Basestation modulation diversity for digital simulcast

A base station modulation diversity scheme is proposed for simulcast systems which use linear QAM (quadrature amplitude modulation) type modulation. With this method the bandwidth efficiency is fully preserved because each base station uses the same base pulse. Modulation diversity is achieved by filtering the input symbols with a symbol-spaced finite impulse response (FIR) filter prior to QAM modulation. The tap weights of the FIR filters at different base stations are different. They are chosen such that a necessary condition for optimum diversity gain in time-selective fading is satisfied. Examples for simulcast with two base stations are given. They demonstrate the impact of the choice of tap weights on the energy efficiency, the system complexity, and the performance in the presence of a propagation delay difference between the signals of different base stations