Coded SOQPSK-TG Using the Soft Output Viterbi Algorithm

Abstract

In this paper we present a system-level description of a serially concatenated convolutional coding scheme for shaped offset quadrature phase shift keying, telemetry group (SOQPSK-TG). Our paper describes the operation of various system modules. In addition, implementation details and references for each module in the system are provided. The modified Soft Output Viterbi Algorithm (SOVA) is employed for decoding inner and outer convolutional codes. The modified SOVA possess strong performance and low-complexity cost. The comparison of the modified (SOVA) and Max-Log-maximum a posteriori (MAP) decoding algorithm is presented. The SOVA after a simple modification displays the same performance as Max-Log-MAP algorithm, which is demonstrated by the simulation results. The advantage of the simple implementation of the modified SOVA makes it superior to Max-Log-MAP for our purposes.