Online ISSN
1751-8636
Print ISSN
1751-8628
IET Communications
Volume 6, Issue 16, 6 November 2012
Volumes & issues:
Volume 6, Issue 16
6 November 2012
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- Author(s): J.D. Vlok and J.C. Olivier
- Source: IET Communications, Volume 6, Issue 16, p. 2513 –2524
- DOI: 10.1049/iet-com.2011.0614
- Type: Article
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A semi-blind method based on principal component analysis and sequence synchronisation is proposed to detect direct sequence spread-spectrum signals in a non-cooperative setting under low signal-to-noise ratio conditions. The intercepted signal is segmented to form a detection matrix from which a feature is extracted through cyclic shifting. Signal detection is then performed using a test statistic based on this feature. The carrier frequency and sequence duration of the signal to be detected are assumed known. Theoretical analysis and a computer simulation study show that the performance of the new detection method is superior to classic energy detection in an additive white Gaussian noise channel. - Author(s): X. Yu ; X. Yin ; S.H. Leung ; Y. Rui
- Source: IET Communications, Volume 6, Issue 16, p. 2525 –2533
- DOI: 10.1049/iet-com.2011.0611
- Type: Article
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In this study, a precoding scheme for minimising bit error rate (BER) subject to a power constraint for space-time-coded multiple-input–multiple-output systems over flat Rayleigh fading channel in the presence of channel estimation error and feedback delay is presented, it includes the precoding with estimation error or feedback delay only as its special cases. With this scheme, an algorithm for attaining the optimal power allocation across multiple beams is developed. It is shown that the Lagrange multiplier for the constrained optimisation does exist and is unique. A practical iterative algorithm based on Newton's method for finding the Lagrange multiplier is proposed. Generally, the optimal power control may result in negative power allocation to some beams. A necessary and sufficient condition for the beams having positive power control is developed that simplifies the optimisation procedure. Simulation results show that the developed precoding scheme can provide BER lower than the equal power allocation scheme and the existing precoding scheme, but has performance degradation when compared with the precoding scheme with estimation error or feedback delay only. - Author(s): A.H. Muqaibel and M.T. Alkhodary
- Source: IET Communications, Volume 6, Issue 16, p. 2534 –2542
- DOI: 10.1049/iet-com.2012.0179
- Type: Article
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Compressive sensing (CS) is proposed by many researchers as a solution to the formidable sampling requirements of promising ultra-wideband (UWB) technology. Previous research was evaluated by simulating the IEEE UWB channel model. This study examines the behaviour of compressive sensing for practical UWB signals and proposes approaches to enhance signal reconstruction performance. Four practical dictionaries are proposed to increase the sparsity of the realistic UWB signals. Those dictionaries account for the practical effects of channel-like pulse dispersion and the unavoidable effects of antenna directivity. Both measured data and a more practical directional model are used for evaluation. It is shown that CS based on the new dictionaries is able to reconstruct the practical UWB signals more efficiently with reasonable complexity. Performance improvement of the proposed practical dictionaries in channel estimation for two different receivers is quantified. - Author(s): M. Dashti ; P. Azmi ; K. Navaie
- Source: IET Communications, Volume 6, Issue 16, p. 2543 –2552
- DOI: 10.1049/iet-com.2011.0822
- Type: Article
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In this article, radio resource allocation in underlay spectrum sharing based on the orthogonal frequency-division multiple access is studied. A cellular-based secondary service is considered in which the licensed spectrum is opportunistically accessed provided that the imposed interference at the primary service receivers because of secondary service transmissions stays below an interference threshold constraint. The main objective here is to maximise the sum capacity of the secondary service and to find the optimal allocated power, subcarrier and rate across all subcarriers and different secondary users. Three different scenarios are considered based on the availability of the channel state information (CSI) between the secondary service base station and primary receivers. The optimal resource allocation for the case of accurate CSI between the secondary base station and the primary receivers is obtained. To manage more practical situations, in the second considered scenario the authors assume that only the channel distribution information information between the secondary base station and the primary receivers is available at the secondary service base station. In the third scenario the authors further propose a novel algorithm, which controls the collision incidences caused by secondary transmissions owing to lack of CSI in secondary base station. Simulation analyses are also conducted in order to investigate the system performance based on the proposed resource allocation algorithms. - Author(s): C. Li
