共查询到19条相似文献,搜索用时 187 毫秒
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在单中继协作通信系统模型下,研究了直接传输、固定解码转发( DF)中继、选择DF中继和增量中继协议。为了提高协作通信系统的频谱效率和中断性能,通过比较源-目的端和中继-目的端的瞬时信道增益来判定是否需要采用协同通信模式,提出一种改进的解码转发方式( IDF)。通过将选择DF中继和增量中继的优点结合,提出了一种增量选择中继( ISR)策略,并给出了2种改进协议任意信噪比的中断概率表达式。仿真结果表明,与传统的单中继解码转发协议相比, IDF和ISR均具有更低的中断概率, ISR具有最低的中断概率。 相似文献
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在基于非正交多址接入技术(NOMA)的多用户多中继协作中继网络中,为优先满足混叠信号中的时延敏感信息的服务质量(QoS)需求,对功率因子进行了简单分析,进而找到了关于信道增益的解码限制条件。在给定中继的情况下,根据解码限制条件建立用户集合,进而找到可以使高QoS信号速率最大化的用户中继对作为最佳“用户-中继”来传递信号。并且对该“用户-中继”选择方案下的系统中断概率的表达式进行推导并求出了其渐进式。仿真结果验证了推导结果的正确性,系统的中断概率随着节点数目的增多而降低,而当信噪比趋于无穷时,系统的分集增益取决于用户数目和中继数目。且与已有文献进行对比,本文提出的用户中继匹配方案的中断性能相对较好。 相似文献
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在Nakagami-m衰落信道下,分析了两跳固定增益放大转发中继通信系统的性能.首先采用基于概率密度函数(PDF)的性能分析法推导了无协作分集时系统的中断概率和平均误符号率(ASER)的闭合表达式,然后采用基于矩生成函数(MGF)的方法推导了有协作分集时系统的中断概率和ASER表达式以及接收信噪比的n阶矩的闭合表达式.仿真结果显示,所推导的闭合表达式与数值仿真结果吻合良好,协作分集和较大的m值可提升系统性能,中继前后两跳的信道质量对系统性能的影响并不相同. 相似文献
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有限反馈机会中继通信系统的中断概率性能 总被引:1,自引:0,他引:1
该文针对放大转发机会中继通信系统,研究了有限反馈条件下系统的中断概率及分集性能。在有限反馈条件下,量化误差将影响最优中继的选择进而恶化机会中继通信系统的性能。该文首先推导了有限反馈条件下机会中继系统的中断概率近似表达式,并在此基础上分析获得两个结论:在有限反馈条件下,无论备选中继数目为何,系统的分集阶数可达且只可达到2;当备选中继个数一定时,随着反馈比特数的增加,系统中断概率将趋近于选择最佳中继节点所能获得的性能。仿真结果验证了中断概率的理论表达式及其分析结论,可为有限反馈条件下的中继传输协议设计提供理论支持。 相似文献
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研究了功率受限情况下多中继协作通信网络的中继选择和功率优化问题。在AF网络中,提出了一种低复杂度中继选择与功率分配算法,其目标是在总功率一定的条件下使系统的中断概率最小。本算法对源节点和所有潜在中继节点进行功率分配,结合当前信噪比选择最优的中继集合,通过最速下降法求出使系统中断概率最低的功率分配因子。该算法不需要知道大量瞬时信道信息、不需要系统在等功率条件下进行中继选择,只需求得中继节点排列矩阵便可根据当前信噪比自适应获得最优中继节点集合。仿真结果表明,在相同条件下,该算法明显优于不同中继节点集合下几种算法的中断性能,并且与传统的SAF及AAF算法相比,有效降低了中断概率,提升了系统性能和功率效率。 相似文献
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《电子学报:英文版》2017,(5):1048-1056
This paper studies the outage performance of a cognitive Amplify-and-forward (AF) relay network subject to Rayleigh fading.Under the condition of imperfect Channel state information (CSI) estimations of the links from the secondary system to the Primary user (PU),the closed-form upper and lower bounds of the outage probability are derived through a geometrical analysis method.An asymptotic analysis of the outage probability is also derived in the high Signal-to-noise ratio (SNR) regime to gain additional insights on the system.The simulation results corroborate our theoretical analysis,and the effectiveness of the geometrical analysis method is verified with the conventional approach as a benchmark.The asymptotic results are very tight with the analytical lower bound in the high SNR regime.It also can be observed from the simulation results that the impact of the number of relays as well as the imperfect CSI on the outage probability and the diversity order. 相似文献
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Selection has been shown to be an effective and practical method of implementing cooperative diversity. However, the available analysis has largely focused on diversity order and the asymptotically high signal to noise ratio (SNR) regimes. We approximate the outage probability of selection cooperation for all SNR levels and arbitrary channel distributions. The approximations are significantly better than the available high-SNR approximations for practical values of outage probability. 相似文献
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We investigate the joint relay and antenna selection performance in a multiple input multiple output (MIMO) Vehicle-to-Vehicle (V2V) communication system employing physical layer network coding (PLNC) with amplify-and-forward (AF) scheme at the relay antenna. Analytic results are derived under the cascaded Nakagami-m fading channel model assumption, which covers cascaded Rayleigh and conventional cellular channel models as well. We evaluate the performance of the system in terms of joint outage probability of sources and derive closed-form expressions for lower and upper bounds while an exact expression is found as a single integral form. Besides, the asymptotic diversity order is analyzed and quantified as a function of number of relays and antennas installed on the