[Show abstract][Hide abstract] ABSTRACT: Recently, energy harvesting (EH) has emerged as a promising way to realize
green communications. In this paper, we investigate the multiuser transmission
network with an EH cooperative relay, where a source transmits independent
information to multiple destinations with the help of an energy constrained
relay. The relay can harvest energy from the radio frequency (RF) signals
transmitted from the source, and it helps the multiuser transmission only by
consuming the harvested energy. By adopting the time switching and the
power-splitting relay receiver architectures, we firstly propose two protocols,
the time-switching cooperative multiuser transmission (TSCMT) protocol and the
power-splitting cooperative multiuser transmission (PSCMT) protocol, to enable
the simultaneous information processing and EH at the relay for the system. To
evaluate the system performance, we theoretically analyze the system outage
probability for the two proposed protocols, and then derive explicit
expressions for each of them, respectively. Moreover, we also discuss the
effects of system configuration parameters, such as the source power and relay
location on the system performance. Numerical results are provided to
demonstrate the accuracy of our analytical results and reveal that compared
with traditional non-cooperative scheme, our proposed protocols are green
solutions to offer reliable communication and lower system outage probability
without consuming additional energy. In particular, for the same transmit power
at the source, the PSCMT protocol is superior to the TSCMT protocol to obtain
lower system outage probability.
Preview · Article · Dec 2014 · Mathematical Problems in Engineering
[Show abstract][Hide abstract] ABSTRACT: This paper investigates the system achievable rate and optimization for the
multiple-input multiple-output (MIMO)-orthogonal frequency division
multiplexing (OFDM) system with an energy harvesting (EH) relay. Firstly we
propose a time switchingbased relaying (TSR) protocol to enable the
simultaneous information processing and energy harvesting at the relay. Then,
we discuss its achievable rate performance theoretically and formulated an
optimization problem to maximize the system achievable rate. As the problem is
difficult to solve, we design an Augmented Lagrangian Penalty Function (ALPF)
method for it. Extensive simulation results are provided to demonstrate the
accuracy of the analytical results and the effectiveness of the ALPF method.
Preview · Article · Dec 2014 · ICIC Express Letters
[Show abstract][Hide abstract] ABSTRACT: Energy harvesting (EH) and network coding (NC) have emerged as two promising
technologies for future wireless networks. In this paper, we combine them
together in a single system and then present a time switching-based network
coding relaying (TSNCR) protocol for the two-way relay system, where an energy
constrained relay harvests energy from the transmitted radio frequency (RF)
signals from two sources, and then helps the two-way relay information exchange
between the two sources with the consumption of the harvested energy. To
evaluate the system performance, we derive an explicit expression of the outage
probability for the proposed TSNCR protocol. In order to explore the system
performance limit, we formulate an optimization problem to minimize the system
outage probability. Since the problem is non-convex and cannot be directly
solved, we design a genetic algorithm (GA)-based optimization algorithm for it.
Numerical results validate our theoretical analysis and show that in such an EH
two-way relay system, if NC is applied, the system outage probability can be
greatly decreased. Moreover, it is shown that the relay position greatly
affects the system performance of TSNCR, where relatively worse outage
performance is achieved when the relay is placed in the middle of the two
sources. This is the first time to observe such a phenomena in EH two-way relay
Preview · Article · Dec 2014 · KSII Transactions on Internet and Information Systems
[Show abstract][Hide abstract] ABSTRACT: This paper investigates the outage performance and optimization for the four-phase two-way transmission network with an energy harvesting (EH) relay. To enable the simultaneous information processing and energy harvesting at the relay, we firstly propose a power splitting-based two-way relaying protocol (PSTWR). Then, we discuss its outage performance theoretically and derive an explicit expression for the system outage probability. In order to find the optimal system configuration parameters such as the optimal power splitting ratio and the optimal transmit power redistribution factor, we formulate an outage-minimized optimization problem. As the problem is difficult to solve, we design a genetic algorithm (GA) based algorithm for it. Besides, we also investigate the effects of the power splitting ratio, the power redistribution factor at the relay, and the source to relay distance on the system outage performance. Finally, extensive simulation results are provided to demonstrate the accuracy of the analytical results and the effectiveness of the GA-based algorithm. Moreover, it is also shown that, the relay position greatly affects the system performance, where relatively worse outage performance is achieved when the EH relay is placed in the middle of the two sources.