- Source: IET Communications, Volume 6, Issue 16, p. 2553 –2560
- DOI: 10.1049/iet-com.2012.0009
- Type: Article
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The authors consider the worst-case transceiver design problem under spectrum bounded channel uncertainty matrices. Their design aims to minimise the trace and the determinant of the estimate error covariance matrix, respectively. The authors relax the formulated problem into an optimisation problem with bilinear matrix inequality constraints (i.e. BMI problem), from which a local optimal solution is obtained by applying semi-definite programming. Furthermore, the authors consider norm bounded source symbols and extend their approach to design the worst-case transceiver with respect to both channel uncertainties and norm bounded source symbols. - Author(s): B. Patnaik and P.K. Sahu
- Source: IET Communications, Volume 6, Issue 16, p. 2561 –2567
- DOI: 10.1049/iet-com.2012.0044
- Type: Article
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An ultra-high bit-rate inter-satellite optical wireless communication (IsOWC) system is proposed in thisstudy. The system is designed and simulated up to the bit-rate of 400 Gbps. The proposed system is a non-diffused link or line-of-sight setup, which uses coherent optical quadrature phase-shift keying (QPSK) modulation technique. The performance of the system is analysed in terms of Q-factor, bit-error rate, eye opening and so on. The coverage distance observed with an input power level of 30 dBm for a bit-rate of 400, 160 and 100 Gbps are 4767, 7542 and 9532 km, respectively. Finally, the maximum bit-rate that can be communicated, for inter-satellite link at different orbits such as low-Earth orbit, medium-Earth orbit and geostationary Earth orbit are presented. To the best of the authors knowledge for the first time they have proposed a novel QPSK modulation technique for the design of IsOWC system for achieving higher coverage distance and data rate, which was not been addressed in any current or earlier publications. - Author(s): A. Sharma and R.S. Kaler
- Source: IET Communications, Volume 6, Issue 16, p. 2568 –2574
- DOI: 10.1049/iet-com.2011.0569
- Type: Article
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This study presents the design of high-speed inter-building connectivity in medical services by free-space optical (FSO) link with wireless backup, which will operate at gigabit rates. The two buildings in medical campus are ∼500 m apart. The FSO link normally uses 1550 nm wavelength but has a radio frequency (RF) link operating at 2.4 GHz as the back-up. In this, 99.999% availability is achieved by combining the optical laser beam with an alternate path RF solution. The laser beam of 1550 nm provides high-bandwidth connectivity in majority of the time, whereas the RF path maintains critical network connectivity during extreme weather events that are detrimental to the FSO link, such as thick fog. Optical wireless links suffer from atmospheric loss mainly because of fog, scintillation and precipitation. The authors investigate here the impact of fog, rain and snow effects and evaluate their performances for the optical propagation through the atmosphere. The wireless back-up link is used only in very dense fog conditions. Hybrid FSO/RF systems have also been examined as a means to provide high-bandwidth point-to-point links in the access network over larger distances. - Author(s): F. Angarita ; J. Marín-Roig ; V. Almenar ; J. Valls
- Source: IET Communications, Volume 6, Issue 16, p. 2575 –2581
- DOI: 10.1049/iet-com.2011.0542
- Type: Article
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This study proposes a new low-complexity decoding algorithm for low-density parity check codes, which is a variation of the offset min-sum algorithm and achieves a similar performance with lower hardware cost. A finite precision study is presented and the hardware cost of the implementation of three very large scale integration architectures is evaluated. As a conclusion, the proposed algorithm achieves similar performance with an area saving of around 18, 10 and 14% for the memory-based partially parallel, fully parallel and sliced message passing implementations, respectively. - Author(s): J.-W. Lee and Y.-H. Lee
- Source: IET Communications, Volume 6, Issue 16, p. 2582 –2592
- DOI: 10.1049/iet-com.2011.0815
- Type: Article
