Resource Allocation Schemes for Multiuser Wireless Communication Systems Powered by Renewable Energy Sources
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In the future cyber-physical systems, such as smart grids, a large amount of sensors will be distributively deployed in di erent locations throughout the systems for the purpose of monitoring and control. Conventionally, sensors are powered by xed energy supplies, e.g., regular batteries, which can provide stable energy output. However, such energy sources require periodical recharging or replacement, which incurs high maintenance cost and may become impractical in hazardous environments. Self-sustaining devices powered by energy harvesting (EH) sources are thus highly desirable. However, energy provided by energy harvesters is uctuating over time and thus introduces the EH constraints to the systems, i.e., the total energy consumed until an arbitrary time cannot be larger than the harvested amount up to this time, which invokes the need of advanced power control and scheduling schemes. This thesis studies both the o ine and online resource allocation strategies for wireless communication systems empowered by EH sources. First, the resource allocation problems for a Gaussian multiple access channel (MAC), where the two transmitters are powered by a shared energy harvester, are studied. For both in nite and nite battery capacity cases, the optimal o ine resource allocation schemes for maximising the weighted sum throughput over a nite time horizon are derived. It is proved that there exists a capping rate for the user with stronger channel gain. Moreover, the duality property between the MAC with a shared energy harvester and its dual broadcast channel powered is demonstrated. Numerical results are presented to compare the performance of several online schemes. Moreover, the utility of a greedy scheme against the optimal o ine one is measured by using competitive analysis technique, where the competitive ratios of the online greedy scheme, i.e., the maximum ratios between the pro ts obtained by the o ine and online schemes over arbitrary energy arrival pro les, are derived. Then, the resource allocation schemes for the Gaussian MAC with conferencing links, where the two transmitters could talk to each other via some wired rate-limited channels and share a common EH source, are studied. The optimal o ine resource allocations are developed for both in nite and nite battery cases. It is shown that the optimal resource allocation in this scenario is more complicated than in the traditional MAC scenario and there exists a capping rate at one of the two transmitters, depending on the weighting factors. Online resource allocation strategies are also examined. Numerical results are used to illustrate the performance comparison of the online schemes. Furthermore, the competitive ratios of the online greedy scheme are derived under di erent weighting factors.
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