Diversity Multiplexing Gain Tradeoff of Co-Ordinate Interleaved Spatial Multiplexing

Spatial multiplexing over multiple-input multiple-output (MIMO) channels significantly improves the data rates over wireless channels. With channel knowledge at both ends of the link, many spatial multiplexing schemes have been proposed in literature, showing improved performance with respect to some performance measure. Co-ordinate interleaved spatial multiplexing (CISM) (Srinivas et al., 2006) is one such scheme that has been shown to achieve improved error rate performance. In this paper, we analyze CISM from diversity-multiplexing gain tradeoff (DMT) perspective. We focus on CISM over MIMO channels having only two degrees of freedom and show that the DMT of CISM is a straight line connecting the two extreme points (0, 2 m) and (2, 0) where m = max{N_t, N_r}. This result shows that CISM outperforms many other schemes that require same amount of feedback.