Showing papers in "IEEE Wireless Communications Letters in 2013"
TL;DR: In this paper, the performance analysis of a dual-hop relay transmission system composed of asymmetric radio-frequency (RF)/free-space optical (FSO) links with pointing errors is presented.
Abstract: In this work, the performance analysis of a dual-hop relay transmission system composed of asymmetric radio-frequency (RF)/free-space optical (FSO) links with pointing errors is presented. More specifically, we build on the system model presented in to derive new exact closed-form expressions for the cumulative distribution function, probability density function, moment generating function, and moments of the end-to-end signal-to-noise ratio in terms of the Meijer's G function. We then capitalize on these results to offer new exact closed-form expressions for the higher-order amount of fading, average error rate for binary and M-ary modulation schemes, and the ergodic capacity, all in terms of Meijer's G functions. Our new analytical results were also verified via computer-based Monte-Carlo simulation results.
253 citations
TL;DR: This letter focuses on the maximization of the energy efficiency of information transmission (bit per Joule) while satisfying the quality-of-service (QoS) requirement, i.e. delay constraint, by jointly optimizing transfer duration and transmit power.
Abstract: In this letter, we consider a large-scale multiple-input multiple-output (MIMO) system where the receiver should harvest energy from the transmitter by wireless power transfer to support its wireless information transmission. The energy beamforming in the large-scale MIMO system is utilized to address the challenging problem of long-distance wireless power transfer. Furthermore, considering the limitation of the power in such a system, this letter focuses on the maximization of the energy efficiency of information transmission (bit per Joule) while satisfying the quality-of-service (QoS) requirement, i.e. delay constraint, by jointly optimizing transfer duration and transmit power. By solving the optimization problem, we derive an energy-efficient resource allocation scheme. Numerical results validate the effectiveness of the proposed scheme.
250 citations
TL;DR: This is the first reported transmission of 4-Gbps uncompressed video over a 60-GHz orbital angular momentum (OAM) wireless channel, and good agreement was achieved between the simulated and measured results.
Abstract: We demonstrate successful transmission of 4-Gbps uncompressed video over a 60-GHz orbital angular momentum (OAM) wireless channel. Matlab simulation was employed to support the experimental work and to generate the holographic masks used. Matlab coding is a unique approach which can produce any desired shape on copper or dielectric plates by mean of a commercial routing tool. We believe this is the first reported transmission of 4-Gbps uncompressed video over the 60-GHz OAM wireless channel. Good agreement was achieved between the simulated and measured results. Practical opportunities for multi-gigabit future wireless communications are available.
241 citations
TL;DR: In this letter, motivated by the recent rediscovery of faster-than-Nyquist (FTN) signaling transmissions, a frequency-domain equalization (FDE)-assisted FTN receiver architecture is conceived, which is capable of attaining a low demodulating complexity.
Abstract: In this letter, motivated by the recent rediscovery of faster-than-Nyquist (FTN) signaling transmissions, we conceive a frequency-domain equalization (FDE)-assisted FTN receiver architecture, which is capable of attaining a low demodulating complexity. The proposed scheme is especially beneficial for a long channel tap FTN scenario. More specifically, in our scheme the resultant inter-symbol interference imposed by FTN signaling is approximated by a finite-tap circulant matrix structure, which allows us to employ an efficient fast Fourier transform operation and a low-complexity channel-inverse-based minimum mean-square error detection algorithm. Our simulation results demonstrate that the proposed scheme is capable of attaining a near-optimal error-rate performance without imposing any substantial demodulating complexity as well as power penalty.
147 citations
TL;DR: This letter proposes joint relay selection and power allocation schemes for maximization of the throughput of an amplify—and—forward cooperative communication system where the source and the relays are energy harvesting nodes.
