共查询到19条相似文献,搜索用时 156 毫秒
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基于信道统计特性的中继选择算法 总被引:2,自引:0,他引:2
该文提出了一种在非再生协作网络中,基于信道统计特性的最优中继选择方法。首先在等功率条件下,根据信道统计特性,定义一个等效信道增益的参数,该参数反映了中继节点在协作过程中两个阶段的信道特性。然后提出一种基于该参数的降序排列的中继选择方法。该方法在不同的信噪比范围内,选择不同的节点集合,使得系统的吞吐率中断概率最小。分析表明该选择方法的分集增益阶数能达到N+1,N为中继节点数目。仿真结果表明这种中继选择算法的中断概率性能优于其他算法。该方法进一步与功率分配相结合,构成了一种低复杂度的次优的中继选择方法。仿真结果表明这种次优算法能够取得和穷举算法相似的性能。 相似文献
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该文针对多源-多中继放大转发协作通信网络,以最小化系统总功率为目标,在保证系统满足一定中断概率的前提下,提出了一种分布式功率分配与中继选择算法.算法由源节点自主选择为其转发信息的中继节点,并引入定时器,通过竞争方式避免了分布式所导致的中继选择冲突.中继收到来自源节点的信号后,只需根据转发门限自主判断是否进行转发,从而完成传输.仿真结果表明该分布式算法能够有效降低传输所需要的总发射功率.并且与集中式控制所获得的最优中继选择与功率分配算法相比性能相近,但所提分布式算法显著降低了系统的控制开销. 相似文献
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网络编码在双向多中继系统中已经得到了广泛地研究,并有效地提高了双向多中继系统的吞吐量。首先本文导出了在译码转发方式时,独立正交信道和多接入信道下基于网络编码的双向多中继系统平均中断概率表达式。Monte Carlo仿真和理论分析非常吻合,验证了理论分析的正确性。之后分析了系统平均中断性能在不同信噪比和不同中继节点个数等多种情形下与功率分配因子的关系,揭示了功率分配因子与系统总功率和中继节点数量之间的内在关系。仿真结果表明,双向多中继系统采用网络编码进行传输时,在独立正交信道下和多接入信道下的功率分配因子取值在区间 内能够获得最优的系统中断概率性能,并且多接入信道下的系统中断性能要好于独立正交信道。 相似文献
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《Wireless Communications, IEEE Transactions on》2007,6(3):793-799
We study power allocation for the decode-and-forward cooperative diversity protocol in a wireless network under the assumption that only mean channel gains are available at the transmitters. In a Rayleigh fading channel with uniformly distributed node locations, we aim to find the power allocation that minimizes the outage probability under a short-term power constraint, wherein the total power for all nodes is less than a prescribed value during each two-stage transmission. Due to the computational and implementation complexity of the optimal solution, we derived a simple near-optimal solution. In this near-optimal scheme, a fixed fraction of the total power is allocated to the source node in stage I. In stage II, the remaining power is split equally among a set of selected nodes if the selected set is not empty, and otherwise is allocated to the source node. A node is selected if it can decode the message from the source and its mean channel gain to the destination is above a threshold. In this scheme, each node only needs to know its own mean channel gain to the destination and the number of selected nodes. Simulation results show that the proposed scheme achieves an outage probability close to that for the optimal scheme obtained by numerical search, and achieves significant performance gain over other schemes in the literature 相似文献
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协作通信与直接通信相比能够显著地提高系统性能,功率分配是协作通信中的一个关键问题。为了获得合理的协作中继通信系统功率分配方案,提出一种基于改进蛙跳算法的多中继节点功率分配方法。首先对功率分配问题进行分析,将其转换为一个非线性优化问题,然后将青蛙表示为源节点,中继节点的功率,以平均信噪比作为青蛙的食物,并通过青蛙的信息交流和协作找到最优的功率分配方案,最后采用仿真对比实验对本文算法性能进行测试。仿真结果表明,相对于其它功率分配方法,改进蛙跳算法有效地提高了系统的信道容量,降低了中断概率,以较低的复杂度提高了系统的性能。 相似文献
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针对反射、散射影响下的非对称无线协作通信网络,提出了一种时变功率分配(Time Variant Power Allocation, TVPA)算法。根据无线协作网络中,各节点之间信道条件实时变化且不对称的特点,在信号传输过程中对信源节点和中继节点的发送信号功率进行优化分配。借助信道编码定理,将系统错误概率最小的非凸优化问题转化为最大化系统容量的凸优化问题来解。与固定功率分配(Fixed Power Allocation, FXPA)算法和平均功率分配(Average Power Allocation, AVPA)算法相比,该算法能充分利用无线信道的时变特性,重新分配功率以降低系统错误概率。在多种网络模型中的仿真结果表明,准静态瑞利衰落信道下,相比于FXPA算法,TVPA算法可获得多达5.5dB的比特错误概率性能增益。随着网络质量的进一步改善,该性能优势也逐步增大。 相似文献
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多中继AF协作系统功率分配研究 总被引:2,自引:0,他引:2