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In the uplink of orthogonal frequency division multiple access (OFDMA) systems, rate adaptation may not be exploitable mainly because of severe inter-carrier interference (ICI). In this study, the authors propose a novel hybrid link adaptation that simultaneously uses power adaptation for ICI adjustment and rate adaptation for capacity improvement in the uplink of OFDMA systems. The proposed hybrid link adaptation determines a maximum allowable transmission power according to the channel gain and velocity of each user, enabling all users to have a guaranteed loss of carrier to interference ratio (CIR). Moreover, the proposed hybrid link adaptation adjusts the transmission rate according to CIR of each user, while keeping the maximum allowable transmission power unchanged. The performance of the proposed hybrid link adaptation is analysed in OFDMA cellular uplink systems. Finally, the analytic results are verified by computer simulation. - Author(s): Q.-T. Vien ; H.X. Nguyen ; J. Choi ; B.G. Stewart ; H. Tianfield
- Source: IET Communications, Volume 6, Issue 16, p. 2593 –2601
- DOI: 10.1049/iet-com.2011.0681
- Type: Article
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This paper is concerned with block acknowledgement (ACK) mechanisms in wireless regenerative relay networks. In an N-relay network, a total of (2N+1) block ACK packets is required to acknowledge the data transmission between source and destination nodes via the N-relay nodes. In this paper, the authors propose a block ACK scheme based on network coding (NC) to significantly reduce the ACK overheads by N block ACK packets. In addition, this achieves a reduction of N(N–1) computational operators. Particularly, we derive the error probability of the determination of the packets to be retransmitted at the source and relays, which shows that the NC-based scheme also improves the reliability of block ACK transmissions. Furthermore, asymptotic signal-to-noise (SNR) scenarios for forward links are considered and a general expression of error probability in multi-relay networks is derived for each SNR scenario. Finally, simulation results are presented to verify the analytical findings and demonstrate a lower number of data retransmissions for a higher system throughput. - Author(s): E.S. Hassan
- Source: IET Communications, Volume 6, Issue 16, p. 2602 –2612
- DOI: 10.1049/iet-com.2012.0051
- Type: Article
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In this study, a new energy-efficient hybrid opportunistic cooperative (HOC) transmission protocol is proposed for single-carrier frequency division multiple access (SC-FDMA)-based cooperative networks. The author considers a single source–destination pair and multiple relays network. The proposed protocol improves the energy efficiency of SC-FDMA-based networks by selecting the most energy-efficient cooperative transmission protocol from a set of available protocols according to the current channel state information. The protocols considered in the development of the HOC protocol are amplify-and-forward, decode-and-forward, compress-and-forward and estimate-and-forward. Computer simulation is done over four different scenarios of channel conditions. The obtained results show that the proposed HOC protocol significantly improves the delay-limited capacity and minimises the outage probability of SC-FDMA-based cooperative networks. The results also show that the minimum required average total power in the proposed HOC protocol is less than that of opportunistic decode-and-forward by 0.55 dB. - Author(s): J. Wang ; Z. Ma ; Z. Lv ; Y. Sheng ; W. Xiang
- Source: IET Communications, Volume 6, Issue 16, p. 2613 –2620
- DOI: 10.1049/iet-com.2011.0392
- Type: Article
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Unlike conventional cellular networks where the evolved Node B (eNB) performs centralised scheduling, future relay-enhanced cellular (REC) networks allow relay nodes (RNs) to schedule users independently. This decentralised nature of the REC networks brings about challenges to maintain fairness. In this study, we formulate the generalised proportional fair (GPF) resource allocation problem, where resource partition and routing are included as part of the overall radio resource management aiming to provide fairness across all users served by the eNB and its subordinate RNs. Although the traditional proportional fair scheduling algorithm is executed independently at the eNB and each RN to maintain local fairness, we propose efficient resource partition and routing algorithms to maintain global fairness by optimising the GPF objective for the whole relay-enhanced cell. Through system level simulations, the proposed algorithms are evaluated and compared with both non-relaying and relaying systems with benchmark resource partition and routing algorithms. The simulation results show that the proposed algorithms outperform the existing algorithms in providing a better trade-off between system throughput and fairness performance. - Author(s): M.G. Adian and H. Aghaeinia
- Source: IET Communications, Volume 6, Issue 16, p. 2621 –2629
- DOI: 10.1049/iet-com.2011.0489
- Type: Article
