Comparison of orthogonal CDMA and slow frequency hopping (SFH)/TDMA for picocell communications

In this analysis, the effects of co-channel interference, unintentional interference, fading on an orthogonal (O)-CDMA and a slow frequency hopping (SFH)-TDMA system are investigated. Both OCDMA and SFH/TDMA are small-cell, low-mobility systems without low-rate speech coding and other heavy-duty baseband signal processing. Further, TDD rather than FDD is used. Both systems have the same number of channels, system bandwidth, cell layout, and voice activity detection. After all the analysis, we have found that OCDMA and SFH/TDMA are very much the same on the basis of performance. One advantage for OCDMA is the ability to achieve a higher order of diversity via the RAKE receiver; L can get up to 3. The advantage of SFH is that coding can be used effectively to improve the performance. This is not true of OCDMA, since we are assuming low-speed mobility, and the signal variations due to multipath will be relatively slow. However, frequency hopping forces the variations to be fast so that coding is effective