Abstract: In this letter, we propose joint relay selection and power allocation schemes for maximization of the throughput of an amplify—and—forward (AF) cooperative communication system where the source and the relays are energy harvesting (EH) nodes. We formulate an offline optimization problem which can be solved optimally by the generalized Bender's decomposition. For real—time implementation with low computational complexity, we propose two suboptimal online power allocation schemes. The performance of the proposed schemes is evaluated via simulations.
108 citations
TL;DR: In this article, a low-complexity precoding algorithm is proposed, which generates constant-envelope (CE) signals at each BS antenna to achieve a desired per-user information rate, the extra total transmit power required under the per-antenna CE constraint when compared to the commonly used less stringent total average transmit power constraint, is small.
Abstract: We consider downlink precoding in a frequency-selective multi-user Massive MIMO system with highly efficient but non-linear power amplifiers at the base station (BS). A low-complexity precoding algorithm is proposed, which generates constant-envelope (CE) signals at each BS antenna. To achieve a desired per-user information rate, the extra total transmit power required under the per-antenna CE constraint when compared to the commonly used less stringent total average transmit power constraint, is small.
98 citations
TL;DR: Performance analysis for underlay cognitive decode-and-forward relay networks with the small Nth best-relay selection scheme is studied over independent and identically distributed Rayleigh fading channels and shows that both the relay selection scheme and the number of relays have great impact on the outage performance of cognitive relay networks.
Abstract: Relay selection is an effective way to achieve considerable performance gains in cognitive relay networks (CRN). In practice, the best relay may not always be selected, thus the study of the small Nth best relay selection will be very beneficial for CRN design. In this paper, performance analysis for underlay cognitive decode-and-forward relay networks with the small Nth best-relay selection scheme is studied over independent and identically distributed (i.i.d.) Rayleigh fading channels. Closed-form expression for the exact outage probability is derived, which can be used to evaluate the impact of the relay selection scheme, the number of relays, the interference power constraint and the transmit power limit on the outage performance. The theoretical analysis is validated by Monte-Carlo simulations. The results show that both the relay selection scheme and the number of relays have great impact on the outage performance of cognitive relay networks.
92 citations
TL;DR: In this letter, an analysis is conducted on the probability of secrecy capacity for wireless communications over the Rician fading channels and a closed-form expression for the possibility of strictly positive secrecy capacity is derived.
Abstract: Communication security is critical in the marine environment as information may be transmitted over large open areas like high seas. In this letter, an analysis is conducted on the probability of secrecy capacity for wireless communications over the Rician fading channels. In particular, a closed-form expression for the probability of strictly positive secrecy capacity is derived. The result is applicable to the scenarios of Rayleigh/Rayleigh, Rician/Rayleigh, Rayleigh/Rician, and Rician/Rician.
91 citations
TL;DR: This paper model the LTE/LTE-A discontinuous reception (DRX) mechanism for MTC applications based on a Semi-Markov chain model and finds the power saving factor and wake up latency can be accurately estimated for a given choice of DRX parameters, thus allowing to select the ones presenting the best tradeoff.
Abstract: Machine type communications (MTC) are considered as key applications in LTE/LTE-A networks, for which lowering power consumption is among the primary requirements. In this paper, we model the LTE/LTE-A discontinuous reception (DRX) mechanism for MTC applications based on a Semi-Markov chain model. With our model the power saving factor and wake up latency can be accurately estimated for a given choice of DRX parameters, thus allowing to select the ones presenting the best tradeoff. The proposed model is validated through simulations. We also investigate the effect of different DRX parameters on performance.
83 citations
TL;DR: Numerical results demonstrate substantial difference in the mutual information between SM with finite alphabet inputs and SM with Gaussian inputs, and show that the precoding scheme achieves significant gains.
