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UBC Theses and Dissertations

Opportunistic scheduling for wireless networks with distributed architectures Ge, Xin


To meet the growing demand of mobile data service with limited radio resources, wireless networks have evolved towards networks with distributed architectures. Moreover, as communication systems evolve, both service providers and users are demanding not only high data rates, but also user fairness and data security. As a result, the main objective of the dissertation is to identify key challenges in opportunistic scheduling design that meet these new needs, and propose solutions to overcome the identified issues. First, we extend the cumulative distribution function based scheduling (CS), which is well-known as an efficient opportunistic scheduling method that satisfies fair resource sharing among users, to satisfy proportional throughput fairness. Then, we investigate the joint CS and power allocation to maximize user throughput subject to the power and resource sharing constraints. Despite increasing interest in distributed antenna systems (DASs), how to guarantee resource-based fairness in multiuser DASs remains largely unexplored. In this direction, we propose a novel CS with flexible beam transmissions (CSFB) to guarantee resource-based fairness in DASs. To realize CSFB in practice, a one-bit-feedback scheme, CSFB-OB, is further proposed to reduce feedback overhead for user selection. Both CSFB and CSFB-OB can efficiently exploit multiuser diversity realized by independent fading channels, as well as spatial multiplexing by effectively utilizing the distributed remote antenna units. Subsequently, we investigate the joint user association (UA) and user scheduling (US) for load balancing in a downlink multi-tier heterogeneous network by formulating a network-wide utility maximization problem. A distributed algorithm is proposed to obtain the UA and US solutions. A remarkable feature of the proposed algorithm is that apart from load balancing, multiuser diversity is exploited in the association time to further improve system performance. Finally, opportunistic scheduling schemes are investigated for uplink wireless channels with multiple asymmetrically located legitimate users and eavesdroppers. The closed-form expressions of the secrecy outage probability and ergodic secrecy rate are derived, illustrating the interplay among system parameters. Through the secrecy outage analysis, we design a channel access ratio adjustment scheme to maximize the secrecy throughput while satisfying the required secrecy level.

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