一种新的基于双中继协同的多跳车间通信网络

文章提出了一种双中继协同的新型传输方案。采用时分方式,将车间通信网络中两个邻近的中继车辆通过无线协同通道信息交互后形成了一对虚拟天线阵。该方案降低了接收机硬件实现复杂度和对准确的同步要求,便于多个单天线中继车辆间共享天线从而实现协同分集。计算机仿真表明,双中继协同提高了系统处于准静态和时变瑞利衰落中继信道下的抗衰落性能,并能有效地抑制中继差错传播,从而获得较高的分集增益。

Outage Probability Analysis of Relay Systems over K-μ Fading Channels

This paper provides an analytical framework for the outage probability evaluation of dual-hop decode-and-forward relay systems operating over K-μfading channels in the presence of co-channel interference. The interferers are independent non-identically distributed K-μfading. An accurate analytical-form expression for the cumulative distribution function of the received signal power to interference and noise ratio is derived. Various numerical results are compared with Monte Carlo simulation results in order to corroborate the accuracy of the proposed expressions. Our results show that increasing the value of kappa of main links will decrease the outage probability of relay systems. Furthermore, the system performance degrades with the number of interferences.

Cognitive amplify-and-forward dual-hop relay networks over α-μ fading channels

This paper provides an analytic performance evaluation of dual-hop cognitive amplify-and-forward (AF) relaying networks over independent nonidentically distributed (i.n.i.d.) fading channels. Two different transmit power constraint strategies at the secondary network are proposed to investigate the performance of the secondary network. In the case of combined power constraint,the maximum tolerable interference power on the primary network and the maximum transmit power at the secondary network are considered. Closed-form lower bound and its asymptotic expression for the outage probability (OP) are achieved. Utilizing the above results,average symbol error probability (ABEP) at high signal-to-noise ratios (SNRs) are also derived. In order to further study the performance of dual-hop cognitive AF relaying networks,the Closed-form lower bounds and asymptotic expressions for OP with single power constraint of the tolerable interference on the primary network is also obtained. Both analytical and simulation are employed to validate the accuracy of the theoretical analysis. The results show that the secondary network obtains a better performance when higher power constraint is employed.

Performance of a Dual-Hop Multi-relay Cooperative Network in a Nakagami-m Fading Environment

An exact average symbol error rate analysis for the distributed dual-hop relay cooperative network with multiple relays in a Nakagami-m fading environment is presented.In the derivation of the moment generation function of receiver Signal-to-Noise Ratio(SNR),the sectional integral method is used,instead of the cumulative density function method which is ordinarily used by the deduction of the outage probability of S-R-D link.The accurate symbol error rate of a dual-hop relay cooperative network is obtained with the closed-form Moment Genoration Function (MGF) expression.The correctness of the symbol error rate is verified through numerical simulations and is compared with other analytical methods.These deductions clearly show that the distributed cooperative diversity network presented has strong superiorities in overcoming severe fading and can achieve full diversity order.

A relay selection scheme based on geometric optimum in cooperative cognitive systems over mixed channels

This paper proposes a relay selection scheme based on geometric optimum principle to maximize the cognitive link＇ s connectivity with limited interference to primary user in cooperative cognitive systems. A dual-hop cognitive relay system is considered, in which the channel impulse response follows independent non-identical distribution （i. n. d. ） each hop, such as Rician, Rayleigh and Nakagami-m distribution. Then, closed-form expressions in terms of outage probability and average bit error rate （ABER） are obtained using amplify-and-forward （AF） relaying protocol over such mixed fading channels. Furthermore, the best range of the relay is derived. Extensive simulation re- suits are conducted to verify the theoretical analysis, which is useful to the network optimal design.

Fundamental capacity for peak interference power constrained cognitive radio relay networks

A Cognitive radio communication link is possible to be interrupted easily when its physical channel suffers severe fading. Relay technology is an effective way to mitigate the fading effect of wireless channels in a network. Based on the highest achievable rate of the relay channels, this paper considers a cognitive radio relay network where the secondary transmitter communicates with the receiver through the best relay node under the peak power constraint of a primary receiver. Intuitively, the secondary transmission can benefit from an intermediate relay node chosen from N possible nodes. To quantify this benefit, outage probability of cognitive radio relay networks is derived and also the closed-form expressions for outage capacity and ergodic capacity of cognitive radio relay networks are obtained in Rayleigh fading channels. Numerical simulation results are provided to show that the outage capacity and ergodic capacity benefit tremendously by properly increasing the number of relaying nodes.

Impact of Maximum Transmit Power Limit on the First-Order and Second-Order Performance of Cognitive Opportunistic Relaying

Abstract： This paper focuses on the first-or- der and second-order performance of dual-hop underlay cognitive radio systems with oppor- tunistic relaying （UCR-OR） over indepen- dent and non-identically distributed （i.ni.d） Rayleigh fading channels. For the UCR-OR systems, the tolerable maximum interference power （TMIP） Q at primary users （PUs） and the allowable maximum transmission power limit （AMTP） P at secondary users （SUs） are considered, simultaneously. We first obtain the closed-form solutions to the first-order performance such as outage probability, ave- rage symbol error ratio （SER）, and ergodic capacity （EC）. Secondly, we investigate the second-order statistical performance, i.e., ave- rage outage rate （AOR） and average outage duration （AOD）. With the consideration that in practice implementation the receiver perfor- mance is primarily influenced by the signal- to-noise ratio （SNR） （not the signal envelope）, the second-order statistical performance is investigated based on the equivalent instan- taneous end-to-end SNR. Finally, we present the detailed performance comparison analysis of UCR-OR systems by defining a random variable ,μ=Pmax/Q. The results show that the effect of μ on the first-order and second-or- der performances is different greatly. For the first-order performance, the perlbrmance gap is negligible when the value of// is relatively large. However, for the second-order one, the gap is distinct.

Secrecy rate analysis of dual-hop AF relay wiretap channel

An amplify-and-forward(AF) dual-hop relay is proposed for secure communication within Wyner s wiretap channel.Based on an information-theoretic formulation,the average secrecy rate is characterized when two legitimate partners communicate over a quasi-static fading channel.Theoretical analysis and simulation results show that both cooperative strategies of average power scaling(APS) and instantaneous power scaling(IPS) are proved to be able to achieve information-theoretic security,and eavesdropper is unable to decode any information.

Performance analysis of relay-aided free-space optical communication system over gamma-gamma fading channels with pointing errors

The average bit error rate(ABER) performance of a decode-and-forward(DF) based relay-assisted free-space optical(FSO) communication system over gamma-gamma distribution channels considering the pointing errors is studied. With the help of Meijer's G-function, the probability density function(PDF) and cumulative distribution function(CDF) of the aggregated channel model are derived on the basis of the best path selection scheme. The analytical ABER expression is achieved and the system performance is then investigated with the influence of pointing errors, turbulence strengths and structure parameters. Monte Carlo(MC) simulation is also provided to confirm the analytical ABER expression.