Research On Power Allocation For Device-to-device Communication Underlaying Cellular Networks

With the development of wireless communication, it is more necessary to increase the communication resource utilization. Device-to-device(D2D) communication which is a promising and challenging technology has attracted many attentions of researchers. D2 D communication means that two adjacent mobile devices can communicate each other without passing base station(BS) or access point(AP). In a cellular network system, it can not only improve spectrum efficiency, but also reduce the transmission power and thus improve the battery life of mobile devices when the D2 D devices share resources with the cellular devices. Therefore, D2 D communication is one of the key technologies of the next generation of mobile communication. There exist two modes for the D2 D communications. They are co-channel mode and orthogonal-channel mode, respectively. The co-channel mode means that D2 D devices and cellular devices share the same frequency-time resource, while the orthogonal-channel mode means that the frequency-time resource is partitioned into two parts for D2 D devices and cellular devices.This thesis will focus on the power allocation scheme for D2 D communication underlying cellular networks. Two major contributions are made in this thesis. 1) We study the traditional power allocation schemes for D2 D communication underlying cellular networks. The optimization objective functions are based on capacity maximization for co-channel mode and orthogonal-channel mode, transmission power minimization for co-channel mode and power-efficiency maximization for co-channel mode, respectively. Theoretical analysis and derivation are given. Besides, the performances of different power allocation schemes are verified by simulations. 2) We propose the dynamic power allocation schemes for the following two channel modes: co-channel mode and orthogonal-channel mode. Based on the D2D-Cellular underlying unit including a D2 D pair, a cellular device, and the base station, we formulate the capacity maximization problem under average power constraint of the D2D-Cellular underlying unit. By some theoretical analysis and derivation, we obtain the closed-form solutions of power allocation schemes with different communication modes. Compared with the static power allocation schemes, the proposed dynamic power allocation schemes can obtain a higher capacity.