Research On The Efficiency Of Equipment - To - Device (D2D) Communication System

In recent years, the goal of communication is to realize high speed and reliable communication in the limited spectrum resources. While with the rapid development of communication technology, the bandwidth requirement of video stream and multimedia is increasing so rapidly that performance of current network cannot support so many colorful multimedia applications today. The next generation cellular systems need to consider non-traditional communication to meet the growth of data rate and system capacity. Device to Device(D2D) communication technology is a modern communication technology that device can communicate with each other while not using the base station to transmit information. D2 D is not need to access to the core network, which can realize the point to point communication. Typically, the distance between the D2 D communication users is relatively close, so the transmission power is also small which can prolong the service life of the mobile terminal battery relatively. In addition, the technology works in the licensed frequency band of cellular networks, which can reuse the resources of cellular networks, thus improving the whole resource utilization. With the introduction of D2 D communication, it can not only improve the reliability of cellular communication, but also expand the coverage of cellular networks. It is of high theoretical and practical significance of D2 D communication technology.This paper studied the current situation and research of D2 D communication technology, including the resource allocation between cellular network and D2 D users,the influence of introducing D2 D communication to cellular network system and the SWIPT(Simultaneous wireless information and power transfer) applications in traditional cellular system and D2 D communication.First, for the problem of resource allocation between cellular users and D2 D users in D2 D, this paper discussed the resource allocation between users in traditional cellular networks. The users calculate the rate at each resource block and achieve if the user has max speed. Secondly, the resource allocation in cellular network while introducing D2 D communication is studied. The game theory is used to help users compete resource with others. According to the conclusion of 3GPP LTE, the cellular networks have higher priorities if the cellular user has conflict with D2 D users while D2 D communication using cellular network to transmit resources. So the optimizationof allocation of resources between cellular users and D2 D communication is to maximize the speed of D2 D communication users which based on satisfying the speed requirement of cellular users. The effectiveness of the proposed scheme is verified by system simulation with higher system total speeds contrasting to the random resource scheme.Secondly, the application of SWIPT technology traditional cellular network is introduced. It includes a base station, several single antenna relays as well as a cellular user in the system model. Firstly, the base station sends data to the relay and transmit to cellular users through the pre-encoding of relay. At the same time, the relay will send a portion of energy information together with the data information to the cellular users in order to satisfy the energy needs of them. The channel estimation error between relay and cellular users is considered and a kind of robust relay pre-encoding scheme is proposed. In the scheme, the data information and energy information are pre-encoded. The paper proved the effectiveness of the scheme with the optimal iterative way by binary pre-coding matrix.Besides, the paper also studies the SWIPT problem of D2 D communication in the cellular network. This model is similar to the model introduced before but with two additional D2 D users outside the cellular network coverage. Since the D2 D communication user is located outside of the network, so the information can transmit to the outside users by the D2 D relay users in the cellular network coverage. And the outside users can also get energy information from D2 D communication relays.Besides, the channel estimation error of different cell D2 D communication users and the interference problem between D2 D users should be considered. The paper proposed a robust D2 D relay pre-encoding scheme and verified the effectiveness.At last, the contents of this paper are summarized and the advantages and disadvantages of the proposed algorithm are analyzed. The further research directions of D2 D communication plan is proposed.