On the coexistence of N-CDMA and analog FM/FDMA cellular telephone systems in adjacent spectrum

Coexisting analog frequency modulation (FM) based on frequency division multiple access (FDMA) and narrow-band code division multiple access (N-CDMA) in adjacent spectrum is studied. The allocation on different spectrum can avoid the serious performance degradation as transitioning from fully loaded analog FM/FDMA to N-CDMA. The guard-band needed between the adjacent spectrum to maintain acceptable performance degradation is derived and evaluated. Numerical results indicate that at least a 255 kHz bandwidth to separate the two systems is necessary. The worst case of the interference from FDMA degrades the performance of N-CDMA, even under appropriate guard-band separation. This study demonstrates the capacity reduction of N-CDMA as coexisting analog FM/FDMA in adjacent spectrum