PERFORMANCE OF CHIP CODING IN FFH SSMA SYSTEMS

This paper proposes chip coding using convolutional codes for fast fre quency-hopping spread-spectrum multiple-access (FFH-SSMA) systems, Its performance is evaluated and compared with that of repetition coding which is most commonly used in FFH systems, In our proposal, an inform ation symbol is encoded by a convolutional code of rate 1/n and n chip s are transmitted through a frequency hopper, We consider three models when perfect side information (PSI) is available, no side information (NSI) is available, and the ratio threshold test (RTT) is used, The p robability density functions (pdf's) of the received signal are derive d for asynchronous hopping systems, The performances of convolutional coding with threshold decoding and Viterbi decoding are presented unde r the constraint of fixed total bandwidth and information bit rate. In comparison with repetition codes, it is found that convolutional code s drastically enhance the system performance, It is identified that Vi terbi decoding with RTT offers the most significant performance improv ement.