Abstract: In this letter, we investigate the effect of finite alphabet inputs on the performance of spatial modulation (SM) for multiple-input-single-output (MISO) channels. The closed-form expression of the mutual information is first derived in an information-theoretic framework. With careful analysis of the expression, we develop a precoding scheme to improve the performance of SM. Utilizing the theory of traditional constellation design, the precoding coefficient is obtained by maximizing the minimum Euclidean distance. Numerical results demonstrate substantial difference in the mutual information between SM with finite alphabet inputs and SM with Gaussian inputs, and show that our precoding scheme achieves significant gains.
83 citations
TL;DR: A distance-based ordered detection algorithm for spatial modulation (SM) to reduce the receiver complexity and achieve a near maximum likelihood (ML) performance and a new low-complexity soft output DBD (SODBD) algorithm is developed for coded SM systems.
Abstract: In this letter, we propose a distance-based ordered detection (DBD) algorithm for spatial modulation (SM) to reduce the receiver complexity and achieve a near maximum likelihood (ML) performance. The proposed algorithm firstly compensates the channel attenuation and obtains the estimated symbols with transmit antenna indices, then orders the indices based on the distances between these symbols and their demodulation constellations. A searching method is developed to obtain the final decision through a trade-off between performance and complexity. The equivalence between DBD and ML algorithms is also proved by theoretical analysis. Furthermore, a new low-complexity soft output DBD (SODBD) algorithm is developed for coded SM systems. The simulation results show that DBD algorithm has a close performance to ML algorithm while effectively reducing the complexity compared to conventional near-ML algorithms.
TL;DR: A new tractable method of sampling UEs by conditionally thinning the BS point process is proposed and the resulting framework can be used as a tractable generative model to study current capacity-centric deployments, where the UEs are more likely to lie closer to the BSs.
Abstract: A recent way to model and analyze downlink cellular networks is by using random spatial models. Assuming user equipment (UE) distribution to be uniform, the analysis is performed at a typical UE located at the origin. At least one shortcoming of this approach is its inability to model non-uniform UE distributions, especially when there is dependence in the UE and the base station (BS) locations. To facilitate analysis in such cases, we propose a new tractable method of sampling UEs by conditionally thinning the BS point process and show that the resulting framework can be used as a tractable generative model to study current capacity-centric deployments, where the UEs are more likely to lie closer to the BSs.
TL;DR: The derivation of post-processing SNR for minimum mean-squared error (MMSE) receivers with imperfect channel estimates is presented and it is shown that it is an accurate indicator of the error rate performance of MIMO systems in the presence of channel estimation error.
Abstract: We present the derivation of post-processing SNR for minimum mean-squared error (MMSE) receivers with imperfect channel estimates, and show that it is an accurate indicator of the error rate performance of MIMO systems in the presence of channel estimation error. Simulation results show the tightness of the analysis.
TL;DR: This letter focuses on the quantitative analysis of the ergodic secrecy sum-rate in terms of feedback amount of the CSI from the legitimate users in multiuser multi-antenna downlink networks.
Abstract: Channel state information (CSI) at the transmitter is of importance to the performance of physical layer security based on multi-antenna networks. Specifically, CSI is not only beneficial to improve the capacity of the legitimate channel, but also can be used to degrade the performance of the eavesdropper channel. Thus, the secrecy rate increases accordingly. This letter focuses on the quantitative analysis of the ergodic secrecy sum-rate in terms of feedback amount of the CSI from the legitimate users in multiuser multi-antenna downlink networks. Furthermore, the asymptotic characteristics of the ergodic secrecy sum-rate in two extreme cases is investigated in some detail. Finally, our theoretical claims are confirmed by the numerical results.
TL;DR: It is shown that significant performance enhancements can be achieved and the derived analysis is validated through Monte Carlo simulation results.
