共查询到20条相似文献,搜索用时 15 毫秒
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《中国科学:信息科学(英文版)》2012,(4):805-814
In this paper,a beamforming (BF) based cooperation scheme with decode-and-forward (DF) protocol is proposed and its performance analysis is provided.Firstly,to solve the issue of carrier synchronization in distributed networks,a backward synchronization (B-Sync) method is introduced,where participating relays synchronize to the reference carrier broadcast by the destination and make signals superimposed coherently at the destination without any phase feedback.Then,based on B-sync,a cooperation scheme with DF protocol is proposed to carry out BF forwarding among relays.The outage probability of this scheme is derived and analyzed,which shows that the full diversity order can be achieved by the proposed scheme.Furthermore,symbol error probability (SEP) analysis is presented to evaluate the practical performance.Simulation results validate the analysis,and show that the proposed scheme outperforms other existing ones in terms of outage probability and SEP. 相似文献
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The opportunistic cooperation schemes,where only the "best" relay is selected to forward the message,have been widely investigated recently for their good performance in terms of outage probability.However,the unfair selections of relays may cause unbalance power consumptions among relays,which reduces the lifetime of energy constrained networks.In this paper,we introduce a novel concept of outage priority based fairness(OPF),aiming at improving the selection fairness among relays appropriately without outage performance deterioration.Then,a cooperation scheme is proposed to meet this concept,and corresponding theoretical analysis is also provided.Afterward,based on OPF,the achievable upper bound of the fairness is derived,and an optimal cross-layer designed scheme is also provided to achieve the bound.Numerical simulations are carried out finally,which not only validate the theoretical analysis,but also show that taking advantages of the proposed schemes,the fairness among all relays,as well as the network lifetime,can be greatly improved without any loss of outage performance,especially in high SNR regime. 相似文献
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针对双向中继协作系统建立了中继节点多用户接收机因子图模型,通过利用高斯参数化对混合高斯分布进行近似,提出了一种联合信道估计、多用户检测与译码的迭代消息传递算法,在合理的复杂度下有效地提高了中继接收机对于多用户混合信号的检测性能. 相似文献
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This paper deals with the superposition coding (SPC) scheme in multiple-input multiple-output two-way relay channels subject to imperfect channel estimation. In this scenario, two multiple antenna terminals, which are unable to communicate directly, exchange information with each other via a multiple antenna relay. We determine the impact of the channel estimation error degradation on the achievable rate region for two main SPC techniques: (a) SPC without channel state information (CSI) at the users, (b) SPC with an imperfect CSI at the users where a waterfilling power allocation is employed. We demonstrate that imperfect CSI significantly improves the achievable rate at low signal-to-noise ratios (SNRs) while it becomes less critical at high SNRs. In addition, a SPC power allocation technique that incorporates the average channel statistics and does not require any instantaneous CSI is also investigated. We show how the available power is split between the two bi-directional (superimposed) data flows in order to maximize the system performance and to support fairness as well as to maximize the achievable sum-rate. 相似文献
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在源节点和中继节点总功率一定条件下,提出一种基于有限反馈的中断率最小的协作策略.在信道增益坐标平面内,对于解码转发和直接发射,文中分别给出了等功率和最优功率分配时系统中断率最小的发射模式区域.根据所提出的算法,目的节点只需查看当前信道状态所属的发射区域,并反馈1个发射参数到源节点和中继节点.相比于传统策略,本文提出的策略准确给出了任何信道增益下中断率最小的发射模式,并极大精简了反馈量和计算复杂度. 相似文献
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针对无线通信系统的两种典型信道—频率选择性的多径Rayleigh衰落信道和Nakagami-m信道,中继方式为解码-转发(DF)和放大-转发(AF)的单中继系统的中断概率问题进行详细且深入的研究。分别计算AF方式和DF方式中继系统信噪比的概率密度函数(PDF)和累积分布函数(CDF),利用CDF可得在给定的系统数据速率要求的前提下相应的中断概率的闭式解。对该中继系统的中断概率模型进行仿真。仿真分析显示,闭合表达式与数值仿真结果吻合良好。 相似文献
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主要研究了瑞利衰落信道下基于放大转发策略的双向中继系统的中断性能及分集性能。首先利用信源节点信噪比间的关系和调和不等式对信噪比的范围进行优化,得到新的中断概率下界,仿真结果表明Monte Carlo仿真得到的中断概率接近新得到的中断概率下界;同时证明了多中继存在时,基于最大最小互信息准则的双向中继系统仍然取得全分集增益且能够优化中断概率下界。 相似文献
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同步协作中继系统的波束形成通信方案的设计* 总被引:1,自引:0,他引:1
从多输入多输出(multiple-input and multiple-output,MIMO)系统所设计的Alamouti码中得到启发,针对在无线协同信道之上的同步协作中继系统提出了一种新的通信方案。为了在大中断率和低成对误码率(PEP)的情况下能有效地传送信号,源天线采用功率分配波束形成技术,中继节点采用放大转发(amplify and forward,AF)技术。研究和仿真表明,对给定效率R,所提出的模型与以前的通信方案尤其是广播通信模型相比,在中断率和成对误码率上都有明显的改善。这一发现可能会对未 相似文献
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SONG Wei Moon Ho Lee GUO Ying 《通讯和计算机》2009,6(1):42-46
In this paper, we propose a simple alamouti code synchronous cooperative relay system over a wireless-hop coherent channel, which each source antenna adopt power allocated beamforming technic, and which relay nodes use AF (amplify and forward) protocol to transmit signals. We analyze the outage probability and pairwise error probability (PEP) of the proposed model. Analysis show that the performance of the proposed model, for given spectral efficiency R, has been improved significantly. 相似文献
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This note studies the existence of solutions to MIMO linear systems under decentralized relay feedback containing hysterisis. A necessary and sufficient condition is presented to guarantee the extended solutions at the so-called intersecting instant. The suggested method is to examine the sign of the first non-zero derivative of each output right after the switches occur. Illustrative examples are given to show the cases of non-existence and non-uniqueness of solutions. 相似文献
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针对外部窃听者对多中继协同通信系统中信息传输带来的安全威胁,提出一种由中继节点在转发信息的同时发送人工干扰信号的协同安全传输方案,并对该方案在Nakagami-m衰落信道中的安全性能进行了分析,推导出了用于评估机会中继系统可靠性的中断概率和安全性截获概率的闭式表达式,并在此基础上从可靠性和安全性两方面对系统的折中性能进行了讨论。通过仿真,验证了推导的正确性,明确了中继个数对系统折中性能的影响。最后,为进一步提高系统折中性能,讨论了系统中人工干扰信号与通信信号间的功率分配问题,并通过仿真得到了能使系统折中性能达到最优的功率分配因子。 相似文献
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This paper derives an asymptotic average symbol error probability(SEP)expression for multiple-input multiple-output(MIMO)two-hop amplify-and-forward(AF)relay systems with optimal beamforming.The analysis at high signal-to-noise ratio(SNR)quantifies the diversity order and array gain,which are valid for any antenna numbers of the terminals and arbitrary channel fading models.It is also proved that the system performance is dominated by the relatively degraded one of the two-hop channels.Our results based on the simple expressions provide valuable insights into the performance and practical design considerations of MIMO AF networks. 相似文献
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