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In the cognitive radio (CR) networks consisting of selfish users competing for spectrum resources, the social optimum is usually not achieved at the Nash equilibrium (NE) of the power control game, since selfish users are only interested in their own benefit. In this study with the aim of improving the NE efficiency, the authors extend the pricing concept to a multi-channel multiple-in multiple-out (MIMO) CR scenario and propose two iterative algorithms for power control and channel allocation in such systems. Specially, the authors consider both linear and non-linear pricing methods and derive the optimal pricing factor for both scenarios and prove the existence and uniqueness of the NE. Simulation results prove the outstanding performance of the proposed MIMO cognitive system considering price-based power control over the non-price-based MIMO cognitive systems. - Author(s): N.N. Tran ; H.H. Nguyen ; H.D. Tuan ; D.E. Dodds
- Source: IET Communications, Volume 6, Issue 16, p. 2630 –2638
- DOI: 10.1049/iet-com.2010.0995
- Type: Article
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Optimal training design and channel estimation for spatially correlated multi-user multi-input multi-output with orthogonal frequency-division multiplexing (MIMO-OFDM) systems is still an open research topic of great interest. This study first applies tractable semi-definite programming (SDP) to obtain the optimal training signal for the general case of spatial channel correlations for multi-user MIMO-OFDM. In order to reduce the computational complexity of the SDP-based solution, an approximate solution in closed-form is then presented. For a special case of transmit correlations, an optimal solution in closed-form expression is also derived. Analytical and simulation results demonstrate the excellent performance of the proposed designs and their performance advantage over the existing equi-powered training designs. - Author(s): M. Long ; Y. Chen ; F. Peng
- Source: IET Communications, Volume 6, Issue 16, p. 2639 –2644
- DOI: 10.1049/iet-com.2012.0103
- Type: Article
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The bit error rate (BER) performance of chaos shift keying is improved for an additive white Gaussian noise channel by applying a trimming operation to the Chebyshev polynomial function of order 2 and the piecewise linear map to make the input source more Gaussian distributed. Analytical expressions for the improved BER are also derived based on the curve-fitting approximation. Numerical results show that the proposed method can achieve performance gains of up to 3.5 dB in signal-to-noise ratio over the conventional method without trimming. - Author(s): M.-H. Ho ; C.-C. Chiu ; S.-H. Liao
- Source: IET Communications, Volume 6, Issue 16, p. 2645 –2653
- DOI: 10.1049/iet-com.2011.0558
- Type: Article
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In this study, the channel capacity of indoor multiple-input multiple-output ultra-wide band (MIMO-UWB) transmission for a smart antenna is described. A particle swarm optimiser (PSO) is used to synthesise the radiation pattern of the directional circular arc array to maximise the capacity performance in an indoor MIMO-UWB communication system. The UWB impulse responses of the indoor channel for any transmitter–receiver location are computed by applying shooting and bouncing ray/image techniques, inverse fast Fourier transform and Hermitian processing. By using the calculated frequency response, the capacity performance of the synthesised antenna pattern on an MIMO-UWB system can be computed. Based on the topography of the circular antenna array and the capacity formula, the array pattern synthesis problem can be reformulated into an optimisation problem and solved by the PSO algorithm. PSO optimisation is applied to a high-order non-linear optimisation problem. The novelties of our approach are not only choosing capacity as the cost function instead of the sidelobe level of the antenna pattern, but also considering the antenna feed length effect of each array element. The cost function for the problem is non-smooth and discontinuous with respect to the antenna pattern. It is difficult to solve by gradient methods, since the derivative is hard to derive. The strong point of the PSO algorithm is that it can find out the solution even if the performance index cannot be formulated by simple equations. The simulation results show that the synthesised antenna array pattern is effective to focus maximum gain on the line-of-sight path which scales as the number of array elements. - Author(s): S.-H. Fang ; J.-Y. Chen ; M.-D. Shieh ; J.-S. Lin
- Source: IET Communications, Volume 6, Issue 16, p. 2654 –2660
- DOI: 10.1049/iet-com.2011.0946
- Type: Article
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Subspace algorithms are commonly used for blind channel estimation in orthogonal frequency-division multiplexing (OFDM) systems as they can establish the relation between the channel impulse response and singular vectors of the noise subspace. However, they are not workable under the conventional cyclic prefix-free OFDM signal model as the corresponding necessary condition of subspace algorithms is not satisfied. To solve this problem, this study proposes two subspace-based blind channel estimation approaches using the real and periodic symbols of time-domain transmitted OFDM blocks. From the simulation results, we can obtain the proposed approaches outperform conventional ones in terms of normalised mean-squared error and bit error rate under time-invariant channel environments. - Author(s): Y.-Y. Cheng ; Y. Lee ; H.-J. Li
