The increasing demand for user capacity is a major challenge to network operators today. In order to increase the capacity of a mobile radio network, it is desirable to exploit the spatial domain in an efficient way. An array adds spatial domain selectivity in order to improve the Carrier-to-Interference ratio(C/I). An adaptive antenna array can further improve the Carrier-to-Interference ratio(C/I) by suppressing interfering signals. The proposed circular array consists of K elements and combines fixed beamformers with interference cancellers. The fixed beamformers use a weight matrix to form multiple beams. The interference canceller suppresses undesired signals, called jammers, leaking into the desired beam. The desired signal is filtered out by the fixed beamforming structure. Due to the side-lobes, interfering signals will also be present in this beam. Two alternative strategies may be chosen to cancel these interferers; use the other fixed beam outputs as inputs to an adaptive interference canceller, or regenerate the outputs from the other fixed beams and generate clean signals which are used as inputs to adaptive interference cancellers. Results are presented using beamformer weights obtained from a Least Square (LS) minimisation as well as minimax.

Ett sätt att öka kapaciteten i dagens mobiltelefoni-system är att använda flera antenner i basstationerna d.v.s använda digital lobformning. Denna rapporten beskriver hur man med hjälp utav digital lobformning kan förbättra kvaliteten på den mottagna signalen.