Capacity Improvement Scheme And Unlicensed Band Access Strategy In 5G Dense Heterogeneous Networks

The mobile traffic will grow up to 1000 times over the next decade.Meanwhile, the short of spectrum is also very severe, and the spectrum deficit is up to 300 MHz. Therefore, the contradiction of capacity demand and spectrum scarcity needs the breakthrough of new wireless technology in the fifth generation (5G) network. This thesis researches on the two technical solutions consisting spatial densification of heterogeneous network and channel access in unlicensed band to solve the traffic demand in 5G, analyzes their impacts on wireless network capacity improvement.This thesis also proposes network parameters configuration algorithms based on fairness of users and networks.The research consists of three parts. The first part is the research of capacity improvemrnt of single LTE network in licensed band. The performance of joint usage of cell range extension and interference coordination technology is analyzed using spatial random model in LTE dense heterogeneous network. Further, this part discusses the impacts on network capacity thanks to deployment density, cell range extension bias and almost blank subframe ratio and also proposes a parameter configuration algorithm considering fairness of different users which the average users throughput increase by 20 Mps and the throughput gap between different decrease 25%. The second part is the research of capacity and channel access problems of LTE in unlicensed band. This part proposes a novel channel access strategy in unlicensed band for LTE which is the joint of energy detection and back-off algorithm, calculates the optimal channel access parameters to maximum the sensing throughput of LTE and decreases the interference to WiFi. The third part is the research of capcacity and coexistence of LTE and WiFi in unlicensed band. Different Markov chain models are established to analyze the performance of WiFi distributed coordination function and two back-off strategies proposed for LTE. Channel access probability and normalized throughput are calculated in two systems. This part also proposes an optimal contention window calculation scheme based on access fairness to guarantee the fair coexistence between LTE and WiFi.Finally, the research is concluded by pointing out the deficiencies of the proposed research and indicating the direction for improvement in future work.