No preview · Article · Oct 2014 · KSII Transactions on Internet and Information Systems
[Show abstract][Hide abstract] ABSTRACT: In this study, the authors consider the robust transceiver design in a dual-hop multi-user multiple-input multiple-output amplify-and-forward relay system. By incorporating the antenna correlation at both ends of the channel and taking the channel estimation errors into account, the authors propose two robust design approaches under the minimum sum mean-square-error criterion. Specifically, they decouple the original problem into three convex sub-problems in the first approach and develop an iterative algorithm with guaranteed convergence. The second approach converts the original problem into simple power allocation problems utilising a certain relaying structure, and the approximate closed-form solutions are derived. Some practical implementation issues are also discussed. Simulation results are provided to demonstrate the effectiveness of the proposed approaches.
No preview · Article · Aug 2014 · IET Communications
[Show abstract][Hide abstract] ABSTRACT: This paper investigates the simultaneous wireless information and power
transfer (SWIPT) for two-hop orthogonal frequency division multiplexing (OFDM)
decode-and-forward (DF) relay communication system, where a relay harvests
energy from radio frequency signals transmitted by the source and then uses the
harvested energy to assist the information transmission from the source to its
destination. The power splitting receiver is considered at the relay, which
splits the received signal into two power streams to perform information
decoding (ID) and energy harvesting (EH) respectively. For better understanding
the behavior and exploring the performance limit of such a system, resource
allocation is studied to maximize the total achievable transmission rate. An
optimization problem, which jointly takes into account the power allocation,
the subcarrier pairing and the power splitting, is formulated. Due to its
non-convexity, a resource allocation policy with low complexity based on
separation principle is designed. Simulation results show that the system
performance can be significantly improved by using our proposed policy.
Moreover, the system performance behavior to the relay position is also
discussed, and results show that in the two-hop OFDM system with EH relay, the
relay should be deployed near the source, while in that with conventional
non-EH relay, it should be deployed at the middle between the source and the
[Show abstract][Hide abstract] ABSTRACT: Fuzzy vault scheme (FVS) is one of the most popular biometric cryptosystems for biometric template protection. However, error correcting code (ECC) proposed in FVS is not appropriate to deal with real-valued biometric intraclass variances. In this paper, we propose a multidimensional fuzzy vault scheme (MDFVS) in which a general subspace error-tolerant mechanism is designed and embedded into FVS to handle intraclass variances. Palmprint is one of the most important biometrics; to protect palmprint templates; a palmprint based MDFVS implementation is also presented. Experimental results show that the proposed scheme not only can deal with intraclass variances effectively but also could maintain the accuracy and meanwhile enhance security.
[Show abstract][Hide abstract] ABSTRACT: Biometric template protection is indispensable to protect personal privacy in large-scale deployment of biometric systems. Accuracy, changeability, and security are three critical requirements for template protection algorithms. However, existing template protection algorithms cannot satisfy all these requirements well. In this paper, we propose a hybrid approach that combines random projection and fuzzy vault to improve the performances at these three points. Heterogeneous space is designed for combining random projection and fuzzy vault properly in the hybrid scheme. New chaff point generation method is also proposed to enhance the security of the heterogeneous vault. Theoretical analyses of proposed hybrid approach in terms of accuracy, changeability, and security are given in this paper. Palmprint database based experimental results well support the theoretical analyses and demonstrate the effectiveness of proposed hybrid approach.
