Improving the spectral efficiency of wireless communication systems based on new duplexing techniques

Abstract

Efficient use of the wireless spectrum is a key objective in wireless communication systems. One research area that is attracting growing interest is the development of novel duplexing technologies. In this thesis, we look into the designs and applications of three novel duplexing techniques for wireless communication systems: single channel full-duplex, subcarrier-based duplexing and spatial-division duplexing. Full-duplex enables devices to transmit and receive signals simultaneously using the same channel, which can potentially double the capacity of wireless communication systems. Subcarrier-based duplexing assigns different subcarriers of an OFDM system for transmission and reception, laying the foundation for various cooperative communication schemes proposed in the literature that require so. Spatial-division duplexing utilizes beamforming techniques to separate transmitting and receiving signals, and can exploit the spatial degree of freedom in MIMO systems to improve the total data rate. In this thesis, we first study the feasibility of full-duplex wireless communications. The effects of various imperfect system characteristics are investigated, and we have proposed a baseband echo cancellation scheme to suppress the self-interference. The performance of the proposed scheme is evaluated by both analysis and simulation, and the improvement in the overall capacity/throughput is studied. Using a similar approach of echo cancellation to suppress the interference between the transmitting and receiving subcarriers, we then propose a transceiver structure that achieves subcarrier-based duplexing, which is applied to a cooperative OFDMA system to examine its performance under realistic conditions. In the third part of this thesis, we investigate full-duplex wireless communication based on multi-antenna techniques. In particular, we consider a multi-user MIMO system where the base station serves multiple uplink and downlink users simultaneously. An efficient algorithm is proposed to jointly design the beamformers of the BS and MSs to suppress self-interference and maximize the weighted sum data rate.

Date of Award	2013
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology