A Reliable Group-Simulcasting Scheme for Distributed Antenna Systems

Simulcasting involves transmitting the same signal simultaneously over several antennas on the same carrier frequency. We derive the optimal grouping condition for simulcasting over a massively distributed antenna system (DAS) employing orthogonal space-time block coding (STBC), where the order of the STBC coding matrix n_o is smaller than the number of remote antenna units (RAUs). While the optimum grouping minimizes the average bit error rate (BER) in the coverage area, we further propose two heuristic grouping rules and derive the corresponding stream-balanced grouping schemes in three DAS topologies, namely, linear, hexagonal and square lattice, to achieve low average BER across the area covered by the DAS. Simulation results for the different topologies confirm the superiority of the proposed grouping schemes compared with the other grouping methods. Also, when either n_o or the RAU density increases, the average BER decreases.