Design And Implementation Of The Key Technologies Of GPON GTC Layer Based On FPGA

Recent years, with the rapid development of telecommunication network, access network has become a bottleneck to further improve network speed. To meet the demand for broadband access, new access network technologies continue to emerge. The current access network technologies mainly include xDSL access technology based on metal cable, Cable Modem access technology based on HFC, Ethernet access technology based on five twisted pair, optical fiber access technology and broadband wireless access technology. Optical access with the features of high bandwidth, long transmission distance and confidentiality is surely to become the mainstream of future broadband access technology. The passive optical network (PON) with the advantages of low-cost, easy to build and upgrade has received extensive attention. PON has been developed from APON, BPON to GPON and EPON. GPON has the characteristics of high rate, full-service support, high efficiency, can provide carrier-class QoS so it is considered to be the ideal technology for broadband optical access technology.The main features of GPON technology are embodied in its transmission convergence layer, also called GTC layer. The core technologies of GPON, including the framing and adaptation of the frames, ranging and time delay compensation, dynamic bandwidth allocation, encryption and decryption and error control are all implemented in this layer. Therefore, research and design of the key functions of GPON GTC layer is important to the achievement of GPON.This paper introduces several major access network technologies, analysis the differences between GPON and APON, EPON, describes the advantages of the GPON technology, and makes a brief introduction of the GPON standard system and its level model, focusing on the GTC layer protocol stack, level structure, the key features of each layer and the implementation requirements. Then the function modules are designed on the base of analyzing the frame structures. A brief introduction of the coding theory and method of NRZ code, CRC8, BIP8, RS and AES that are used in the system is made. The disadvantages of the major DBA algorithms are analyzed and a new algorithm based on the T-CONT priority and bandwidth requirements is proposed. And at last, a simulation of each module is made using the Xilinx ISE software and Verilog hardware description language. The simulation results of uplink and downlink processing and DBA algorithm are gived.This paper is a useful try and explore on the key technologies of GPON.