Comparative study of uplink and downlink beamforming algorithms in UTRA/TDD

The arrival of new multi-media and Internet services to mobile cellular subscribers has led to the development of new techniques, such as antenna array or smart antennas (SA), to improve spectrum efficiency. SA provides a means for spatial filtering for separating users based on angular characteristics, a method also known as beamforming. In this contribution, the performance of various beamforming algorithms is studied for the uplink and downlink of an UTRA/TDD system under realistic deployment and channel models. The algorithms are evaluated in terms of improvement in signal to interference plus noise ratio (SINR) and coded bit error rate (BER) with a RAKE receiver structure and compared to a more complex space-time multiuser detection receiver. We consider three different beamforming algorithms, namely: switched beams (SB), dynamically phased arrays (DPA) and sample matrix inversion (SMI). The results indicate that on the uplink, SMI has the potential to perform better than both DPA and SB but DPA outperforms both SB and SMI on the downlink.