A multicarrier (multihopping) scheme for multilevel frequency-shift keying/frequency-hopping code-division multiple access (MFSK/FH-CDMA) systems is proposed. In order to improve the frequency diversity capability for the proposed multicarrier MFSK/FH-CDMA system, several hopping frequencies per time slot are employed and transmitted in parallel. The frequency band is partitioned into N (N/spl les/P, P is a prime number) disjoint subbands on which N hop carrier frequencies are simultaneously transmitted. In previous work on multicarrier systems, it has been assumed that the hopping frequencies of N disjoint subbands are identical. We consider the FH patterns without this assumption. These FH patterns have cross correlation no greater than one in order to minimize mutual interference. In addition, we analyze the performance of the system in order to show the improvement of user capacity. Our results show that the proposed scheme performs better than the conventional one in both nonfading and fading channels.

There has been much interest in the application of frequency hopping-spread spectrum multiple access (FH-SSMA) to wireless systems because of its frequency diversity and resistance to the near-far problem. In FH-SSMA systems, cochannel interference (CCI) is the dominant factor limiting the user capacity. Various techniques used to resolve the CCI problem have been extensively investigated. We propose several multiuser detection schemes based on canceling CCI to increase user capacity in a multilevel frequency shift keying (MFSK)/FH-SSMA system. The performance of systems with the proposed interference cancellers over a Rayleigh fading channel are analyzed and compared with those of the conventional and other interference cancellers. Our results show that the proposed schemes have the best performance in both nonfading and fading channels.