IET Communications
Volume 10, Issue 17, 24 November 2016
Volumes & issues:
Volume 10, Issue 17
24 November 2016
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- Author(s): Haifeng Zhao and Zhibin Pan
- Source: IET Communications, Volume 10, Issue 17, p. 2261 –2268
- DOI: 10.1049/iet-com.2016.0268
- Type: Article
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For relay terminals in wireless communication systems, the difference of the power consumed for relaying signals means unfairness, which may reduce the network lifetime when the system is energy-constrained. Classic opportunistic relay selections always cause unequal power consumption among all relays. In this study, the authors propose a novel distributed relay selection strategy, named the fair opportunistic relay selection (FORS) strategy, for amplify-and-forward (AF) opportunistic cooperative systems. The FORS strategy is designed based on physical-layer fairness that means all available relays cumulatively consume equal power. They use a set of weight coefficients to adjust the channel fading coefficients effectively and then change the selection probabilities for all relays on the basis of proportional fair scheduling. Considering that the ‘optimal’ relay can be selected proactively in quasi-static Rayleigh fading channels based on local channel state information, the overhead of the proposed scheme is small. Then, they analyse the performance of the FORS strategy and provide an exact analytical expression for the outage probability (P out) and the average symbol error probability. Numerical simulation results validate their analysis. The results show that the FORS strategy approximately achieves the upper bound of physical-layer fairness in the AF relaying system.
- Author(s): Bin Sun ; Haowen Chen ; Huanxin Zou
- Source: IET Communications, Volume 10, Issue 17, p. 2269 –2275
- DOI: 10.1049/iet-com.2016.0436
- Type: Article
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The authors address the problem of coherent multitarget localisation for distributed multiple-input multiple-output (MIMO) radar, in the presence of phase synchronisation mismatch between each transmitter-receiver pair. The inherent sparsity of targets in the surveillance area can be exploited to represent radar data and then target locations are accurately estimated using sparse reconstruction. However, due to the difficulty of perfect phase synchronisation, the localisation technique is usually required to eliminate the phase errors. This study jointly considers the phase error correction problem in the context of multitarget localisation. In this novel method, the direct position determination of multitarget is obtained by estimating the spare reflection coefficients and phase errors alternately. Numerical simulation results demonstrate that the authors’ iterative block sparse Bayesian learning via maximum likelihood estimation algorithm obtains enhanced estimation accuracy against the phase synchronisation mismatch.
- Author(s): Zihao You ; I-Tai Lu ; Wenhao Li
- Source: IET Communications, Volume 10, Issue 17, p. 2276 –2280
- DOI: 10.1049/iet-com.2015.0727
- Type: Article
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Presented in this study is a novel precoding scheme for orthogonal frequency division multiplexing systems to suppress the out-of-band emission (OOBE). The scheme suppresses the OOBE by making the transmitted signal satisfy the continuous derivative property and the notched frequency (NF) property, which have been proposed separately in some existing schemes. Unlike most of the continuous derivative related schemes that require iterative decoders, authors’ scheme employs a non-iterative decoder. Numerical results show that their proposed scheme achieves superior OOBE suppression than the other non-iterative continuous derivative precoding schemes and NF schemes. Computational complexity, peak-to-average power ratio, and bit error rate are also analysed.
- Author(s): Pengfei Du ; Qinghai Yang ; Qingsu He ; Kyung Sup Kwak
- Source: IET Communications, Volume 10, Issue 17, p. 2281 –2289
- DOI: 10.1049/iet-com.2015.1064
- Type: Article
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In this study, the authors investigate the energy-aware quality of information (QoI) maximisation problem by jointly optimising the sensor selection, sampling rate, packet-dropped rate, and transmit power in wireless sensor networks. By introducing the weight parameters, the authors first present a revenue-cost (RC) function which combines the optimisation objectives of the QoI and energy expenditure into a single objective to capture the tradeoff between them. Then, a stochastic optimisation programming is formulated to maximise the long-term average RC value subject to the network stability constraint. Using the Lyapunov drift theory, the authors develop a collaborative sensing and transmit power control algorithm that can guarantee the worst-case delay for each packet. Simulation results demonstrate the advantages of the proposed algorithm.
