Research On The Key Technologies Of Copper And Fiber Integration Transmission System

With the emergence of HDTV, video conferencing and a series of high-bandwidth services,the traditional DSL(Digital Subscriber Line) technology has been difficult to meet the needs of the bandwidth. Although the fiber has a high transmission rate, if you want to fully achieve fiber entry, construction costs are too high and takes too long. As a result, the industry to improve the bandwidth and reduce construction costs, put forward the "copper and fiber integration" as a transition program."Copper and fiber integration" is that the central equipment and remote equipment both integrate and separate the copper signal, while the client still use the DSL access network and. By reviewing the existing literature, there is still no specific transmission system design about" copper and fiber integration".In this paper, the signal processing scheme of "copper and fiber integration " is put forward, and the key technology is designed and simulated in detail. Then, the key technology is implemented on the FPGA(Field-Programmable Gate Array) platform.Finally, the system is tested and analyzed. The specifically include the following:Firstly,this paper introduces the application scene of "copper and fiber integration"transmission system, and puts forward the improvement scheme. The original center equipment moves closer to the room, can carry one or two remote devices. The remote device can guarantee up to 48 users in a separate running state. If two remote devices are running at the same time, each device can carry up to 24 users. The system uses DS-CDMA(Code Division Multiple Access) as the multiple access technology, selects 64-bit Walsh code as the spreading code, 17.664MHz of single-user bandwidth, and the total bandwidth is 1130.496MHz, and the paper designs 8 road parallel according to the signal-free frame structure and high bandwidth.Then, the paper designs the key technology in the system. Firstly, the algorithm of digital IF module is deduced on the architecture of 8 parallel data transmission. In order to ensure the user's data rate of upstream and downstream is 50Mbps and 100Mbps respectively, the paper designs a time coarse synchronization scheme and a high precision time synchronization scheme with precision of 1/256 Chip because of the high demand of DS-CDMA(Direct Sequence-Code Division Multiple Access) technology for time synchronization.Finally, the paper verifies the performance of the system on the FPGA platform and analyzes it. The test data show that the intermediate channel has a large frequency selective fading, and there is a large crosstalk between the DSL signals. In the receiver side of the channel frequency domain equalization, and improve the performance of the hard war,measured the user's upstream and downstream is measured at 42.4Mbps and 87.1Mbps.