GSM base-station antenna diversity using soft decision combining on up-link and delayed-signal transmission on down-link

Two branch base-station antenna diversity performance for the GSM (Groupe Speciale Mobile) system is simulated. For the uplink combining, soft decision signals from two SOVA data-detectors are used for a (nearly) optimum post-detection combining. For downlink, a delayed-signal (on the order of 2-b periods) is transmitted on a second antenna branch in order to introduce "artificial" time dispersion in the radio channel. This technique takes advantage of the equalizing properties of the GSM data-detector. The simulation results show that the multipath fading margin can be reduced by 6-13 dB on uplink and by 3-10 dB on downlink for the GSM specified test channels RA250 and TU50.