Transmit diversity for high data rates in WCDMA indoor systems

One of the vital issues when regarding WCDMA, is the need to provide variable and high data rates. In the first stage of the WCDMA standard, data rates up to 2 Mbps are considered and the need for these data rates is expected especially in indoor environments and in the downlink. To improve system performance in terms of coverage and capacity, transmit diversity (TxD) with multiple antennas at the base station can be used. In fact, the current standard contains three different modes applicable to dedicated channels. In this work we first compare the three different modes with link level simulations. We conclude that for a 2 Mbps service in an indoor environment with small time dispersion, at least 3.5 dB lower transmit power is required if TxD with feedback information is used. With this preferred TxD mode, system simulations show that the service probability, in a sample office building, is almost completely determined by the number of available codes.