[Show abstract][Hide abstract] ABSTRACT: The wireless butterfly network is a representative model for multi-source multi-destination relay communication scenario, where opportunistic network coding (ONC) can be deployed to improve the system's throughput. However, ONC requires feedback information and this may deteriorate the throughput performance and counteract the advantage of ONC. To this end, in this paper, we firstly propose a new transmission protocol by combing fountain codes and network coding into the transmission strategy design for wireless butterfly network. Then, we formulate and analyse the throughput performance for the proposed protocol. Finally, numerical and simulation results are presented, which shows that our proposed protocol outperforms traditional ONC scheme.
No preview · Article · Feb 2014 · Elektronika ir Elektrotechnika
[Show abstract][Hide abstract] ABSTRACT: In this paper, we investigate the robust transceiver design for a downlink multiuser multiple-input multiple-output (MIMO) amplify-and-forward (AF) relay system with imperfect channel state information (CSI). We consider that the actual channel is within the neighborhood of a nominal channel and formulate two optimization problems following the philosophy of worst-case robustness, i.e., minimizing the sum mean-square-error (SMSE) and minimizing the total transmit power for any channel realization in the uncertainty region. In order to efficiently find the solutions, we transform the original problems into suitable forms using the sign-definiteness lemma and then propose an alternating iterative algorithm with guaranteed convergence. To further reduce the computational complexity, the cutting-set method is developed, which alternates between transceiver design and channel determination steps. Moreover, some interesting extensions of the proposed methods are discussed, including various types of uncertainty models and transmit power constraints, nonlinear transceiver structure, and uncertain noise covariance. Simulation results are presented to demonstrate the effectiveness of the proposed robust designs.
No preview · Article · Jan 2014 · IEEE Transactions on Wireless Communications
[Show abstract][Hide abstract] ABSTRACT: This paper presents a cooperative transmission scheme for cooperative multi-relay high-speed railway mobile communication system, where fountain codes and mutual information accumulation (IA) method are adopted. The spreading codes are used to separate and detect the signal with interference from multiple relays, and the signal detection process and information receiving strategy at the destination are designed. Then we analyze the performance of the system in terms of the transmission rate, where the probability density function of the transmission rate of IA is derived, as well as the corresponding average transmission rate. For comparison, the traditional energy accumulation (EA) based receiving scheme is also analyzed. Results show when spreading codes are not orthogonal, if the signal to noise ratio (SNR) is relatively low, the performance of IA-based information receiving method is worse than that of EA-based one, and if SNR is relatively high, the performance of IA-based information receiving method is superior to that of EA-based one.
[Show abstract][Hide abstract] ABSTRACT: This paper studies the beamforming design of two-way relay systems for simultaneous information and power transfer with consideration of imperfect channel state information (CSI). To this end, we seek the robust beamforming design to maximize the weighted sum rate under the power constraint at relay nodes and the energy harvesting constraints at the two source nodes. Due to the infinitely many nonconvex constraints, the robust beamforming design problem is challenging. Therefore, we firstly propose an approximate to the signal to interference plus noise ratio (SINR). Then an iterative algorithm is developed based on the semidefinite relaxation (SDR), S-procedure and successive convex approximation (SCA) techniques. Furthermore, the effectiveness of the proposed algorithm is validated by numerical experiments.
[Show abstract][Hide abstract] ABSTRACT: Weighted sum-rate maximization with transmit power limit and energy harvesting constraints is considered in the context of two-way collaborative relay systems. We discuss an ideal scheme where the source nodes can decode information signal and harvest energy, simultaneously. An iterative algorithm based on semidefinite relaxation (SDR) and successive convex approximation (SCA) is developed to obtain (at least) a local optimal solution. In view of the limitation of the current circuits, we propose a practical ping-pong scheme wherein the source node can only perform one operation at a time. Furthermore, the iterative algorithm and its convergence are extended to such a case. The efficacy of the proposed algorithms is validated by numerical experiments.
[Show abstract][Hide abstract] ABSTRACT: To enhance the symbol error rate (SER) performance of the two-way relay channels with physical layer network coding, this letter proposes a relay selection scheme, in which the relay with the maximal minimum distance between different points in its constellation among all relays is selected to assist two-way transmissions. We give the closed-form expression of minimum distance for binary phase-shift keying and quadrature phase-shift keying. Additionally, we design a low-complexity method for higher-order modulations based on look-up tables. Simulation results show that the proposed scheme improves the SER performance for two-way relay networks.
