Field test results of downlink smart antennas and power control for IS-136

Abstract

We present field test results obtained from our IS-136 smart antenna test bed showing the improvement in performance obtained using downlink smart antennas and power control for IS-136. We describe the test bed which consists of an adaptive uplink system with dual polarization antennas and a downlink multibeam antenna with power control. Tests were conducted at 1900 MHz on drive routes in a typical cellular base station site located in a suburban environment. We implemented and tested the performance of downlink power control algorithms which slowly adjust the transmit power based on the downlink or uplink RSSI while adaptively adjusting the RSSI threshold based on the BER. The field test results show that our beamforming technique with a fixed multibeam antenna with power control provides additional gain and can closely track channel variations thereby requiring less margin and less average transmit power while maintaining the C/I level needed for good signal quality. We show that power control improves the C/I by 2 to 3 dB for a 1% BER for both vehicular and pedestrian fade rates when the uplink RSSI is used to estimate the downlink received power. The field test demonstrates the feasibility of using smart antennas on the uplink and downlink to increase both the range and capacity of the IS-136 system.