MIMO capacity loss for real world signal constellations and channel degradations

We provide a capacity analysis of different MIMO techniques such as spatial multiplexing and space-time block coding. In contrast to most capacity evaluations which consider only Gaussian transmit symbols, we take into account restrictions on the transmit symbol alphabet and analyze real world signal constellations. Moreover, we include different detectors such as maximum likelihood, MMSE, zero-forcing, BLAST in the capacity evaluation. Furthermore, we consider not only spatially uncorrelated full rank channels but also channel degradations such as spatial correlation and keyhole effects. The results show that in many practical relevant cases, simple space-time block codes are a robust solution which achieves similar, sometimes even better capacities than spatial multiplexing even though they do not exploit all available MIMO dimensions.