共查询到18条相似文献,搜索用时 62 毫秒
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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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为了最大限度地利用移动终端的发射功率,提出了基于中断概率限制的混合转发协作通信功率分配方案。根据目的节点和中继节点的译码情况,选择合适的协作转发方式,充分利用了放大转发(AF)和译码转发(DF)方式的优点。在满足中断概率限制的条件下,采用图形和数值分析的方法,得到了源节点和中继节点的最优功率分配。仿真分析表明,在相同的中断概率限制下,采用的功率分配方案比等功率分配方案消耗的总功率少约2.8 dBm。 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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为克服信息处于深度衰落情况下单中继协作困难,减少多中继协作目的端信号处理的复杂度,给出了双中继节点参与协作通信的功率分配方案。两个中继节点分别采用放大转发(AF)、译码转发(DF)以及混合译码放大转发(HDAF)3种协作方式进行通信。在满足一定的中断概率和节点功率限制情况下,利用MATLAB软件中的Fmincon优化函数,得到了各节点的最小发射功率。数值分析表明,在相同条件下,两个中继节点采用HDAF协作方式比采用AF协作方式、DF协作方式消耗的系统总功率分别少4~9 dBm、0.5~1 dBm,最大限度地节约了系统功率的消耗。 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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协作分集不仅能提升数据传输速率,还可以提高数据传输的稳定性。协作通信方法使用带有一根天线的移动台,在多用户环境中可以共享其他移动用户的天线,这样可产生多根虚拟发射天线,进而得到相应的分集增益,改善移动通信系统的性能。现在通过研究发现,在多中继协作通信中,非对称信道采用放大转发方式下的中继传输,在AF重复转发和机会转发2种方式下表现出了较小的链路中断概率,系统性能得到明显的提升。 相似文献
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This paper proposes a modified decode and forward (DAF) protocol with a three node model, which contains two users and one destination. Each user can be either the source or the relay in different frames. We analyze the four cooperative cases in the first frame and run simulations to obtain the optimal power allocation coefficients in the second frame. The closed form expression of outage probability is derived over Nakagami m fading channels. Furthermore, we show that the proposed model has better performance than the non cooperation system and traditional DAF strategy based on the derived outage probability. 相似文献
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An amplify-and-forward (AF) based multi-relay network is studied. In order to minimize the system outage probability with a required transmission rate, a joint power allocation (PA) and multi-relay selection scheme is proposed under both total and individual power constraints (TIPC). In the proposed scheme, the idea of ordering is adopted to avoid exhaustive search without losing much system performance. Besides the channel quantity, the ordering algorithm proposed in this article also takes relays' maximal output ability into consideration, which is usually ignored in traditional relay ordering algorithms. In addition, simple power reallocation method is provided to avoid repetitive PA operation during the process of searching all possible relay subsets. By Adopting the idea of ordering and using the proposed power reallocation method lead to remarkable decrease of the computation complexity, making the scheme easier and more feasible to implement in practical communication scenarios. Simulations show that the proposed multi-relay selection scheme provides similar performance compared to the optimal scheme with optimal PA and exhaustive search (OPAES) but with much lower complexity. 相似文献
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Cooperative diversity systems have recently been proposed as a way to form virtual antenna schemes without utilizing collocated multiple antennas. In this paper, we consider the Nth best opportunistic amplify‐and‐forward (AF) cooperative diversity systems. The AF type can be regarded as one on the basis of modified channel state information. Wireless channels between any pair of nodes (i.e., direct and dual hop links) are assumed quasi‐static independent and nonidentically distributed (INID) Rayleigh fading. The best opportunistic AF (OAF) scheme requires two phases of transmission. During the first phase, the source node transmits a signal to all relays and the destination. In the second phase, the best relay is only selected on the basis of highest signal‐to‐noise ratio (SNR) scheme to forward the source signal to the destination. Therefore, the indirect link (i.e., source‐selected relay destination) can give the highest received SNR. However, the best relay selection cannot be available so that we might choose the second, third, or generally the Nth best relay. In this paper, we derive the approximated outage probability and channel capacity for the Nth best OAF relay systems over INID Rayleigh fading channels. At first, the indirect link's received SNR is approximated as harmonic mean upper bound. With this information, we obtain the given relay's Nth best selection probability as the closed form. Finally, both outage probability and channel capacity are derived as the closed forms. Simulation results are finally presented to validate the analysis. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Md Fazlul Kader 《International Journal of Electronics》2013,100(6):1050-1062
Non-orthogonal multiple access (NOMA) has attracted a significant attention to the research community as a potential candidate for 5G or future radio access. This article presents a NOMA-based cooperative network where a transmitter considered as a base station communicates simultaneously with two users treating as a far user and a near user via the help of a half-duplex decode-and-forward relay. We investigate the outage probability and the outage capacity of the proposed network over independent Rayleigh slow fading channels. Closed-form expressions of the outage probabilities are derived for both users. Approximate outage capacity of the users are also investigated at high signal to noise ratio regime. It has been shown that the proposed cooperative NOMA can achieve superior performance compared to the non-cooperative NOMA in terms of outage probability. The tightness between the simulation and theoretical results confirms the efficiency of the proposed protocol. 相似文献
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介绍了BR-OFDMA技术的基本原理,并基于BR-OFDMA系统模型,分析了不同块重复因子下用户与基站间距离、传播损耗、小区负荷等因素对BR-OFDMA系统中断概率性能的影响.相关研究结果表明,随着块重复因子的增大,用户性能不断改善,对BR-OFDMA的组网有一定实际应用意义. 相似文献