Modulation and processing gain tradeoffs in DS-CDMA spread spectrum systems

Continuous phase modulation (CPM) schemes are examined for use in DS-CDMA spread spectrum systems. Since the power spectra of CPM schemes are narrower than BPSK schemes, a larger processing gain can be used for the same overall bandwidth after spreading. The processing gain, relative to BPSK, that can be used with CPM is calculated. As an example, it is shown that the performance of an MSK system is better than a BPSK system for an equivalent overall bandwidth.