Demonstration of real-time wideband transmit diversity at the handset in an indoor wireless channel

The next generation CDMA standard, wideband CDMA (W-CDMA), has provision for many performance enhancement options to support high data-rate services. Transmit diversity has been proposed as one mechanism for performance enhancement. This paper presents a real-time implementation of a wideband transmit diversity system. The implementation was carried out to demonstrate transmit diversity in an indoor wireless channel at the handset with a two-element antenna array at 2.05 GHz for a bandwidth of 5 MHz. The diversity algorithm is a closed loop technique and is based on scanning the phase of signal on one antenna relative to the other. Single antenna measurements were also performed to serve as a baseline measure. Measurements were carried out both in line-of-sight (LOS) and in non-LOS (NLOS) environments. The diversity gains when assessed using a cumulative distribution function (CDF), showed gains of 2 dB and 7 dB respectively compared to individual antenna element for the LOS environment (at 1% CDF level). For the NLOS case, the diversity gains were more than 10 dB at the 1% CDF level.