Study of Optical Code Division Multiple Access Communication Systems
Date Issued
2005
Date
2005
Author(s)
Gu, Fong-Ray
DOI
en-US
Abstract
In this thesis, we propose three novel techniques for the optical code division multiple access (OCDMA) communication systems. For the synchronous OCDMA (SOCDMA) systems, we analyze the jitter performance of SOCDMA-based Ethernet passive optical network (EPON) communication systems using perfect difference codes (PDC). We propose the joint jitter estimator and canceller (JJEC) to reduce the impact of jitter and multiple-user interference (MUI). The bit error rate (BER) of the system with JJEC is formulated analytically based on the correlator and the simple sampler receiver structures. The numerical results show that the proposed scheme can significantly suppress the MUI and improve the system performance.
For asynchronous OCDMA (ASOCDMA) systems, we propose two construction schemes of variable weight optical orthogonal codes. The first scheme uses pairwise balanced design (PBD) which is a research topic in the combinatorial theory. PBD produces a family of blocks with unequal block size. Therefore we can use PBD to construct codewords with variable code weights. The lower bound of code size of the codes from PBD is derived in this thesis. A second scheme employs packing design with partition to generate blocks with unequal block sizes. The variable weight optical orthogonal codes can be constructed by partitioning a larger weight codeword into a family of codes with smaller code weight. The upper bound and lower bound of code size of the second scheme is discussed in this thesis. The BER performances of the two proposed codes are evaluated analytically. The simulation results show that the codes from the first scheme have the same BER performance as that of conventional code while the second scheme has larger maximum number of simultaneous users than that of conventional codes.
For the two-dimensional (2-D) wavelength/time OCDMA systems, we propose a new family of 2-D wavelength/time optical orthogonal codes. The construction scheme uses the difference family (DF) which is an assemblage of difference sets in the combinatorial theory. We prove that the proposed 2-D optical orthogonal codes satisfy the correlation properties required for the asynchronous OCDMA systems. The code dimension of the proposed codes is more flexible than that of the conventional 2-D optical orthogonal codes. We analyze the performance of the system with the proposed codes by using Markov chain method. Numerical results show that the BER has a minimal value given the number of simultaneous users. We also observe that the maximum number of simultaneous users of the OCDMA system can be achieved by properly choosing both the code weight and cross correlation of the optical orthogonal codes
Subjects
相差族群
二維光正交碼
劃分包裝設計
成對平衡設計
光分碼多工
完美相差碼
被動式乙太光網路
交互時脈擾動估測與消除電路
可變權重光正交碼
difference family
two-dimensional optical orthogonal codes
packet design with partition
pairwise balanced design
joint jitter estimator and canceller
variable weight optical orthogonal codes
passive optical network
perfect difference codes
optical code division multiple access
Type
thesis
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