- Source: IET Communications, Volume 6, Issue 16, p. 2661 –2670
- DOI: 10.1049/iet-com.2011.0567
- Type: Article
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In this study, a semi-blind channel estimation algorithm for uplink multiuser orthogonal frequency division multiplexing with receiver diversity is proposed. The proposed algorithm combines simple multiuser channel estimates obtained from pilot subcarriers with subspace-based channel estimates to obtain accurate estimates for the multiuser channel gains. Minimum mean square error linear diversity combining is then performed based on the estimated channel. Simulation results show that a performance gain in excess of 1–2 dB is achievable by the proposed approach. - Author(s): I.S. Amiri ; R. Ahsan ; A. Shahidinejad ; J. Ali ; P.P. Yupapin
- Source: IET Communications, Volume 6, Issue 16, p. 2671 –2675
- DOI: 10.1049/iet-com.2011.0773
- Type: Article
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This study investigates the non-linear behaviours of light known as bifurcation and chaos during the propagation of light inside a non-linear silicon microring resonator (SMRR). The aim of the research is to use the non-linear behaviour of light to control the bifurcation and chaos of SMRR, which are used in engineering, biological and security systems. Bifurcation and chaos control deals with the modification of bifurcation characteristics of a parameterised non-linear system by a designed control input. The parameters of the SMRR cause bifurcation to happen in smaller round-trips among the total round-trip of 20 000 or input power. Effective parameters such as the refractive indices of a silicon waveguide, coupling coefficients (κ) and the radius of the ring (R) can be selected properly to control the non-linear behaviour. Simulated results show that rising non-linear refractive indices, coupling coefficients and radii of the SMRR lead to descending input power and round-trips when bifurcation occurs. Therefore bifurcation behaviour can be seen at a lower input power of 44 W, where the non-linear refractive index is n2=3.2×10−20 m2/W. The smallest round-trips of 4770 and 5720 can be seen for the R=40 µm and κ=0.1, respectively. - Author(s): H. Sakran ; M. Shokair ; O. Nasr ; S. El-Rabaie ; A.A. El-Azm
- Source: IET Communications, Volume 6, Issue 16, p. 2676 –2687
- DOI: 10.1049/iet-com.2011.0638
- Type: Article
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In this study, the physical layer security for cognitive radio network (CRN) will be investigated in which a secondary user transmitter (SU-Tx) sends confidential information to a SU receiver (SU-Rx) on the same frequency band of a primary user (PU) in the presence of an eavesdropper receiver. Moreover, relay selection scheme is proposed for the security constrained CRNs with single eavesdropper, multiple eavesdroppers and PUs. The proposed scheme selects a trusted decode and forward relay to assist the SU-Tx and maximise the achievable secrecy rate that is subjected to the interference power constraints at the PUs for the different number of eavesdroppers and PUs under available channel knowledge. The SU cooperates with relays only when a high secrecy rate is achieved. Secrecy rate and secrecy outage probability are the two performance metrics that are used to verify the effectiveness of the proposed scheme although asymptotic approximations of the secrecy outage probability are also derived. Simulation and analytical results demonstrate that the performance improvement of the proposed scheme reaches to the double relative to the conventional scheme for the secrecy capacity. - Author(s): J. Tsai and C.-C. Chang
- Source: IET Communications, Volume 6, Issue 16, p. 2688 –2694
- DOI: 10.1049/iet-com.2011.0383
- Type: Article
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For self-organised networks, neither the identity nor the number of processes is known to all participants at the beginning of the computation because no central authority exists to support such context information. Hence, achieving consensus in such networks cannot be accomplished in the ways for traditional fixed networks. In the literature, the consensus problem has been studied in a new computational model corresponding to self-organised networks. Such a variant of the traditional consensus problem is called ‘consensus with unknown participants’ (CUP). Particularly, the CUP problem relaxes the requirement for the original knowledge owned by every process about participants in the computation. Moreover, the aforementioned work considers asynchronous networks without process crashes, and has determined the necessary and sufficient knowledge connectivity condition for solving the CUP problem, which is called ‘one sink reducibility’ (OSR). In this study, we investigate the possibility of finding a less restrictive knowledge connectivity condition than OSR, based on which, consensus can still be achieved in self-organised networks. We demonstrate that with some certain global information inherently required for solving the CUP problem, such a possibility really exists. - Author(s): J. Du ; P. Xiao ; J. Wu ; Q. Chen
