scholarly journals Direct Sequence-Optical Code-Division Multiple Access (DS-OCDMA): Receiver Structures for Performance Improvement

Multiplexing ◽  
2019 ◽  
Author(s):  
Younes Zouine ◽  
Zhour Madini
Keyword(s):  
Performance Improvement ◽  
Code Division Multiple Access ◽  
Multiple Access ◽  
Direct Sequence ◽  
Code Division Multiple ◽  
Receiver Structures

Source coherence impairments in a direct detection direct sequence optical code-division multiple-access system

2007 ◽  
Vol 46 (4) ◽  
pp. 456 ◽  
Author(s):  
Ihsan Fsaifes ◽  
Catherine Lepers ◽  
Mounia Lourdiane ◽  
Philippe Gallion ◽  
Vincent Beugin ◽  
...  
Keyword(s):  
Code Division Multiple Access ◽  
Multiple Access ◽  
Direct Detection ◽  
Direct Sequence ◽  
Access System ◽  
Code Division Multiple ◽  
Multiple Access System

scholarly journals A fractional Fourier transform–based channel estimation algorithm in single-carrier direct sequence code division multiple access underwater acoustic communication system

2019 ◽  
Vol 15 (1) ◽  
pp. 155014771982600 ◽  
Author(s):  
Lin Zhou ◽  
Qingsheng Zhao ◽  
Shukai Chi ◽  
Yanlong Li ◽  
Lanjun Liu ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Communication System ◽  
Code Division Multiple Access ◽  
Multiple Access ◽  
Fractional Fourier Transform ◽  
Direct Sequence ◽  
Underwater Acoustic ◽  
Single Carrier ◽  
Sequence Code ◽  
Code Division Multiple

Due to the complexity and variability of the underwater acoustic channel, the communication signal is affected by multi-path, time delay, and Doppler frequency shift. Based on the advantageous characteristics of fractional Fourier transform on chirp signal processing, a fractional Fourier transform–based algorithm using combined linear frequency–modulated signal is proposed, which can estimate parameters of underwater acoustic channel and has a better performance than the existing methods. To distinguish multi-user in underwater acoustic communication system, a single-carrier direct sequence code division multiple access communication system combined with the fractional Fourier transform–based algorithm is proposed. Thus, a preliminary study on underwater multi-target identification is carried out. The simulation and experimental results show that the fractional Fourier transform–based algorithm is simple and effective, and the energy can be focused at the “best” fractional order, which can directly determine the multi-path number and complete the channel estimation. The proposed single-carrier direct sequence code division multiple access communication system has good performance on bit error rate when we use corresponding spreading code to distinguish multi-user.

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