Signal Design for FH-SSMA Communication System using Pseudo Random Sequences

The paper describes a method of design of addresses using PN sequences for a frequency hopping spread spectrum multiple access (FH-SSMA) system meant for speech communication. The frequency of the transmitted signal is hopped in L equal time intervals in a sequence determined by the PNS derived address. A system is suggested for digital speech at 31.25 kbps to be transmitted in a channel band width of 36 MHz. Correlation functions of PN sequences of lengths 31, 63 and 127 and coincidence functions for the addresses have been computed. It is found that the derived addresses are less correlated as compared to the PN sequences. System performance in a random access environment has been computed. For a false detection probability PF≪ 10¿4, the system would support six simultaneously active subscribers.