Self-Interference Cancellation In Polarization Based Full Duplex Systems

Full Duplex(FD)wireless communication has been reflected as one of the qualifying communication system towards the execution of 5th generation wireless communication system.Combining the two bidirectional communication system in same time and frequency resources to perform both way communication,FD offer excessive potential to improve the capacity,spectral efficiency and throughput.Therefore,FD,has gained lot of interest from both the industrial and academic side.Polarization is the key characteristic of electromagnetic wave.Polarization based full duplex communication have gained a lot of interest because it helps in the double growth of network capacity.Polarization based FD communication can provide the best in performance by understanding its characteristics.The performance of same time same frequency transmission and reception in a single channel is limited due to the huge power gain of receiver from its own transmitter called self-interference(SI).The SI imposes the problem linear and non-linear impairments which produce residual SI which limits the performance of FD communication.This research analyze some of the limitations and gives two solutions for those limitation to achieve the better performance in FD communication.This work is supported by the National Natural Science Foundation of China under Grant No.61501050 and No.61271177.The main contributions of this dissertation are listed as follows.1)The limitation and interrogation in design of FD communication system are underlined in the framework.The prior arts associated to the design of SI cancellation is presented in in-depth explanation.Passive,analog and digital cancellation mechanisms are discussed.Polarization signal processing and its properties for polarization based SI cancellation in FD are highlighted in the framework.2)The performance of polarization based antenna SI cancellation is characterized and analyzed with directional isolation and cross polarization of antenna.Different setup for directional isolation and cross polarization characterization have been made on the polarization based FD platform.The SI reduction on the receiver has been analyzed through practical experiments.The experimental analysis of these techniques are made to encounter the limitations in direct path of SI signal and design a FD system that takes these restrictions,limitations and abilities to achieve an efficient FD communication system.The experiments are combined and evaluated by its performance.3)A polarization based optimal detection(POD)scheme for digital SI cancellation in FD system is proposed.The problem of detecting the desired binary phase shift keying signal in the presence of residual SI signal and noise is considered.The POD scheme exploits polarization domain to estimate and isolate the desired signal from the SI signal and then cancel the SI to obtain the interference free desired signal.The problem is formulated to build likelihood ratio expression for polarization based FD communication system which isolates and estimates the desired signal from the SI signal when the residual SI is maximum in FD communication.After isolation the POD scheme cancels the SI to obtain interference free desired signal.The performance and simulation results of the scheme are derived.POD scheme can minimize the SI,gives a clear constellation diagram and increases the receiver cancellation performance in low signal to interference ratio(SIR)and low signal to interference noise ratio(SINR)environment.