Performance Evaluation of Fast Frequency Hopping Type CDMA Mobile Radio Communication Schemes

Performance evaluation is made of Fast Frequency Hopping (FFH) type Code Division Multiple Access (CDMA) mobile radio communication schemes subjected to Additive White Gaussian Noise (AWGN), urban/suburban multipath, multiple access interference, and near-far effects commonly encountered in ground mobile radio environment. It is commonly believed that the FFH type CDMA schemes are generally superior to the direct-sequence type CDMA schemes in combatting the near-far effects. This belief stems from approximate analyses that ignored the effects of the spectral spillover of the signals into adjacent channels, which suggests that it is possible to minimize these effects by designing the frequency-hopping patterns in such a way that the number of frequency hops over which any two user´s signals hop to the same frequencies at the same time are minimized. It is shown here that there is no such advantage if the spectral spillover effects of signals into the adjacent channels are accounted for in the analysis. It is further shown that, while spectral shaping of the signals improves the performance of the FFH type CDMA schemes, such improvement is not as significant when the spectral spillover effects are included in the analysis. The performance of random hopping patterns is compared with that of hopping patterns based on the Reed-Solomon Codes as well as with that of random direct-sequence codes under various fading conditions.