Random Assignment of Shifted Carrier-Hopping Prime Codes to Enhance Confidentiality in Wavelength-Time Optical CDMA Networks

• Main Authors: Yao-Hsin Kuo, 郭耀新
• Other Authors: Jen-Fa Huang
• Format: Others
• Language: en_US
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/31095077491792455741

碩士 === 國立成功大學 === 電腦與通信工程研究所 === 97 === Conventional optical code division multiple access (OCDMA) techniques suffer from inherent security disadvantages has been studied. In order to overcome vulnerability to eavesdropping of on-off-keying based OCDMA scheme, we propose a new scheme for confidentiality enhancement based on multi-code (M-code) keying approach of wavelength-hopping/time-spreading (WH/TS) OCDMA networks and applied to code reconfiguration mechanism. The code reconfiguration is achieved by exclusively assigning to each user a set of M shifted carrier-hopping prime codes (CHPC) and randomly selecting code word among M codes to represent user’s data bits. In addition, a central controller monitors network condition and regulates transmitter/receiver to perform code word selection. To integrate M-code keying with code reconfiguration mechanism, we utilize an optical switch not only switches symbol-to-symbol performing M-ary data modulation but following central controller’s instruction performing code changing. Hence, the assignment of code word and changing code word mechanism is more flexibility and easy to implement. In this thesis, we also analyze the security performance of proposed system. Evaluating the probability of code word interception is quantified the degree of data confidentiality. The result shows that the probability of error-free code detection gets worse when M increases and the eavesdropper processes code word detection more difficult, thus data confidentiality could be significantly increased. In addition, the proposed scheme using shifted CHPC appears to be a promising coding type for generating OCDMA code space that are large enough to prevent successful brute force code search attacks. Moreover, rapid code reconfiguration mechanism can increase the difficulty of interception but also makes the network management more difficult.