[Show abstract][Hide abstract] ABSTRACT: Intelligent closed-loop control is a main development tend of future drilling technologies. To fully explore the potential capacity of the closed-loop control function for future measurement/logging-while-drilling systems, in this paper we put forward a real-time channel-adaptive transmission strategy based on RaptorQ codes. To further enhance the system performance, we further extend it to a new version with channel adaptive function, in which the ground control center periodically tracks the variation of channel quality during the process of drilling, and then adaptively adjusts the transmission parameters within the underground sensors through the feedback closed-loop control channel, to maintain the real-time and reliability performance of the data transmission. The framework and the steps of the RaptorQ code based transmission strategy are designed. Finally, we present extensive experimental results performed with real logging data, which show that our proposed solution can improve the transmission efficiency and reliability for M/LWD system greatly, especially when the channel is with high packet loss rate. The results also provide some valuable insights for designing fast stable log data transmission systems with very low feed-back channels.
[Show abstract][Hide abstract] ABSTRACT: In this paper, we investigate the transceiver design in a dual-hop multi-user multiple-input multiple-output amplify-and-forward relay system. By taking the bounded channel uncertainties into account, we propose two robust design methods under the minimum sum mean-square-error (SMSE) criterion. The original problem is first transformed into a tractable one applying the generalized sign-definiteness lemma, and then the transceiver is achieved by employing an iterative algorithm based on alternating optimization. Moreover, in order to reduce the complexity, a novel cutting-set method is developed to solve the considered problem efficiently by solving an alternating sequence of SMSE minimization and worst-case analysis problems. Simulation results are provided to demonstrate the effectiveness of the proposed methods.
[Show abstract][Hide abstract] ABSTRACT: In cognitive radio networks, spectrum sensing is an essential functionality to detect the presence of primary users (PUs). Cyclostationary detector, that can robustly detect weak primary signals, is becoming a promising candidate for spectrum sensing. In this paper, we focus on a weighted cooperative spectrum sensing algorithm based on cyclostationarity. Since the proposed method improves the contributions of the sensing node with high reliability by adapting the weight to the local SNR, it is more reliable than the traditional cyclostationarity based schemes. The simulation results show that the proposed weighted cooperative spectrum sensing scheme outperforms the conventional methods even in low SNR conditions.
[Show abstract][Hide abstract] ABSTRACT: Multicell coordinated beamforming (MCBF), where multiple base stations (BSs) collaborate with each other in the beamforming design for mitigating the intercell interference (ICI), has been a subject drawing great attention recently. Most MCBF designs assume perfect channel state information (CSI) of mobile stations (MSs); however CSI errors are inevitable at the BSs in practice. Assuming elliptically bounded CSI errors, this paper studies the robust MCBF design problem that minimizes the weighted sum power of BSs subject to worst-case signal-to-interference-plus-noise ratio (SINR) constraints on the MSs. Our goal is to devise a distributed optimization method to obtain the worst-case robust beamforming solutions in a decentralized fashion with only local CSI used at each BS and limited backhaul information exchange between BSs. However, the considered problem is difficult to handle even in the centralized form. We first propose an efficient approximation method for solving the nonconvex centralized problem, using semidefinite relaxation (SDR), an approximation technique based on convex optimization. Then a distributed robust MCBF algorithm is further proposed, using a distributed convex optimization technique known as alternating direction method of multipliers (ADMM). We analytically show the convergence of the proposed distributed robust MCBF algorithm to the optimal centralized solution. We also extend the worst-case robust beamforming design as well as its decentralized implementation method to a fully coordinated scenario. Simulation results are presented to examine the effectiveness of the proposed SDR method and the distributed robust MCBF algorithm.
No preview · Article · Jun 2012 · IEEE Transactions on Signal Processing