Title :
Space-time Rake receiver with optimal beamforming for the uplink of CDMA-based wireless systems
Author :
Boche, Holger ; Schubert, Martin
Author_Institution :
Broadband Mobile Commun. Networks, Heinrich-Hertz-Inst. fur Nachrichtentech. Berlin GmbH, Germany
Abstract :
In this paper a new spatial filtering approach for the uplink space-time Rake receiver is investigated. Recent field trials have shown that classical beamforming algorithms are not always reliable in the presence of strong interference and rapidly time-varying channels. More robust beam pattern control can be achieved by combining null steering and directivity optimisation. The necessary directional information can be extracted from the covariance matrix, e.g. by code filtering. The main focus of this work is the analytical investigation of the capability of the beam pattern to suppress self-interference and multiple access interference (MAI). It is proved that for a large number of equally spaced interferers and under assumption of ideal power control, the SNIR is optimised by maximising the directivity of the beam pattern. In case of less ideal scenarios, additional nulls of the beam pattern may be placed. This approach can also be extended by an additional pilot signal, if available
Keywords :
array signal processing; cellular radio; code division multiple access; covariance matrices; radio receivers; radiofrequency interference; space-time adaptive processing; time-varying channels; CDMA-based wireless systems; beam pattern; code filtering; covariance matrix; directivity optimisation; ideal power control; multiple access interference; null steering; optimal beamforming; rapidly time-varying channels; self-interference; space-time Rake receiver; spatial filtering approach; Array signal processing; Covariance matrix; Data mining; Fading; Information filtering; Information filters; Multipath channels; Multiple access interference; Robust control; Time-varying channels;
Conference_Titel :
Circuits and Systems, 2000. Proceedings. ISCAS 2000 Geneva. The 2000 IEEE International Symposium on
Conference_Location :
Geneva
Print_ISBN :
0-7803-5482-6
DOI :
10.1109/ISCAS.2000.856008