Showing papers in "IEEE Communications Letters in 2013"
TL;DR: It is shown that the proposed antenna selection based SM systems are capable of attaining a significant gain in signal-to-noise ratio (SNR) compared to conventional SM systems, and also outperform the conventional MIMO systems employing antenna selection at both low and medium SNRs.
Abstract: Novel transmit antenna selection techniques are conceived for Spatial Modulation (SM) systems and their symbol error rate (SER) performance is investigated. Specifically, low-complexity Euclidean Distance optimized Antenna Selection (EDAS) and Capacity Optimized Antenna Selection (COAS) are studied. It is observed that the COAS scheme gives a better SER performance than the EDAS scheme. We show that the proposed antenna selection based SM systems are capable of attaining a significant gain in signal-to-noise ratio (SNR) compared to conventional SM systems, and also outperform the conventional MIMO systems employing antenna selection at both low and medium SNRs.
225 citations
TL;DR: This paper addresses the problem of amplify-and-forward (AF) relaying in a hybrid satellite-terrestrial link, where a masked destination node receives the relayed transmission from a terrestrial link and direct transmission from the satellite link.
Abstract: In this paper, the transmission of signals in a hybrid satellite-terrestrial link is considered. In particular, we address the problem of amplify-and-forward (AF) relaying in a hybrid satellite-terrestrial link, where a masked destination node receives the relayed transmission from a terrestrial link and direct transmission from the satellite link. The satellite-relay and satellite-destination links are assumed to follow the Shadowed-Rician fading; and the channel of the terrestrial link between the relay and destination is assumed to follow the Nakagami-m fading. The average symbol error rate of the considered AF cooperative scheme for M-ary phase shift keying constellation is derived for these generalized fading channels. Moreover, analytical diversity order of the hybrid system is also obtained.
192 citations
TL;DR: It is proved analytically that such physical MIMO channels have a finite upper capacity limit, for any channel distribution and SNR, and it is proved that the relative capacity gain of employing MIMo is at least as large as with ideal transceivers.
Abstract: The capacity of ideal MIMO channels has a high-SNR slope that equals the minimum of the number of transmit and receive antennas. This letter analyzes if this result holds when there are distortions from physical transceiver impairments. We prove analytically that such physical MIMO channels have a finite upper capacity limit, for any channel distribution and SNR. The high-SNR slope thus collapses to zero. This appears discouraging, but we prove the encouraging result that the relative capacity gain of employing MIMO is at least as large as with ideal transceivers.
191 citations
TL;DR: In this paper, a new molecular modulation scheme for nanonetworks is proposed, and the error probability of the proposed scheme as well as that of two previously known schemes, the concentration and molecular shift keying modulations, are derived for the Poisson model by taking into account the error propagation effect of previously decoded symbols.
Abstract: In this letter, a new molecular modulation scheme for nanonetworks is proposed. To evaluate the scheme, a system model based on the Poisson distribution is introduced. The error probability of the proposed scheme as well as that of two previously known schemes, the concentration and molecular shift keying modulations, are derived for the Poisson model by taking into account the error propagation effect of previously decoded symbols. The proposed scheme is shown to outperform the previously introduced schemes. This is due to the fact that the decoding of the current symbol in the proposed scheme does not encounter propagation of error, as the decoding of the current symbol does not depend on the previously transmitted and decoded symbols. Finally, fundamental limits on the probability of error of a practical set of encoders and decoders are derived using information theoretical tools.
187 citations
TL;DR: An analytical characterization of the globally optimal resource sharing strategy is provided, and two suboptimal strategies with less complexity are proposed, demonstrated through numerical examples.
Abstract: The benefit of device-to-device (D2D) communication hinges on intelligent resource sharing between cellular and D2D users. This letter aims to optimize resource sharing for D2D communication to better utilize uplink resources in a multi-user cellular system with guaranteed quality of normal cellular communications. Despite the nonconvex difficulty, we provide an analytical characterization of the globally optimal resource sharing strategy, and furthermore propose two suboptimal strategies with less complexity. The superiority of the proposed resource sharing strategies is demonstrated through numerical examples.