- Author(s): Li Xu ; He Fang ; Zhiwei Lin
- Source: IET Communications, Volume 10, Issue 17, p. 2290 –2299
- DOI: 10.1049/iet-com.2016.0049
- Type: Article
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In order to fully utilise limited spectrum resources of multiple channels and multiple radios in cognitive radio networks, the authors propose a potential game model for opportunistic spectrum access based on both accurate and inaccurate spectrum state estimation with considering the interference constraints of licensed users. Three algorithms are proposed to achieve equilibrium of the proposed game. First, assuming spectrum sensing results are accurate, a joint strategy fictitious play-based channel selection algorithm with incomplete information is presented, and it can achieve a pure Nash equilibrium (NE) of the proposed game. Second, in order to make the outcomes of game robust, an evolutionary spectrum access mechanism with complete information is introduced by using evolutionary game theory based on inaccurate spectrum state estimation so that evolutionary stable strategy (ESS) can be achieved. Finally, with incomplete network information, a distributed learning algorithm is proposed to achieve a mixed NE, which is proved to be an ESS. Simulation results show that these algorithms can significantly improve spectrum allocation efficiency while reducing mutual collision.
- Author(s): Fadia Taleb ; Fethi Tarik Bendimerad ; Daniel Roviras
- Source: IET Communications, Volume 10, Issue 17, p. 2300 –2307
- DOI: 10.1049/iet-com.2016.0411
- Type: Article
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In this study, a new non-coherent communication system, i.e. very high efficiency differential chaos shift keying system, is proposed. This system is a generalised form of the high efficiency differential chaos shift keying (HE-DCSK) system, with an arbitrary number (N) of transmitted bits per frame. The major advantage of this new proposition is its ability to significantly improve the spectral efficiency compared with DCSK and HE-DCSK. The theoretical bit error rate of this system is found using the Gaussian approximation method under different communication channels: additive white Gaussian noise and two-ray Rayleigh fading channels. Simulations in both environments show a perfect match with the analytical expressions for large spreading factors. Simulation results for the two-ray Rayleigh fading channel show clearly the diversity gain compared with the single-ray Rayleigh channel.
- Author(s): Peng Zhou and Xiaojing Gu
- Source: IET Communications, Volume 10, Issue 17, p. 2308 –2314
- DOI: 10.1049/iet-com.2016.0331
- Type: Article
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Hypertext transfer protocol secure (HTTPS) relies on a group of pre-trusted certificate authorities (CAs) for authentication and hence can avoid man-in-the-middle attacks. However unfortunately, this authentication architecture can be completely subverted in case any one (usually the weakest one) of CAs has been compromised. To tackle this critical flaw, pioneer works such as notary-based systems and pre-shared secrets have been proposed. These state-of-the-art techniques can neither seek maximal protection from available CAs nor resist potential man-in-the-middle variants. In this study, the authors propose HTTPAS, a new HTTP Active Secure framework that can enhance the HTTPS authentication against man-in-the-middle attacks by actively utilising available CAs and exploiting Internet path diversity as much as possible. In particular, HTTPAS is designed with four practical solutions, each of which can make a unique trade-off among authentication capability, deployment difficulty and efficiency. They have implemented HTTPAS using the open secure sockets layer (SSL) suite, and also evaluated the implementation through experiments on several public certificate data sets and the Internet. Their results have successfully confirmed the authentication effectiveness of HTTPAS with only a few performance overheads and moderate deployment effort.
- Author(s): Zhi Chen ; Pingyi Fan ; Khaled Ben Letaief
- Source: IET Communications, Volume 10, Issue 17, p. 2315 –2318
- DOI: 10.1049/iet-com.2015.1205
- Type: Article
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In this study, the caching problem is investigated. Assuming that the users are only equipped with buffer of small sizes, the peak rate of caching problem is investigated in this study. In contrast to recent results in the literature, this study shows that under some specific condition, i.e. if the number of users is no less than the amount of files in the server, a lower peak rate of caching is achievable. Furthermore, this new presented peak rate of caching is demonstrated to coincide with the well-known cut-set bound.
