HIGH-CAPACITY DIGITAL RADIO WITH TRELLIS CODING

In this paper we analyze the performance of Trellis Coded Modulation (TCM) for high capacity digital radio. Some error correcting code is needed to comply with the low background bit error rates prescribed for this application, despite practical imperfections unavoidable in modems and nonlinear distortion of high power amplifiers. The redundancy that can be accepted is very limited, however, due to the strict bandwidth constraints. TCM schemes are very effective in conserving bandwidth. Therefore, they look very promising for digital radio applications. We analyze many aspects of TCM, including multidimensional schemes. We consider the performance of TCM in the AWGN channel and in multipath fading channels, and we evaluate the effect of nonlinear amplification. Finally, we consider decoder complexity. Significant coding gains can be obtained from codes of acceptable complexity. A good compromise between performance and complexity turn out to be 8-state codes. The complete Viterbi decoder for these codes can be fully integrated on just one chip. As a typical application, a system transporting the first level of the Synchronous Digital Hierarchy (STM - 1; 155.52 Mbit/s) operating on 30 MHz interleaved crosspolarized frequency arrangements is analyzed in detail.