Research On Wireless Resource Allocation Algorithm For D2D Communication In Heterogenous Networks

With the development of wireless communication, the requirement of data transmission rate of local communication is improved constantly.How to maximize the spectrum utilization in cellular networks is always an important research issue in wireless resource management because of the severe shortage of wireless cellular network spectrum resources.Device-to-Device (D2D) communication technology allows users to communicate directly by sharing the spectrum resources of the cellular users, which can solve the problem of lack of spectrum in wireless cellular networks to a certain extent. A key problem in the realization of D2D communication in the wireless cellular network environment is how to efficiently allocate wireless spectrum resources, reduce the interference in the cell, and improve the system's spectrum utilization and system throughput. Based on the research background and research status of D2D communication technology, this thesis has deeply researched the wireless resource allocation problem of D2D communication in different scenarios,and obtained some innovative research results.Firstly, this paper studies the algorithm of D2D resource allocation in single-cell scenario. The traditional radio resource allocation algorithm for D2D communication is based on the assumption that each D2D user can only reuse one spectrum resource for one user, and the spectrum resource of each cell user can be multiplexed by only one D2D user. Therefore, the resource allocation algorithm in this paper considers the following multiplexing scenarios: each D2D user pair can reuse the spectrum resources of multiple cellular users while the spectral resources of each cellular user Can be multiplexed by multiple D2D users. The algorithm of this paper obtains the optimal solution of D2D resource allocation by multiple interaction optimization of power allocation matrix and interference control matrix. Interaction optimization includes: 1)optimizing the power allocation matrix according to the interference control matrix; 2) optimizing the interference control matrix according to the power allocation matrix. Among them, the power distribution matrix to achieve D2D user channel selection and power allocation, interference distribution matrix control D2D users on the interference of cellular users,to ensure the quality of communication of cellular users.Then, under the different load, the proposed algorithm is simulated and analyzed, and the three advantages of the algorithm are shown. 1) the algorithm can get higher spectrum utilization, improve the system throughput; 2) compatible with or without idle channel two load conditions. When the number of cellular users in the system reaches the maximum capacity of the system, there is no idle channel in the system.When the number of cellular users in the system is smaller than the maximum capacity of the system, there are some idle channels in the system. The existing resource allocation algorithm can only be applied to one of the above load conditions, and this algorithm is to achieve the above two kinds of load conditions compatible, 3) increased D2D communication coverage. In order to ensure the communication quality of the cellular user, the area close to the base station is prohibited from conducting D2D communication due to excessive interference. The algorithm proposed in this paper reduces the area where D2D communication is forbidden, and increases the coverage of D2D communication.Finally, based on the D2D resource allocation algorithm of single cell,the D2D resource allocation algorithm in multi-cell scene is studied.Aiming at the problem of mutual interference between D2D users in adjacent cells, two improved algorithms are proposed: 1) Fractional frequency reuse (FFR) resource allocation algorithm, which introduces the spectral multiplexing factor in the system, in which the spectrum of the area near the center of the cell The multiplexing factor is set to 1, and the spectral multiplexing factor in the cell edge area is set to 1/3. In this way,the interference of the D2D user pairs in adjacent cells is reduced. 2) The resource allocation algorithm under the collaboration between base stations. Through the cooperative communication between base stations,each base station obtains the spectrum allocation information of neighboring cells when allocating communication resources for D2D users,so that the interference of the D2D users of the cell can be calculated , And then iteratively computes the optimized power allocation matrix. The simulation results show that the two algorithms can effectively improve the system throughput.