Technology Of D2D Communication Based On Cellular Systems

With the requirements of user increasing greatly, the traditional communication mode is more and more difficult to meet the requirement for high volume business, therefore, a new communication system called IMT-Advanced was put forward to change this situation, LTE-Advanced communication system, which is a new powerful candidate system standard of IMT-Advanced, has drawn much attention in the communication field, and one of the hottest technology in 5G direction is Device-to-Device(D2D) communication. Different from traditional cellular system, the datas in D2D communication do not pass through the base station, so the burden of base station will be mitigated, on the other hand, the D2D communication is a short distance communication,which means the single user throughput will has a lot to improve, at the same time, the D2D communication can also reuse the existing time-frequency resources of cellular systems, thus, the system spectrum efficiency will also get further improve, because of its numerous advantages, the D2D communication has broad application prospects.However, D2D communication technology also has many technical difficulties to be solved, for example, in TD-LTE-Advanced system, the D2D communication datas don't pass through the base station, so the synchronization between the D2D pair UEs will be a big problem to be solved, on the other hand, because of allowing the D2D communication reusing the existing time-frequency resources of the cellular systems,thus, the interference between D2D communication users and the original cellular UEs will be a new question to answer, which means how to optimize resource allocation has become one of the key problems of the D2D communication technology, and further, unauthorized frequency band of the D2D communication technology can also be used as a complement of D2D communication applications, at this point, how to use the unauthorized frequency band efficiently for the D2D communication system will be one of the difficulties.A brief introduction on the background for LTE-Advanced system will be present first, which mainly focuses on describing the synchronization technology, resource scheduling algorithm and the application of unauthorized frequency band. Under the background of the existing technology, this paper conducted the following three aspects:First, this paper proposes a clustering synchronization algorithm based on center node, which can improve the efficiency of Mesh network synchronization, the implementation is simple , and the system robustness is also good enough.Second, the thesis puts forward a resource allocation scheme based on maximizing system throughput, it can reduce system interference through a good power control strategy, so as to improve the system throughput.Third, this article uses the thinking of interfering with the equivalent to choose the best unauthorized frequency band to access in,which will help us to use the unauthorized frequency band resource efficiently.