A Study of Network assisted Device-to-Device Discovery Algorithms, a Criterion for Mode Selection and a Resource Allocation Scheme

Abstract: Device-to-Device (D2D) communications is a term used to describe the new technology that allows two devices to communicate with each other directly, without using the base stations or the access points of the network infrastructure. D2D communication leads to better network performance for a number of reasons. Among the challenges of D2D communications are, the discovery of a new D2D communication pair, a criterion for mode selection and the optimum resource allocation for the new D2D pair. The discovery process of the new D2D pair includes transmissions of a number of messages that will provide the network with all the necessary information which will be used by the mode selection criterion and determine whether the new pair will use D2D or traditional cellular communication. The possibility of Network Assited Device-to-Device Communication, underlaying a cellular network is deliberated in this paper. Specically, two discovery algorithms are developped, one Centralized, Fully-Network Dependent discovery algorithm and a second Semi-Centralized, Semi-Network Dependent discovery algorithm are introduced and a comparative analysis of both is performed and presented. The criteria used for the evaluation of the Discovery Algorithms are time eciency and signal overhead. The results show that the second algorithm is faster in discovering new D2D pairs and requires minimum number of message exchanges. Moreover, the second algorithm is more ecient than the rst one, in case that the new pair is found not to be D2D. In addition, the importance of a Selection Criterion that allows the eN-odeB to decide whether traditional Cellular or D2D Communication between a pair of devices should be used is addressed. An optimum criterion, in terms of maximizing the total achieved throughput, is suggested and results are analyzed and evaluated. Results show that the proposed criterion is eective in performing mode selection for the new pair. Results are present in many dierent scenarios in order to provide generalizability to the new criterion.