Beamforming and Interference Cancellation for Capacity Gain in mobile Networks

Document type: Journal Articles
Article type: Original article
Peer reviewed: Yes
Full text:
Author(s): Sven Nordholm, Jörgen Nordberg, Ingvar Claesson
Title: Beamforming and Interference Cancellation for Capacity Gain in mobile Networks
Translated title: Kapacitet vinster i mobila system genom att använd lobformning och störnings undertryckning
Journal: Annals of Operations Research
Year: 2000
Volume: 98
Issue: 1-4
Pagination: 235-253
ISSN: 0254-5330
Publisher: Kluweer
ISI number: 000169227200013
Organization: Blekinge Institute of Technology
Department: Department of Telecommunications and Signal Processing (Institutionen för telekommunikation och signalbehandling)
Department of Telecommunications and Signal Processing S-372 25 Ronneby
+46 455 38 50 00
Authors e-mail: jno@bth.se
Language: English
Abstract: The growth of wireless communication continues. There is a demand for more user capacity from new subscribers and new services such as wireless internet. In order to meet these expectations new and improved technology must be developed. A way to increase the capacity of an existing mobile radio network is to exploit the spatial domain in an efficient way. An antenna array adds spatial domain selectivity in order to improve the Carrier-to Interference ratio (C/I) as well as Signal-to-Noise Ratio (SNR). An adaptive antenna array can further
improve the C/I by suppressing interfering signals and steer a beam towards the user. The suggested scheme is a combination of a beamformer and an interference canceller.

The proposed structure is a circular array consisting of K omni-directional elements and combines fixed beamforming with interference cancelling. The fixed beamformers use a weight matrix to form multiple beams. The interference cancelling stage suppresses undesired signals, 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 were chosen to cancel these interferers; use the other beamformer outputs as inputs to an adaptive interference canceller; or regenerate the outputs from the other beamformer outputs and generate clean signals which are used as inputs to adaptive interference cancellers.

Resulting beamformer patterns as well as interference cancellation simulation results are presented. Two different methods have been used to design the beamformer weights, Least Square (LS) and minimax optimisation. In the minimax optimisation a semi-infinite linear programming approach was used. Although the optimisation plays an essential role in the performance of the beamformer, this paper is focused on the application rather then the optimisation methods.
Summary in Swedish: I denna artikel undersöks fördelarna med att använda lobformning och undertryckning av störande signaler i mobila system. Genom att ta imot signaler med flera antenner, kan man välja att lyssna på signaler i från en viss riktning medans man samtidigt ignorerar signaler som kommer ifrån andra riktningar.
Subject: Telecommunications\General
Signal Processing\Beamforming
Signal Processing\General
Keywords: Beamforming, Spatial Interference Cancellation, Adaptive Interference Cancellation
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