Estimation of the self-interference channel with received signal in full-duplex radios

A major challenge in realising a full-duplex (FD) transceiver is to decode the received signal in presence of the strong transmit signal termed as self-interference (SI). Usually SI is suppressed by reconstructing it using the transmit signal and subtracting it at the FD receiver. For good cancellation, an accurate estimate of the SI channel is essential. However, training for obtaining the SI channel in the presence of intended received signal requires a large training period. This can be addressed by designating a separate training period during which received signal is turned off, and the SI channel is estimated. However having a separate training period impacts the overall achievable rate. In this paper, we propose a technique that exploits the structure of the received signal to train for SI channel in the presence of received signal. Specifically, we propose a time domain symmetric preamble packet in the received signal to create effective samples in which the received signal is absent. Further, we bound the variance of the channel estimates thus obtained and observe that the performance is same as that of having a separate training period. The performance of the proposed technique is also evaluated by an experiment setup.