Smart Antennas as Key Technology for ISI Cancellation in Low-Cost/Low-Power Receivers

The performance and capacity of wireless mobile communication systems are often limited by intersymbol interference (ISI). Intersymbol interference is caused by the superposition of direct and reflected signal components at the receiving antenna with propagation delay differences of up to several symbol durations. The required digital signal processing to combat this effect will increase both the cost and the power consumption of the mobile terminal.

A particularly appealing solution for ISI-cancellation in low-cost/low-power receivers is the combination of an analogue antenna combiner and a cascaded digital equalizer. In this thesis several combinations of equalization methods in the analogue and digital domains are derived and the tradeoff between performance and computing expenditure is investigated. A new high-performance and low-complexity combination of equalization in the analogue domain and equalization in the digital domain has been developed, which turns out to be a very attractive solution for low-cost/low-power receivers.

Another major part is the investigation of the required accuracy and the acceptable imperfections in the analogue antenna combiner, which are very important for production cost and power consumption of the mobile terminals. In order to cope with combiner imperfections several algorithms to increase the robustness against statistical variations are derived and discussed with respect to their applicability, performance and complexity. Since the performance of the receiver is also limited by the accuracy of the synchronization and parameter estimation algorithms, these issues are considered, too. Finally a demonstration system, which has been built throughout this work, is explained and results from field trials are compared with simulation results.