Online ISSN
1751-8636
Print ISSN
1751-8628
IET Communications
Volume 6, Issue 1, 4 January 2012
Volumes & issues:
Volume 6, Issue 1
4 January 2012
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- Author(s): Q. Wang ; D.-W. Yue ; F.C.M. Lau
- Source: IET Communications, Volume 6, Issue 1, p. 1 –12
- DOI: 10.1049/iet-com.2010.0747
- Type: Article
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In this study, the authors investigate the optimal sensing settings that can maximise the throughput of the cognitive radio (CR) users under the constraint that the signals from the primary users (PUs) are sufficiently protected. They focus on the throughput at the data link layer where end-to-end delivery of data packets is considered. Consequently, the throughput is defined as the rate at which correct data are received. They reconsider the tradeoff between the sensing settings and the throughput. They also separately perform optimisation on the throughput when cooperative spectrum sensing (CSS) is/is not used. In order to evaluate the throughput, they further derive the exact symbol-error-rate (SER) expressions in the presence of co-channel interference. After proving that the throughput functions are unimodal, they proposed two efficient and effective algorithms that can derive the optimal settings for maximising the throughput. Finally, the authors show that their numerical results and compare optimal results with those found by exhaustive searches. They conclude that their algorithms produce optimal results very close to those found by exhaustive searches. - Author(s): X.W. Yao ; W.L. Wang ; S.H. Yang
- Source: IET Communications, Volume 6, Issue 1, p. 13 –21
- DOI: 10.1049/iet-com.2010.1013
- Type: Article
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Transmitting delay-sensitive video streaming over IEEE 802.11e wireless local area networks (WLANs) is becoming increasingly popular. However, the transmission of real-time video streaming is very challenging because of the time-varying wireless channels and video content characteristics. The authors propose an accurate model to assess the perceived quality of video streaming over WLANs with enhanced distributed coordination function (EDCF) mechanism. The analytical model considers not only the packet loss caused by wireless interference and channel fading, but also the effects of loss from channel access competition. Based on the Markov chain, the authors then present the discrete probability distribution of medium access control (MAC) layer packet service time by using the signal transfer function of the generalised state transition diagram. Moreover, the coding relation of lost video frames is also explored in the performance analysis of the proposed model. Simulations based on Network Simulator 2 (NS-2) are conducted to verify the performance of the analytical model. The results show that the proposed model provides superior accuracy for the perceived quality of MPEG-4 video streaming over IEEE 802.11e EDCF-based WLANs. - Author(s): R. Verghese ; S. Thai Subha ; V. Bhaskar
- Source: IET Communications, Volume 6, Issue 1, p. 22 –28
- DOI: 10.1049/iet-com.2011.0442
- Type: Article
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The authors analyse ergodic capacity for a system employing multi-element antenna array at the transmitter and receiver side. The signal is assumed to have both line-of-sight and non-line-of-sight (NLOS) components characterised by Rician fading distribution. The presence of the cluster of scatterers which gives rise to NLOS components is modelled using Von Mises Fisher (VMF) distribution. The impact of spatial correlation on capacity is graphically presented using MATLAB. The effect of channel state information at the transmitter side is analysed and plotted. Uniform circular array (UCA), which has been proved to outperform uniform linear array, is used at both the transmitter and the receiver. Furthermore, the effect of the radiation pattern of a UCA on the received signal-to-noise ratio is also plotted. Closed-form expressions for asymptotic tightness and upper bound of the system incorporating VMF distribution are obtained and plotted. - Author(s): H. Sadeghi ; P. Azmi ; H. Arezumand
- Source: IET Communications, Volume 6, Issue 1, p. 29 –38
- DOI: 10.1049/iet-com.2011.0269
- Type: Article
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Reliable detection of primary users (PUs) in the presence of interference and noise is a crucial problem in cognitive radio networks. To address the above issue, cooperative spectrum sensing based on cyclostationary feature detection that can robustly detect weak primary signals has been proposed in the literature. Among different cooperative techniques, in this study the authors focus on combination of soft decisions derived based on asymptotic properties of cyclic autocorrelation estimates. The objective is to maximise deflection coefficient performance metric at the fusion centre, where linear combination of cyclostationary soft decisions is performed. Since the proposed method allows for distributed cyclostationarity spectrum sensing, it is more reliable and faster than non-cooperative traditional multi-cycle cyclostationarity detection schemes. To reduce the computational complexity of the exact distribution of proposed test statistic at fusion centre, the authors derive efficient approximations for the distribution under null and alternative hypotheses. Extensive simulation results in different scenarios demonstrate the advantage of the proposed method and confirm the analytic performance characterisations. In addition, the authors study the impact of mobility of cognitive devices on the cyclostationarity of received signals and verify our analysis via simulation. - Author(s): N. Nguyen-Thanh and I. Koo