145 citations
TL;DR: D2D communication is introduced into the problem of secrecy capacity, such that D2D pair could achieve its own transmission while the secrecy requirement of cellular communication is still satisfied and the optimal transmission power is derived.
Abstract: Device-to-device (D2D) communication is a promising technology for wireless communication in the near future. Since D2D communication usually reuses the resource of cellular users, interference management is a key element. However, when secrecy capacity is taken into consideration, the interference caused by D2D communication could be taken advantage of as a kind of help against eavesdroppers. In this paper, we novelly introduce D2D communication into the problem of secrecy capacity, such that D2D pair could achieve its own transmission while the secrecy requirement of cellular communication is still satisfied. Moreover, we utilize secrecy outage probability to better depict the imperfect channel state information at the eavesdropper. We also derive the optimal transmission power and propose the access control mechanism.
144 citations
TL;DR: This paper investigates several important performance metrics of cognitive amplify-and-forward (AF) relay networks with a best relay selection strategy and subject to non-identical Rayleigh fading with the result that the diversity gain is defined by the number of relays pertaining to the SU network, being therefore not affected by the interference power constraint of the PU network.
Abstract: This paper investigates several important performance metrics of cognitive amplify-and-forward (AF) relay networks with a best relay selection strategy and subject to non-identical Rayleigh fading. In particular, assuming a spectrum sharing environment consists of one secondary user (SU) source, K SU relays, one SU destination, and one primary user (PU) receiver, closed-form expressions for the outage probability (OP), average symbol error probability (SEP), and ergodic capacity of the SU network are derived. The correctness of the proposed analysis is corroborated via Monte Carlo simulations and readily allows us to evaluate the impact of the key system parameters on the end-to-end performance. An asymptotic analysis is also carried out and reveals that the diversity gain is defined by the number of relays pertaining to the SU network (i.e., K), being therefore not affected by the interference power constraint of the PU network.
143 citations
TL;DR: The effective signal-to-noise-and-distortion ratios at both transmitter nodes are obtained and used to deduce exact and asymptotic closed-form expressions for the outage probabilities (OPs), as well as tractable formulations for the symbol error rates (SERs).
Abstract: Hardware impairments in physical transceivers are known to have a deleterious effect on communication systems; however, very few contributions have investigated their impact on relaying This paper quantifies the impact of transceiver impairments in a two-way amplify-and-forward configuration More specifically, the effective signal-to-noise-and-distortion ratios at both transmitter nodes are obtained These are used to deduce exact and asymptotic closed-form expressions for the outage probabilities (OPs), as well as tractable formulations for the symbol error rates (SERs) It is explicitly shown that non-zero lower bounds on the OP and SER exist in the high-power regime-this stands in contrast to the special case of ideal hardware, where the OP and SER go asymptotically to zero
132 citations
TL;DR: This work proposes an enhanced jump-stay (EJS) algorithm, which lowers the upper-bounds of both the maximum time-to-rendezvous (MTTR) and the expected time- to-hendezvous (E(TTR) under the asymmetric model.
Abstract: Rendezvous is a fundamental operation for cognitive users to establish communication links. In [5], we proposed a jump-stay (JS) rendezvous algorithm which was shown to have the overall best performance. In this work, we propose an enhanced jump-stay (EJS) algorithm. Compared with JS, EJS lowers the upper-bounds of both the maximum time-to-rendezvous (MTTR) and the expected time-to-rendezvous (E(TTR)) from O(P3) to O(P2) under the asymmetric model, while keeping the same order O(P) of upper-bounds of MTTR and E(TTR) under the symmetric mode, where P is the smallest prime number greater than the total number of channels.
126 citations
TL;DR: An energy-efficient genetic algorithm mechanism to resolve quality of service (QoS) multicast routing problem, which is NP-complete, depends on bounded end-to-end delay and minimum energy cost of the multicast tree.