Abstract: Spatial modulation (SM) is a multiple-input multiple-output (MIMO) transmission scheme that draws momentous attention lately due to its reported performance enhancements over other MIMO techniques. However, a major drawback of SM system is that the achieved diversity gain is limited to the number of receive antennas and poor performance is reported for small number of receive antennas. Therefore, it is the aim of this paper to study the performance of SM with multiple decode and forward (DF) relays in which the relays that correctly detect the source signal forward the decoded message to the destination in pre-determined orthogonal channels. A closed form expression of the pair wise error probability (PEP) is obtained for a system consisting of two transmit antennas, multiple DF relays and single receive antenna. As well, asymptotic expression for the PEP at high signal to noise ratio (SNR) is derived. It is shown that significant performance enhancements can be achieved and the derived analysis is validated through Monte Carlo simulation results.
TL;DR: This paper investigates the performance of a Full-Duplex Block Markov (FD-BM) relaying scheme with self interference at the relay under independent non-identically distributed Nakagami-m fading, and derives tight closed-form approximate expressions for the outage probability and throughput.
Abstract: This paper investigates the performance of a Full-Duplex Block Markov (FD-BM) relaying scheme with self interference at the relay under independent non-identically distributed Nakagami-m fading. Relying on efficient approximations proposed elsewhere in the literature for the sum of Gamma random variables (RVs), and based on a new, accurate approximation for the product of two Nakagami-m RVs, tight closed-form approximate expressions for the outage probability and throughput are derived. Representative numerical results show the accuracy of the proposed approximations.
TL;DR: In this paper, the problem of relay selection and optimal resource allocation for two-way relaying cognitive radio networks using half duplex amplify-andforward and decode-and-forward protocols is investigated.
Abstract: In this letter, the problem of relay selection and optimal resource allocation for two-way relaying cognitive radio networks using half duplex amplify-and-forward and decode-and-forward protocols is investigated. The primary and secondary users are assumed to access the spectrum simultaneously, in a way that the interference introduced to the primary users should be below a certain tolerated limit. Dual decomposition and subgradient methods are used to find the optimal power allocation. A suboptimal approach based on a genetic algorithm is also presented. Simulation results show that the proposed suboptimal algorithm offers a performance close to the optimal performance with a considerable complexity saving.
TL;DR: This problem of finding optimal energy management policies in the presence of energy harvesting sources to maximize network performance is considered in the discounted cost Markov decision process framework and two reinforcement learning algorithms are applied.
Abstract: In this paper, we consider the problem of finding optimal energy management policies in the presence of energy harvesting sources to maximize network performance. We formulate this problem in the discounted cost Markov decision process framework and apply two reinforcement learning algorithms. Prior work obtains optimal policy in the case when the conversion function mapping energy to data transmitted is linear and provides heuristic policies in the case when the same is nonlinear. Our algorithms, however, provide optimal policies regardless of the form of the conversion function. Through simulations, our policies are seen to outperform those of in the nonlinear case.
TL;DR: Performance of selection combining (SC) receiver has been derived over two-wave diffused power (TWDP) fading channels with arbitrary and non-identical fading parameters to derive expression of cumulative distribution function of signal-to-noise ratio (SNR) and probability density function of SNR at the output of SC receiver.
Abstract: Performance of selection combining (SC) receiver has been derived over two-wave diffused power (TWDP) fading channels with arbitrary and non-identical fading parameters. An expression of cumulative distribution function (CDF) of signal-to-noise ratio (SNR) for TWDP fading channel has been derived, which is used to obtain the probability density function (PDF) of SNR at the output of SC receiver. The PDF of output SNR has been used to derive expressions of outage probability and average bit error rate for coherent and non-coherent modulation schemes. Effect of total number of branches M and the fading parameters K and Δ on the system performance has been studied. The obtained results are verified with the special case results available in literature and by Monte Carlo simulation.
TL;DR: In order to support higher order constellations, this letter presents a smart loading scheme that enables the multiplexing of two 16-QAM signals over the air.
