Performance of frequency recovery algorithms for a poly-polarization multiplexing satellite system

Frequency recovery is a critical element in virtually all high data-rate communications systems, and in order to enhance the performance of our recently proposed poly-polarization multiplexing (PPM) satellite system, we have investigated the performance benefits of distributing the unique word (UW) symbols. The mean square error is calculated for different correlation based algorithms with increasing pilot spacing. We show that pilot separation provides an additional means to improve performance without increasing latency or complexity. A modified estimator is also proposed that can operate with an arbitrary UW symbol spacing and increased frequency offset range. The estimator performances are compared for different UW lengths, averaging sizes and pilot separation. A 0.67 dB gain was achieved at the BER of 1E-6 as pilot separation was increased from 4 to 8 using a modified L&R algorithm with LDPC and UW length 64.