Internference Suppression For Device-To-Device Communication Underlaying Cellular Networks

Communication technologies, especially mobile communication, are developing rapidly and continuously. The way people get information singly from a wired network has changed. Nowadays people are more likely to depend on the mobile network. Years ago people could only access the Internet through the telephone line connected to the modem. Now people can have more options. The increasing data traffics enrich people’s applications; on the other hand, the higher demands on the transmission rate have become big challenges to the existing mobile network. The current operating Third Generation Network (3G) and Wireless Local Access Network (WLAN) have some obvious disadvantages in system bandwidth and network coverage, thus they are not able to afford more and more users’access. Therefore,3GPP organization has been focusing on advancing the long-term evolution (LTE) system and it has become the next generation communications standards recognized demestically and globally. In addition, as one of the mainstream Fourth-Generation mobile communication technologies, the LTE enhanced version of LTE-Advance (LTE-A) is becoming a globally supported communications network standard around the world.Since the mobile communication is gradually developing towards the high-speed and high-capacity system, the problem of spectrum resources shortage is getting more and more obvious. Device-to-Device (D2D) technology in the mobile network is able to provide a more flexible and convenient network access and communication methods. The characteristics of D2D communication include high data-rate and low transmission overhead. In addition, D2D communications can offer access to both the licensed and unlicensed spectrum, which can effectively improve the network coverage and spectrum utilization.When D2D transmission mode is applied in the mobile network, how to ease and eliminate the negative impact brought by D2D is the key to the research. To solve the caused interference problem, this paper is focusing on the studies of interference suppression and resource allocation methods for D2D communication in orthogonal frequency division multiplexing (OFDM)-based mobile cellular networks. First the overview of LTE/LTE-A system and their key technologies are introduced. Second, the basic principles of the D2D technology and the D2D system model are studied. In order to coordinate the inter-cell interference suffered by D2D, this research will be on the basis of a multi-cell scenario with Soft Frequency Reuse (SFR) scheme. When D2D is reusing several cellular users’ resources, an interference limited area control scheme is proposed in this research for the D2D. And the calculation methods of the interference limited areas are discussed. The proposed scheme can make a comprehensive utilization of the users’ location information and the channel link information of cellular users to allocate resources for D2D. It can optimize the network performance while guaranteeing the quality of cellular communication. Compared to the existing resource allocation methods for D2D, the proposed scheme can effectively reduce the interference between D2D and cellular networks, while improving the total throughput of network. In addition, this scheme does not require the whole channel state information in cellular networks, thereby reducing the network control information overhead.In the simulation, the performance of the proposed resource allocation scheme based on the interference limited area method, the random resource allocation scheme, and the maximum data rate resource allocation scheme are comparied. Simulation results indicate that the random allocation scheme causes large interference between cellular networks and D2D due to the shortage of interference control function. On the other hand, the maximum rate scheme can achieve the highest throughput in theory. However, it is of high complexity and low feasibility in practice since it requires the whole accurate channel information of all users. The proposed resource allocation scheme can significantly reduce the interference between D2D and cellular networks because of the implementation of the interference control and the D2D resource optimization. In addition, the proposed scheme can decrease the implementation complexity by reducing the network control overhead. It can effectively improve the overall system throughput and spectrum utilization, while at the same time guaranteeing the cellular communication performance.