AbstractMobile satellite communication systems at Ka/K band (30/20 GHz) are attractive because of their large bandwidth availability and potentiality to support smaller earth‐stations and satellite antennas compared with L‐band (1·6/1·5 GHz) systems. In this paper, multiple‐symbol Viterbi decoding and dual‐space equal‐gain diversity reception for trellis‐coded differential M‐ary phase‐shift‐keying (DPSK) modulation are investigated as two mitigation techniques for severe channel impairments expected from a land mobile satellite communication channel at K band and, for comparison purposes, at L band. The multiple‐symbol Viterbi decoder (MSVD) is a modified Viterbi decoder with inputs from multiple differential detectors. The channel is modelled as Rayleigh distributed multipath fading with a lognormally distributed line‐of‐sight (LOS) component due to shadowing. Four trellis‐coded modulation (TCM) schemes are studied. The dependency of the system performance improvement on the decoder structure, the TCM scheme, and the system RF frequency band is presented.