Abstract: The consideration of energy consumption in wireless ad hoc networks prevents the problem of the network exhausting batteries, thus partitioning the entire network. Power-aware multicasting is proposed to reduce the power consumption. This letter presents an energy-efficient genetic algorithm mechanism to resolve quality of service (QoS) multicast routing problem, which is NP-complete. The proposed genetic algorithm depends on bounded end-to-end delay and minimum energy cost of the multicast tree. Simulation results show that the proposed algorithm is effective and efficient.
123 citations
TL;DR: This paper derives tractable upper and lower bounds on W, denoted as W-1, and illustrates their usefulness in identifying conditions under which user cooperation can yield a lower outage probability than non-cooperative transmission.
Abstract: Problems formulated in terms of logarithmic or exponential equations often use the Lambert W function in their solutions. Expansions, approximations and bounds on W have been derived in an effort to gain a better understanding of the relationship between equation parameters. In this paper, we focus on one of the branches of W, denoted as W-1, we derive tractable upper and lower bounds and we illustrate their usefulness in identifying conditions under which user cooperation can yield a lower outage probability than non-cooperative transmission.
TL;DR: An improved version of the simplified successive-cancellation decoding algorithm that increases decoding throughput without degrading the error-correction performance is presented.
Abstract: The serial nature of successive-cancellation decoding results in low polar decoder throughput. In this letter we present an improved version of the simplified successive-cancellation decoding algorithm that increases decoding throughput without degrading the error-correction performance. We show that the proposed algorithm has up to three times the throughput of the simplified successive-cancellation decoding algorithm and up to twenty-nine times the throughput of a standard successive-cancellation decoder while using the same number of processing elements.
TL;DR: A new power allocation algorithm is introduced that optimizes the effective capacity of the terrestrial link for given Quality of Service (QoS) requirements while guaranteeing a specified outage probability for the satellite link.
Abstract: The increasing demand for high-speed multimedia services and the underutilization of scarce satellite spectral resources have recently led the researchers to propose the concept of cognitive satellite terrestrial networks. Considering this novel architecture, we propose an efficient resource management mechanism for the terrestrial network that acts as the secondary system. We introduce a new power allocation algorithm that optimizes the effective capacity of the terrestrial link for given Quality of Service (QoS) requirements while guaranteeing a specified outage probability for the satellite link. Both perfect and imperfect channel estimation cases are considered in the power allocation scheme and analytical results are presented. Numerical calculations evaluate the performance of the proposed scheme.
TL;DR: An novel concept for integrating visible light produced by LEDs with indoor positioning using multiple optical receivers is presented, using the received signal strength indication (RSSI), which changes by on transmission distance and angle.
Abstract: An novel concept for integrating visible light produced by LEDs with indoor positioning using multiple optical receivers is presented in this study. We propose an algorithm using the received signal strength indication (RSSI), which changes by on transmission distance and angle. In order to estimate the position, the transmitters location code was received using multiple optical receivers. The validity of the proposed scheme was demonstrated by determining the local position using distances between the transmitter and receivers, and the relative position between receivers.
TL;DR: This paper uses the non-decision directed maximum likelihood criterion for estimating the channel delay and derives the Cramer-Rao lower bound and evaluates the performance of the proposed synchronization algorithm by investigating its mean square error.
Abstract: Synchronization is an essential feature of any communication system. Due to the very low throughput of molecular communications systems, blind synchronization is preferred in order to reduce communications overhead. In this paper, we present the first blind synchronization algorithm for the diffusion-based molecular communication channel. Considering a diffusion-based physical channel model, we use the non-decision directed maximum likelihood criterion for estimating the channel delay. We then derive the Cramer-Rao lower bound and evaluate the performance of the proposed synchronization algorithm by investigating its mean square error.
TL;DR: The performance of multihop half duplex relaying is studied as a benchmark, showing that FDR outperforms HDR, in terms of the outage probability, for sufficiently large values of PLIR.
