Throughput optimization of precoded OFDM with hierarchical modulation

This paper investigates the throughput optimization of precoded Orthogonal Frequency Division Multiplexing (OFDM) with hierarchical modulation. Using the asymptotic analysis approach we derive the limit bit error rate (BER) of the high priority and the low priority streams. We then use the effective Signal to Interference plus Noise Ratio (SINR) corresponding to each stream to calculate the aggregate throughput achieved by the system. We study the behavior of the throughput as a function of the two design parameters: the coding rate and the constellation ratio. Simulation results show that the asymptotic expressions provide a very good approximation of the BER and that the throughput can be maximized by choosing appropriate values for the design parameters. We conclude on when it is advantageous to use hierarchical modulation and on the optimal values of the constellation ratio and the coding rate to be used for each Signal to Noise Ratio (SNR).