Joint Mode Selection and Resource Allocation for Device-to-Device Communications.

<bold>Device-to-device</bold> (D2D) communications have been recently proposed as an effective way to increase both spectrum and energy efficiency for future cellular systems. In this paper, joint mode selection, channel assignment, and power control in D2D communications are addressed. We aim at maximizing the overall system throughput while guaranteeing the <bold>signal-to-noise-and-interference ratio</bold> of both D2D and cellular links. Three communication modes are considered for D2D users: cellular mode, dedicated mode, and reuse mode. The optimization problem could be decomposed into two subproblems: power control and joint mode selection and channel assignment. The joint mode selection and channel assignment problem is NP-hard, whose optimal solution can be found by the branch-and-bound method, but is very complicated. Therefore, we develop low-complexity algorithms according to the network load. Through comparing different algorithms under different network loads, <bold>proximity gain</bold>, <bold>hop gain</bold>, and <bold>reuse gain</bold> could be demonstrated in D2D communications. [ABSTRACT FROM PUBLISHER]