Abstract: MIMO systems have become an indispensable part of modern wireless standards, eg LTE advanced However, in applications with strict energy and size constraints, an alternative MIMO scheme with reduced hardware complexity would be attractive Towards this direction, parasitic antennas with a single feeding port have been proposed to emulate MIMO transmission with PSK signaling In order to support higher order constellations, this letter presents a smart loading scheme that enables the multiplexing of two 16-QAM signals over the air Accompanying simulations show that this can be achieved by using a single feeding port and parasitic antennas
TL;DR: This letter presents three novel approaches, namely peak detection, modified maximum peak-to-leaking ratio detection and channel frequency response (CFR) reconstruction, in order to improve the high resolution TOA estimation technique when using OFDM-based WLAN preamble.
Abstract: This letter presents three novel approaches, namely peak detection, modified maximum peak-to-leaking ratio detection and channel frequency response (CFR) reconstruction, in order to improve the high resolution TOA estimation technique when using OFDM-based WLAN preamble. Computer simulations show that all the proposed approaches outperform the state-of-the-art in the WINNER A1 LOS channel. Moreover, the proposed approaches demonstrate their advantages in WARP2 board based Wi-Fi testbed.
TL;DR: This analysis demonstrates that as the strength of the LI decreases and the spectral efficiency increases, the FD Alamouti scheme significantly outperforms conventional half-duplex designs.
Abstract: In this letter, we present a new distributed full-duplex (FD) Alamouti scheme for a three-node cooperative network. The proposed scheme exploits the FD operation at the relay node and forms the Alamouti codewords in three block periods. We characterize the outage probability and the diversity-multiplexing tradeoff of the investigated FD scheme. Our analysis demonstrates that as the strength of the LI decreases and the spectral efficiency increases, the FD Alamouti scheme significantly outperforms conventional half-duplex designs.
TL;DR: This letter performs soft-Kalman filtering for channel estimation in conjunction with soft-interference canceling at the receiver to reduce the inter-carrier interference and proposes two simplified implementations of the soft- Kalman filter for the case of constant-modulus signal constellations.
Abstract: This letter addresses the problem of channel estimation in fast time-varying frequency selective channels. Considering orthogonal frequency division multiplexing in a multiple-input multiple-output system, we perform soft-Kalman filtering for channel estimation in conjunction with soft-interference canceling at the receiver to reduce the inter-carrier interference. We also propose two simplified implementations of the soft-Kalman filter for the case of constant-modulus signal constellations that allow considerable reductions in the receiver computational complexity, while performing more or less closely to the exact soft-Kalman estimator, depending on channel conditions. For non-constant-modulus signal constellations, however, the exact formulation of the soft-Kalman filter should be used.
TL;DR: The maximum periodic correlation magnitude of the proposed optimal QCSS achieves the derived periodic correlation lower bound asymptotically.
Abstract: Compared with the perfect complementary sequence sets, quasi-complementary sequence sets (QCSSs) have the advantage of supporting more users in multicarrier CDMA communications. Constructions for optimal and near-optimal periodic QCSSs are proposed in this paper by using the Singer difference sets and the existing optimal quaternary sequence sets. The maximum periodic correlation magnitude of the proposed optimal QCSS achieves the derived periodic correlation lower bound asymptotically. To the authors' best knowledge, such optimal QCSSs haven't been reported before.
TL;DR: The optimal spectrum sensing algorithm at the secondary user (SU) that could discriminate the PU's' transmitting power is proposed and the related performance is analyzed and a new SU transmission strategy is designed.
Abstract: In this letter, we consider a more practical scenario when the primary user (PU) transmits with multiple levels of power in a cognitive radio (CR) network. The optimal spectrum sensing algorithm at the secondary user (SU) that could discriminate the PU's' transmitting power is proposed and the related performance is analyzed. We also designed a new SU transmission strategy where one transmit power is found for each estimation of the PU's power. The strategy is further optimized according to the SU's achievable rate. In the end, we validate our study by various simulations.
TL;DR: It is proved that the PCF in MPP type II is decreasing convex function of the pairwise distance, using the convexity property to propose simple bounds for thePCF and subsequently for the mean interference which are always tighter than the existing bounds.
