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Communications, IET

Issue 13 • Date Sept. 5 2012

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Displaying Results 1 - 25 of 30
  • Multiple-access channel with correlated states and cooperating encoders

    Page(s): 1857 - 1867
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (316 KB)  

    In this study, a two-user discrete memoryless multiple-access channel with two correlated states known non-causally at the corresponding encoder is considered. Each encoder transmits a message independent of the other encoder's and tries to cooperate with it. To consider cooperative encoders, it is assumed that each encoder strictly-causally receives and finds out the other encoder's transmitted signals and tries to cooperate with the other encoder by transmitting its message. A special case is also studied in which the common part of the states is known at the both encoders, resulting in a larger rate region. For these two scenarios, achievable rate regions are derived using a combination of block-Markov and Gel'fand-Pinsker coding techniques, and outer bounds are also established. For the second scenario, the achievable rate region of the Gaussian model is derived, and some implications of the results are discussed. View full abstract»

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  • Symbol-based iterative decoding of convolutionally encoded multiple descriptions

    Page(s): 1868 - 1875
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (418 KB)  

    Transmission of convolutionally encoded multiple descriptions over noisy channels can benefit from the use of iterative source-channel decoding. The authors first modified the BCJR algorithm in a way that symbol a posteriori probabilities can be derived and used as extrinsic information to improve the iterative decoding between the source and channel decoders. The authors also formulate a recursive implementation for the source decoder that processes reliability information received on different channels and combines them with inter-description correlation to estimate the transmitted quantiser index. Simulation results are presented for two-channel scalar quantisation of Gauss-Markov sources which demonstrate the error-resilience capabilities of symbol-based iterative decoding. View full abstract»

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  • Analysis of cognitive radio scenes based on non-cooperative game theoretical modelling

    Page(s): 1876 - 1883
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    A non-cooperative game theoretical approach for analysing opportunistic spectrum access (OSA) in cognitive radio (CR) environments is proposed. New concepts from evolutionary game theory are applied to spectrum access analysis in order to extract rules of behaviour for an emerging environment. In order to assess OSA scenarios of CRs, two oligopoly game models are reformulated in terms of resource access: Cournot and Stackelberg games. Five CR scenes are analysed: simultaneous access of unlicensed users ('commons regime') with symmetric and asymmetric costs, with and without bandwidth constraints and sequential access ('licensed against unlicensed'). Several equilibrium concepts are studied as game solutions: Nash, Pareto and the joint Nash-Pareto equilibrium. The latter captures a game situation where players are nonhomogeneous users, exhibiting different types of rationality - Nash and Pareto. This enables a more realistic modelling of interactions on a CR scene. An evolutionary game equilibrium detection method is used. The Nash equilibrium indicates the maximum number of channels a CR may access without decreasing its payoff. The Pareto equilibrium describes a larger range of payoffs, capturing unbalanced as well as equitable solutions. The analysis of the Stackelberg modelling shows that payoffs are maximised for all users if the incumbents are Nash oriented and the new entrants are Pareto driven. View full abstract»

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  • Adaptive energy detection for spectrum sensing in unknown white Gaussian noise

    Page(s): 1884 - 1889
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (366 KB)  

    Most previous works on energy detection for spectrum sensing have assumed that the noise power in the licensed band is constant over time and known a priori. However, it is widely known that this assumption does not hold in practice. In order to deal with this issue, the author has presented an adaptive energy detection strategy which adjusts its detection threshold according to the noise power estimation and analysed its sensing performance for the case of employing a single receive antenna at the secondary user terminals. The author extend this work to the case of multiple receive antennas. Analytical results show that the proposed scheme can maintain a target false alarm rate irrespective of the noise power level. Also, they demonstrate that it can achieve a closer approximation of the performance of the energy detector with an ideal detection threshold by increasing the number of the receive antennas and/or the time bandwidth product of the noise waveform used to estimate the noise power. View full abstract»

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  • Soft-output decision feedback equalisation for orthogonal frequency division multiplexing over doubly selective channels

    Page(s): 1890 - 1897
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (455 KB)  

