The Study Of The Real-Time Processing Module In OFDM-Pon System

With the proposed "Broadband China" strategy, the4G wireless communication technology has been commercial used in a large-scale. It on one side shows that the goverment want to benefit the people by strengthening the construction of infrastructure, improving the network bandwidth and reducing the price, on the other side, it reflects that the bandwidth requirements of the users are growing rapidly. Currently, the development of cloud computing, Internet and mobile Internet technology which all depend on high capacity bandwidth has received extensive attention worldwide. Access network which is known as the "last one kilometer" which is used to connect the client end network and backbone network is the most cost sensitive part in the whole telecom network. The access network is the key factor to improve the users’access bandwith since it has the characteristic including slow change of technologies, greatest regulation impact and the worst environment. Because of its huge capacity and good anti-noise performance, more and more research has been done on the optical fiber-based access network. Thereinto, the orthogonal frequency division multiplexing access (OFDMA) based passive optical network (PON) become the next generation access network’s (NG-PON) evolution direction since it has high frequency efficiency, good anti-dispersion performance and dynamic bandwidth allocation (DBA). OFDM technology can be realized by the digtal signal process (DSP). The development of the large scale integrated circuit and anolog/digital converter with high sampling rate make it possible to realize a real-time OFDM-PON system. The transceiver in the real-time OFDM not only strictly verifies the OFDM technology, but also sets up a stable platform to evaluate its flexibility. On the basis of the OFDM technology and PON structure, the main research of this paper can be divided into the following three aspects:1) The performance of the OFDM-PON systemIn this paper, an OFDM-PON system has been established, basing on which the simulation and analysis in the aspect of different transimision conditions, modulation formats, transimision distances and resolution can be made. The BER (Bit Error Rate) results establish a reference model for the real-time OFDM-PON system.2) The software and hardware settings of the DSP-based OFDM systemOn the basis of the DSP-based OFDM technology, this paper realizes the IFFT/FFT module and the RAM module which are the key element of the OFDM system by setting up the parameters of the IP core. What’s more, the study on the parameters of the hardware has been made, basing on which can get the configuration parameters and methods used in the real-time OFDM system.3) The realization of real-time OFDM transceiver based on FPGAIn accordance with the research achievements mentioned above, a real-time OFDM system has been successfully completed and every module has been separately simulated. Besides, for the first time this paper proposes to use an S-G filter to smooth the OFDM signal at the transmitter. Simulation results show that the S-G filter based OFDM system has better BER performace.