A Software Simulation Study of a MD DS/SSMA Communication System with Adaptive Channel Coding

Studies have shown that adaptive forward error correction (FEC) coding schemes enable a communication system to take advantage of varying channel conditions by switching to less powerful and/or less redundant FEC channel codes when conditions are good, thus enabling an increase in system throughput. The focus of this study is the simulation performance of a complete simulated multi-dimensional (MD) direct-sequence spread spectrum multiple access (DS/SSMA) communication system that employs an advanced adaptive channel coding scheme. The system is simulated and evaluated over a fully user-definable software-based multi-user (MU) multipath fading channel simulator (MFCS). Channel conditions are varied and the switching and adaptation performance of the system is monitored and evaluated. Sensing for adaptation is made possible by a sophisticated quality-of-service monitoring unit (QoSMU) that uses a sophisticated pseudo-error-rate (PER) extrapolation technique to estimate the system´s true probability-of-error in real-time, without the need for known transmitted data. The system attempts to keep the estimated bit-error-rate (BER) performance within a predetermined range by switching between different FEC codes as conditions change. This paper commences with a short overview of each of the functional units of the system. Lastly, the simulation results for the coded and uncoded BER performances, as well as the real-time adaptation performance of the system are presented and discussed. This paper conclusively proves that adaptive coded systems have large throughput utilization advantages over that of fixed coded systems