the modified session initiation protocol (SIP), which is used to manage calls establishment among the network nodes. MATLAB codes were written for both SIP server and client nodes. The modified SIP protocol was implemented on an experimental network which is built to demonstrate the operation of the enhanced authentication procedure. - Author(s): J. Li ; X. Liu ; H. Cao ; N. Jin
- Source: IET Communications, Volume 6, Issue 6, p. 613 –617
- DOI: 10.1049/iet-com.2011.0686
- Type: Article
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In this study, an efficient ordering scheme for sphere detection (SD) is presented. The proposed scheme can substantially reduce SD computation complexity which combines Vertical Bell Laboratories Layered Space–Time (V-BLAST) with gradient-based (GB) ordering and smartly modifies them based on iterative successive interference canceling (SIC), attempting to exploit the potential of both the channel matrix and the received noisy signal as full as possible, whereas offering almost the same preprocessing complexity as balanced sorted QR (BSQR) and V-BLAST ordering. The simulation results show that, in terms of the number of visited nodes, the proposed scheme can achieve a significant complexity reduction, especially for high numbers of antenna and large constellation sizes in the low signal-to-noise ratio (SNR) region. Compared with SD under BSQR decomposition and GB orderings at SNR=5 dB, the average number of visited nodes under our proposed ordering is reduced by >30% in 4×4 16QAM system, and by almost 30 and 50% reduction in 6×6 16QAM system, respectively. For 4×4 64QAM system, >70% reduction at SNR=0 dB and >40% reduction at SNR=5 dB can be achieved, respectively. - Author(s): A. Papadogiannis ; G.C. Alexandropoulos ; A. Burr ; D. Grace
- Source: IET Communications, Volume 6, Issue 6, p. 618 –627
- DOI: 10.1049/iet-com.2011.0174
- Type: Article
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Adding fixed relay nodes (RNs) to wireless access networks requires additional costly infrastructure. Utilising mobile RNs, that is, user terminals that relay signals intended for other users being the destination nodes (DNs), is an appealing cost-effective solution. However, the changing node topology increases the required signalling for relay selection (RS). The signalling overhead consists of control signals that need to be exchanged between the RNs, the source node (SN) and the DN, to achieve the objectives of cooperation. To reduce signalling without penalising performance, the authors propose a three-step approach exploiting statistical knowledge on the likelihood of attaining performance gains by using RNs as a function of the node position (position of DNs and RNs). In the first step only the cell DNs that are likely to gain from relaying request the assistance of RNs. In the second step, for each DN that requests relaying, a limited set of RN candidates is formed. These decisions are made with the aid of thresholds applied to inter-node distances whose values are based on the acquired statistical knowledge. In the final step, RN candidates feed back the relevant channel state information to the SN that performs RS. Furthermore, the authors investigate the attained gains from mobile RNs as a function of the fading environment and they show that mobile RNs can help overcome the effects of severe fading. - Author(s): S.M. Hosseini Andargoli and K. Mohamed-pour
- Source: IET Communications, Volume 6, Issue 6, p. 628 –637
- DOI: 10.1049/iet-com.2011.0211
- Type: Article
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This study addresses resource allocation for weighted sum throughput maximisation (WSTM) in a sectorised two-cell downlink orthogonal frequency-division multiple access systems impaired by multicell interference. It is well known that the optimisation problem for this scenario is NP-hard and combinational, which is here converted to a novel WSTM problem based on the intercell interference limitation. In the new problem, we use a lower bound of throughout as a cost function which is convex, and so it simplifies the power allocation algorithm and offers a better convergence. Then, two subclasses of this new problem are solved based on the dual Lagrange framework. By the first subclass, on the assumption that subcarrier allocation parameters are fixed, an algorithm for optimal power allocation (OPA) is obtained. However, the optimal resource allocation requires an exhaustive search, including the OPA which cannot be implemented in practice because of its high complexity. By the second subclass, the joint subcarrier allocation and power distribution for two adjacent cells as a general problem is solved. Here, the algorithm allocates simultaneously the subcarriers and the power of the considered two cells while the resource allocation parameters of both cells are coupled mutually. After that, we propose a new centralised algorithm which combines the proposed power allocation with the non-convex subcarrier allocation without increase in the complexity. Simulation results show that the proposed algorithms achieve efficient performance in many practical situations. - Author(s): A.E. Abharian ; H. Khaloozadeh ; R. Amjadifard
- Source: IET Communications, Volume 6, Issue 6, p. 638 –648
- DOI: 10.1049/iet-com.2011.0120
- Type: Article
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Most conventional active queue management (AQM) methods are established on the first stochastic moment (mean value) of queue length variation. Yet, these conventional methods have been inefficient so far. Regarding the stochastic attributes of communication networks, AQM methods based on stochastic theory perform better in comparison with conventional AQM methods. A new stochastic AQM advances is advised for the control of queue length probability density function (PDF) for transmission control protocol (TCP). The Parzen window estimate of PDFs exploitation the kernel function is used to constitute the queue PDFs of the TCP/AQM routers. This study proposes a novel stochastic AQM algorithm called hyperbolic random early detection (PDF-HRED) as an appendage of random early detection (RED). The PDF-HRED is based on a stochastic PDF estimation, an HRED controller and particle swarm optimisation (PSO). The numerical simulation results by NS2 demonstrate that the PDF-HRED controller outperforms the existing AQM schemes with respect to performance characteristics. - Author(s): E.S. Altubaishi and X. (Sherman) Shen