- Author(s): Ilsun You ; Jae Deok Lim ; Jeong Nyeo Kim ; Hyobeom Ahn ; Chang Choi
- Source: IET Communications, Volume 10, Issue 17, p. 2319 –2327
- DOI: 10.1049/iet-com.2016.0480
- Type: Article
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Mobility management has become a core function in internet services and networks as mobile devices have been widely used and their capabilities have dramatically advanced. It is expected that proxy mobile IPv6 (PMIPv6), which is the most prominent solution, will play an important role in supporting these devices’ mobility. To protect PMIPv6 networks, several authentication schemes have been presented. However, due to their static approach, the existing schemes failed to keep a good balance between security and efficiency. Motivated by this, the authors study an adaptive authentication scheme for mobile devices in PMIPv6 networks. In particular, the proposed scheme considers mobile nodes’ context information to decide authentication strength, based on which adaptive authentication is performed. It is shown from the formal security verification and the example study that the proposed scheme is not only correct, but also achieves a good trade-off between security and efficiency
- Author(s): Wei Wang ; Meixia Hu ; Yongzhao Li ; Hailin Zhang ; Zan Li
- Source: IET Communications, Volume 10, Issue 17, p. 2328 –2335
- DOI: 10.1049/iet-com.2016.0062
- Type: Article
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In multiple-input–multiple-output broadcast channels, lattice reduction (LR) preprocessing technique can significantly improve the precoding performance. Among the existing LR algorithms, the fixed complexity Lenstra–Lenstra–Lovasz (fcLLL) algorithm applying limited number of LLL loops is suitable for the real-time communication system. However, fcLLL algorithm suffers from higher average complexity. Aiming at this problem, a computationally efficient fcLLL (CE-fcLLL) algorithm for LR-aided (LRA) precoding is developed in this study. First, the authors analyse the impact of fcLLL algorithm on the signal-to-noise ratio performance of LRA precoding by a power factor (PF) which is defined to measure the relation of reduced basis and transmit power of LRA precoding. Then, they propose a CE-fcLLL algorithm by designing a new LLL loop and introducing new early termination conditions to reduce redundant and inefficient LR operation in fcLLL algorithm. Finally, they define a PF loss factor to optimise the PF threshold and the number of LLL loops, which can lead to a performance-complexity tradeoff. Simulation results show that the proposed algorithm for LRA precoding can achieve better bit-error-rate performance than the fcLLL algorithm with remarkable complexity savings in the same upper complexity bound.
- Author(s): Xingyu Han and John Schormans
- Source: IET Communications, Volume 10, Issue 17, p. 2336 –2343
- DOI: 10.1049/iet-com.2015.0704
- Type: Article
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p.
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Packet loss and delay in wireless networks is a function of both the traffic characteristics (e.g. load, burstiness) and the characteristic behaviour of the fading channel. In this study, the authors propose and analyse a new queue model in which the server process is controlled by the adaptive modulation and coding (AMC) algorithm, and with aggregated ON–OFF packet arrivals to a finite buffer. In the scenarios, where users require multiple services, aggregated ON–OFF arrivals approximate bursty behaviour better than the Poisson arrivals analysed in many earlier queueing models. They focus on the packet drop probability, the packet loss probability, the average queueing delay and the throughput, showing significant differences in these metrics between the cross-layer models using aggregated ON–OFF arrivals and Poisson arrivals. This indicates that in wireless packet network performance evaluation, the traffic model is at least as important as the effect of the fading channel modelling.
- Author(s): Bong-seok Kim and Kwonhue Choi
- Source: IET Communications, Volume 10, Issue 17, p. 2344 –2351
- DOI: 10.1049/iet-com.2016.0083
- Type: Article
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Unlike the conventional distributed Alamouti coded orthogonal frequency division multiplexing (OFDM), over-sampling substantially improves the performance of frequency asynchronous distributed Alamouti coded (FADAC) OFDM. This exclusive effectiveness of over-sampling in FADAC-OFDM comes from two factors. One is the unique characteristics of residual inter carrier interference term in FADAC-OFDM and the other factor is moving away the cyclic harmonic inter-carrier interference (ICI) by over-sampling. In addition, the authors confirm that over-sampling factor of 2, i.e. 2N point fast Fourier transform (FFT) is sufficient to move the cyclic harmonic ICI. From this investigation, the authors propose 2N point FFT FADAC-OFDM. The proposed scheme achieves the significantly improved performance not only in the flat fading channel but also in the selective fading channels. For example, while the non-oversampled FADAC-OFDM has the unacceptable error rate level near to or above 0.1 at the band edges even with high signal to noise ratio, the proposed scheme achieves near intersymbol interference-free performance. This leads the proposed scheme to achieve 50% reduction of the required number of null subcarriers to achieve ICI free performance compared with the non-oversampled FADAC-OFDM. Moreover, in terms of implementation feasibility and computational complexity, the proposed scheme is shown to be acceptable.
