Digital Self-interference Cancellation In Single Channel Full-duplex Communication System

One of the fundamental assumptions in the design of wireless networks is that the wireless devices have to be half-duplex, in other words, wireless devices cannot simultaneously transmit and receive in the same frequency band. Therefore, current deployed wireless communication systems employ devices which use either a time-division or frequency-division approach for wireless transmission and reception of signals. This requires dividing the temporal and/or spectral resources into orthogonal resources and results in an orthogonalization of the transmissions and receptions performed by a wireless device, single uplink or downlink cannot achieve full-duplex communication. It is a quite important problem to employ limited frequency band resources effectively today, when the wireless frequency resources is more and more sparse. People is working on a variety of wireless technology and algorithm which can save wireless resource or maximize the use of wireless resources, all kinds of wireless communication system arises at the historic moment. This dissertation proposes single channel full-duplex as a new paradigm for wireless system design that can mitigate some of the throughput and reliability problems of today’s wireless systems.With full-duplex wireless radios, a node can receive and transmit data at the same time, without using multiple wireless channels. At the physical layer, these capabilities can double the available throughput at a node. Further, sending and receiving at the same time allows a wireless node to exchange control messages while receiving data, making real-time feedback schemes possible. But as a novel technology, the key challenge in achieving full-duplex wireless communications, where a device can transmit and receive signals over-the-air at the same time and in the same frequency band, is the large power differential between the self-interference created by a device’s own wireless transmissions and the received signal of interest coming from a distant transmitting antenna. This large power differential is due to the fact that the self-interference signal has to travel much shorter distances than the signal of interest. The large self-interference spans most of the dynamic range of the Analog to Digital Converter (ADC) in the received signal processing path, which in turn dramatically increases the quantization noise for the signal-of-interest. Thus to achieve full-duplex it is essential to suppress the self-interference before the analog received signal is sampled by the ADC. In the last three years, many works or researchers have reported experiments and/or models for full-duplex communications. This dissertation discusses various passive cancellation, active analog and digital self-interference cancellation techniques to cancel this strong self-interference, and we first classify all known full-duplex self-interference cancellation techniques based on how they compute their cancelling signal and when or where the cancelling signal is injected to cancel self-interference. Then, the principle of adaptive interference offset technology is discussed and three types of time-domain adaptive algorithm are introduced. We test and verify the effectiveness that time-domain adaptive algorithm is used to cancel the strong interference signal by the simulation. We propose an adaptive digital self-interference cancellation scheme based on the interference signal analysis, combining joint channel estimation. In the end, we presents the whole building of Single channel full duplex system, our adaptive full-duplex wireless system that combines passive cancellation, active analog and digital adaptive self-interference cancellation to remove up to90dB of self-interference. Finally, implementation issues are considered, including system imperfections and RF impairments such as phase noise. We derive signal to interference plus noise radio of the full duplex system after digital self-interference cancellation, this lay the foundation for the system performance comparison between full-duplex and half duplex in the future.