Design And Implementation Of The TD-LET Physical Layer Dwnlink In The ENodeB

With the development of science and technology and human needs growing, mobile communication has completed three changes, and is going fourth change. Compared to the third generation mobile communication system (3G),the fourth generation mobile communication system (4G) were the evolution of wireless access technologies and network architecture, which is characterized by broadband and multi-functional integration. The fourth change began in LTE (Long Term Evolution). LTE is launched as largest new technology research and development projects by3GPP in2006, it is claimed as "quasi-4G" technology, including FDD LTE and TDD LTE, they use different duplex modes. As soon as LTE Release8was released in2008, countries began to initiate the development and deployment of LTE devices.Now many countries and areas have deployed LTE commercial network; China also issued its the TD-LTE license in December2013, that marked the formal coming of china’s4G era. As the global4G standard, LTE has broad market prospects. LTE radio access network is divided into physical layer, data link layer and the RRC layer. Physical layer is the lowest layer of the protocol, which is the basis of the wireless communication system. The normal data transmission and transmission rate of whole system is dependent on the physical layer. Compared to3G, LTE significantly improve spectrum efficiency and peak transmission rate, this is mainly due to the introduction of new wireless technologies in LTE physical layer,such as OFDM and MIMO.So the study to LTE physical layer is of great significance.I mainly focus on TD-LTE base station physical layer downlink in my project, the main work are as follows:the design of physical layer downlink simulation platform, the implementation of high speed bus Serial RapidIO between FPGA and DSP on the BBU, achieving the physical layer downlink on a BBU and verifying他the typical signaling processes. The main research work and innovation include:(1) Design and implement the TD-LTE physical layer downlink matlab simulation platform. It has following features:supporting various system bandwidth, implementing the sending and receiving of all physical downlink channels and signals, supporting Normal CP and extended CP modes, supporting three MIMO modes of SISO、transmit diversity and space division multiplexing, the sending antennas or receiving antennas not more than two,etc. In our tests, the entire simulation platform works normally and the sending part is verified by Agilent89600VSA. I study many key algorithms, carry out performance simulations of receiving part and improve some key algorithms, the simulation results indicate that PCFICH and PDCCH BER test results meet the LTE specifications, PBCH and PDSCH BER test results are worse than the LTE specification.PBCH and PDSCH receiving parts need further research.(2) Implement the Single-lane3.125Gbps Serial RapidIO in FPGA. Because of the multi-antenna、high-bandwidth characteristics of LTE, Hyplink and Serial RapidIO are used to meet the high-speed data transmission requirements between chips on BBU. In this paper, I study the RapidIO protocol standards including RapidIO physical layer、transport layer、logic layer、GTP、link initialization, etc. A single lane3.125Gbps SRIO is achieved in FPGA, and it is confirmed to work properly by chipscope and other testing tools.(3) Complete the TD-LTE physical layer downlink on a baseband processing unit based on TMS320C6670and do verification. I study TMS320C6670keystone DSP and use its internal FFTC、BCP coprocessors to complete TD-LTE physical layer downlink. Matlab simulation platform and Agilent89600VSA are used to debug the DSP codes, and finally test results show that each channel can work properly.(4) Study TD-LTE initial access procedure and realize it based on physical layer downlink.Generally all the protocol layers are needed to run one whole signalling flow.But only the physical layer downlink is developed, it may impossible to run one signalling flow using just physical layer downlink. A method of data stub is proposed to solve this problem and the previous steps of TD-LTE initial access procedure are successfully verified with physical downlink by data stub. Data stub can accelerate the project development schedule and promote the combination of software and hardware as early as possible. In the process of TD-LTE eNB development, comparing with the method of traditional serial development and debugging, we have shortened nearly half of the time taken to develop and debug TD-LTE attach procedure by data stub.