- Source: IET Communications, Volume 6, Issue 6, p. 649 –658
- DOI: 10.1049/iet-com.2011.0207
- Type: Article
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In this study, the authors propose two schemes to enhance the spectral efficiency of the decode-and-forward adaptive relaying with adaptive modulation. The first scheme, called the minimum error rate scheme, uses cooperative transmission all the time to achieve transmit diversity whereas the second scheme, called the maximum spectral efficiency scheme, tries to avoid cooperative transmission if the spectral efficiency cannot be improved. For each scheme, the authors introduce a policy that depends on the channel state information of each link. They provide performance analysis in terms of average spectral efficiency, average bit error rate and outage probability over independent non-identically Rayleigh fading channels. Our analysis is verified by simulation results. These results show that our proposed schemes lead to an improvement in the performance of cooperative wireless systems. - Author(s): D. Wu ; L. Zhou ; Y. Cai
- Source: IET Communications, Volume 6, Issue 6, p. 659 –667
- DOI: 10.1049/iet-com.2011.0625
- Type: Article
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Owing to the evolution of green communications, energy efficiency is treated as an important performance metric of a uplink orthogonal frequency division multiple access (OFDMA) system. In this study, the authors propose an energy-efficient resource allocation scheme by using the correlated equilibrium (CE). At first, the authors construct an energy-efficient resource allocation game, where each subcarrier is viewed as a player to choose the most satisfying user, and the objective is to balance the tradeoff between the total energy efficiency and the fairness. Since the CE can achieve better performance by helping the non-cooperative players coordinate their strategies, the authors employ the CE to analyse the proposed game. Next, the authors derive the condition under which the CE is Pareto optimal and employ linear programming duality to show its closed-form expressions. Furthermore, the authors present a linear programming method and a distributed algorithm based on the regret matching procedure to implement the CE, respectively, which can help us determine the desired resource allocation. Simulation results demonstrate that our scheme is able to achieve good convergence, Pareto optimality and fairness. - Author(s): Y. Zhao ; L. Huang ; T.-Y. Chi ; S.-Y. Kuo ; Y. Yao
- Source: IET Communications, Volume 6, Issue 6, p. 668 –675
- DOI: 10.1049/iet-com.2011.0660
- Type: Article
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This article focuses on channel model and capacity of multiple-input multiple-output (MIMO) relay system in a low-rank line-of-sight environment. According to the channel characteristics of MIMO and the correlations among antenna arrays, the expression for system capacity is deduced. Various factors influencing MIMO relay system are analysed based on this expression, and the numerical simulation is performed for verification. The simulation results show that system capacity is greatly increased by adding relay nodes. However, the antenna array spacing and angle at the transmitting and receiving ends, relay node position, Rice K-factor and other factors can all produce certain effects on the capacity of MIMO relay system. - Author(s): R. Deng ; S. He ; J. Chen ; J. Jia ; W. Zhuang ; Y. Sun
- Source: IET Communications, Volume 6, Issue 6, p. 676 –684
- DOI: 10.1049/iet-com.2011.0565
- Type: Article
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Nowadays, with the dramatically increased penetration of wireless access, the conflict between spectrum scarcity and under-utilisation is becoming more and more aggravating. A promising technology to tackle such challenge is cognitive radio, of which spectrum sensing is one of the most important functionalities. In this study, the authors consider an essential problem of energy-efficient spectrum sensing in cognitive radio networks. Although most existing works of spectrum sensing mainly focus on determining an optimal sensing time to maximise the detection probability and/or to minimise the false alarm probability, our problem of how to schedule the power-constrained sensor is much more challenging, because of the trade-off among interests of the primary user, secondary user and sensor. The authors formulate it as a non-linear optimisation problem to maximise the sensor lifetime, with necessary constraints of quality and delay of spectrum sensing, and throughput for performance guarantee of primary and secondary users. Moreover, the authors incorporate the distribution information of channel occupancy/vacancy durations into the problem to yield a desirable solution. They propose a novel framework to obtain the optimal energy-efficient periodic scheduling by adopting both non-linear programming and linear programming. Extensive simulation results are provided to validate our theoretical analysis.
Optimal and robust communication for a uniform source
A family of minimum mean square error multiuser detectors for three-domain spread multi-carrier direct sequence-code division multiple access
Repeated correlative coding scheme for mitigation of inter-carrier interference in an orthogonal frequency division multiplexing system
Security enhancement of voice over Internet protocol using speaker recognition technique
Efficient iterative ordering scheme based on successive interference cancelling for sphere detection in multiple input multiple output system
Bringing mobile relays for wireless access networks into practice–learning when to relay
Weighted sum throughput maximisation for downlink multicell orthogonal frequency-division multiple access systems by intercell interference limitation
Stochastic hyperbolic random early detection controller based on probability density function estimator and particle swarm optimisation algorithm
Performance analysis of decode-and-forward relaying schemes with adaptive quadrature amplitude modulation (QAM)
Energy-efficient resource allocation for uplink orthogonal frequency division multiple access systems using correlated equilibrium
Capacity analysis for multiple-input multiple-output relay system in a low-rank line-of-sight environment
Energy-efficient spectrum sensing by optimal periodic scheduling in cognitive radio networks
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