Abstract: We consider a multihop full duplex relaying (FDR) system, where multiple full duplex decode-and-forward relays are connected in cascade so as to forward the information from a source terminal to a destination terminal Since FDR causes additional "echo" interference at the relay, we introduce a parameter that captures the ability of the relays to isolate transmission from reception This parameter is defined as the ratio of the received desired signal power to the received interference power, when the transmit power is the same for the useful and the interfering signals, and dubbed as quotedblleft path-loss-to-interference ratioquotedblright (PLIR) For given values of the PLIR, we investigate the number of full duplex relays that lead to the minimum outage probability The performance of multihop half duplex relaying (HDR) is also studied as a benchmark, showing that FDR outperforms HDR, in terms of the outage probability, for sufficiently large values of PLIR
TL;DR: An effective algorithm named QoS-aware energy-efficient resource scheduling is proposed to address the problem and can effectively achieve the optimal solution and bring remarkable improvements on energy efficiency with QoS guarantees.
Abstract: In this letter, the energy-efficient radio resource scheduling is studied with quality of service (QoS) guarantees in a multi-user OFDMA system. In contrast to existing works on QoS-aware scheduling, which mostly take sum throughput or total transmission power as optimization objectives, we formulate an optimization problem to maximize the energy efficiency subject to users' QoS requirements. Based on Lagrangian duality then, an effective algorithm named QoS-aware energy-efficient resource scheduling is proposed to address the problem. Simulation results show that our proposed algorithm can effectively achieve the optimal solution and bring remarkable improvements on energy efficiency with QoS guarantees.
TL;DR: A unified metric for energy efficiency (EE) and spectral efficiency (SE) tradeoff design in wireless networks and shows that the objective function of this SOO problem is quasi-concave with the transmit power and a unique globally optimal solution is derived.
Abstract: In this letter, we propose a unified metric for energy efficiency (EE) and spectral efficiency (SE) tradeoff design in wireless networks. Different from previous EE-based or SE-based design, we simultaneously optimize both EE and SE. First, we formulate our design problem as a multi-object optimization (MOO) problem, in which the Pareto optimal set is characterized. After normalizing EE and SE to make them comparable, we then convert the MOO problem into a single-object optimization (SOO) problem by the weighted product scalarization method. We further show that the objective function of this SOO problem, i.e., our proposed EE and SE tradeoff (EST) metric, is quasi-concave with the transmit power and a unique globally optimal solution is derived. Numerical results validate the effectiveness of the proposed unified EST metric.
TL;DR: A joint design of energy-efficient sensing and transmission durations for a cognitive radio system in which the primary user (PU) is protected and a sub-optimal algorithm that maximizes the energy efficiency for the CR system is presented.
Abstract: In this paper, we consider a joint design of energy-efficient sensing and transmission durations for a cognitive radio (CR) system in which the primary user (PU) is protected. The design problem is formulated as a function of two variables, which are sensing and transmission durations, subject to the interference to the PU. The optimal solutions are analyzed and a sub-optimal algorithm that maximizes the energy efficiency for the CR system is presented. The performance of the proposed energy-efficient design for the CR system is also evaluated.
TL;DR: It is demonstrated that the maximum secrecy outage diversity gain of NA NB is achieved and the physical layer secrecy of TAS/GSC is characterized via the new closed-form expressions for the exact and the asymptotic secrecy outage probability.
Abstract: We propose and analyze transmit antenna selection with receive generalized selection combining (TAS/GSC) for physical layer security enhancement in multiple-input multiple-output wiretap channels. In this protocol, a single antenna out of NA antennas is selected at the transmitter and LB antennas out of NB antennas are combined at the legitimate receiver. We characterize the physical layer secrecy of TAS/GSC via our new closed-form expressions for the exact and the asymptotic secrecy outage probability. We demonstrate that the maximum secrecy outage diversity gain of NA NB is achieved.
TL;DR: This work accounts for the relay self-interference, and exploits the cooperative diversity offered by the independently fading source/relay message replicas that arrive at the destination, and proposes a relay transmit power optimization scheme that only requires the relay knowledge of channel statistics.