功率分配是协作通信中一个重要的研究方向,文章分析了放大转发(AF)协作方式下,基于正交信道的多协作中继系统模型,在此基础上推导了系统中断概率。并以最小化系统中断概率为目标,给出系统功率分配约束表达式,进一步分析了功率分配与中继节点位置的关系,计算求得单中继和两中继情况系统最优功率分配系数。系统仿真表明最优功率分配相对常规的等功率分配,系统性能明显提升。 相似文献
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针对采用无线携能通信的多中继底层协作认知非正交多址接入网络,提出一种两阶段中继选择策略。认知中继执行功率划分的无线携能通信协议为次级用户提供解码转发服务,其能量开销源于所采集到的能量。考虑了实际的非正交多址接入网络中,中继节点与次级用户均无法完全消除多址干扰,即无法实现理想连续干扰消除。在干扰阈值约束下,推导了非理想连续干扰消除下两次级用户端中断概率的精确表达式,并通过蒙特卡洛仿真验证其正确性。此外,定量分析了各系统相关参数(最大发射功率、干扰阈值、功率分配系数等)的选取对次级用户中断性能的具体影响。结果表明,在相同的系统参数设置下,所提方案次级用户中断性能远优于现有部分中继选择方案。 相似文献
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Wireless transmission systems are constrained by several parameters such as the available spectrum bandwidth, mobile battery
energy, transmission channel impairments and users’ minimum quality-of-service. In this paper, a new strategy is investigated
that aims at improving the allocation of resources in a dual hop OFDMA cooperative network consisting in multi source–destination
pairs and multiple decode-and-forward relays. First, the joint optimization of three types of resources: power, sub-channel
and relay nodes, is formulated as a problem of subchannel-relay assignment and power allocation, with the objective of minimizing
overall transmission power under the bit-error-rate and data rate constraints. However, the optimal solution to the optimization
problem is computationally complex to obtain and may be unfair. Assuming knowledge of the instantaneous channel gains for
all links in the entire network, an iterative three-step resource allocation algorithm with low complexity is proposed. In
order to guarantee the fairness of users, several fairness criteria are also proposed to provide attractive trade-offs between
network performance (i.e. overall transmission power, average network lifetime and average outage probability) and fairness
to all users. Numerical studies are conducted to evaluate the performance of the proposed algorithm in two practical scenarios.
Simulation results show that the proposed allocation algorithm achieves an efficient trade-off between network performance
and fairness among users. 相似文献
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非对称信道下协作通信系统中断概率的研究 总被引:1,自引:0,他引:1
首先建立了非对称信道下协作系统的数学模型,考虑了源节点到目的节点的直通链路,利用特征函数法推导出协作系统的平均中断概率公式,通过仿真验证了该中断概率公式的精确性,理论和仿真都表明协作系统的中断概率和中继节点的个数、位置分布以及协作系统的功率分配因子有着密切关系,并且考虑源到目的节点的直通链路相对于不考虑直通链路的情况具有更高的性能增益;然后又在此公式基础卜就协作系统中继节点的位置分布对最优功率分配因子的影响进行了仿真分析,并指出协作系统的最优功率分配因子受制于中继节点的位置分布情况. 相似文献
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The self-similarity nature of network traffic has been discovered to be a ubiquitous phenomenon in communication networks; meanwhile, heterogeneous wireless cooperative relay networks have received considerable interests in both academia and industry fields. The mechanism of cooperative relay selection is very essential for the design of heterogeneous wireless relay networks. In this paper, based on the self-similar nature of network traffic in heterogeneous wireless cooperative relay network, we propose a new relay selection mechanism called conditional relay selection which can effectively decrease the system outage probability. Compared to conventional relay selection mechanism, the proposed mechanism considers the traffic queue condition of the relay nodes rather than just comparing the signal-to-noise ratio (SNR). Through extensive comparisons with traditional cooperative relay selection mechanisms, the proposed scheme can significantly improve the system outage probability. 相似文献