Practical Analysis of 802.11 Single Antenna IBFD Systems

A shared wireless channel with limited resources and an exponential increase in the number of wireless devices and the enormous data rates motivated the researchers to innovate solutions that improve the spectral efficiency within the available spectrum bands. Most current wireless standards share a channel on Half-Duplex principle, where the transmission and the reception of signals are occurring in two separate time slots or two different frequency bands. Even though technologies like MIMO, OFDM have hugely improved the spectral efficiency of the wireless communications, to fulfill the future data and the growing user demands, even more advanced techniques are needed in the ultrahigh frequency (UHF) band, which perhaps is the most congested piece of the spectrum. To overcome this spectrum scarcity, wireless In-Band Full-Duplex (IBFD) communication is the recent advancement in the next steps towards the full utilization of the spectral resources. In an IBFD system, a transceiver can transmit and receive simultaneously using the same carrier frequency. This theoretically doubles the spectral efficiency and avoids the usage of separate frequency bands for transmission and reception. Nevertheless, an IBFD system suffers from self-interference from the strong transmit signal coupling back into its own receiver chain, which has to be mitigated for the efficient operation of the full-duplex system. In this thesis, work has been presented on, 1) Surveying full-duplex with its brief history and recent advances, 2) Critical analysis on widely implemented methods of self-interference cancellation in propagation, analog, and digital domains, 3) A selected digital least square channel and SI model estimation method is expanded, 4) Performance of the cancellation methods are evaluated with real-time hardware impairments using MATLAB simulations, and 5) Practical implementation of IBFD systems using software defined radios (SDRs). The obtained residual SI show that, with the help of these SI cancelers, the SI can be canceled almost perfectly, proving that a true IBFD operation is indeed possible. This demonstration on the implementation of an IBFD transceiver under practical constraints paves the way towards the commercial deployment of IBFD radio transceivers.