Interference reduction in time duplex systems by space-time beamformers

In cellular mobile radio systems, and more especially in the third-generation wireless communication systems, transmit beamformers can be used to reduce the multiple access interference (MAI) in the downlink in order to increase the quality of service and the capacity of communication systems. However, for the most conventional beamforming methods, the inter-symbol interference (ISI) or the inter-chip interference (ICI) is not taken into account, which limits the performances of these methods. In this paper, we propose a new method which uses frequency-selective beamformers to reduce jointly the MAI and the ICI. Uplink data obtained with an UMTS-TDD measurement campaign have been used to show the behaviour of the proposed method. Simulations show the efficiency of this method which improves the performances obtained with classical methods.