- Source: IET Communications, Volume 6, Issue 16, p. 2695 –2704
- DOI: 10.1049/iet-com.2012.0029
- Type: Article
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Orthogonal frequency division multiplexing (OFDM) technique has gained increasing popularity in both wired and wireless communication systems. However, in the conventional OFDM systems the insertion of a cyclic prefix (CP) and the transmission of periodic training sequences for purpose of channel estimation decrease the system's spectral efficiency. As an alternative to OFDM, isotropic orthogonal transform algorithm (IOTA)-based multicarrier system adopts a proper pulse shaping with good time and frequency localisation properties to avoid interference and maintain orthogonality in real field among sub-carriers without the use of CP. In this study, the authors propose linearly precoded IOTA-based multicarrier systems to achieve blind channel estimation by utilising the structure of auto-correlation and cross-correlation matrices introduced by precoding. The results show that the proposed IOTA-based multicarrier systems achieve better power and spectral efficiency compared with the conventional OFDM systems. - Author(s): H. Liang
- Source: IET Communications, Volume 6, Issue 16, p. 2705 –2714
- DOI: 10.1049/iet-com.2011.0886
- Type: Article
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Orthogonal frequency-division multiplexing (OFDM) has been recommended as the standard for numerous wireless transmission systems. However, OFDM still has deficiencies that must be improved, such as a high peak-to-average power ratio (PAPR) occurring in the transmission signal. A constellation extended scheme (CES) is one technology for reducing high PAPR. The PAPR performance of the CES is directly correlated to the amount of candidate signals, high PAPR in OFDM systems will be significantly reduced as the candidate signals increase. However, because calculating the PAPR values of candidate signals requires more inverse fast Fourier transform operations, the CES hardware circuit is difficult to achieve. Therefore this study combines the CES, partial transmit sequences (PTSs) and block-coded modulation (BCM) codes to propose a BCM–CES–PTS technology, which simultaneously improves the high computation of the CES, the necessary side information delivered in PTS and the lack of error correction capabilities in the transmitted signal itself, applying this to a 16-QAM modulation OFDM system. In addition, this study proposes two structures of the CES by arranging the extended constellation points in symmetrical and asymmetrical forms, called S-BCM–CES–PTS and AS-BCM–CES–PTS, respectively. The generator matrices of the two structures were proposed to simplify the division of the circuit into sub-blocks. - Author(s): Md.M. Morshed ; A. Atkins ; H. Yu
- Source: IET Communications, Volume 6, Issue 16, p. 2715 –2724
- DOI: 10.1049/iet-com.2011.0807
- Type: Article
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The radio frequency identification (RFID) technology is expected to play a vital role in identifying objects and serving to prevent counterfeiting and fraud. The use of RFID tags may cause privacy violation of users carrying an RFID tag. Owing to the unique identification number of the RFID tag, the possible privacy threats are information leakage of a tag, traceability of the consumer, denial of service attack and impersonation of a tag. Owing to the large number of tags in any application individual secret value for each tag requires a large number of complex hash computations in the database side. To reduce the computation overhead many protocols use a group secret value for tags in the database side. This study proposes a new authentication protocol which provides privacy and security in a more efficient manner using individual secret values for each tag and also avoids many complex hash operations in the database side. The evaluation indicates that the proposed protocol requires a low storage, computation and communication cost but offers larger ranges of privacy and security protection. - Author(s): N. Reisi ; M. Ahmadian ; V. Jamali ; S. Salari
- Source: IET Communications, Volume 6, Issue 16, p. 2725 –2733
- DOI: 10.1049/iet-com.2011.0401
- Type: Article
