Adaptive Antenna Arrays for CCI/ISI Reduction in Broadband F/TDMA Cellular Networks

Adaptive array antennas are very effective in mitigating the effects of co-channel interference (CCI) and multipath propagation in wireless communication systems. Here, antenna arrays applied to uplink reception in a broadband F/TDMA cellular system are investigated. The system employs QPSK with 15.36 Mbit/s. For low complexity spacetime equalization a mixed solution is proposed based on a MMSE-type space-time filter (STF) followed by a MLSE. The STF suppresses CCI and reduces inter-symbol interference (ISI) while capturing spatial diversity. The MLSE removes the residual inter-symbol interference (ISI). The channel estimation and the beamforming are performed jointly, so that constraints on tap weights have to be introduced to avoid the trivial solution problem. The resulting cellular performance is analyzed by means of link and system level simulations for system deployment in the 5 GHz band. For small arrays of only 4 antenna elements the system capacity is enhanced by 50%, for 8 element arrays it is even doubled.