    The author proposed soft decision feedback equalisation for orthogonal frequency division multiplexing (OFDM) transmission over doubly selective channels which is used for turbo equalisation. The doubly selective channel is approximated using the basis expansion model (BEM). The decision feedback equaliser (DFE) is obtained and updated for every sub-carrier which results in a per-tone DFE. On the basis of the Gaussian approximation, expressions for the a priori, the a posteriori and the extrinsic information have been derived for quadrature phase shift keying (QPSK) modulation. For turbo equalisation, where iterative joint channel equalisation and channel decoding is executed, in the first iteration, estimates are based on the feed-forward filter which are fed to the channel decoder. These estimates are not reliable and may incur error propagation and poor turbo equalisation performance. For more reliable estimates in the first iteration, the DFE is initialised as a linear minimum mean square error (LMMSE) equaliser. The per-tone LMMSE soft-output equaliser is also derived, and expressions for the a priori, a posteriori and extrinsic information are obtained viewing the LMMSE equaliser as a special case of the DFE. The extrinsic information in both cases was derived based on the Gaussian approximation. Numerical results for bit-error rate performance assuming the BEM channel model and Jakes' channel model are shown to confirm our findings. View full abstract»

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  • Outage probability over composite η - μ fading-shadowing radio channels

    Page(s): 1898 - 1902
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (217 KB)  

    The authors analyse the outage probability over compound η - μ - fading-log-normal shadowing radio channels. The gamma distribution is used as a substitute to the log-normal shadowing model, and new finite-integral expressions for the probability density and cumulative distribution functions of the composite η - μ - gamma distribution. Approximate estimates obtained by reducing the considered problem to that over generalised K-fading are also presented. View full abstract»

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  • Performance analysis of a suboptimum fast frequencyhopped/M-ary frequency-shift-keying maximumlikelihood receiver over Rician-fading channels with composite effects of partial-band noise jamming and multitone jamming

    Page(s): 1903 - 1911
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (526 KB)  

    Bit-error rate (BER) expressions of a suboptimum maximum-likelihood (ML) receiver with the composite effect of partial-band noise jamming and multitone jamming are derived for fast frequency-hopped systems employing M-ary frequency-shift-keying modulation over Rician-fading channels. These BER expressions can be used to study the system performance under Rayleigh fading as a special case. Owing to the fact that the computation of the logarithm of the modified Bessel function is non-linear in nature, one of the existing approximations is required to derive the BER expressions for the analysed system. A suboptimum ML receiver structure is therefore proposed and analysed. The analytical results are compared with simulation results. Under various jamming and fading conditions, the proposed suboptimum ML receiver is found to be able to suppress interference effectively. View full abstract»

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  • Scheduling performance enhancement by network coding in wireless mesh networks

    Page(s): 1912 - 1919
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (471 KB)  

    When a wireless mesh network accommodates interactive applications with quality of service requirements, schedulebased protocols are more suitable than contention-based protocols. In this paper, the problem of determining an appropriate schedule assignment for multiple group transmissions within a spatial time division multiple access link scheduling network is referred to as an integrated multiple-group communication and link scheduling problem. A polynomial-time scheduling algorithm, designated as a source-parallel-aware assignment (SPAA), is proposed to increase the spatial utilisation within each time slot in order to enhance the network throughput. Furthermore, an advanced version of SPAA, designated as joint sourceparallel- aware assignment with network coding (JSANC), is proposed to reduce the effects of bottleneck paths on the schedule frame length by flexibly applying conventional or opportunistic network coding approaches. Simulation results show that the proposed algorithms achieve a better network throughput than existing flow-based or particular order-based scheduling schemes. View full abstract»

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  • Statistical interference modelling and deployment issues for cognitive radio systems in shadow fading environments

    Page(s): 1920 - 1929
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (605 KB)  

    The authors deal with the issues of statistical modelling of the aggregate interference because of cognitive radios (CRs) at primary users and the deployment of CR systems in real world environments. The authors explore the possibilities of modelling the interference by two- and three-parameter log-normal distributions. The authors find that the traditional approach of using a two-parameter log normal is not a suitable option on account of the massive skewness difference between the actual interference and the log-normal variable used for fitting purposes. Similarly, the authors observe that the recently proposed three-parameter log-normal approximation works only under specific scenarios. While probing these issues, the authors also arrive at a considerably simpler way of deriving the cumulants of the total interference. Owing to analytical difficulties, the authors resort to simulations to assess different CR deployment schemes. Based on CRs equipped with a priori knowledge of the radio environment map (REM), the authors compare various CR system design parameters achieved by the proposed techniques. Furthermore, the authors describe the effect of imperfections in the REM information on the performance of CR systems. Via analysis and simulations the authors explore the relationship between the required precision of the REM and various system properties. View full abstract»

