Cooperative diversity is one of the most effective ways to mitigate the fading effect of wireless channels and obtain the spatial gain in wireless networks. In this paper, an optimal power allocation (OPA) scheme fo...Cooperative diversity is one of the most effective ways to mitigate the fading effect of wireless channels and obtain the spatial gain in wireless networks. In this paper, an optimal power allocation (OPA) scheme for a cooperative communication system using the amplify-and-forward (AF) transmit strategy with multiple relay users is proposed by minimizing the bit-error-rate (BER) at the destination under the constraint of the total transmit power of both the source user and the relay users. Simutation resutts indicate that the proposed power allocation method can achieve significant BER performance improvement than using the equal power allocation (EPA) scheme, while still attains low complexity. The system performance is improved significantly with the increasing of the number of relay users at high signal-noise ratio (SNR). However, at low SNR, the system performance decreases when the relay number increases. Thus, an adaptive relay selection scheme may be used to choose the appropriate relay numbers in different transmission scenarios to provide system performance improvement and keep the power allocation scheme with low complexity.展开更多
This paper investigates the effects of the outdated channel state information(CSI)on the secrecy performance of an underlay spectrum sharing cognitive radio networks(CRNs),where the secondary user(SU)source node(Alice...This paper investigates the effects of the outdated channel state information(CSI)on the secrecy performance of an underlay spectrum sharing cognitive radio networks(CRNs),where the secondary user(SU)source node(Alice)aims to transmit the trusted messages to the full-duplex(FD)aided SU receiver(Bob)with the assistance of cooperative relay(Relay).Considering the impact of feedback delay,outdated CSI will aggravate the system performance.To tackle such challenge,the collaborative zero-forcing beamforming(ZFB)scheme of FD technique is further introduced to implement jamming so as to confuse the eavesdropping and improve the security performance of the system.Under such setup,the exact and asymptotic expressions of the secrecy outage probability(SOP)under the outdated CSI case are derived,respectively.The results reveal that i)the outdated CSI of the SU transmission channel will decrease the diversity gain from min(NANR,NRNB)to NRwith NA,NRand NBbeing the number of antennas of Alice,Relay and Bob,respectively,ii)the introduction of FD technique can improve coding gain and enhance system performance.展开更多
In this study,we investigate the relay selection(RS)problem in full-duplex energy-harvesting(FDEH)relay networks,where the relays are wirelessly powered by harvesting a portion of the received signal power from the so...In this study,we investigate the relay selection(RS)problem in full-duplex energy-harvesting(FDEH)relay networks,where the relays are wirelessly powered by harvesting a portion of the received signal power from the source.We extend the investigation of the relay selection problem in FDEH relay networks to enable multiple relays to be selected simultaneously for improved performance.This is in contrast with existing studies on RS in similar setups,where only one relay can be selected in a transmission cycle.Our simulations show that selecting only a single relay is not always optimal,especially at low signal-to-noise ratios(SNRs).Furthermore,in this paper,we present the design of a greedy RS method with quadratic complexity for FDEH relay networks.Compared with the exhaustive-search-based RS,the proposed greedy RS achieves near-optimum performance in terms of the end-to-end capacity with significantly reduced complexity.展开更多
This article studies the closed-form expressions of outage performance for opportunistic relay under aggregate power constraint in decode-and-forward (DF) relay networks over Rayleigh fading channels, assuming that ...This article studies the closed-form expressions of outage performance for opportunistic relay under aggregate power constraint in decode-and-forward (DF) relay networks over Rayleigh fading channels, assuming that multiple antennas are available at the relay node. According to whether instantaneous signal-to-noise ratio (SNR) or average SNR can be utilized for relay selection, two opportunistic relay schemes, opportunistic multi-antenna relay selection (OMRS) and average best relay selection (ABRS) are proposed. The performances of both two schemes are evaluated by means of theoretical analysis and simulation, it is observed that OMRS is outage-optimal among multi-antenna relay selection schemes and closely approaches the beamforming (BF) scheme known as theoretical outage-optimal. Compared with previous single-antenna opportunistic relaying (OR) scheme, OMRS brings remarkable performance improvement, which is obtained from maximum ratio combining (MRC) and beamforming techniques. It is also shown that the performance of ABRS in asymmetric channels is close to OMRS in the low and median SNR range.展开更多
基金supported by the National Natural Science Foundation of China (60972055)the Shanghai Educational Development Foundation (09CG40)the Science and Technology Commission of Shanghai Municipality (10220710300)
文摘Cooperative diversity is one of the most effective ways to mitigate the fading effect of wireless channels and obtain the spatial gain in wireless networks. In this paper, an optimal power allocation (OPA) scheme for a cooperative communication system using the amplify-and-forward (AF) transmit strategy with multiple relay users is proposed by minimizing the bit-error-rate (BER) at the destination under the constraint of the total transmit power of both the source user and the relay users. Simutation resutts indicate that the proposed power allocation method can achieve significant BER performance improvement than using the equal power allocation (EPA) scheme, while still attains low complexity. The system performance is improved significantly with the increasing of the number of relay users at high signal-noise ratio (SNR). However, at low SNR, the system performance decreases when the relay number increases. Thus, an adaptive relay selection scheme may be used to choose the appropriate relay numbers in different transmission scenarios to provide system performance improvement and keep the power allocation scheme with low complexity.
