标题: 合作式通讯下以正交分频多工之接收端使用白化处理对抗多重频率偏移
Combat Multiple Carrier Frequency Offsets in Cooperative Communication OFDM Systems
作者: 郭琬瑜
Kuo, Wan-Yu
桑梓贤
Sang, Tzu-Hsien
电子工程学系 电子研究所
关键字: 正交分频多功;载波间干扰;多输入多输出;多重频率偏移;传输分集;空间多功;OFDM;ICI;MIMO;MCFOs;transmit diversity;spatial multiplexing
公开日期: 2013
摘要: 在正交分频多功(OFDM)通讯系统下,载波频率飘移导致载波间干扰(ICI)和传输效能的衰减,载波间干扰让通道矩阵不再只有对角线方向有值,这种情形使得在正交分频多功信号接收变的困难,在合作式通讯下,同步是一个很重要的议题,不像传统的多输入多输出(MIMO)系统,合作式的天线是分属于不同的传送端,因此,对目的端而言,很难同时补偿多重频率偏移(MCFOs),另外,传统的讯号侦测方法在这边可能不是很适用。在这篇论文里,我们考虑从传送端到目的端的通道是频率选择性衰减通道,提出的方法是结合两个已分别做完同步的讯号来消除载波间干扰,白化处理被进一步用来获得良好的位元错误率以及对于多重频率偏移有更好的容忍度。
除了传输分集(transmit diversity)之外,这篇论文也探讨了空间多功(spatial multiplexing)的情况,我们使用两个已分别做完同步的讯号,经过符号的重新排列,白化处理被进一步用来获得良好的位元错误率以及对于多重频率偏移有更好的容忍度。更进一步,在这篇论文使用了线性最小均方误差(LMMSE)来降低复杂度,并且实做在数位信号处理板(DSP board)上,相对于最大可能序列估计,这个方法在良好的侦测性能和低复杂度间提供另一折衷选择。
Synchronization is an important issue in cooperative communications. Unlike in conventional MIMO systems, the cooperative antennas belong to different source nodes. Therefore, it is hard for the destination node to compensate multiple carrier frequency offsets (MCFOs) simultaneously and conventional signal detection strategies may not be capable enough to deal with the situation. In this paper, we consider cooperative transmission with MCFOs when the channels from source nodes to the destination node are frequency selective fading. The proposed strategy combines two sets of separately synchronized signal to mitigate inter-carrier interference (ICI) caused by MCFOs. Block-wise whitening is deployed to further enhance the tolerance of MCFOs and improve BER performance.
In addition to transmit diversity, in this paper we also consider the case of spatial multiplexing. Techniques such as using two sets of separately synchronized signal, index reassignment, and block-wise whitening are utilized to mitigate ICI. To go a step further, in this paper we use linear minimum mean square error detection to reduce complexity and implement the algorithm on DSP boards. The method is shown to provide good performance complexity trade-off compared to other ICI countermeasures.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT070050235
http://hdl.handle.net/11536/72866
显示于类别:Thesis