Adaptive filter-based turbo equalization with trellis coded modulation and frequency hopping

A serially concatenated trellis coded modulation system (SCTCM) with 16-QAM modulation and frequency hopping is tested on an unknown and time-varying frequency-selective channel. The channel at each hop is estimated by inserting a training sequence at the start and end of each frequency hop block, and is tracked both by using linear interpolation, and by using a weighted sum of forward and backward interpolators. Two different outer and inner code rate combinations are compared, the first one with rate 1/2 outer encoder and rate 1 inner TCM encoder, and the second one with rate 2/3 outer encoder and rate 3/4 inner TCM encoder. Both systems are optimized with regard to the signal-to-noise ratio (SNR) for iterative convergence.