Résumé: In this paper, the performance of a direct-sequence (DS)/ SFH-SSMA communication system using overlapping binary frequency-shift keying (BFSK) modulation technique is analyzed in the additive white Gaussian noise (AWGN), multiple-access interference (MAI), and multitone jamming (MTJ) channel. An SSMA system is considered that the DS spread spectrums are overlapped and maximum overlapping limitation is 1/T, which is the minimum spacing for noncoherent FSK signaling. As the amount of overlapping increases, multiple-access interference as well as processing gain becomes larger. Thus, the bit error rate (BER) can be improved by optimizing the overlap ratio. The phase angles and time delays of the received signals, and the phase angles of tone jamming signals, are assumed to be mutually independent random variables. A BER equation is derived for the overlapping BFSK DS/SFH-SSMA communication system in the AWGN, MAI, and MTJ channel. From the numerical analyses and the simulation results, BER performance is improved by about 3 dB at the level of BER of 10<superscript>-<superscript>3 in the optimized overlapping system over the nonoverlapping system in the condition that total processing gain is 39 dB, the number of total user is 100, jammer-to-signal ratio is 20 dB, and the number of jamming tone is ten.

Langue: Anglais