Research And Design Of Cpri Interface In Radio Remote System Of Gsm Base Station

In the field of radio communication, in order to satisfy the wireless signal coverage requirement of business areas, and to solve signal coverage problems of some remote or obturated areas, the mobile operators bring in the radio remote technology. It divides the traditional radio base station in the cellular communication system into baseband part and radio remote part, which are connected by cable or fiber. However, different base stations need different radio remote units because of lack of a unified interface standard. It is not conducive to the open development of radio base station. For above reasons, Common Public Radio Interface league developed an open interface specification Common Public Radio Interface, which defines the interface between Radio Equipment Control and Radio Equipment in radio base station. These RECs and REs follow the CPRI specification can be connected with one another.Thus, CPRI interface is the key of modularization of REC and RE in radio base station, and interconnection of different products from different manufacturers. And it is also an effective means of implementation of distributed coverage in wireless communication network. In the future of radio communication field, especially in 3G, it will be one of the indispensable technologies which ensure wireless network coverage and quality of service. Therefore, the study of CPRI has great significance.This paper firstly outlines the research background and development status quo of CPRI, pointing out the role and significance of CPRI specification in the field of radio communication. Secondly, it introduces the physical layer and data link layer of CPRI, and describes the frame structure and subchannels in detail. Thirdly it analyses the architecture of GSM radio remote system, and introduces the hardware environment and software platform of implementation of CPRI. The most important part of this paper is the implementation of CPRI based on FPGA. Through analyzing the function of physical layer and data link layer of CPRI as above, it proposes a design project based on FPGA. The design divides the CPRI interface into three modules, which are CPRI frame/deframe module, high speed transceiver and clock module. Then the paper discusses the function and implementation of the three modules, giving the logic simulation diagram. In order to transmit GSM baseband IQ data through the CPRI interface, it designs a new data mapping rule based on original mapping rules when implementing the CPRI frame/deframe module. Finally, it verifies the feasibility and capability on the FPGA development board, and gives the next step for improvement after analyzing the test results.