- Author(s): Junghoon Ko ; Kyoungtae Lee ; Yeon-Jea Cho ; Sangmin Oh ; Sooyoung Hur ; Noh-Gyoung Kang ; Jeongho Park ; Dong-Jo Park ; Dong-Ho Cho
- Source: IET Communications, Volume 10, Issue 17, p. 2352 –2362
- DOI: 10.1049/iet-com.2015.0318
- Type: Article
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This study presents analyses of the feasibility for the 28 GHz band with a comprehensive overview of important channel parameters. A channel measurement system with a time synchronisation scheme is also introduced which is a sliding correlator channel sounder using 250 Mcps (Mega-chips-per-second) pseudo-random noise sequences. The system enables the observation of the behaviour of 28 GHz wave propagation not only to use of forming narrow beams in certain directions (classical narrow beam beamforming) but also omni-likely. This novel synchronised system makes it possible to analyse the wideband channel characteristics. The outdoor channel measurements are conducted considering various features such as foliage effects, signal outage, path loss and outdoor-to-indoor conditions. Furthermore, the spatial channel modelling for omni-like observations with temporal characteristics is firstly interpreted through analysing the essential channel modelling parameters, including the number of clusters, excess delay, root-mean-square (RMS) delay spread, power delay spectrum, and angular spread. In the authors’ measurements, the average number of clusters was 2.41 with standard deviation of 1.44. The average RMS delay spread was 36.06 ns with standard deviation of 46.73 ns. Furthermore, the mean values of the RMS azimuth spreads of the angle of departure and arrival were 6.65° and 24.04°, respectively.
- Author(s): Sima Bahrani ; Mostafa Derakhtian ; Alireza Zolghadrasli
- Source: IET Communications, Volume 10, Issue 17, p. 2363 –2371
- DOI: 10.1049/iet-com.2015.0768
- Type: Article
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Automatic modulation classification (AMC) techniques enable the estimation of the bit allocation table in adaptive orthogonal frequency division multiplexing (OFDM) systems. In this study, the authors investigate the classification performance of a low-complexity maximum-a-posteriori (MAP) algorithm for AMC. Also, they derive an approximation of the probability of classification error in a subcarrier for this classifier. Furthermore, based on these theoretical derivations, a novel modified rate adaptive (RA) bit loading algorithm with additional classification error constraint is proposed. Numerical results show that the authors’ proposed method outperforms the RA algorithm significantly in terms of classification performance, while providing reasonable data throughput specifically at higher signal-to-noise ratios.
- Author(s): Muhammad Ajmal Khan ; Raveendra K. Rao ; Xianbin Wang ; Asrar Sheikh
- Source: IET Communications, Volume 10, Issue 17, p. 2372 –2379
- DOI: 10.1049/iet-com.2016.0372
- Type: Article
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In a dual-hop relaying system without a direct link between the source and the destination, the source broadcasts information signal to the relay and relay broadcasts it to the destination, thus it uses two phases to transmit one symbol. This study proposes a novel scheme to incorporate signal space diversity into a dual-hop relaying system with multiple decode-and-forward (DF) relays to enhance its spectral efficiency. The proposed dual-hop signal space cooperative relaying scheme transmits two symbols in three phases while the conventional dual-hop DF relaying system uses four phases to transmit the same two symbols. Therefore, the proposed scheme improves the spectral efficiency without additional complexity, bandwidth or transmit power. The proposed scheme is analysed over Rayleigh fading channel and error probability performance is derived. Moreover, an asymptotic approximation for the error probability is obtained to illustrate the impact of different system parameters and diversity gain. In addition, this study discusses the power allocation optimisation, relay position optimisation and the joint optimisation of both. Furthermore, closed-form expression for the average channel capacity is derived. In the end, analytical results are compared and validated through Monte Carlo simulations.
- Author(s): Shiwen He ; Yongming Huang ; Yanru Shi ; Chenhao Qi ; Shi Jin ; Luxi Yang
- Source: IET Communications, Volume 10, Issue 17, p. 2380 –2390
- DOI: 10.1049/iet-com.2015.1045
- Type: Article
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This paper studies joint beamforming and power allocation for multicell multiuser multi-antenna systems with the objective of maximising the minimum signal-to-interference-plus-noise ratio (max–min SINR). The authors first consider developing an iterative algorithm to achieve the optimal performance by extending the uplink–downlink duality for finite-scale wireless communication systems. The solution is then generalised to achieve the asymptotically optimal multicell beamforming with the aim to reduce the overhead of signalling exchange between coordinated base stations based on large dimension random matrix theory. Based on that, an efficient multicell beamforming algorithm is proposed to asymptotically achieve the max–min SINR. To further solve the complexity issue of large dimensional matrix inversion involved in the calculation of beamforming vectors, they propose a low-complexity beamforming calculator based on truncated polynomial expansion approach. Numerical results validate the effectiveness of the authors’ proposed algorithms and show that they can achieve the optimal or asymptotically optimal performance in a massive multi-input multi-output system with low complexity and small backhaul overhead.
