Beamforming performance measurements in a DCS 1800 smart antenna testbed

In cellular mobile communications the radio link is one key issue for further system development in terms of data rate and system capacity. Smart antenna arrays are seen as powerful possibility for improvement of the radio link because they are maximising antenna sensitivity for one selected mobile in the uplink and minimising the total amount of downlink radiated power. In addition to that, with the increasing power of digital signal processors it becomes more and more reasonable to integrate sophisticated signal processing for smart antenna array control in the base transceiver stations (BTS). This basic context can be used for system improvements in terms of range extension, frequency reuse and transmission quality. In Alcatel Research Center a smart antenna testbed has been implemented for detailed investigations of the smart antenna technique. In this paper the beamforming behaviour is studied for further optimisation. Depending on the kind of application as range extension, spatial filtering (capacity increase by adapted frequency reuse) or space division multiple access (SDMA) the beam design has to be optimised. New results concerning the beamforming performance of the system with measured array antenna beam patterns are reported. With precise knowledge of sidelobes and nulls efficient design of algorithms, signal processing will be possible.