Turbo-code performance with imperfect carrier synchronization

The threshold performance of deep-space telemetry is characterized for four turbo codes. The mathematical models given here are based on simulations that account for imperfect carrier synchronization. These models are valid for coherent detection of binary phase-shift keyed (BPSK) telemetry when the carrier synchronization is based on either a residual-carrier loop or a (suppressed-carrier) Costas loop. The required Eb/N0 depends on the code, the threshold frame error rate, the bit rate, and the signal-to-noise ratio and bandwidth of the carrier synchronization loop. For residual-carrier tracking, these mathematical models are used to calculate the optimum modulation index.