UBC Theses and Dissertations
Energy efficient and secure wireless communication systems Ng, Wing Kwan
Orthogonal frequency division multiple access (OFDMA), multiple--input multiple--output (MIMO), and base station (BS) cooperation are the core techniques for the next generation wireless communication systems. As the communication systems evolve, both service providers and users are demanding not only high data rates, but also energy efficiency and data security. As a result, it is necessary to design novel resource allocation algorithms that meet these new needs. This dissertation develops four resource allocation algorithms which are tailored for different design goals and communication environments. For systems employing the combination of OFDMA and decode-and-forward (DF) relaying technologies, we propose a novel resource allocation algorithm for secure communication. The proposed algorithm takes into account artificial noise generation to combat a passive multiple antenna eavesdropper and the effects of imperfect channel state information at the transmitter (CSIT). Subsequently, we investigate the energy efficiency of OFDMA systems which also provide communication security. We formulate the resource allocation algorithm design as a non-convex optimization problem. By exploiting the properties of fractional programming, the considered non-convex optimization problem is transformed to an equivalent convex optimization problem with a tractable solution, which can be obtained with an iterative algorithm. Thirdly, we study resource allocation for energy efficient communication in OFDMA downlink networks with a large number of transmit antennas. Our proposed resource allocation algorithm takes into account the circuit power consumption, imperfect CSIT, a minimum data rate requirement, and a maximum tolerable channel outage probability. Lastly, we propose a resource allocation algorithm for energy efficient communication in OFDMA downlink networks with cooperative BSs. The resource allocation algorithm design problem is formulated as a non-convex optimization problem which takes into account the circuit power consumption, the limited backhaul capacity, and the minimum required data rate for joint BS zero-forcing beamforming (ZFBF) transmission. By using the concept of perturbation function, we show that the duality gap in the considered system is always zero under some general conditions, despite the non-convexity of the primal problem. Thus, an efficient closed-form power allocation solution for maximization of the energy efficiency of data transmission is derived.
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