Performance of MPSK and 16QAM in the satellite communication environment

This paper presents computer simulation results on the performance of quadrature phase shift keying (QPSK), 8-ary phase shift keying (8PSK), and 16 quadrature amplitude modulation (16QAM) schemes in a satellite communication environment employing frequency division multiple accessing (FDMA). The end-to-end communication system, which includes the modulator, klystron amplifier, satellite transponder, carrier and timing recovery loops, and the channel filters, is modeled using the cadence signal processing work system (SPW) tool. The satellite transponder components modeled in SPW include filters, up/down converters, digital channelizer filters, and high-power amplifiers (HPAs). Measured data is used to characterize the transmitter klystron and the transponder HPA. The performance of the filtered signal of interest is evaluated in the presence of filtered QPSK, 8PSK, and 16QAM signals in adjacent channels. Due to the complex waveforms, the nonlinear channel model, and the multi-user scenario involved in the simulations, it is very difficult to develop an analytical expression to accurately predict the received signal power level. Therefore, a power calibration process is developed to determine the received signal power level, required to compute the bit energy to noise spectral density ratio (E_b/N_o) used in any specific SPW simulation run. Simulation results of the paper show that the bit error rate (BER) performance of the simulated communication system is significantly impacted by the presence of the adjacent channel interference (ACI) and the intermodulation (IM) noise.