An Interference Cancellation Scheme for Mobile Communication Radio Repeaters

Moohong LEE  Byungjik KEUM  Young Serk SHIM  Hwang Soo LEE  

IEICE TRANSACTIONS on Communications   Vol.E92-B   No.5   pp.1778-1785
Publication Date: 2009/05/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E92.B.1778
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Radio Access Techniques for 3G Evolution)
interference cancellation,  repeater,  feedback,  stability,  signal quality,  

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An interference cancellation (ICAN) scheme for mobile communication radio repeaters is presented. When a radio repeater has a gain that is larger than the isolation between its transmit and receive antennas, it oscillates due to feedback interference signals. To prevent feedback oscillation of a radio repeater, we first formulate a feedback oscillation model of the radio repeater and then derive an ICAN model from that model. From the derived ICAN model, we show that the stability and the signal quality of the repeater depend on the repeater's gain and delay, the propagation delay on feedback paths, feedback channel characteristics, and the capability of the feedback channel estimation algorithm. It is also shown that the stability condition of the repeater does not guarantee the quality of the repeater's output signal. To guarantee repeater's stability and signal quality, an ICAN scheme based on an iterative algorithm is subsequently proposed. The simulation results confirm the relationship between the stability and signal quality of the repeater and the impact of the aforementioned factors. Using the proposed ICAN scheme, a mean error vector magnitude (quality indicator) of about 6.3% for the repeater's output signal was achieved.