- Source: IET Communications, Volume 6, Issue 1, p. 39 –45
- DOI: 10.1049/iet-com.2011.0019
- Type: Article
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To reduce the bandwidth requirement for reporting channel, the application of maximum-distance generalised quantiser for cooperative spectrum sensing (CSS) in cognitive radio is considered. The maximum-distance generalised quantiser, which uses Matsushita distance, is turn out to be a minimum mean square error quantiser of log-likelihood ratio (LLR) under absence hypothesis. Therefore the maximum-Matsushita distance quantiser CSS is achieved by utilising the well-known Lloyd–Max quantisation algorithm without the requirement of the prior probabilities of primary signal at each user. The probability density function of the LLR of the sensing information is also formulated for designing the quantiser. Simulation results reveal that the proposed quantiser with only few quantisation bits can provide the same sensing performance of the LLR test using raw data when primary signal has low signal-to-noise ratio. - Author(s): H. Venkataraman ; A. Chowdhary ; A. Sikora ; G.-M. Muntean
- Source: IET Communications, Volume 6, Issue 1, p. 46 –54
- DOI: 10.1049/iet-com.2010.0864
- Type: Article
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There is an increasing demand by an ever-growing number of mobile customers for transfer of rich media content. This requires very high bandwidth which either cannot be provided by the current cellular systems or puts pressure on the wireless networks, affecting customer service quality. This study introduces COARSE – a novel cluster-based quality-oriented adaptive radio resource allocation scheme, which dynamically and adaptively manages the radio resources in a cluster-based two-hop multi-cellular network, having a frequency reuse of one. COARSE is a cross-layer approach across physical layer, link layer and the application layer. COARSE gathers data delivery-related information from both physical and link layers and uses it to adjust bandwidth resources among the video streaming end-users. Extensive analysis and simulations show that COARSE enables a controlled trade-off between the physical layer data rate per user and the number of users communicating using a given resource. Significantly, COARSE provides 25–75% improvement in the computed user-perceived video quality compared with that obtained from an equivalent single-hop network. - Author(s): J.J. Sánchez-Sánchez ; C. del Castillo-Vázquez ; M.C. Aguayo-Torres ; U. Fernández-Plazaola
- Source: IET Communications, Volume 6, Issue 1, p. 55 –61
- DOI: 10.1049/iet-com.2010.1001
- Type: Article
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Since many years the Gaussian or normal distribution has been a useful tool to model data observations in fields as physics or astronomy. In communication systems, for instance, this distribution is widely used to model thermal noise. However, there exist many natural physical phenomena that exhibit tails decay following a power law that cannot be modelled by the classical Gaussian distribution. In many of these cases, Student's t distributions can be useful for modelling these kind of data because they allow heavy tails which are more realistic. This study provides a brief introduction to those distributions and their convolutions, which are distributed according to the Behrens–Fisher distributions. The goal is to highlight the potential application of non-Gaussian distributions to the analysis of communication systems. With this purpose, the authors present their work applying those distributions to describe the enhanced noise when zero-forcing (ZF) equalisation is used to compensate the effects of a selective fading Rayleigh channel. Obtained results allows the analysis of enhanced noise in three different scenarios: an orthogonal frequency division multiplexing (OFDM) transmission, an OFDM-based relay network and a single carrier frequency division multiple access (SC-FDMA) transmission. - Author(s): C. Li ; X. Wang ; L. Yang ; W.-P. Zhu
- Source: IET Communications, Volume 6, Issue 1, p. 62 –68
- DOI: 10.1049/iet-com.2010.0844
- Type: Article
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A joint source-and-relay beamforming scheme is proposed for multiple-input multiple-output (MIMO) systems with distributed single-antenna relays. First, a lower-bound of the signal-to-noise ratio at the destination is derived as an objective function to formulate a constrained beamforming optimisation problem. The joint beamforming problem is then divided into two sub-optimisation problems corresponding to the source and the relay beamforming, respectively. The first sub-problem is shown to be a quadratic concave minimisation, and is tackled by developing an iterative algorithm with each iteration solving a linear problem. The second one corresponds to a Rayleigh–Ritz ratio problem which is then solved by the generalised singular-value decomposition in a closed form. Based on the solutions to the subproblems, a global iterative algorithm is designed to implement the joint source-and-relay beamforming. Simulation results show that the proposed method outperforms some existing relaying schemes in terms of the capacity and outage probability of the whole MIMO relay system. - Author(s): C.-M. Yu