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In this study, the authors consider the problem of cooperative spectrum sensing (CSS) based on linear combination of observations over correlated log-normal shadow-fading channels. To reduce the effects of imperfect reporting channels, a cluster-based CSS framework and a new cluster head selection algorithm are proposed. Using the received energies (as local observations) from different clusters, the fusion centre can make the final decision by linearly combining the noisy cluster observations. To calculate the combination weights, the authors come across the problem of joint distribution approximation of sum of the correlated log-normal random variables corresponding to different clusters. A joint moment generating function (MGF) matching algorithm is proposed in this study to estimate the summations by a single log-normal vector. Monte Carlo simulations confirm the accuracy of the proposed MGF-based approach in estimating the desired statistics and efficiency of the cluster-based spectrum-sensing algorithm in terms of primary signal detection. - Author(s): S. Hu ; Y.L. Guan ; G. Bi ; S. Li
- Source: IET Communications, Volume 6, Issue 16, p. 2734 –2739
- DOI: 10.1049/iet-com.2012.0130
- Type: Article
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This study presents a cluster-based transform domain communication system (TDCS) to improve spectrum efficiency. Unlike the utilities of clusters in orthogonal frequency division multiplex systems, the cluster-based TDCS framework divides entire unoccupied spectrum bins into L clusters, where each one represents a data stream independently, to achieve L times of spectrum efficiency compared to that of the traditional one. Among various schemes of spectrum bin spacing and allocation, the TDCS with random allocation scheme appears to be an ideal candidate to significantly improve spectrum efficiency without seriously degrading power efficiency. In multipath fading channel, the coded TDCS with random allocation scheme achieves robust bit error rate (BER) performance owing to a large degree of frequency diversity. Furthermore, this study shows that the smaller spectrum bin spacing should be configured for the cluster-based TDCS to achieve higher spectrum efficiency and more robust BER performance. - Author(s): K. Shahtalebi and G. Bakhshi
- Source: IET Communications, Volume 6, Issue 16, p. 2740 –2749
- DOI: 10.1049/iet-com.2012.0124
- Type: Article
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Partial feedback in multiple-input multiple-output communication systems provides tremendous capacity gain and enables the transmitter to exploit channel condition and to eliminate channel interference. In the case of severely limited feedback, constructing a quantised partial feedback is an important issue. To reduce the computational complexity of the feedback system, this study introduces an adaptive partial method in which at the transmitter, a set of easy to implement least-square adaptive algorithms is engaged to compute the channel state information. In the proposed method, at the receiver, the time-varying step-sizes of the algorithms are computed and replied to the transmitter via a reliable feedback channel. The transmitter iteratively employs this feedback information to estimate the channel weights. This method is independent of the employed space–time coding schemes and gives all channel components. Complementary solution is given to reduce the computational complexity and simulation examples are given to evaluate the performance of the proposed method. - Author(s): T.T. Duy and H.Y. Kong
- Source: IET Communications, Volume 6, Issue 16, p. 2750 –2759
- DOI: 10.1049/iet-com.2012.0235
- Type: Article
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In this study, the authors analyse the outage performance of a cognitive two-way relaying system under an interference constraint. In the proposed protocol, the best relay which is chosen by an opportunistic relay selection strategy, combines the received packets using XOR operation and then forwards the combined packet to two secondary sources. The authors derive an exact closed-form expression of outage probability over flat and block Rayleigh fading channels. Various Monte-Carlo simulations are presented to verify the theoretical analyses and to compare the performance of the proposed protocol with that of the two-way relaying protocol without network coding. - Author(s): M.F. Feteiha and M. Uysal
- Source: IET Communications, Volume 6, Issue 16, p. 2760 –2768
- DOI: 10.1049/iet-com.2012.0115
- Type: Article
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Cooperative communication has been recently applied to vehicular networks to enable coverage extension and enhance link reliability through distributed spatial diversity. In this study, the authors investigate the performance of a cooperative vehicular network over a doubly selective (i.e. frequency-selective and time-selective) fading channel. Under the assumption of amplify-and-forward relaying with orthogonal cooperation protocol, the authors derive a pairwise error probability (PEP) expression and demonstrate the achievable diversity gains. The authors’ results demonstrate that, through proper linear constellation precoding, the cooperative vehicular scheme is able to extract the maximum available diversity in frequency (through multipath diversity), time (through Doppler diversity) and spatial (through cooperative diversity) dimensions. The effect of imperfect channel state information is also studied through an asymptotical PEP analysis. The authors further conduct Monte-Carlo simulations to confirm the analytical derivations and present the error rate performance of the vehicular scheme under various mobility conditions and scenarios. - Author(s): O. Muta
