Optimal rate error protection for coded M-ary FSK FFH/CDMA mobile radio channels

Forward link capacity of fast frequency-hopping code-division multiple access (FFH/CDMA) cellular mobile communication systems is analyzed. M-ary FSK with noncoherent detection is assumed. Coding is used for both random address sequencing and error correction. Selection diversity reception is also applied. The channel cutoff rate of an interference-limited coded FFH/CDMA channel with a hexagonal cell layout is analyzed for both synchronous and asynchronous cases. The theoretical capacity limit is calculated from the channel cutoff rate. The optimal rate that maximized the user capacity is then determined. Reed-Solomon (RS) codes are then applied as a practical approach. It is shown that optimal RS code rate is 0.8 for 256-ary FSK with 19 hops/symbol, which is almost the same as that derived from the channel cutoff rate