Wideband digital cancellation for full-duplex communications

In this paper, we consider the problem of canceling self-interference received by a wireless node from the transmitted signal from the same node. We consider separate antennas for transmission and reception. The self-interference signal is partly known to the node since the transmitted signal is known at the received antenna with the exception of the channel gain and multipath effect. We investigate the limitation of digital cancellation in solving the problem of self-interference cancellation and seek efficient algorithms that can be used in wideband and frequency selective channels as well as the narrowband and frequency flat channels. We show that limitations of analog to digital converters (ADC) such as the dynamic range and quantization resolution are the main obstacle in restricting the isolation levels of the self-interference signal that can be achieved by employing digital cancelation. We provide design guidelines and a specific digital cancelation system with an enhanced effective resolution and larger dynamic range by an intelligent feedback loop. We also address the problem of wideband digital cancellation by using the theory of sparse signal recovery.