Research On Mode Selection Algorithm Of Device-to-device Communication Underlying Hetergeneous Wireless Networks

With the gradual evolution of 5G technology and the development of intelligent terminal, there is an increasingly higher transmission demand for video streams, mixed flow and large amount of data. However, the spectrum resources of mobile communication are limited so that the way in which a high-speed and large-capacity communication can be achieved within limited frequency resources has become the research focus. D2D technology can realize an end-to-end direct communication. Also, the base station can effectively monitor the channel information and control interference because D2D technology works in the licensed spectrum.Therefore, the quality of service of the business is ensured. Meanwhile,the D2D technology can reduce the burden on the base station, reduce the energy consumption of the terminal, shorten the time delay and improve the robustness of the network infrastructure. Besides, D2D technology can reuse the resources in micro-cell to improve the utilization factor of spectrum effectively.A mode selection algorithm based on ensuring the communication quality of original network user is put forward.At first, the original user's SINR is ensured through the interference analysis. Meanwhile, the maximization of D2D user's throughput is taken as the principle to work out the user transmit power. Then, the maximum throughput is taken as the principle under three modes to conduct the mode selection of single D2D user. Finally, a multi-user mode selection algorithm based on the maximum matching of weighted bipartite graph is used to maximize the total throughput of the heterogeneous network users.Also, the working characteristics of three modes are analyzed through simulation. A situation where the mode selection based on the changed number of WLAN users is changed as the maximum distance between the users is analyzed as compared to the number of D2D users that remain to be accessed. Three aspects are compared with the existing methods, i.e.the CDF curve of total throughput, the total throughput is changed as Dmax, the total throughput is changed as the number of D2D users.Therefore, the effectiveness of this algorithm in improving the total throughput of the whole network is proved when the transmit power is the same.A mode selection algorithm that guarantees cell edge user's QoS is proposed.It first analyzes a real problem that the D2D business with a high concurrency and throughput is difficult to be completed since the cell edge user's communication quality is relatively weak. Thus, it is suggested that a multi-attribute decision algorithm should be used to conduct mode selection of cell edge user in order to ensure the strategy of business QoS. Then, the improvement measure of multiple-attribute pattern selection is proposed to guarantee the cell edge user's QoS from four aspects, i.e. combining with setting weighting of subjective and objective factors, changing the relative value of the weak attribute to reduce the buckets effect, solving the reverse order of mode selection caused by TOPSIS algorithm, and using inter-network resource management strategy to reduce the time of useless mode switching.