Precoding for Spatial Modulation Against Correlated Fading Channels
空间调制(SM)，已成为一种新的通信技术与实用设计指南。传入比特的一部分用于选择一个发送天线，使其在每个信号发送时刻被激活，而其余的比特都是用于选择的调制符号，从激活的发送天线发出。
尽管SM具有避免信道间干扰(ICI)和简化传输链等基本优点，但同时利用天线和信号空间来传输信息也是其主要缺点的原因。具体来说，如果由于
- insufficient separation and/or
- a direct line-of-sight channel component (i.e., Rician fading)
导致发射天线之间存在空间相关性，则接收机在处理有源发射天线时的性能会显著下降。这反过来又导致SM收发信机整体平均误码率(ABER)的大幅上升。
- 这个问题，即 the unequal error vulnerability of the antenna and symbol bits against adverse fading channel effects,，已经在一些早期的工作中被处理，如[3]-[6]。
- 尽管他们没有直接考虑这个问题，但是其他替代方法，比如 [6] 基于 trellis-coding 的方法，也显示了对这些影响的健壮性。然而，在所有这些解决方案中，收发器中增加了编码器-解码器对，结果延迟和计算复杂度显著增加。
- Recently, another line of work in [7]、[11] has addressed the signal shaping by precoding at the transmitter to provide transmit diversity and performance improvement for SM systems. Here, the precoder is designed to shape the constellation observed at the receiver in a way to enhance the minimum Euclidean distance or the bit-error probability.
- In [12]–[14], similar precoding strategies based on amplitude scaling have also been proposed for space-shift keying (SSK) [15], which is a special form of SM where only the transmit antenna dimension is used to bear information, making the receiver to only detect which antenna was emitting power.
- However, regardless of the fact that they are employed in SM or SSK, these precoders are designed
only for time-invariant channelsand for cases wherethe full channel information is available at the transmitter. - In [10] and [11], partial channel state information (CSI) is also considered where the transmitter is assumed to know an erroneous version of the channel. However, these works still rely on fixed or block-fading channel realizations and do not consider time-varying or correlated fading channels.