Research On Resource Optimization In OFDMA-Based Heterogeneous Networks

With the rapid increase of mobile data traffic, the demand of the communication system data rates is becoming higher, and it is also becoming more and more important to ensure high quality coverage for indoor users and enhance system capacity in hotspot. The Small Cell is introduced to satisfy these requirements in the existing macro cellular networks. The femtocell among small cell could improve the Quality of Service (QoS) for indoor users and indoor coverage area, while the picocell among small cell could protect cell edge users and increase system capacity in hotspot. Therefore, the research on small cell has been a popular field in academia and industry organization.In this paper, the technology of radio resource optimization in LTE-A heterogeneous networks deploying Small Cell has been researched deeply. Previous mobile communication coverage technologies are summarized and analyzed; besides, we introduce the concept of heterogeneous network and explain its key technology in more detail. In order to assign radio resource optimally in heterogeneous networks, mitigate interference and improve the system capacity, a theory-based sub channel allocation algorithm in Macro-Femto heterogeneous networks is introduced to solve the interference mitigation in chapter three, and a joint resource block assignment and power control in Macro-Pico heterogeneous networks is introduced to solve capacity enhancement. Finally, simulation results of two algorithms are compared and analyzed.The purpose of the theory-based sub channel allocation algorithm is to mitigate co-tier interference. In a sector, a center controller finds the set of users’ interference neighbor based on the information user transmits over backhaul, and reuse sub channel as much as possible among users who have non-interference relation. Simulation results show the algorithm could mitigate co-tier interference effectively and improve spectrum efficiency.The purpose of joint resource block assignment and power control in Macro-Pico heterogeneous networks is to protect cell edge users and enhance system capacity. Firstly, users choose their service base stations based on downlink received signal strength and cell range extension bias. Then a sequential RB assignment rule is adopted among all users. At last, the utility function combining throughput and interference is calculated by using differential evolution algorithm. Simulation results show the algorithm could perform inter cell load balance, effectively protect cell edge users and improve total system capacity largely.