An achievable Pre-log Region for the Non-coherent Block Fading MIMO Multiple Access Channel

We study the two-user MIMO block fading MAC in the non-coherent setting, where the terminals have neither transmit nor receive knowledge of the channel realizations. We propose a joint transmission scheme and derive the prelog region achievable by the proposed scheme, by applying a geometric approach. The geometric approach is based on the understanding of the geometric structures which arise as relevant to the problem of communicating non-coherently over the multiple access channel. We show that the proposed scheme achieves the pre-log upper bound for the sum-rate. Comparison with TDMA (both coherent and non-coherent) indicates that in most of the scenarios of practical relevance, the proposed transmission scheme outperforms TDMA.