Resource optimisation and interference management for multiuser communication systems in a cooperative environment

• Main Author: Barman Roy, Swagato
• Other Authors: A S Madhukumar
• Format: Theses and Dissertations
• Language: English
• Published: 2017
• Subjects: DRNTU::Engineering::Computer science and engineering::Information systems::Information systems applications; DRNTU::Engineering::Electrical and electronic engineering::Wireless communication systems
• Online Access: http://hdl.handle.net/10356/69826
• Institution: Nanyang Technological University

As a result of the rapid exhaustion of available electromagnetic spectra and industry trend towards power limited devices, various cooperation schemes have been proposed as ways to achieve better performance in wireless systems. The currently deployed systems use a combination of time and frequency division multiplexing to grant each communication link an exclusive degree of freedom. While this limits the interference among users, the achievable performances are suboptimal under such circumstances. In contrast, when multiple users share the same time-frequency resource block, they suffer from channel noise as well as interference from each other. Mitigating the effect of interference in multiuser cooperative systems is a critical issue and the main focus of this work. Even though the best methods to deal with interference in a most general network is still unknown, two important classes, viz. the Broadcast (BC) and Multiple Access (MAC) channels have been well investigated. This thesis extends some of the known duality results to more general system models of multiuser relays and multicell environments. The existing duality principles state that same quality of service factors (error exponent, throughput or signal to interference and noise ratio) can be achieved via same total power in broadcast and multiple access channels. These duality principles allow the intractable problems in broadcast systems to be projected in multiple access systems for which efficient algorithms can be used to solve them. The main contributions of this thesis are several optimisation algorithms based on power and rates in various system models. The rate region boundary of a broadcast channel is established first. Along with that, the thesis also proposes some novel power allocation algorithms and decoding order to achieve the efficient boundary (known as Pareto frontier) of a system. It is expected the efficiency of the proposed algorithms in terms of complexity and performance will ensure better service and computational ease for cellular service providers. Furthermore, the existing duality principle for single-cell system has been a cornerstone of research on cellular information theory and optimisation. This result has prompted different optimisation approaches in literature and made the use of convex techniques possible in this context. The later part of this thesis extends the duality principle to a multicell system using two different cooperation paradigms, viz. Coordinated Beamforming and Partial Data Cooperation. While duality can be established for these two systems, optimal solution of the resource allocation problem proved to be infeasible for Partial data cooperation. However, it is expected that analysis of duality and the proposed suboptimal power allocation in this context will inform further research into basestation cooperation. The results have the potential to be useful for the standardisation of 5G standards based on significant Intercell cooperation to enhance user experience.