说明： Trellis coded modulation (TCM) is a well known
scheme that reduces power requirements without any bandwidth
expansion. In TCM, only certain sequences of successive
constellation points are allowed (mapping by set partitioning).
The novel idea in this paper is to apply the TCM concept
to the antenna constellation points of spatial modulation (SM).
The aim is to enhance SM performance in correlated channel
conditions. SM considers the multiple transmit antennas as
additional constellation points and maps a first part of a block
of information bits to the transmit antenna indices. Therefore,
spatial multiplexing gains are retained and spectral efficiency