- Source: IET Communications, Volume 6, Issue 1, p. 69 –75
- DOI: 10.1049/iet-com.2010.0659
- Type: Article
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Blueweb is a self-organising Bluetooth-based multihop network equipped with a scatternet formation algorithm and a hybrid routing protocol. The hybrid routing protocol combines the reactive method globally and the proactive method locally to discover the optimal path for packet transmission. This protocol can be configured for a particular network through adjustment of a single parameter, the number of routing tier. A global configured method is proposed by the authors to determine the desired configuration for Blueweb routing protocol. The global configured method is used in the route master and designs three blocks, including the traffic generator, the query packet estimator and the global tier decision blocks. The traffic generator block uses a uniform end-to-end traffic model in each master to generate the query packets for various N-tiers. The query packet estimator block measures the local and global query packets to compute the local query probability. The global tier decision block uses the parameter of local query probability to determine the proper number of routing tier. Computer simulation results show that this method can efficiently improve the routing performance and make the routing tiers configurable for a Blueweb routing protocol. - Author(s): P. Venkata Krishna ; V. Saritha ; G. Vedha ; A. Bhiwal ; A.S. Chawla
- Source: IET Communications, Volume 6, Issue 1, p. 76 –83
- DOI: 10.1049/iet-com.2010.0763
- Type: Article
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Mobile ad hoc networks (MANETs) are dynamically changing and self-configuring networks. Owing to their widespread use for many applications, multipath routing in MANETs has been widely discussed for providing fault-tolerance routing, quality-of-service (QoS) and various other purposes. The authors propose a quality of service enabled ant colony-based multipath routing (QAMR) algorithm based on the foraging behaviour of ant colony for selecting path and transmitting data. In this approach, the path is selected based on the stability of the nodes and the path preference probability. The authors have considered bandwidth, delay and hop count as the QoS parameters along with the stability of node, number of hops and path preference probability factors. Simulations performed with network simulator 2 shows that the proposed algorithm is scalable and performs better at higher traffic load compared to the existing algorithms. - Author(s): Z.-M. Liu ; Z.-T. Huang ; Y.-Y. Zhou
- Source: IET Communications, Volume 6, Issue 1, p. 84 –89
- DOI: 10.1049/iet-com.2010.0678
- Type: Article
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Most of previous blind parameter estimation methods of frequency hopping (FH) signals with a single channel do not adapt to overlapped signals, whereas the multi-channel-based ones are computationally much too expensive. Moreover, all the single- and multiple-channel-based methods use batch processing techniques, and they are not able to give real-time estimates of the hopping frequencies. This study establishes a temporal autoregressive moving average (ARMA) model of the temporally overlapped FH signals, which is then used to detect the frequency hops once they happen, and track the hopping frequencies online. Numerical examples are carried out to demonstrate the effectiveness of the proposed method. - Author(s): B.S. Tan ; K.H. Li ; K.C. Teh
- Source: IET Communications, Volume 6, Issue 1, p. 90 –96
- DOI: 10.1049/iet-com.2011.0271
- Type: Article
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Bit-error rate (BER) expressions of generalised selection combining with low-density parity-check (LDPC) codes, using binary phase-shift keying signals, over an independent and identically distributed Rayleigh-fading channel are derived using the Gaussian approximation (GA) approach. BER results for both selection combining and maximum-ratio combining can be computed from this BER expression as special cases. The symmetry and stability conditions of both density evolution (DE) and GA analysis are also studied. The degree distribution for irregular LDPC codes is optimised using differential evolution. The theoretical results are compared with both simulation results and DE thresholds. These BER expressions allow us to achieve a significant reduction in computational complexity for analysing the system performance as compared to simulation and DE. - Author(s): Z. Chen ; T. Luan ; X.-D. Zhang
- Source: IET Communications, Volume 6, Issue 1, p. 97 –106
- DOI: 10.1049/iet-com.2010.1038
- Type: Article
