Two-dimensional W-of Ocdma System Multi-user Detection And Channel Coding Techniques

Optical code division multiple access(OCDMA) technology is one of hot research points in optical communication. OCDMA technology is the most prospective multiple access technology in wireless optical communication, as well as in fiber optical communication. In wireless OCDMA communication system, signals that a user receives are interfered by the other user's signals (which is called multi-user interference or multi-access interference, MAI) and channel noise, like background light and atmospheric turbulence induced by wireless optical communication channel. To reduce the effect of channel noise on system performance, we suggest adopting forward error correction (FEC) technology. Performances of free space OCDMA system using BCH codes and RS codes concatenating BCH codes, as well as performances of atmospheric OCDMA system using Turbo codes are analyzed. Results show that FEC can eliminate the effect of channel noise effectively. To reduce the effect of MAI on system performance, multi-user detection is introduced. Among all kinds of multi-user detection technologies, parallel interference cancellation (PIC) is suggested. Since conventional PIC receiver is not practical in optical communication, a new structure of PIC receiver based on system with MPC/OOC is developed. Performance improvement using the proposed PIC receiver is analyzed in free space OCDMA system and atmospheric OCDMA system. Proposed PIC receiver is proved to be effective in eliminating MAI. Finally, we conclude that high bit rate and low BER OCDMA communication system can be realized with FEC and multi-user detection.