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  • Joint iterative power allocation and linear interference suppression algorithms for cooperative DS-CDMA networks

    Page(s): 1930 - 1942
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (676 KB)  

    This work presents joint iterative power allocation and interference suppression algorithms for spread spectrum networks, which employ multiple hops and the amplify-and-forward cooperation strategy for both the uplink and the downlink. The authors propose a joint constrained optimisation framework that considers the allocation of power levels across the relays subject to individual and global power constraints and the design of linear receivers for interference suppression. The authors derive constrained linear minimum mean-squared error (MMSE) expressions for the parameter vectors that determine the optimal power levels across the relays and the linear receivers. In order to solve the proposed optimisation problems, the authors develop cost-effective algorithms for adaptive joint power allocation, and estimation of the parameters of the receiver and the channels. An analysis of the optimisation problem is carried out and shows that the problem can have its convexity enforced by an appropriate choice of the power constraint parameter, which allows the algorithms to avoid problems with local minima. A study of the complexity and the requirements for feedback channels of the proposed algorithms is also included for completeness. Simulation results show that the proposed algorithms obtain significant gains in performance and capacity over existing non-cooperative and cooperative schemes. View full abstract»

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  • Green heterogeneous networks: a cognitive radio idea

    Page(s): 1952 - 1959
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (423 KB)  

    From an energy-saving perspective, the authors investigate the downlink power control issue of the two-tier heterogeneous networks (HetNets) using a cognitive radio train of thought. The authors consider the HetNets scenario of one macro-cell evolved-NodeB (eNB) and multiple femto-cell Home evolved NodeBs (HeNBs) cooperatively coexisting to provide better services. A specific HeNB allows macro-mobile station (macro-MS) previously associated with eNB to access to it for better signal-to-interference plus noise ratio (SINR) guarantee. As a reward, the macro-MS pays a certain of revenue to HeNB as the incentive mechanism for this HeNB's downlink extra power consumption, which is manifested in the design of the price function. The throughput bound of Macro-MSs in HeNB cell is given. Then, the authors select the SINR as the performance measure and formulate the power control of selected HeNBs as multi-constrained optimisation problem. Meanwhile, the authors derive the sub-optimal and closed-form power control of individual HeNB, based on which the authors design the distributed algorithm with the aid of eNB and HeNBs cooperatively to implement the pricing information exchange. Simulation results show the improved performance of the convergence, the energy-efficiency measured by 'energyper- bit' and the throughput of the 'Proposed-Cognitive-x' power control algorithm. View full abstract»

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  • Noise-robust feedforward synchronisation for resource-constrained Gaussian minimum shift keying system in wireless body area network

    Page(s): 1960 - 1968
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (401 KB)  

    As Gaussian minimum shift keying (GMSK) modulation scheme is adopted for wireless body area network (WBAN) applications, simple and noise-robust synchronisation algorithms for GMSK are desired to meet the limited resources of power, storage and size in WBAN. However, the current synchronisation algorithms for GMSK are either too complicated or have unsatisfactory performance for low signal-to-noise ratio (SNR), especially for coded GMSK systems. The authors will propose the synchronisation algorithms for general GMSK systems with three unknown synchronisation parameters, namely, timing, frequency and phase offsets estimation. By incorporating noise/interference-reduction methods, the authors propose low-complexity synchronisation algorithms for GMSK that can achieve satisfactory performance in low SNR region. Furthermore, their new feedforward timing and frequency recovery algorithms can provide much better performance than those in the literature by using reliability-measuring mechanism for timing estimation and two-phase frequency estimation. The data-aided Cramer-Rao bounds (CRBs) for the joint estimation of GMSK synchronisation parameters are also derived. The numerical results show that the performance of their proposed synchronisation algorithms is close to the CRBs. The overall bit error rate performance for both uncoded and Bose-Chaudhuri-Hocquenhem BCH-coded GMSK systems are examined. The performance loss owing to synchronisation errors can be reduced to about 1 dB with their proposed algorithms. View full abstract»

