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Di Zhang, Yuhua Liu, Cui Xu, Yongqiang Qi

Di Zhang, Yuhua Liu, Cui Xu, Yongqiang Qi. ISNIT 2013 Taiyuan, China. One OCDMA PON System with 2D Multi-Length Two-Weight CHPCs. Paper ID: IT207. Correspondence Email: yhliu@mail.ccnu.edu.cn, zhd87@hotmail.com School of Computer, Central China Normal University Wuhan, China. 2013-4-7.

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Di Zhang, Yuhua Liu, Cui Xu, Yongqiang Qi

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  1. Di Zhang, Yuhua Liu, Cui Xu, Yongqiang Qi ISNIT 2013 Taiyuan, China One OCDMA PON System with 2D Multi-Length Two-Weight CHPCs Paper ID: IT207 Correspondence Email: yhliu@mail.ccnu.edu.cn, zhd87@hotmail.com School of Computer, Central China Normal University Wuhan, China 2013-4-7

  2. Outline • Introduction • Objectives • The OCDMA System Based on 2D Multi-Length Two-Weight CHPCs • System Performance • Simulation • Conclusion

  3. Introduction • The research of CHPCS Carrier Hopping Prime Codes: Carrier Hopping Prime Codes proposed by Guu Chang Yang, etc. Latest research focuses on the mutiple dimensional CHPCs • The lower capacity of 1-D OCDMA Systems • The BER problems of OCDMA Systems

  4. Objectives • To obtain Large Capacity of Optical Networks, taking the Multiple-Dimensional CHPCs into OCDMA System • To obtain Less BER, taking double hard limiter into the system

  5. Generation of 2-D Multi-Length Two-Weight CHPCs Given two positive integers and , if , , for Galois field and , the shorter matrix can be obtained as: A longer matrix can be obtained as: Where , donates modulo-p multiplication.

  6. Generation of 2-D Multi-Length Two-Weight CHPCs • Take for instance, the length of matrix of this double-long CHPC codes is 3. It is The length of matrix is 8. They are:

  7. Generation of 2-D Multi-Length Two-Weight CHPCs • If use the horizontal and vertical axes of the matrix to represent the positions and transmission carriers of the data segments. Its schematic diagram can be shown as follow: Thus, they can be expressed as some forms of sequence: S1=W0W1W2, S2,0=W00W2W1, S2,1=W00000W10W2, S2,2=W0000W2000W1.

  8. The OCDMA System Based on 2-D Multi-Length Two-Weight CHPCs • The Basic structure of this OCDMA System

  9. System Performance • For users that use low-weight code of a double 2DMCHPC. The high-weight codes will always result in a complete hit. After hard limiter, the BER of receive end can be found as: Where is the code weigh of low weight code, is the code weight of high weight code, donates the number of low weight codes, stands for the number of high weight codes, is the number of one complete hit by low weight codes, is the number of one complete hit by high weight codes.

  10. System Performance • For user that uses high weight code, high weight code always contributes a complete hit. But low weight code can only built hits. In other words, there should have low weight codes to complete a complete hit. Where stands for the ceiling function.

  11. System Performance • After the hard limiter, high weight code error rate in the receiver ends can be expressed as: Where is the transmission number of low weight codes, is the transmission number of high weight codes, stands for the probability of one complete hit by the high weight codes once, donates the probability of one complete hit by the low weight codes.

  12. System Performance • Because of the equal probability of transmitting 0 and 1 in OOK, for a given code word, the probability that interrupted by the hit in each condition can be expressed as:

  13. Simulation • Suppose that the system adopts double 2-D MCHPCs, the system performance with selection of low weight and high weight codes can be shown:

  14. Simulation • As can be seen, the initial selection of low-weight code will bring small error rate. • as the number of users increasing, the bit error rate of low-weight code increases more quickly. • For system utilizes low-weight codes, the initial error rate is low, error rate increases more rapidly • With the increasing number of users, bit error rate is on the rise. The error rate increase becomes much placid with the increasing number of access users.

  15. Simulation • In order to maintain good system performance, the system can alternately select the program of high weight codes and low-weight codes. • In the case of small number of users, the article mainly uses low-weight code as transmission coding schemes. As the number of users increases, the system will use high weight code as the encoding scheme to get better performance.

  16. Conclusion • It can get better performance by using multiple 2-D MCHPCs OCDMA PON system, which can accommodate more concurrent users. The use of spectrum is also increased to some degree in this way. • Hard limiter used in the receiving end reduces some bits of noises and inter-symbol interferences.

  17. Thank you for attention!

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