Transmit beamforming design in wide angle spread scenarios for B3G MC-CDMA systems

Standard receive beamforming concepts assume narrow band transmission and pointing towards a specific direction in order to maximize signal to noise ratio (SNR). However, realistic scenarios for next mobile applications (beyond 3G) exhibit significantly large angle spread (even for suburban channels) and use wide band transmission. In this situation, transmit beamforming could be a powerful technique to improve performance but some insights have to be addressed in order to obtain expected performance. We present an alternative with partial channel knowledge, based on the spatial autocorrelation function estimated in uplink, that outperforms standard beamforming techniques. Assuming that both links are correlated in terms of spatial correlations, this scheme can be applied both for FDD or fast fading TDD without specific channel knowledge at transmitter side. Several simulations with realistic channel model will corroborate this performance.