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  • Hierarchical virtual network mapping algorithm for large-scale network virtualisation

    Page(s): 1969 - 1978
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (636 KB)  

    Virtual network(VN) mapping deals with the allocation of network resources from the shared physical substrate to individual VNs is one of the key challenges for the application of realising network virtualisation. Whereas a variety of state-of-the-art algorithms have attempted to address this issue from different aspects, the challenge still remains for mapping VNs across multiple network domains which only maintain partial information of the overall substrate network. A novel hierarchical algorithm to address this issue by formulating such VN mapping problem as a hierarchical linear programme model has been presented. Through the use of the primal decomposition and subgradient optimisation technique, in conjunction with the proposed hierarchical algorithm, the substrate network resource can be appropriately allocated to the VN instances with enhanced scalability, because of the parallelism in individual domains. In addition, the algorithm could find the best trade-off between the number of optimisation iterations (computation time) and cost by selecting an appropriate number of iterations. The proposed method has been assessed through a collection of numerical simulation experiments for a range of network scenarios and the result shows that nearly optimal performance as well as improved VN mapping request acceptance ratio and revenue can be achieved. View full abstract»

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  • Cubic convolution interpolation function with variable coefficients and its application to channel estimation for IEEE 802.16 initial downlink

    Page(s): 1979 - 1987
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (606 KB)  

    In this study, the authors propose to use the cubic convolution interpolation function with a free variable to generate a class of constant-coefficient interpolation functions. The interpolations functions can be applied to an orthogonal frequencydivision multiplexing-based receiver for channel estimation. For a given channel, different interpolation functions from the class have different bit error rates (BERs). Therefore by using a search algorithm, a better interpolation function is chosen with the aid of a performance indicator, such as the estimated mean-squared error (EMSE). Although the uneven distribution of pilots in the IEEE 802.16e system prohibits direct utilisation of the cubic interpolation function, a simple approach has been proposed to solve this problem. The proposed method is validated in the IEEE 802.16e downlink system by Monte Carlo simulation. The simulation results also confirm that channels with different statistical properties should use different interpolation functions. In addition to the Monte Carlo simulation, we also analyse the BER of the proposed approach. We find that the BERs based on the analytical evaluation and on the simulation closely match each other. Finally, it is shown that the EMSE is an acceptable performance indicator for medium-to-high signal-to-noise ratio. View full abstract»

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  • Performance of cooperative spectrum sensing over fading channels with low signal-to-noise ratio

    Page(s): 1988 - 1999
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (908 KB)  

    Transmission error because of fading in the cognitive radio-fusion centre (CR-FC) links can severely degrade the performance of cooperative spectrum sensing. In this study, the upper and lower bounds of the overall false alarm probability and overall detection probability are derived as functions of the bit-error probabilities (BERs) of the CR-FC links. Based on these bounds, the constraints that the BERs of the CR-FC links should satisfy are addressed given the target overall false alarm probability or overall detection probability. Furthermore, channel coding schemes and cooperative schemes that provide reliable transmissions in the CR-FC links are studied. Particularly, inspired by the cluster-based cooperative spectrum sensing, a multiuser cooperative scheme is proposed. Finally, the relationship between the overall detection probability and the overall false alarm probability is investigated when the SNR of the primary user signal at each CR node is small. View full abstract»

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  • Optimal rate irregular low-density parity-check codes in binary erasure channel

    Page(s): 2000 - 2006
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (233 KB)  

    In this study the authors design the optimal rate capacity approaching irregular low-density parity-check code ensemble over binary erasure channel, by using practical semi-definite programming approach. The method does not use any relaxation or any approximate solution unlike previous works. The simulation results include two parts. First, we present some codes and their degree distribution functions that their rates are close to the capacity. Second, the maximum achievable rate behaviour of codes in our method is illustrated through some figures. View full abstract»

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  • Bandwidth mapping model for IEEE 802.11 DCF in unsaturated condition

    Page(s): 2007 - 2015
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (536 KB)  

