Power and bandwidth efficient modulation and coding for small satellite communication terminals

The objective of this project is to maximise the power and bandwidth efficiency of small satellite Earth communication terminals whose main limitation to satellite capacity is a nonlinear transmitting power amplifier. A form of envelope equalisation is presented in which regular QPSK modulation is used together with instantaneous data magnitude modulation so as to produce a near constant envelope signal when filtered with root 35% raised cosine filtering. The algorithm for deriving the magnitude values is presented along with results using a data lookup table approximation. Bit error rate figures are presented for envelope equalisation combined with a (4096,3249) binary product code and MAP decoding. It is shown that at 10^-6 BER the E_b/N₀ is 3.52 dB, some 0.26 dB from the linear system. When used with a nonlinear power amplifier, the benefit of envelope equalisation is approximately 3 dB. The power spectrum is identical to that of the linear system with no spectral spreading and no increase in adjacent channel interference.