source and relay vehicles, and channel parameters. Finally, we verify the analytic derivations by computer simulations. Our results show that the outage probability performance decreases with the increasing cascading degrees of the channels but joint relay and antenna selection enhances the performance of the system superbly with the increasing number of relays and antennas. Also it is shown throughout all the simulation results, the lower bound for the joint outage probability seems to consistently be well tight for large SNR. Therefore it can be used for practical design of inter-vehicular communication systems which contain multiple relays and antennas. 相似文献
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针对存在多个非共谋窃听者,研究了一种基于全双工中继和两阶段中继选择(TSRS)的非正交多址接入(NOMA)物理层安全通信方案。每个通信过程包含一个传输时隙,系统在每个时隙开始由TSRS策略选择最优中继,所选中继在从源节点接收NOMA叠加信号的同时,向两个目的节点转发上一时隙的再编码叠加信号,两个目的节点采用串行干扰消除(SIC)技术从中继叠加信号中解码获取各自的期望信号。推导了非理想SIC下系统安全中断概率的近似表达式,进行了蒙特卡洛(Monte-Carlo)仿真验证,同时分析了各仿真参数(SIC残余干扰系数、目标安全速率、中继规模等)与系统安全中断概率的关系。理论分析与模拟仿真的结果表明,全双工技术与TSRS的结合方案能有效提升系统的安全中断性能。将该方案应用于实际通信系统设计时,选择合适传输信噪比(SNR)、提高串行干扰消除能力或适当增加中继数量均可实现更好的保密性能。 相似文献
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Michalopoulos D.S. Karagiannidis G.K. 《Wireless Communications, IEEE Transactions on》2008,7(3):1073-1082
We deal with the concept of physical-layer fairness in amplify and forward cooperative diversity systems, which reflects the need for equally allocating the consumed power among the relays. To this end, we propose a method which utilizes knowledge on both the instantaneous and average channel conditions in order to encompass this concept, by attributing a weight coefficient to each relay depending on its average channel state and then selecting the relay with the best instantaneous "weighted" channel conditions. We also provide a performance analysis of the proposed scheme that includes an analytical expression for the outage probability, together with a closed form one in the high signal-to-noise-ratio (SNR) regime. Through the latter expression, the average symbol error probability (ASEP) for high SNRs is also derived. Numerical results demonstrate that, for small number of available relays or for high SNRs, the performance of the proposed scheme resembles that of the "best relay selection" scheme, in terms of outage probability and ASEP, despite maintaining the average power consumptions equal. 相似文献
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Avestimehr A.S. Tse D.N.C. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2007,53(4):1401-1415
In slow-fading scenarios, cooperation between nodes can increase the amount of diversity for communication. We study the performance limit in such scenarios by analyzing the outage capacity of slow fading relay channels. Our focus is on the low signal-to-noise ratio (SNR) and low outage probability regime, where the adverse impact of fading is greatest but so are the potential gains from cooperation. We showed that while the standard Amplify-Forward protocol performs very poorly in this regime, a modified version we called the Bursty Amplify-Forward protocol is optimal and achieves the outage capacity of the network. Moreover, this performance can be achieved without a priori channel knowledge at the receivers. In contrast, the Decode-Forward protocol is strictly suboptimal in this regime. Our results directly yield the outage capacity per unit energy of fading relay channels 相似文献
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《Wireless Communications, IEEE Transactions on》2008,7(10):3718-3724
We provide closed-form expressions for the outage and bit error probability (BEP) of uncoded, threshold-based opportunistic relaying (OR) and selection cooperation (SC), at arbitrary signal to noise ratios (SNRs) and number of available relays, assuming decode-and-forward relays and Rayleigh fading channels. Numerical results demonstrate that SC performs slightly better in terms of outage probability; in terms of BEP, both systems may outperform one another, depending on the SNR threshold that determines the set of relays that participate in the forwarding process. 相似文献