TSI-OQPSK for Multiple Carrier Satellite Systems

The performance of TSI-OQPSK (two-symbol-interval-offset QPSK) modems in nonlinearly amplified (saturated or hard-limited), adjacent channel interference (ACI) satellite earth station environment is studied. In closely spaced mobile satellite channels and higher frequency (≥ 14 GHz) earth stations, the effect of ACI on the
P_{e} = f(E_{b}/N_{0})
performance of faded systems may become very significant. Simulation results indicate that for the frequently used close channel spacing case (≤ 77 percent of the bit rate) and a practical fade depth (≥ 12 dB), our new TSI-OQPSK signal
(n = 2)
has 1 dB less degradation than IJF-OQPSK and 3 dB less than OQPSK, and that conventional QPSK could not operate in such an environment.