    In multi-hop ad hoc networks, sources may pump more traffic into the networks than that can be supported, resulting in high end-to-end delay and packet-loss rate. Controlling the offered load at the sources can eliminate this problem. To conduct traffic control, the throughput of the network is necessary. In addition, the authors propose a concept of bandwidth mapping to analyse how much traffic in application can be injected to make the network supporting the maximum throughput. A multi-dimensional Markov model is built to analyse the performance of IEEE 802.11 DCF in unsaturated condition, in which M/G/1/K queuing model is used to analyse the service condition of the packet queue inside the node. The effects of carrier sensing property, hidden-node problem and signal capture property are considered together to analyse the contention experienced by the nodes in the network. Furthermore, the bandwidth mapping situation of voice and video traffic is analysed in string topology of a multi-hop ad hoc network. This analysis can provide a theoretical guide for the traffic admission control. View full abstract»

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  • Adaptive synchronisation of diffusionless Lorenz systems and secure communication of digital signals by parameter modulation

    Page(s): 2016 - 2026
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1123 KB)  

    Diffusionless Lorenz system of equations is a simplified one-parameter version of the Lorenz system of equations. This system is used here as transmitter and receiver for secure communication. An adaptive control procedure is presented, which causes a rapid convergence of the receiver parameter to the transmitter parameter. This convergence can be used for secure communication of digital signals by parameter modulation. Compared with the Lorenz system, the diffusionless Lorenz system leads to faster communication, smoother parameter adaptation and enhanced security. The proposed scheme is robust with respect to relatively large differences in the delay times for the transmission of three chaotic variables from the master to the slave system. The scheme can be scaled up to allow simultaneous transmission of several signals. View full abstract»

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  • Channel prediction in non-regenerative multi-antenna relay selection systems

    Page(s): 2027 - 2032
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (324 KB)  

    The use of multiple antennas in two-hop amplify-and-forward relay selection is analysed, where the source, relay and destination are each equipped with multiple receive but single transmit antennas. Since relay switching is based upon feedback information which is delay-limited, channel power prediction is employed to mitigate against the effect of outdated channel state information being used to make switching decisions. During transmission, a source selects a best relay on the basis of predicted signal-to-noise ratio over all available links. A chosen relay then employs maximal ratio combining at its receiver, and applies a variable gain to the received signal before forwarding to the destination. Closed form outage probability and bit error rate solutions are found for arbitrary numbers of relays and receive antennas, and used to explore trade offs between number of relays and number of antennas compared with single antenna alternatives. To assess predictor performance in combatting switching delay, comparison is made to non-predictive systems. View full abstract»

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  • High throughput sequential decoding with state estimation

    Page(s): 2033 - 2039
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (621 KB)  

    Sequential decoding can achieve high throughput convolutional decoding with much lower computational complexity when compared with the Viterbi algorithm (VA) at a relatively high signal-to-noise ratio (SNR). A parallel bidirectional Fano algorithm (BFA) decoding architecture is investigated in this paper. In order to increase the utilisation of the parallel BFA decoders, and thus improve the decoding throughput, a state estimation method is proposed which can effectively partition a long codeword into multiple short sub-codewords. The parallel BFA decoding with state estimation architecture is shown to achieve 30-55% decoding throughput improvement compared with the parallel BFA decoding scheme without state estimation. Compared with the VA, the parallel BFA decoding only requires 3-30% computational complexity of that required by the VA with a similar error rate performance. View full abstract»

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  • Moments-based analysis of dual-hop amplify-and-forward relaying communications systems over generalised fading channels

    Page(s): 2040 - 2047
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (437 KB)  

    The authors present an alternative moments-based approach for the performance analysis of dual-hop relaying communications systems over generalised fading channels. A unified analytical approach for the computation of the nth moment of the harmonic mean of N ⩾ 2 arbitrarily distributed random variables (RVs) is proposed. On the basis of this statistical result, we analyse the outage and the average error rate performance of dual-hop cooperative wireless systems employing amplify-and-forward (AF) relays. Moreover, our newly derived results can be applied to evaluate the average sum rate of AF relaying systems. Extensive numerical and simulation results are presented to substantiate the proposed analysis. View full abstract»

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  • New frequency-hopping sequence sets with optimal average and good maximum Hamming correlations

    Page(s): 2048 - 2053
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (132 KB)  

