Performance analyses of DPSK-FFHSS and DPSK-FFH-SSMA systems over Nakagami fading channels

Performances and capacities of differential phase-shift keying (DPSK) fast frequency-hopping (FFH) spread spectrum (SS) transmission and multiple-access (MA) systems over Nakagami fading channels are analyzed and compared with simulated results. The proposed transmitter can operate without an output hopping filter. The secured transmission can be obtained by the proposed DPSK FFHSS system. The results show that bit error rate (BER) is improved in the system with higher number of hops/bit. Furthermore, the number of hops/bit can guarantee BER for the most values of Nakagami fading figure with small maximum variations of average signal-to-noise ratio (SNR). For the single user system with 16 hops/bit, the maximum variations of SNR of 1.99, 2.82, and 3.62 dB give the BERs of 10^-3, 10^-4, and 10^-5, respectively. The system capacities with the perfect knowledge of side information have been evaluated and can be proportionately improved by the number of hops/bit, total hopping frequencies, and average SNR. The maximum capacities are about 48, 124, and 227 users for the system at 4, 8, and 16 hops/bit, respectively, with BER of 10^-3 and 200 total hopping frequencies. In addition, capacity degradation of the system has been evaluated.