Design of Bipolar Optical Code-Division Multiple-Access Techniques Using Phase Modulator for Polarization Coding in Wireless Optical Communication

In this study, a bipolar optical code-division multiple-access (Bi-OCDMA) technique based on spectral amplitude coding (SAC) was proposed by using a phase modulator to realize polarization coding through a free-space optical (FSO) channel. Various types of noise, such as amplified spontaneous emission (ASE) noise, thermal noise, and shot noise, were included in the simulation to approach the real application. The first simulation, utilizing a modified M-sequence as signature code, demonstrated that the proposed Bi-OCDMA system could be implemented in FSO communication. The proposed Bi-OCDMA scheme improves the transmission rate and power efficiency compared with the previous scheme. The structure of the proposed system alleviates multiple-access interference (MAI) with a simple and cost-effective design. The second simulation observed the performance of the proposed Bi-OCDMA for two users with several well-known SAC codes, i.e., multi-diagonal (MD) code, modified quadratic congruence (MQC) code, modified maximum length sequence (M-sequence) code, and Walsh–Hadamard code, in extreme weather conditions, both for additive white Gaussian noise (AWGN) and turbulence-induced fading channel. The simulation results indicated that the Walsh–Hadamard code has superior performance compared to other codes. The results show the MD code can be implemented in the proposed Bi-OCDMA scheme for a medium-distance FSO.

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Performance Analysis of Bipolar Optical Code Division Multiple Access with Dual Electro-Optical Modulator Scheme for Free-Space Optical Communication

Techné Jurnal Ilmiah Elektroteknika ◽

10.31358/techne.v20i2.270 ◽

2021 ◽

Vol 20 (2) ◽

pp. 67-82

Author(s):

Eddy Wijanto

Keyword(s):

Optical Communication ◽

Fading Channel ◽

Code Division Multiple Access ◽

Multiple Access ◽

Optical Modulator ◽

Free Space Optical ◽

Electro Optical Modulator ◽

M Sequence ◽

Code Division Multiple ◽

Hadamard Code

In this study, the performance of bipolar optical code division multiple access (OCDMA) with dual electro-optical modulator (EOM) scheme for multi-user scenario was tested and analyzed with OptiSystem version 10. The performance measurement was implemented for free-space optical (FSO) communication and includes the common noises in optical communication. Two different channels were used in the measurement, i.e., additive white Gaussian noise (AWGN) and fading channel. Two extreme weather conditions, strong rain and storm, were considered in the simulation. The performance between three spectral amplitude coding (SAC) codes, i.e., Modified M-Sequence code, Walsh-Hadamard code, and random diagonal (RD) code were measured and compared. The simulation results indicate that Modified M-Sequence code had the highest BER while RD code achieved the lowest BER in the short-range and Walsh-Hadamard code got the lowest BER for the medium-range of FSO, both for AWGN only and AWGN with fading channel. In strong turbulence condition, the performance of all codes become comparable after 500 m of FSO range. Modified M-Sequence suffered the lowest performance degradation while RD code endured the highest performance deterioration in all-weather condition. The results show that Modified M-Sequence can be applied for medium to long-range FSO.

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THE STUDY OF BIT ERROR RATE EVOLUTION IN A MOBILE COMMUNICATIONS SYSTEM USING DS – CDMA TECHNOLOGY

Journal of Engineering Studies and Research ◽

10.29081/jesr.v18i2.226 ◽

2017 ◽

Vol 18 (2) ◽

Author(s):

ION POPA

Keyword(s):

Mobile Communications ◽

Bit Error Rate ◽

Error Rate ◽

Code Division Multiple Access ◽

Additive White Gaussian Noise ◽

Direct Sequence ◽

Access Technology ◽

M Sequence ◽

Code Division Multiple ◽

Communications System

<p>This paper follows the study of bit error rate evolution in a mobile communications system using DS – CDMA (Direct Sequence – Code Division Multiple Access) technology. We have assessed the bit error rate (BER) based on the signal/noise ratio, Eb/N0, and the number of users in the system. For this purpose, we have used M sequence and Orthogonal Gold sequence and the AWGN (Additive white Gaussian noise) transmission medium<strong>.</strong></p>

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A proposed method for determination of weighted despreading sequences for a DS/CDMA system

African Journal of Information & Communication Technology ◽

10.5130/ajict.v3i3.304 ◽

2007 ◽

Vol 3 (3) ◽

Author(s):

Younes Jabrane ◽

Radouane Iqdour ◽

Brahim Ait Es Said ◽

Najib Naja

Keyword(s):

Interference Cancellation ◽

Fuzzy Systems ◽

Code Division Multiple Access ◽

Multiple Access ◽

Additive White Gaussian Noise ◽

Multiple Access Interference ◽

Code Division Multiple ◽

Parameter Values ◽

Gaussian Noise Channels

The steeping chip weighting waveforms are used in multiple access interference cancellation by emphasizing the received spreading signal, therefore, that allows to solve the problem of orthogonality for the chip waveforms. Our paper presents a useful method based on fuzzy systems to determine the despreading sequences weighted by the steeping chip weighting waveforms for Direct Sequence Code Division Multiple Access DS/CDMA. The validity of our proposed method has been tested by numerical examples for an Additive White Gaussian Noise channels and shows that the parameter values of the chip weighting waveforms are good and the Bit Error Rate performance of the system does not undergone any degradation.

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