QOS aware channel and power allocation scheme for D2D enabled cellular networks

Device-to-device (D2D) communication enabled cellular system is capable of enhancing the spectrum utilization and throughput performance of the system. However, D2D users (D2Ds) in close proximity share its radio resources with the cellular users (CUs), thereby adding an additional amount of interferences from D2D transmitters and affecting the performance of cellular networks. To reduce these problems, we propose a novel channel selection and power allocation scheme incorporating quality of service (QOS) parameter for CU and D2D pairs. In order to improve the spectral efficiency, an efficient resource sharing strategy wherein multiple channels of CUs can be reused by each D2D pair is introduced. To cope up with the overloaded traffic at the base station (BS) due to the coexistence of different types of users and to reduce the computational complexity of the network, we divide our problem of resource sharing into two sub-problems. The channel assignment which is a linear programming problem determines the number of channels that can be shared by each D2D pair. Secondly, the power allocation for D2D pairs is a non-convex non-linear programming problem and is difficult to solve. Thus, the problem is transformed into a convex form using the exponential form of transmit power in the Laplace domain. By using Lagrangian method, the optimal power of D2Ds is determined such that it maximizes D2D sum-rate while preserving QOS of CU, thereby not affecting the normal cellular communication. The paper also elaborates on the throughput performances of D2D pairs which is affected by the position of D2Ds and CUs and distance of separation between D2Ds and CUs. Thus, we choose the radius of coverage as a metric for D2D communication. The effectiveness of proposed resource sharing and power allocation scheme is also illustrated through numerical examples.