Space-time matrix modulation: Rank-deficient channels and multi-user case

We extend a previously introduced space-time modulation scheme (which we call matrix modulation) to the practically important cases of rank-deficient channels and multiple users. In particular, we prove an identifiability result and present an efficient demodulation method for these cases. Our matrix modulation technique does not require channel state information at the transmitter or receiver side. Its structure is strong enough to permit joint data and channel estimation without knowledge of the data alphabet. In the multi-user case, matrix modulation yields a flexible transmission scheme that can easily be adapted to different data-rate requirements of individual users. Numerical simulations demonstrate the good performance of the matrix modulation/demodulation technique.