Research And Simulation Of Resource Allocation Algorithms In Heterogeneous Cellular Networks

To cope with the recent rapid growth of data services of mobile communication systems, meeting the performance requirements of the users and enhancing the overall network performance, the 3rd Generation Partnership Project (3GPP) proposes the notion of Heterogeneous Cellular Networks (HetCNets) in the standardization process of LTE-Advanced (LTE-A). With the rise of heterogeneous cellular network technology, we are facing a lot of technical challenges. Due to the significant increase of the overlapped coverage areas between Base Stations (BSs), a more complex interference relationship between cells appears in heterogeneous cellular network environment. Strong cell interference will degrade the network performance of users and even cause dropped calls. Meanwhile, compared with the traditional homogeneous networks, many different types of BSs coexist in the heterogeneous networks, which lead to a large increase in the number of cell-edge users. Users located at cell edges will suffer more complicated interferences; therefore higher technical requirements are necessary for the inter-cell interferences coordination. In addition, in heterogeneous networks, the low-power nodes are deployed more freely unlike traditional macrocell BSs with a planning nature. Therefore, the traditional anti-interference technologies are not suitable for the heterogeneous networks.In order to reduce the interferences between a macrocell BSs and low-power cellular BSs within its coverage, our thesis proposes a resource allocation algorithm for heterogeneous cellular networks. Firstly, the interference graph is established based on the interference relationships between the BSs, and the corresponding orthogonal resources are assigned to the cellular BSs through interference graph. Then, the users in the cellular BSs are classified into center and edge users, respectively. The former can use all frequency resources in the cellular networks, while the latter can only utilize orthogonal frequency resources to eliminate interferences between the cellular BSs. Finally, users select the appropriate resource blocks according to an improved proportional fair algorithm. On the basis of resource allocation algorithm in heterogeneous cellular networks while meeting the basic performance requirements of different users, BSs in heterogeneous cellular networks assign the transmission power to different user resource blocks for further improve the network throughput. The proposed algorithm can reduce mutual interferences between BSs and users, improving the performance of users under cellular BSs and improving the throughput of the entire cellular networks as a result.In order to evaluate the performance of the proposed algorithms, simulations are conducted in this thesis, which demonstrates the effectiveness of our method. This is because our method can not only improve the utilization of spectrum resources in heterogeneous cellular network and reduce interferences between cellular BSs to balance network loads, but also improve the performance of edge users and enhance network throughput.