Abstract: We evaluate the outage performance in a three-terminal full-duplex relay channel that adopts a selective decode-and-forward protocol, taking relay self-interference into account. Previous work focused on coverage extension scenarios where direct source-destination transmissions are neglected or considered as interference. In this work, we account for the relay self-interference, and exploit the cooperative diversity offered by the independently fading source/relay message replicas that arrive at the destination. We present an approximate, yet accurate, closed-form expression for the end-to-end outage probability that captures their joint effect. With the derived expression in hand, we propose a relay transmit power optimization scheme that only requires the relay knowledge of channel statistics. Finally, we corroborate our analysis with simulations.
TL;DR: By using the analytical expressions of the capacity, it is observed that the optimal power and rate adaptation provides better capacity than the optimal rate adaptation with constant power from low to moderate signal-to-noise ratio values over dissimilar Rician fading channels.
Abstract: In this letter, we derive the probability density function (PDF) and cumulative distribution function (CDF) of the minimum of two non-central Chi-square random variables with two degrees of freedom in terms of power series. With the help of the derived PDF and CDF, we obtain the exact ergodic capacity of the following adaptive protocols in a {decode-and-forward} (DF) cooperative system over dissimilar {Rician} fading channels: (i) constant power with optimal rate adaptation; (ii) optimal simultaneous power and rate adaptation; (iii) channel inversion with fixed rate. By using the analytical expressions of the capacity, it is observed that the optimal power and rate adaptation provides better capacity than the optimal rate adaptation with constant power from low to moderate signal-to-noise ratio values over dissimilar Rician fading channels. Despite low complexity, the channel inversion based adaptive transmission is shown to suffer from significant loss in capacity as compared to the other adaptive transmission based techniques over DF Rician channels.
TL;DR: Asymptotic results reveal that the expected diversity gain cannot be realized when CSI is outdated during the antenna selection process, and the validity of the formulations is corroborated by Monte Carlo simulations.
Abstract: Multiple antennas at the transmitter enhance the diversity performance of multiple-input single-output (MISO) wiretap channels by selecting a single antenna that maximizes the instantaneous signal-to-noise ratio (SNR) at the intended receiver. However, the expected diversity performance may not be fully realized when channel state information (CSI) is outdated at the transmitter. Owing to this fact, in this letter we analyze the effects of outdated CSI on the secrecy outage performance of MISO wiretap channels with transmit antenna selection. More specifically, assuming Nakagami-m fading, a closed-form expression for the exact secrecy outage probability is derived, from which an asymptotic analysis is carried out. Our asymptotic results reveal that the expected diversity gain cannot be realized when CSI is outdated during the antenna selection process. The validity of our formulations is corroborated by Monte Carlo simulations.
TL;DR: This letter considers a multi-antenna downlink network where a secure user (SU) coexists with a passive eavesdropper, and combines the physical layer security technique based on switched beam beamforming with an energy-efficient power allocation scheme.
Abstract: In this letter, we consider a multi-antenna downlink network where a secure user (SU) coexists with a passive eavesdropper. There are two design requirements for such a network. First, the information should be transferred in a secret and efficient manner. Second, the quality of service (QoS), i.e. delay sensitivity, should be take into consideration to satisfy the demands of real-time wireless services. In order to fulfill the two requirements, we combine the physical layer security technique based on switched beam beamforming with an energy-efficient power allocation. The problem is formulated as the maximization of the secrecy energy efficiency subject to delay and power constraints. By solving the optimization problem, we derive an energy-efficient power allocation scheme. Numerical results validate the effectiveness of the proposed scheme.
TL;DR: This letter presents the outage performance analysis for a cognitive relay network (CRN) with imperfect channel knowledge estimations, and results show that increasing the number of relays is an effective approach to mitigate the outageperformance degradation caused by the imperfect CSI.
Abstract: This letter presents the outage performance analysis for a cognitive relay network (CRN) with imperfect channel knowledge estimations. Under the condition of imperfect channel state information (CSI) estimations of interference links between primary and secondary systems, especially the links from both secondary transmitter and secondary relays to primary users, the exact outage probability is derived over Rayleigh fading channels and is verified through simulations. The simulation results show that: 1) increasing the number of relays is an effective approach to mitigate the outage performance degradation caused by the imperfect CSI; 2) the imperfect CSI of the secondary transmitter-primary user (PU) link has a greater impact on the outage performance than that of the secondary relay-PU link.