- Author(s): Raed Mesleh ; Salama Said Ikki ; Fares S. Almehmadi
- Source: IET Communications, Volume 10, Issue 17, p. 2391 –2395
- DOI: 10.1049/iet-com.2016.0631
- Type: Article
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Quadrature spatial modulation (QSM) is proposed recently as an efficient multiple-input–multiple-output wireless communication technique. In QSM, spatial multiplexing gain is achieved through modulating a two-dimensional spatial constellation diagram in addition to conventional signal modulation. It was demonstrated that QSM can be designed with single in-phase and quadrature (IQ) transmitter. However, the impact of IQ modulator imperfections, which degrade signal fidelity and overall system performance, has not been studied in the literature. In this study, typical IQ modulator/demodulator is considered for QSM system and the performance of the system is analysed and discussed. In particular, IQ imbalance channel modelling, pair-wise error probability, and average bit error ratio are discussed. Results reveal that IQ imbalance can lead to significant performance degradation of QSM system and should be carefully addressed for any future deployment.
- Author(s): Jianhua Cui ; Zhongyong Wang ; Chuanzong Zhang ; Zhengyu Zhu ; Peng Sun
- Source: IET Communications, Volume 10, Issue 17, p. 2396 –2401
- DOI: 10.1049/iet-com.2016.0155
- Type: Article
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For localisation algorithms of wireless sensor networks (WSNs), the communication overhead and the computational complexity are two main bottlenecks that should be considered beside the positioning accuracy. In this study, the authors focus on cooperative localisation in WSNs and propose a low-complexity distributed cooperative localisation algorithm by employing variational message passing (VMP) on factor graphs. In order to decrease the communication overhead, Gaussian parametric message representation is adopted. With regard to the non-Gaussian messages caused by the non-linear ranging model, they approximate them to Gaussian messages by exploiting second-order Taylor expansion to reduce the computational complexity. Simulation results show that the proposed algorithm performs quite similar to sum-product algorithm over a wireless network and Gaussian VMP algorithm based on minimising Kullback–Leibler divergence with lower computational complexity.
- Author(s): Md. Noor-A-Rahim ; Khoa D. Nguyen ; Gottfried Lechner
- Source: IET Communications, Volume 10, Issue 17, p. 2402 –2406
- DOI: 10.1049/iet-com.2016.0001
- Type: Article
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This paper presents the design and analysis of spatially coupled low-density parity-check (SC-LDPC) codes for Gaussian multiple access channel (GMAC). For two-user GMAC, we consider that each user encodes their messages by SC-LDPC codes while joint belief propagation decoding is considered at the receiver. We present low complexity density evolution analysis of SC-LDPC GMAC codes and show simple optimisation procedure. For the asymptotic case, we observe that SC-LDPC code-based GMAC code outperforms existing irregular LDPC code-based GMAC code.
- Author(s): Sandip Karar ; Suman Ghosh ; Abhirup Das Barman
- Source: IET Communications, Volume 10, Issue 17, p. 2407 –2415
- DOI: 10.1049/iet-com.2016.0339
- Type: Article
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This study proposes an incentive-based femtocell cooperation scheme for indoor macrocell users (MUs) in an underlay two-tier heterogeneous network which helps the indoor MUs to achieve higher data rate through time sharing access from the femtocell. Due to underlay spectrum sharing nature of the femtocell, the network suffers from severe cross-tier interference. To manage this cross-tier interference, a price-based power control scheme is also proposed for the femtocell access point (FAP) whereby the macrocell base station (MBS) controls the transmit power of the FAP by pricing their resulted cross-tier interference power level subject to a maximum tolerable interference limit. A Stackelberg game has been formulated and analysed for joint pricing-based power control and incentive-based cooperation game. Numerical results show the performance of the proposed scheme in terms of achievable rate of indoor users and utilities of both the MBS and the FAP for different locations of the femtocells.
- Author(s): Chong-Dao Lee and Yan-Haw Chen
- Source: IET Communications, Volume 10, Issue 17, p. 2416 –2421
- DOI: 10.1049/iet-com.2016.0404
- Type: Article
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This study extends the authors’ earlier work to show that the Gaussian integer sequences of period p m − 1 with p − 2 non-zero out-of-phase autocorrelation values can be constructed from the known families of two-tuple-balanced p-ary sequences over the finite field 𝔽 p m , where p is an odd prime and m ≥ 2. The proposed Gaussian integer sequences have high energy efficiency and are superior to the perfect Gaussian integer sequences (introduced by Hu et al. in 2012) for the peak-to-average power ratio reduction in orthogonal frequency-division multiplexing systems.