Abstract: The calculation of mean interference at a reference point of Matern point process (MPP) type II involves integrals of the pair correlation function (PCF) which are in general difficult to handle. In this letter, we prove that the PCF in MPP type II is decreasing convex function of the pairwise distance. Using the convexity property we propose simple bounds for the PCF and subsequently for the mean interference which are always tighter than the existing bounds.
TL;DR: The physical layer security of multiple-input multiple-output (MIMO) wiretap channels with orthogonal space-time block codes (OSTBCs) and arbitrary antenna correlation is investigated and general correlation matrices with arbitrary eigenvalue distributions are considered.
Abstract: In this paper, the physical layer security of multiple-input multiple-output (MIMO) wiretap channels with orthogonal space-time block codes (OSTBCs) and arbitrary antenna correlation is investigated. In our analysis, we consider general correlation matrices with arbitrary eigenvalue distributions. Also, in order to study the impact of the line-of-sight condition on the secrecy performance, the main channel is assumed to undergo Rician fading, while the eavesdropper one experiences Rayleigh fading. An easy-to-evaluate, closed-form expression for the secrecy outage probability is derived, from which an asymptotic analysis is carried out. Representative numerical results are plotted and validated through Monte Carlo simulations. Insightful discussions regarding the impact of the multiple antennas, correlation, and Rician factor on the secrecy outage performance are provided.
TL;DR: A framework for admission control and session-level performance analysis is proposed by taking into account several factors such as channel reservation for handoffs secondary users (SUs), buffers for handoff SUs and newly arriving SUs, limited buffer size, and queued SUs' leaving due to impatience.
Abstract: For session-level quality-of-service (QoS) provisioning in cognitive radio networks (CRNs), it is essential to adopt an effective admission control scheme with appropriate parameters. In this paper, a framework for admission control and session-level performance analysis is proposed by taking into account several factors such as channel reservation for handoff secondary users (SUs), buffers for handoff SUs and newly arriving SUs, limited buffer size, and queued SUs' leaving due to impatience. The whole system is modeled by a multi-dimensional continuous-time Markov chain, where important session-level QoS performance metrics, i.e., dropping probability and blocking probability are derived.
TL;DR: The derived series are shown to rapidly converge over the range of practical TWDP fading parameters and the BER of a BPSK system operating in TWDP fades is evaluated as an application of the results.
Abstract: Two infinite series expressions are derived for the TWDP fading PDF and CDF. The derived series are shown to rapidly converge over the range of practical TWDP fading parameters. An efficient low-complexity algorithm is also proposed for evaluation of these series. Infinite series solution are derived for the TWDP moments, and the integral of the TWDP fading PDF against the complementary error function for performance analysis purposes. The BER of a BPSK system operating in TWDP fading is evaluated as an application of the results.
TL;DR: Four Q-ary intensity modulation schemes satisfying high-order intensity modulation condition are proposed and can be used with shift-OSTBC to mitigate inter-symbol interference (ISI) and provide diversity gain in asynchronous FSO MIMO channels.
Abstract: Recently, Simon-Vilnrotter and Premaratne-Zheng modified the binary pulse-position modulation (PPM) to support free-space optical (FSO) multi-input multi-output (MIMO) systems with orthogonal space-time block coding (OSTBC) that requires the use of negative symbols. In this paper, we extend the investigation to optical OSTBC schemes with high-order intensity modulation. A necessary and sufficient condition for the high-order intensity modulation to maintain the orthogonality of the applied OSTBC is derived, and four Q-ary intensity modulation schemes satisfying this condition are proposed. In asynchronous FSO MIMO channels in which the signals from different transmitters arrive at the receiver with timing misalignment, the proposed modulation schemes can be used with shift-OSTBC to mitigate inter-symbol interference (ISI) and provide diversity gain.