Enhanced Fec Based On Optical Wireless Communications Research

Relative to the existing microwave communication technology, wireless optical communication technology has its own advantages, low cost, no frequency application, large information capacity, small size of equipment, high secrecy, etc. However, wireless optical communication by transmission medium in the atmosphere also has its inherent disadvantages, especially atmospheric attenuation and atmospheric turbulence on the absorption, scattering and random turbulence of laser signals, and serious obstacle to the development of wireless optical communication. From the atmospheric attenuation and atmospheric turbulence affecting the optical signals in the wireless optical communication, the research results show that the atmospheric attenuation caused light signal noise by the random errors mainly, but the atmospheric turbulence caused by the burst error mainly, which was concentrated in a position of the optical signal in a codeword. Therefore, aiming at the channel particularity for wireless optical communication, we must choose an appropriate FEC (Forward Error Correction) technology solution which has large correction capability.From the channel particularity of wireless optical communication, the EFEC (Enhanced FEC) structure (Outer code (RS) + Interleaver + Internal Code (RS) + Interleaver) suitable for wireless optical communication was designed. The key role of interleaver in this structure was to disrupt and rearrange the symbols in different codewords, aiming at assigning the burst errors evenly into the different codewords. Under the improved structure, different kind of concatenated codes -- RS + Convolutional code, RS + BCH concatenated codes and RS + RS concatenated code were simulated, and its performance was analysised in detail; an effective solution program -- RS (255,239) + RS (31,21) concatenated codes was proposed according to the inherent shortcoming in wireless optical communication, and interleaver of the program in different positions in the concatenated code performance of the error correction were simulated and analyzed. The simulation results show that the coding gain of RS + RS concatenated was improved greatly because of interleaver adopted and the appropriate location of interleaver selected in the improved structure. In addition, a EFEC system also was designed for wireless optical communication, including the FPGA processing module, optical transceiver module, some of which FEC adopted RS(255,239) + Conv (2,1,9) concatenated codes scheme. If you want to achieve a better performance for a wireless optical communication system, the optical receiver module is very important. This article has also designed an improved optical receiver module, improving the receiver sensitivity nearly 2.5dB by contrast with a common one. Finally, the performance of the enhanced FEC system was tested, and when the received optical power is at -37.74dBm , error-free output can achieve after FEC.