UC Irvine

Recently Full-Duplex (FD) communication has gained significant interest due to demonstrable increase in throughput and spectral efficiency. Conventional Half-duplex (HD) communication systems use either time-duplexing or frequency-duplexing to avoid self-interference. In contrast, full-duplex systems transmit and receive simultaneously on the same frequency band, thus optimally utilizing available resources. The main challenge in FD systems is managing the self-interference (SI) signal at each node, which is typically orders of magnitude larger than the intended signal of interest (SOI). To achieve sufficient SI suppression, FD systems rely on cancellation across multiple domains such as spatial, analog, and digital. However, number of practical, FD specific challenges arise impacting quality of service, when at least one node in a network operates in full-duplex mode.

\par In this thesis, we consider practical issues of wireless networks containing a full-duplex node. The ultimate goal of this work is to design and implement real-time, end-to-end networks consisting of at least one FD node that is capable of improving network performance under limited available bandwidth constraint. First, we identify synchronization issues in a network consisting of a full-duplex base station communicating with half-duplex nodes. Novel synchronization techniques specific for full-duplex networks are proposed that allow compensation of synchronization errors in time and frequency. The proposed techniques are implemented and tested experimentally on a real-time full-duplex wireless network. Second, we characterize the dynamic environment impact on the received self-interference in the FD system, which is equipped with a reconfigurable antenna as a passive SI suppression mechanism. The self-interference channel delay profile is measured using the FD system operating on 5MHz, 10MHz, and 20MHz bandwidths. The measured channel profiles collected under suppressing and non-suppressing antenna patterns are compared, and channel changes in static, as well as dynamic environments, are highlighted. We then statistically model the SI channel by performing probability distribution fitting to SI channel data. Third, the thesis proposes a Wi-Fi compliant self-interference active cancellation technique for amplify and forward, as well as decode and forward full-duplex relays. Finally, we design and implement an end-to-end wireless network extended with the aid of a custom-designed amplify and forward full-duplex relay. We then analyze the relay coverage limitation under the stability and transmit power constraints. The network performance is analyzed as a function of relay location for constant gain and constant transmit power modes, consequently suggesting optimal relay location that will maximize signal to noise plus interference ratio (SINR) at the destination node. We evaluate the overall network performance by simulation, as well as experimentally in outdoor/indoor environments.