Performance analysis of trellis coded multi-pulse pulse position modulation for deep space optical communication systems

The deep space optical communication is unguided optical communication without fiber, but is power and bandwidth limited. Technique used for communication in such a system is usually IM/DD and the choice of modulation is pulse position modulation since it is extremely power efficient, but it results in an exponential increase in required bandwidth. To overcome this limitation, multi-pulse PPM is used. This scheme increases the throughput without bandwidth expansion, but penalty is paid in terms of degraded BER performance because the signal sets are no more orthogonal. In this paper, Trellis coded modulation schemes using Ungerboeck’s set partitioning methodology to increase the minimum distance among the symbols with simple convolution encoder followed by a mapper is considered for the improvement in the performance.