    In frequency-hopping multiple-access systems, the average Hamming correlation (AHC) among frequency-hopping sequences (FHSs) as well as the maximum Hamming correlation (MHC) is an important performance measure. Moreover, each FHS is required to be balanced for its robustness against jamming or fading environments. In this study, the authors investigate FHS sets with optimal AHC and (near-)optimal MHC, whose FHSs are balanced. The authors first show that any uniformly distributed FHS set has optimal AHC with respect to the Peng-Niu-Tang bound. The authors also present two classes of FHS sets with optimal AHC and (near-)optimal MHC, whose FHSs are (perfectly) balanced. The authors then analyse the AHC of FHS sets constructed by interleaving techniques, and present some new FHS sets with optimal AHC and MHC, whose FHSs are perfectly balanced. View full abstract»

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  • Eigenvalue-based spectrum 'hole' detection for Nakagami-m fading channels with Gaussian and impulse noise

    Page(s): 2054 - 2064
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1008 KB)  

    The detection of spectrum 'holes' is one of the primary tasks of a cognitive radio (CR). Blind detection techniques using eigenvalues have attracted a great amount of interest because of the fact that no a-priori knowledge is needed. The majority of the literature only considers the effect of thermal noise in detector performance; however in practice, man-made noise also exists and degrades detector performance. This motivated one to consider the performance of blind eigenvaluebased spectrum sensing for the dual condition of thermal (Gaussian) and man-made (impulse) noise. In the literature, most of the sensing schemes perform very well for large sample length. This can be achieved either by increasing the sensing duration or by oversampling the signal. The former increases the frequency of missed opportunities, whereas the latter causes samples to become highly correlated thus degrading the detector performance. Hence, the authors are motivated to investigate algorithms that perform well for smaller sample length. Three new eigenvalue-based sensing algorithms are proposed, viz. maximum-eigenvalue-harmonic-mean (ME-HM), maximum-eigenvalue-contra-harmonic-mean-p (ME-CHM-p) and contraharmonic- mean-minimum-eigenvalue (CH-ME). ME-HM outperforms all existing eigenvalue-based sensing schemes including the maximum-eigenvalue-geometric-mean (ME-GM) algorithm previously presented by the authors of this paper, for smaller sample length, low signal-to-noise ratio (SNR) and increased number of cooperative secondary users. The MECHM-p algorithm, which only allows negative values of p, the filter order, performs identically to ME-HM when p = -1. However, for smaller values of p the probability of detection (PD) improves significantly more until p = -5. The CH-ME algorithm also exhibits an improvement in PD but does not outperform ME-GM. In addition, the proposed schemes and MEGM exhibit a significant degree of immunity to impulse noise compared to existing schemes. The analyt- cal and simulation results are presented for the proposed schemes and ME-GM for the Gaussian and impulse noise scenario in the Nakagami-m fading channel. In addition, the algorithms are evaluated for wireless microphone (WM) signals and show improved performance. The ME-CHM-p algorithm performed the best compared with other algorithms, for small and large sample lengths, low SNR, correlated signals and for increased number of cooperating secondary radios, with and without impulse noise. View full abstract»

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  • Single-carrier frequency domain equalisation with hierarchical constellations: an efficient transmission technique for broadcast and multicast systems

    Page(s): 2065 - 2073
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (534 KB)  

    Orthogonal frequency division multiplexing (OFDM) schemes are the choice modulation for broadband wireless broadcast and multicast systems. However, OFDM schemes have important limitations such as high-envelope fluctuation of the transmitted signals and its sensibility to carrier frequency errors. When these limitations prove critical the authors consider single-carrier frequency-domain equalisation (SC-FDE) schemes, that allow much higher power efficiency because of lower envelope fluctuations. The overall performance can be further improved if the conventional linear FDE is replaced by an iterative FDE such as an iterative block decision feedback equaliser (IB-DFE). Conventional IB-DFE are usually designed for a quadrature phase shift keying constellation. However, it is strongly recommended that broadcast and multicast systems employ hierarchical constellations with several classes of bits with different error protection. In this study the authors consider the use of SC-FDE schemes combined with IB-DFE receivers in broadband wireless broadcast and multicast systems. The authors emphasise the advantages of these schemes and the authors present IB-DFE designs suitable for hierarchical constellations with several classes of bits with different error protection. View full abstract»

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