基金supported by the National Natural Science Foundation of China(No.62201606 and No.62071486)the Project of Science and Technology Planning of Guizhou Province(No.[2020]-030)+3 种基金the Project of Science and Technology Fund of Guizhou Provincial Health Commission(gzwkj2022524)the Project of Youth Science and Technology Talent Growth Guizhou Provincial Department of Education(No.KY[2021]230)the Key Research Base Project of Humanities and Social Sciences of Education Department of Guizhou Provincethe Project of Science and Technology Planning of Zunyi City(No.2022-381 and No.2022-384)。
文摘This paper investigates the effects of the outdated channel state information(CSI)on the secrecy performance of an underlay spectrum sharing cognitive radio networks(CRNs),where the secondary user(SU)source node(Alice)aims to transmit the trusted messages to the full-duplex(FD)aided SU receiver(Bob)with the assistance of cooperative relay(Relay).Considering the impact of feedback delay,outdated CSI will aggravate the system performance.To tackle such challenge,the collaborative zero-forcing beamforming(ZFB)scheme of FD technique is further introduced to implement jamming so as to confuse the eavesdropping and improve the security performance of the system.Under such setup,the exact and asymptotic expressions of the secrecy outage probability(SOP)under the outdated CSI case are derived,respectively.The results reveal that i)the outdated CSI of the SU transmission channel will decrease the diversity gain from min(NANR,NRNB)to NRwith NA,NRand NBbeing the number of antennas of Alice,Relay and Bob,respectively,ii)the introduction of FD technique can improve coding gain and enhance system performance.
基金This work was supported by the National Natural Science Foundation of China(Nos.61622101 and 61571020)The associate editor coordinating the review of this paper and approving it for publication was G.R.Ding.
文摘In this study,we investigate the relay selection(RS)problem in full-duplex energy-harvesting(FDEH)relay networks,where the relays are wirelessly powered by harvesting a portion of the received signal power from the source.We extend the investigation of the relay selection problem in FDEH relay networks to enable multiple relays to be selected simultaneously for improved performance.This is in contrast with existing studies on RS in similar setups,where only one relay can be selected in a transmission cycle.Our simulations show that selecting only a single relay is not always optimal,especially at low signal-to-noise ratios(SNRs).Furthermore,in this paper,we present the design of a greedy RS method with quadratic complexity for FDEH relay networks.Compared with the exhaustive-search-based RS,the proposed greedy RS achieves near-optimum performance in terms of the end-to-end capacity with significantly reduced complexity.
基金supported by the Hi-Tech Research and Development Program of China (2009AA01Z247,2007AA01Z265)the National Natural Science Foundation of China (60972076)
文摘This article studies the closed-form expressions of outage performance for opportunistic relay under aggregate power constraint in decode-and-forward (DF) relay networks over Rayleigh fading channels, assuming that multiple antennas are available at the relay node. According to whether instantaneous signal-to-noise ratio (SNR) or average SNR can be utilized for relay selection, two opportunistic relay schemes, opportunistic multi-antenna relay selection (OMRS) and average best relay selection (ABRS) are proposed. The performances of both two schemes are evaluated by means of theoretical analysis and simulation, it is observed that OMRS is outage-optimal among multi-antenna relay selection schemes and closely approaches the beamforming (BF) scheme known as theoretical outage-optimal. Compared with previous single-antenna opportunistic relaying (OR) scheme, OMRS brings remarkable performance improvement, which is obtained from maximum ratio combining (MRC) and beamforming techniques. It is also shown that the performance of ABRS in asymmetric channels is close to OMRS in the low and median SNR range.