标题: 针对无线感测器网路的讯息中继考虑通道参数不匹配的低冗余波束形成设计
Low-Overhead Cooperative Beamforming for Information Relaying in Wireless Sensor Networks Under Mismatched Inter-Node Link CSI
作者: 胡仲萱
Hu, Chung-Hsuan
吴卓谕
Wu, Jwo-Yuh
电信工程研究所
关键字: 无线感测器网路;合作式通讯;放大转发;波束形成;低冗余;量化;wireless sensor networks;Cooperative communications;amplify and forward;beamforming;overhead reduction;quantization
公开日期: 2011
摘要: 于低讯号冗余合作式通讯系统中的高效能讯号处理演算法在实现节能的第四代中继网路中扮演着重要的角色。在这篇论文中,我们研究在无线感测器网路中针对讯息中继来考虑在通道参数不匹配的情况下的低冗余合作式波束形成设计。在我们所考虑的系统中,为了达到降低传送通道状态资讯的讯号冗余,每一个中继端会将其测得之讯源与中继端的链结讯杂比量化成一位元的讯息。为了反映无线感测器网路严格的传送功率限制,每一个讯杂比的量化讯息在传输过程中因此假设为不理想的,于数学上视为经由一个带有非零交叉机率的二元对称通道来传送。当接收端接收这些可能有位元翻转的一位元讯杂比讯息,且假设中继端与接收端间链结的通道估测是完美的,则我们首先可以考虑藉由最大化接收讯号的讯杂比期望值所得的波束形成系数设计,其中此讯杂比公式是针对二元对称通道中位元翻转的统计特性所求得的期望值。接着,我们进一步延伸考虑中继端与接收端间链结的通道估测可能会产生误差的情况,在数学上我们以独立同分布的高斯随机变数才表示。在这两种情况下,我们可以透过针对讯杂比不确定性或是通道状态资讯不确定性作平均,以分别推导出具封闭形式的条件平均接收讯杂比。因为如此推导出来的讯杂比公式对波束形成系数来说是一高度非线性函数,所以针对这两种讯杂比公式,我们分别进一步地推导出各自的可分析下界以利于分析。藉由最大化各自的讯杂比下界,相应的亚最佳波束形成系数解即可透过解广义特征值问题来求得。最后,电脑模拟结果用以检验我们提出方法的成效。
High-performance signal processing algorithms for cooperative communication systems with reduced signaling overhead play a key role toward realizing energy-efficient relay networks for 4G and beyond. In this thesis, we study the problem of low-overhead cooperative beamforming design for information relaying in wireless sensor networks (WSNs) by taking account of the effect of mismatched inter-node channel state information (CSI). In the considered system, each relay node quantizes the signal-to-noise ratio (SNR) of the source-to-relay (S-R) link into one bit in order to reduce the signaling overhead dedicated to CSI transmission. To reflect the severe transmit power limitation of WSNs, the transmission link of the quantized SNR message is assumed to be non-ideal, and is modeled by a binary symmetric channel (BSC) with a non-zero crossover probability. With the flipped one-bit SNR messages received at the destination and assuming that the relay-to-destination (R-D) link channel estimation is perfect, we first study the beamforming design based on maximization of the expected receive SNR, averaged with respect to the bit-flipping distributions of BSC's. Next, the proposed approach is extended to the scenario wherein the R-D link channel estimation errors occur, and are modeled as i.i.d. Gaussian random variables. In both cases, we derive closed-form expressions for the conditional receive SNR averaged over the distributions of the SNR/CSI uncertainty. Since the SNR measures thus obtained are highly nonlinear functions of the beamforming coefficients, we further derive for each case a tractable SNR lower bound to facilitate analyses. By conducting maximization with respect to the derived SNR lower bounds, suboptimal beamformers can be obtained via solving generalized eigenvalue problems. Computer simulations are used to illustrate the performances of the proposed schemes.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT079913514
http://hdl.handle.net/11536/49296
显示于类别:Thesis


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