Resource Allocation for D2D Communication Systems

The rapid growth of mobile traffic has motivated the development of enabling technologies for enormous network capacity enhancement in future wireless net- works. Device-to-Device (D2D) communication is considered as a key technique to meet the increasing demand of high data rate and capacity. With D2D commu- nication, user equipments (UEs) in close proximity can communicate with each other directly without going through the base station (BS), which reduces the traffic load in the core network. In addition, due to the short-range communi- cation links, D2D communication can also improve the system energy efficiency (EE). Moreover, for the dense networks, which will be deployed in the future, D2D communication improves the system spectral efficiency significantly because of the spectrum reuse.
However, D2D communication may generate interference to the existing cellu- lar networks if not designed properly. In this thesis, we investigated the resource allocation problem for D2D underlay communication aiming to maximize network performance (such as the overall throughput or system fairness), while guaran- teeing the quality of service (QoS) requirements for both cellular and D2D links. Novel efficient resource allocation algorithms with low complexity and acceptable system performance were proposed.
Firstly, two heuristic algorithms with low computational complexity were pro- posed to solve the resource allocation problem aiming to maximize the overall throughput. Secondly, a joint mode selection, relay selection and resource allo- cation problem was optimally solved by an efficient algorithm. Thirdly, a more general and uninvestigated D2D communication scenario, where the channels are simultaneously allocated to both cellular and D2D links, was considered. An effi- cient Graph Colour-based Resource Allocation (GCRA) algorithm was proposed to achieve the close-to-optimal performance with low complexity.
Finally, the system fairness was investigated for D2D-based Vehicle-to-Vehicle (V2V) communication. In vehicular communication, due to the mobility of vehi- cles, message loss is inevitable. The situation that one or a few vehicles take all the loss must be avoided because they may become invisible to their surround- ing vehicles and cause serious safety concerns. Therefore, we proposed a novel resource allocation scheme aiming to enhance the system fairness to make sure all users have the same priority to access the system resource.