LTE MAC Layer Protocol Stack Design And Implementation Based On C-RAN Prototype System

The rapid development of mobile Internet technology has brought opportunities to the traditional telecom industry, but also brought new challenges. In order to meet the growing user demand for data traffic, operators need to build more and more wireless base stations. But the huge problem of base stations to bring the energy consumption and upgrade and maintenance problems to operators caused a heavy financial burden. To address this issue, China Mobile proposed the concept of C-RAN, C-RAN’s goal is to build a new mobile network access network architecture, by centralizing the data base processing, to reduce the number of base stations and reduce operating costs. In order to explore the key issues of combining general-purpose processor platform with common hardware platform under C-RAN architecture, Laboratory collaborating with the China Mobile Research Institute.This paper focuses on the design and development of the MAC layer.Firstly, the background and significance of C-RAN architecture and the LTE air interface protocol stack architecture is introduced. Combining with the needs of C-RAN prototype project,this paper divide the protocol stack from the perspective of implementation platform, and then gives the overall implementation framework of the MAC layer.Subsequently,this paper do the research and design of random access module、HARQ module and scheduling module successively.In the part of random access module,This paper design random access multi-process model, so that the e Node B can simultaneously respond to multiple random access request,then design the process status based on the interaction step between the UE and e Node B. In the part of HARQ module,this paper do a design about HARQ process entity. By the process entity, the scheduler can better control the UE uplink and downlink data transmission and reception. In the part of scheduling procedure, This paper analyzes the three classical insufficient downlink scheduling algorithm and propose a new scheduling priority calculation formula on the basis of PF algorithm.Then this paper gives the detail flow of scheduling procedure.Finally, this paper implement the modules which are designd in the previous section on Lenovo S30 general purpose processor platform, and elaborated the code of interface definition、data structure and critical process. Then by manual trigger, regular feedback, build virtual UEs and other means, this paper validate the designed modules of the MAC layer and test test improved scheduling algorithm. Verification results show that the above process can work properly. The scheduling algorithm proposed in this paper can significantly reduce the system packet loss rate.