A Novel Code Construction Technique and Detection Scheme for the Double Weight Code Family for SAC OCDMA
Spectral Amplitude Coding Optical Code Division Multiple Access (SAC OCDMA) systems are gaining more attention, due to the fact that when using appropriate detection technique, the Multiple Access Interference (MAl) can totally be canceled. There have been many codes proposed for SAC Optical CDMA...
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| Format: | Thesis |
| Language: | English |
| Published: |
2007
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| Subjects: | |
| Online Access: | http://utpedia.utp.edu.my/7026/1/2007%20-%20A%20Novel%20Construction%20Technique%20and%20Detection%20Scheme%20for%20the%20Double%20Weight%20Code%20Family%20for%20.pdf http://utpedia.utp.edu.my/7026/ |
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| Summary: | Spectral Amplitude Coding Optical Code Division Multiple Access (SAC OCDMA)
systems are gaining more attention, due to the fact that when using appropriate detection
technique, the Multiple Access Interference (MAl) can totally be canceled. There have
been many codes proposed for SAC Optical CDMA systems, such as Hadamard code,
Modified Frequency Hopping (MFH) code and Double Weight (DW) code family.
The motivation of this research is to enhance the DW code family to give an overall
better performance. Three aspects are tackled in this research. Firstly, the existing code
construction technique is studied, and trying to find a more efficient method to construct
the codes. Secondly, alternative detection techniques are investigated and compared to
the existing ones. Thirdly, a software simulation of the SAC OCDMA system with the
OW code family using the Virtual Photonics Instrument (VPI) Transmission Maker
software version 7.1 is implemented.
A new code construction technique is proposed to overcome the drawbacks of the
existing method, which is complicated and time consuming. Two equation-based code
construction techniques are proposed. Both techniques provide a simplified and more
efficient method of constructing codewords then the previous technique.
When the mapping technique is applied to increase the number of users for the DW code
family, the SAC OCDMA detection (Complementary detection) cannot be used to
retrieve desired signals due to unfixed cross-correlation between code sequences. A
hybrid Wavelength Division Multiplexing/Spectral Amplitude Coding (WDM/SAC)
system can be used to resolve this problem. A reduced set of Fiber Bragg Gratings (FBG)
is proposed for the hybrid WDM/SAC to reduce cost and improve the performance.
Theoretical calculations show an improvement for the proposed method over the hybrid
WDM/SAC method.
Simulation results using VPI software show for the same transmission quality the
proposed method can support longer transmission than the other methods. |
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