Particle Filter Based Inversion of Nonlinear Satcom Channels

Bidirectional satellite communication between earth terminals on the same frequency at the same time is an emerging means of doubling spectral efficiency on satellite channels. With a linear satellite repeater, cancellation of self-interference can be done with standard echo cancelling methods. However, satellite amplifiers are normally operated in a highly-nonlinear regime, for maximum power output, and this complicates the interference removal process. This paper studies a particle filter based algorithm for ´inverting´ the nonlinearity at the receiving terminal, making the resulting channel roughly linear, so echo cancelation again becomes attractive. The particle filtering approach approximates the MMSE estimate of the input signal, given the output sequence. This output sequence is followed by a matched filter and an adaptive echo canceller to remove the co-channel interference.