Experimental results for a narrowband full duplex communications system

Full duplex communications systems may double throughput in a bandlimited channel. Full duplex is especially attractive for relatively simple point-to-point, highly directional links used in satellite communications. A testbed was developed to study the feasibility of achieving sufficient self-interference cancellation for very long distance links. The difficulty with long-distance full duplex links lies in the extreme power difference between the transmitted and received signals. A full-duplex system meant for satellite communications needs to be relatively small, further constraining hardware options. On the other hand, sensitivity to cost of individual components is dramatically lower than for commercial terrestrial systems. In this paper we provide a detailed description of the testbed, including hardware choices and tradeoffs, as well as real-time measurement results. The results presented in this paper match, but do not surpass, the best published to date. This paper presents technical approaches that are not addressed elsewhere and provides a summary of challenges likely to be encountered by other researchers.