TL;DR: A general algorithm procedure embedded with an iterative power allocation algorithm (IPAA) is proposed, which has good performance with the advantages of fast convergence, low complexity and insensitivity to initial values.
Abstract: This letter investigates the fundamental tradeoff between energy efficiency (EE) and spectral efficiency (SE) for interference-limited wireless networks (IWNs), which is a nonconvex optimization and NP-hard problem. A general algorithm procedure (GAP) embedded with an iterative power allocation algorithm (IPAA) is proposed, which has good performance with the advantages of fast convergence, low complexity and insensitivity to initial values. Simulation results explicitly depict the EE-SE tradeoff curve for IWNs.
TL;DR: This work provides a parameterized linear power model which covers the individual aspects of a BS which are relevant for a power consumption analysis, especially the transmission bandwidth and the number of radio chains.
Abstract: Power models are needed to assess the power consumption of cellular base stations (BSs) on an abstract level. Currently available models are either too simplified to cover necessary aspects or overly complex. We provide a parameterized linear power model which covers the individual aspects of a BS which are relevant for a power consumption analysis, especially the transmission bandwidth and the number of radio chains. Details reflecting the underlying architecture are abstracted in favor of simplicity and applicability. We identify current power-saving techniques of cellular networks for which this model can be used. Furthermore, the parameter set of typical commercial BSs is provided and compared to the underlying complex model. The complex model is well approximated while only using a fraction of the input parameters.
TL;DR: The benefits of the proposed selection scheme, as the number of receive antennas increases, are further substantiated by comparing its relative energy gain over the TAS method for a target uncoded Symbol Error Rate (SER).
Abstract: In this Letter, a low-complexity Euclidean distance-based method for antenna subset selection in Spatial Modulation systems is presented The proposed method avoids the high complexity of both the optimal exhaustive search and of a recently proposed Euclidean distance-based algorithm for performing the selection Moreover, as the number of receive antennas increases and for practical signal-to-noise ratio (SNR) values, it offers better error performance than the conventional transmit antenna selection (TAS) algorithm In addition, the benefits of the proposed selection scheme, as the number of receive antennas increases, are further substantiated by comparing its relative energy gain over the TAS method for a target uncoded Symbol Error Rate (SER)
TL;DR: A novel algorithm is proposed for automatic modulation classification in multiple-input multiple-output spatial multiplexing systems, which employs fourth-order cumulants of the estimated transmit signal streams as discriminating features and a likelihood ratio test (LRT) for decision making.
Abstract: A novel algorithm is proposed for automatic modulation classification in multiple-input multiple-output spatial multiplexing systems, which employs fourth-order cumulants of the estimated transmit signal streams as discriminating features and a likelihood ratio test (LRT) for decision making. The asymptotic likelihood function of the estimated feature vector is analytically derived and used with the LRT. Hence, the algorithm can be considered as asymptotically optimal for the employed feature vector when the channel matrix and noise variance are known. Both the case with perfect channel knowledge and the practically more relevant case with blind channel estimation are considered. The results show that the proposed algorithm provides a good classification performance while exhibiting a significantly lower computational complexity when compared with conventional algorithms.
TL;DR: Simulation results show that the proposed hybrid automatic repeat request (HARQ) scheme can perform as well as the existing schemes based on turbo codes and low-density parity-check codes under a low-complexity successive cancellation decoder.
Abstract: A hybrid automatic repeat request (HARQ) scheme based on a novel class of rate-compatible polar (RCP) codes is proposed. The RCP codes are constructed by performing punctures and repetitions on the conventional polar codes. Simulation results over binary-input additive white Gaussian noise channels show that, under a low-complexity successive cancellation decoder, the proposed HARQ scheme can perform as well as the existing schemes based on turbo codes and low-density parity-check codes. The proposed transmission scheme is only about 1.0 to 1.5dB away from the channel capacity with the information block length of 1024 bits.