High Mobility Wireless Communications With Doppler Diversity: Fundamental Performance Limits
High Mobility Wireless Communications With Doppler Diversity: Fundamental Performance Limits
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DOI：
10.1109/twc.2015.2463276
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发表时间：
2015-07
影响因子：
10.4
通讯作者：
Weixi Zhou;Jingxian Wu;P. Fan
中科院分区：
文献类型：
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作者：
Weixi Zhou;Jingxian Wu;P. Fan
本文的目的是量化的多普勒分集和信道估计误差之间的高移动性系统的基本权衡。高移动性系统中的快速衰落变化引入了多普勒分集，其可以有益于系统性能。另一方面，快速变化的信道的估计和跟踪更加困难，因此信道估计误差是不可忽略的，并且它们可能严重降低系统性能。这种权衡关系的研究，通过确定两个性能指标的精确解析表达式：最大多普勒分集阶可实现与不完善的信道状态信息（CSI），和信道估计误差造成的信噪比（SNR）的损失。分析研究是通过一个简单的重复码在发射机，和一个新的最佳分集接收机的信道估计误差的统计特性分析。利用分析结果，得到了在最大化多普勒分集阶数和最小化信噪比损失的同时，导频符号和数据符号之间传输能量的最优分配，从而实现了两者之间的最优折衷。结果揭示了多普勒分集系统在非理想信道状态下的基本性能极限，可用于指导实际系统的设计。
The objective of this paper is to quantify the fundamental tradeoff between Doppler diversity and channel estimation errors in high mobility systems. Fast fading variation in high mobility systems introduces Doppler diversity that can benefit system performance. On the other hand, it is more difficult to estimate and track a fast changing channel, thus channel estimation errors are non-negligible and they may seriously degrade system performance. Such a tradeoff relationship is studied by identifying the exact analytical expressions of two performance metrics: the maximum Doppler diversity order achievable with imperfect channel state information (CSI), and the loss in signal-to-noise ratio (SNR) caused by channel estimation errors. The analytical study is enabled by a simple repetition code at the transmitter, and a new optimum diversity receiver developed by analyzing the statistical properties of channel estimation errors. With the analytical results, the optimum allocation of transmission energy between pilot symbols and data symbols are obtained to simultaneously maximize the Doppler diversity order and minimize the SNR loss, thus achieve the optimum tradeoff between the two. The results reveal the fundamental performance limits of Doppler diversity systems operating in the presence of imperfect CSI, and they can be used to guide the design of practical systems.