Comparison of selection and switched diversity systems for error-rate reduction at base-station sites in digital mobile radio systems

Recorded envelope data from field trials in which a mobile transmitted a CW signal to a base station equipped with two vertically spaced antennas has been used in a computer simulation of diversity reception. The cumulative distribution function, level-crossing rate and average fade duration have been determined for 2-branch selection and switched diversity systems and the results have been compared with theoretical calculations. Considerable improvements are obtained in general, although switched diversity is not effective in reducing the duration of fades. Provided an optimum switching threshold is used, both types of diversity can reduce BER for uncorrelated envelopes.