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The detection of orthogonal frequency division multiplexing (OFDM) for cognitive radio is considered in this paper. A frequency-selective fading channel is considered and the receiving process is modeled with timing and frequency offsets. Firstly, the authors propose a new decision statistic based on time-domain cross-correlation of the cyclic prefix (CP) embedded in OFDM signals. The probability distribution functions (PDFs) of the statistics under both hypotheses of primary signal absence and presence are derived. Estimation of the timing and frequency offset is obtained through the maximum likelihood method and the received signals are modified. Then another new decision statistic based on frequency-domain cross-correlation of the pilot tones (PTs) is proposed whose PDF is also analyzed. Then, through the likelihood ratio test, the authors utilize CP and PT jointly and propose a global test statistic. The theoretical probabilities of false alarm (PFA) and detection are derived, and the theoretical threshold for any given PFA is proposed. The simulation results show that the proposed spectrum-sensing scheme has excellent performance, especially under very low signal-to-noise ratio (SNR). - Author(s): Y. Li ; C. Wang ; X. You ; H.-H. Chen ; W. She
- Source: IET Communications, Volume 6, Issue 1, p. 107 –115
- DOI: 10.1049/iet-com.2010.1031
- Type: Article
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IEEE 802.16 can provide wireless broadband access with its support to both single-hop and multi-hop mesh modes. It defines several traffic/service categories and offers differentiated quality of service assurance through scheduling algorithms. However, it is not quite clear how well an IEEE 802.16 network could support real-time services such as video streaming and voice over Internet protocol services, especially in its mesh-mode operation. This study aims to analyse delay and throughput properties of an IEEE 802.16 mesh network for evaluating the performance of various real-time applications. The authors establish an analytical model to calculate delay and throughput of IEEE 802.16 distributed scheduling schemes. The proposed model helps to investigate how delay and throughput vary in terms of network parameters in order to optimise the system design via proper parameter configuration. Extensive simulations have been conducted to demonstrate the accuracy of the model. - Author(s): W. Feng ; L. Zhang ; J.M.H. Elmirghani
- Source: IET Communications, Volume 6, Issue 1, p. 116 –124
- DOI: 10.1049/iet-com.2011.0275
- Type: Article
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Geographic routing (GR) algorithms are attractive in ad hoc wireless networks owing to their efficiency, scalability, and in particular energy efficiency. In a two-dimensional ad hoc wireless network, the authors propose the optimal range forward (ORF) algorithm, which is based on the optimal transmission range to reduce the energy consumption of the network. Furthermore, the energy balance of each node based on the ORF algorithm is considered, and an optimal forward with energy balance (OFEB) algorithm is proposed to balance the residual energy of each node and to prolong the network lifetime. The authors compare the proposed algorithms with the existing GR algorithms, such as the most forward within radius and the nearest forward progress algorithms. The network lifetime, the network throughput, the number of packets successfully received by the destination and the average energy cost of each successfully received packet, resulting from all the algorithms mentioned above, are compared based on different node densities. It is shown that the performance of the OFEB algorithm is significantly better than the others.
Optimisation of throughput in cognitive radio networks: an analysis at the data link layer
Video streaming transmission: performance modelling over wireless local area networks under saturation condition
Ergodic capacity analysis and asymptotic tightness for multi-element antenna array with spatial correlation and transmit water-filling
Cyclostationarity-based soft cooperative spectrum sensing for cognitive radio networks
Application of maximum-distance generalised quantiser for cooperative spectrum sensing in cognitive radio
COARSE: a cluster-based quality-oriented adaptive radio resource allocation scheme
Application of Student's t and Behrens–Fisher distributions to the analysis of enhanced noise after zero-forcing frequency domain equalisation
Joint source-and-relay beamforming for multiple-input multiple-output systems with single-antenna distributed relays
Global configured method for Blueweb routing protocol
Quality-of-service-enabled ant colony-based multipath routing for mobile ad hoc networks
Hopping instants detection and frequency tracking of frequency hopping signals with single or multiple channels
Bit-error rate analysis of low-density parity-check codes with generalised selection combining over a Rayleigh-fading channel using Gaussian approximation
Sensing orthogonal frequency division multiplexing systems for cognitive radio with cyclic prefix and pilot tones
Delay and throughput performance of IEEE 802.16 WiMax mesh networks
Energy saving geographic routing in ad hoc wireless networks
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