Relay self-interference minimisation for QAM signals

This paper introduces a self-interference (SI) minimisation technique for amplify and forward (AF) relays. Relays are used to help forward signals between a source and a destination. The AF relay amplifies the signal it receives then transmits it to the destination. Due to imperfect antenna isolation between the receiving and transmitting antennas at both ends of the relay, the transmitted signal will interfere with the relay´s received signal. This will cause a SI problem. A solution is proposed in this paper to combat such a case by two tapped filter before the amplification stage. One of this filter´s weights will be evaluated adaptively using the least mean squared (LMS) algorithm. The solution achieved does not require a priori knowledge of the SI channel weight. Simulation results are provided in this paper to verify the proposed methods performance.