- Author(s): Wei Hou ; Shan Lu ; Jun Cheng
- Source: IET Communications, Volume 10, Issue 17, p. 2422 –2426
- DOI: 10.1049/iet-com.2015.1031
- Type: Article
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A family of rate-compatible capacity-approaching codes is obtained by spatially coupling multiple identical copies of rate-compatible base codes. The base code consists of a given regular low-density parity-check (LDPC) code and a parameter-adjustable repeat-accumulate (RA) extension. The RA-extension repeatedly accumulates all of the variable nodes of the given LDPC code by q + 1 times to generate q + 1 blocks of accumulated nodes, in which all of the accumulated variable nodes in the first q blocks and the α-fractional accumulated variable nodes in the last block are transmitted. The spatially coupled versions of the base codes, called RA-extended spatially coupled LDPC (SC-LDPC) codes, achieve arbitrary rates by simply adjusting parameters q and α, and thus they are rate-compatible. The potential thresholds of the base code ensembles are calculated to predict the iterative decoding performance of the proposed RA-extended SC-LDPC codes. Numerical results and simulations show that the authors’ proposed rate-compatible codes are capacity-approaching over binary erasure channels.
- Author(s): Jianqing Dou ; Zaichen Zhang ; Jian Dang ; Liang Wu ; Yuxin Wei ; Chen Sun
- Source: IET Communications, Volume 10, Issue 17, p. 2427 –2434
- DOI: 10.1049/iet-com.2016.0150
- Type: Article
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In this study, the authors propose a cyclic prefix (CP) based imperfect reconstruction (IPR) filter bank multicarrier (FBMC) system in the uplink of multiuser networks, known as filter bank multiple access (FBMA). The prototype filter in the system is a common low-pass filter without any perfect reconstruction (PR) or nearly perfect reconstruction (NPR) constraint. CP appended input signal format is applied to avoid inter-symbol interference and facilitate the equalisation task. The received signal is jointly processed by multi-subband equalisation. Besides, the input data symbols can be complex-valued due to IPR design. Some properties and achievable data rate of the proposed system are discussed. Simulations illustrate that the proposed system with uniformly/non-uniformly designed filter bank has a similar achievable data rate to orthogonal frequency division multiple access (OFDMA). Bit error rate performance of the proposed system is better than OFDMA and an error floor always exists when applying conventional PR FBMC to multi-user networks. In addition, OFDMA is more sensitive to carrier frequency offset than FBMA because of full synchronisation requirement. Therefore, it suggests that the proposed CP based IPR FBMA system works well without PR/NPR conditions and more extensive development is feasible for the filter banks in the foreseeable future.
- Author(s): Anis Charrada and Abdelaziz Samet
- Source: IET Communications, Volume 10, Issue 17, p. 2435 –2444
- DOI: 10.1049/iet-com.2016.0132
- Type: Article
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In this study, the estimation of fast-fading long term evolution (LTE) downlink channels in high-speed applications of LTE advanced is investigated by the authors. A robust channel estimation and interpolation algorithm is essential in order to adequately track the fast time-varying channel response. In this contribution, the multipath fast-fading channel is modelled as a discrete, tapped-delay and finite impulse response filter. Using support vector machine regression (SVR), they develop an extended algorithm to jointly estimate the complex-valued channel frequency response in time and frequency domains, in the presence of fading and non-linear noise from the transmission of known pilot symbols. Furthermore, the channel estimates at the known pilot symbols are interpolated to the unknown data symbols by using the non-linear SVR approach exploiting kernel features. This study integrates both channel estimation at pilot symbols and interpolation at data symbol into the complex SVR interpolation method. The bit error rate and mean square error performances of the authors’ fast-fading channel estimation scheme is demonstrated via simulation for LTE downlink with 64-QAM modulation and 500 km/h velocity under non-linearities.
