spectrum radio for two diversity antennas. The top envelope represents Max{R1, R2}, while the bottom envelope represents Min{R1, R2}. Note that, for the most part, the maximum has nulls that seem to follow a pattern consistent with the probabilities described above. Measurements taken by Cylink seem to confirm that diversity antennas require about 20 dB of power control to overcome fading owing to multi- path inside buildings. Deep fades beyond this control limit will be allowed to cause loss of signal but will do SO infrequently. When such loss of signal occurs in a deep fade, recovery is generally very quick and the effects are short noise bursts. In today's analog cordless telephones and cellular phones, such noise bursts are very common and generally much more frequent than expected here. Experience with current spread-spectrum voice modems confirms this behavior. APPENDIX 3B. ERROR BOUNDS FOR INTERFERENCE-LIMITED CHANNELS Appendix 3B follows the presentation in Part 1, Chapter 4, Appendix 4A and Part 2, Chapter 1, Section 1.2. Appendix 3B. Error Bounds for Interference-Limited Channels We assume ideal coherent detection of DS/BPSK with the spreading code- word-matched filter output sampled at the correct time for the intended spread-spectrum signal with energy per bit of . Without interference, the output sample of the matched filter is A if a 0 data bit is sent and - A if the data bit is a 1. Assuming interference I at the spreading codeword-matched filter output sample when a 1 bit is sent, the bit error probability is given by the general expression (3B.1) based on the probability distribution of the interference random vari- able I. Although we can assume that the probability density function of the ran- dom interference variable I is symmetric about the origin, it is generally dif- ficult to obtain an error expression for such interference caused by other signals in the microcell network, given the difficulty in obtaining a closed- form expression. We derive an easy-to-evaluate Chernoff bound expression