Hardware-Efficient Implementation of the SOVA for SOQPSK-TG

Abstract

In this paper, we present a hardware-efficient architecture of a demodulator for shaped offset quadrature phase shift keying, telemetry group version (SOQPSK-TG). The demodulation is done using the soft-output Viterbi algorithm (SOVA), which is implemented by the two-step traceback method. In this method, two traceback operations are employed to find the maximum-likelihood (ML) path and the competing path. Using the proposed architecture, the tracebacks are done at the same time as the demodulator is generating output bits and their reliabilities. This method has been shown to require less storage than the well-known register-exchange method. Finally, we present the performance results from the FPGA implementation.