- Author(s): Mingyue Zhou and Xiaohui Zhao
- Source: IET Communications, Volume 10, Issue 17, p. 2445 –2451
- DOI: 10.1049/iet-com.2016.0274
- Type: Article
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Most of traditional power allocation algorithms are often based on maximum capacity technology (MCT) in cognitive radio networks (CRNs) at the expense of higher energy consumption. The optimisation of energy efficiency power allocation schemes are important performance in green communication. This study investigates the energy efficient power allocation for orthogonal frequency division multiplexing based CRNs in underlay mode. The authors’ scheme is obtained by optimising an objective function consisting of the users’ performance degradation and the network interference, in the same time to track time-varying target of signal to inference plus noise ratio (SINR) under maximum transmit power for each cognitive user and interference power constraint from primary user. A convex optimisation problem is formulated where the tradeoff between energy consumption and transmission capacity is considered, and a distributed algorithm is developed to solve this problem. Simulation results show that the authors’ proposed algorithm can guarantee an acceptable target SINR for all cognitive users and significantly improves energy efficiency compared with throughput per Joule and MCT schemes. Furthermore, the proposed algorithm with the introduced appropriate weight parameters can get higher transmission capacity.
- Author(s): Xiaolan Liu ; Fengye Hu ; Wei Xiong ; Yu Du ; Ling Cen
- Source: IET Communications, Volume 10, Issue 17, p. 2452 –2460
- DOI: 10.1049/iet-com.2016.0458
- Type: Article
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This study concerns sensor selection problem in wireless body area network (WBAN), which can reduce the burden of the human body and improve the energy efficiency. The authors highlight the sparse sensor array synthesis algorithm for different shapes of sensor arrays via convex optimisation to solve this problem. For simplicity, one regular spherical sensor array and five regular cuboid sensor arrays are considered to simulate the sensor distribution around the human body. As a comparison, the conventional method with one objective method is used to synthesise the sensor array first. Then the proposed algorithm which includes two objective variables: the l 1-norm of weight vector and the peak side-lobe level is used. Simulations demonstrate that the proposed sparse sensor array synthesis algorithm achieves array sparsity with lower side lobe and more concentrated main lobe when operated in spherical and cuboid sensor array. Hence, the sensor selection problem is achieved by the sparse sensor array synthesis.
- Author(s): Qing Yang ; Ting Jiang ; Zheng Zhou
- Source: IET Communications, Volume 10, Issue 17, p. 2461 –2472
- DOI: 10.1049/iet-com.2015.1148
- Type: Article
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Blind interference alignment (BIA) can eliminate users’ interference without channel state information and greatly improve the channel capacity, which has been regarded as a promising technique in next generation wireless systems. However, current BIA mechanisms neglect noise accumulations, resulting in final signal-to-noise ratio (fSNR) deterioration and reduced transmission rates. Motivated by ameliorating such negative impact induced by noise accumulations, this study establishes an SNR aware semi-BIA (SNR SBIA) framework in the multi-input–single-output broadcast channel, where the users form different groups performing BIA for different SNR reductions. An SNR SBIA algorithm is further proposed based on tabu search for maximising the overall performance ensuring all users’ fSNRs higher than an SNR threshold. Extensive evaluations demonstrate that SNR SBIA can adapt to the users’ diverse received SNRs and the corresponding achievable sum rate is about 1.38 times and 1.92 times that in standard BIA and grouped hierarchical BIA, respectively.
- Author(s): Adam Muhammad Evans ; Tahmid Quazi ; Hongjun Xu
- Source: IET Communications, Volume 10, Issue 17, p. 2473 –2479
- DOI: 10.1049/iet-com.2016.0676
- Type: Article
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Hierarchical quadrature amplitude modulation (HQAM) allows for transmission of multiple classes of data (such as voice, video and file transfer), provides flexibility in terms of coverage area and allows for network upgrades while maintaining backwards compatibility. However, the addition of hierarchical layers leads to higher-order modulation schemes which make the system increasingly susceptible to noise and fading. To mitigate fading while maintaining backwards compatibility, maximum ratio transmission (MRT) is incorporated into the HQAM system to maximise signal-to-noise ratio for a given number of diversity branches. This study presents a theoretical bit error rate (BER) performance analysis of an MRT enhanced HQAM (MRT-HQAM) system in Rayleigh fading. The BER performance gains of the proposed system over single-input–single-output and single-input–multiple-output HQAM systems are shown. The HQAM hierarchical modulation parameter is varied and the effects are presented. Furthermore, the authors present the effects of varying the number of antennas on the transmitting and receiving ends and discuss the optimal antenna configuration. The theoretical BER expressions used in the performance analysis are verified using simulation results.