- Source: IET Communications, Volume 6, Issue 16, p. 2769 –2774
- DOI: 10.1049/iet-com.2012.0139
- Type: Article
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As a solution to high peak-to-average power ratio (PAPR) problems in vector coding (VC) systems, phase control-based methods such as selected mapping (SLM) and partial transmit sequence have been investigated. As described in this study, a phase sequence blind estimation method is presented for PAPR reduction based on phase control in multi-input multi-output (MIMO) adaptive modulated VC systems, where turbo code is employed. On the receiver side, the phase sequence component is estimated using a maximum likelihood method that selects the most likely sequence among all candidate sequences by exploiting soft-output information of the decoder. Computer simulation results show that when the number of candidate sequences in SLM is M=16, instantaneous power of the transmit signal at the complementary cumulative distribution function of 10−5 can be reduced by about 4.0 and 3.5 dB for single-input single-output and MIMO cases as compared with the case without PAPR reduction, although almost identical block error rate performance and the same throughput performance as in the case of perfect phase sequence estimation are achieved in an attenuated six-path Rayleigh fading condition.
Non-cooperative detection of weak spread-spectrum signals in additive white Gaussian noise
Precoding scheme for space-time-coded multiple-input–multiple-output system with estimation error and feedback delay in Rayleigh fading channel
Practical application of compressive sensing to ultra-wideband channels
Radio resource allocation for orthogonal frequency division multiple access-based underlay cognitive radio networks utilising weighted ergodic rates
Worst-case mean square error (MSE) transceiver design for imperfect estimate multi-input-multi-output communication channels
Inter-satellite optical wireless communication system design and simulation
Designing of high-speed inter-building connectivity by free space optical link with radio frequency backup
Low-complexity low-density parity check decoding algorithm for high-speed very large scale integration implementation
Hybrid link adaptation for inter-carrier interference adjustment in orthogonal frequency division multiple access cellular uplink systems
Network coding-based block acknowledgement scheme for wireless regenerative relay networks
Energy-efficient hybrid opportunistic cooperative protocol for single-carrier frequency division multiple access-based networks
Fairness-aware resource partition and routing in relay-enhanced orthogonal-frequency-division-multiple-accessing cellular networks
Spectrum sharing and power allocation in multiple-in multiple-out cognitive radio networks via pricing
Training signal designs for spatially correlated multi-user multi-input multi-output with orthogonal frequency-division multiplexing systems
Bit error rate improvement for chaos shift keying chaotic communication systems
Optimisation of channel capacity for multiple-input multiple-output smart antenna using a particle swarm optimiser
Blind channel estimation for cyclic prefix-free orthogonal frequency-division multiplexing systems with particular input symbols
Semi-blind channel estimation for multi-user orthogonal frequency division multiplexing with receiver diversity
Characterisation of bifurcation and chaos in silicon microring resonator
Proposed relay selection scheme for physical layer security in cognitive radio networks
Less restrictive knowledge connectivity condition for achieving consensus with unknown participants
Design of isotropic orthogonal transform algorithm-based multicarrier systems with blind channel estimation
Combining block-coded modulation codes and improved constellation extended schemes to reduce peak-to-average power ratio in orthogonal frequency-division multiplexing systems
Efficient mutual authentication protocol for radiofrequency identification systems
Cluster-based cooperative spectrum sensing over correlated log-normal channels with noise uncertainty in cognitive radio networks
Cluster-based transform domain communication systems for high spectrum efficiency
Simple adaptive partial feedback method for full multiple-input multiple-output channel estimation
Exact outage probability of cognitive two-way relaying scheme with opportunistic relay selection under interference constraint
Cooperative transmission for broadband vehicular networks over doubly selective fading channels
Effect of phase control-based peak-to-average power ratio reduction on multi-input multi-output adaptive modulated vector coding systems
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