- Author(s): Jun Zhu ; Lei Zhang ; Hong-Chuan Yang ; Mazen O. Hasna
- Source: IET Communications, Volume 10, Issue 17, p. 2480 –2487
- DOI: 10.1049/iet-com.2016.0048
- Type: Article
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(8)
In this study, the authors investigate the downlink area spectral efficiency (ASE) of infrastructure relay enhanced cellular systems. ASE for cellular systems is defined as the maximum achievable data rate per unit bandwidth per unit area supported by a base station. In relay enhanced systems, ASE can serve as an attractive performance metric by capturing the benefit of the relatively smaller spatial footprint of relay transmission and the resulting lower co-channel interference. In this study, by applying a moment generating function based approach, the authors first derive the general closed-form statistics of the total interference from dominant co-channel cells over Rayleigh fading channels. These interference statistics are readily applied to the calculation of the resulting ASE. The authors also propose a novel in-cell frequency reuse scheme to further exploit the smaller transmission power of relay stations (RSs). Through selected numerical examples, the authors show that in relay enhanced systems, the cell size, transmission power and RS positions should be properly selected to gain better ASE performance than the conventional systems without relays.
- Author(s): Tiantian Yu ; Yanliang Jin ; Weisi Guo ; Changli Fang ; Wei Deng ; Tao Wang
- Source: IET Communications, Volume 10, Issue 17, p. 2488 –2495
- DOI: 10.1049/iet-com.2015.1075
- Type: Article
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Energy-efficient wireless communication is important for wireless devices with a limited battery life and cannot be recharged. In this study, a bit allocation algorithm to minimise the total energy consumption for transmitting a bit successfully is proposed for a two-way orthogonal frequency-division multiplexing relay system, whilst considering the constraints of quality-of-service and total transmit power. Unlike existing bit allocation schemes, which maximise the energy efficiency (EE) by measuring ‘bits-per-Joule’ with fixed bidirectional total bit rates constraint and no power limitation, their scheme adapts the bidirectional total bit rates and their allocation on each subcarrier with a total transmit power constraint. To do so, they propose an idea to decompose the optimisation problem. The problem is solved in two general steps. The first step allocates the bit rates on each subcarrier when the total bit rate of each user is fixed. In the second step, the Lagrangian multipliers are used as the optimisation variants, and the dimension of the variant optimisation is reduced from 2N to 2, where N is the number of subcarriers. They also prove that the optimal point is on the bounds of the feasible region, thus the optimal solution could be searched through the bounds.
Distributed relay selection strategy based on physical-layer fairness for amplify-and-forward relaying systems
Sparsity-aware multitarget localisation for distributed MIMO radar against phase synchronisation mismatch
High-performing orthogonal frequency division multiplexing precoding scheme for OOBE suppression
Energy-aware quality of information maximisation for wireless sensor networks
Evolutionarily stable opportunistic spectrum access in cognitive radio networks
Very high efficiency differential chaos shift keying system
HTTPAS: active authentication against HTTPS man-in-the-middle attacks
Fundamental limits of caching: improved bounds for users with small buffers
Adaptive authentication scheme for mobile devices in proxy MIPv6 networks
Computationally efficient fixed complexity LLL algorithm for lattice-reduction-aided multiple-input–multiple-output precoding
Cross-layer queueing analysis for aggregated ON–OFF arrivals with adaptive modulation and coding
Over-sampling effect in distributed Alamouti coded OFDM with frequency offset
Feasibility study and spatial–temporal characteristics analysis for 28 GHz outdoor wireless channel modelling
Performance analysis of a low-complexity MAP algorithm for automatic modulation classification in adaptive OFDM systems
Dual-hop signal space cooperative systems using multiple DF relays
Coordinated multicell beamforming for massive multiple-input multiple-output systems based on uplink–downlink duality
Impact of IQ imbalance on the performance of QSM multiple-input–multiple-output system
Variational message passing-based localisation algorithm with Taylor expansion for wireless sensor networks
SC-LDPC code design for Gaussian multiple access channel
Promoting femtocell cooperation through incentive for improving data rate of indoor users in underlay heterogeneous network
Families of Gaussian integer sequences with high energy efficiency
Rate-compatible spatially coupled LDPC code ensembles based on repeat-accumulate extensions
Properties and achievable data rate of a cyclic prefix based imperfect reconstruction filter bank multiple access system
Joint interpolation for LTE downlink channel estimation in very high-mobility environments with support vector machine regression
Energy-efficient power allocation algorithm in cognitive radio networks
Sparse array synthesis for WBAN with minimised side lobe via convex optimisation
SNR aware SBIA in multiple-input–single-output broadcast channel
BER performance of an MRT-HQAM system over Rayleigh fading channels
Area spectral efficiency of infrastructure relay enhanced cellular systems
Low-complexity energy-efficient resource allocation for delay-tolerant two-way orthogonal frequency-division multiplexing relays
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