SUPPRESSION OF MULTIPLE ACCESS INTERFERENCE IN UPLINK OFDMA OF MOBILE WiMAX

2015 ◽  
Vol 74 (14) ◽  
pp. 1257-1268
Author(s):  
M. Lakshmanan ◽  
P. S. Mallick ◽  
L. Nithyanandan
Keyword(s):  
Multiple Access ◽  
Multiple Access Interference ◽  
Mobile Wimax

scholarly journals WON-OCDMA System Based on MW-ZCC Codes for Applications in Optical Wireless Sensor Networks

Sensors ◽  
2021 ◽  
Vol 21 (2) ◽  
pp. 539
Author(s):  
Saleh Seyedzadeh ◽  
Andrew Agapiou ◽  
Majid Moghaddasi ◽  
Milan Dado ◽  
Ivan Glesk
Keyword(s):  
Optical Networks ◽  
Video Surveillance ◽  
Multiple Access ◽  
Optical Sensing ◽  
Multiple Access Interference ◽  
Service Differentiation ◽  
Sensor Data ◽  
Variable Weight ◽  
Code Division Multiple ◽  
The Impact

The growing demand for extensive and reliable structural health monitoring resulted in the development of advanced optical sensing systems (OSS) that in conjunction with wireless optical networks (WON) are capable of extending the reach of optical sensing to places where fibre provision is not feasible. To support this effort, the paper proposes a new type of a variable weight code called multiweight zero cross-correlation (MW-ZCC) code for its application in wireless optical networks based optical code division multiple access (WON-OCDMA). The code provides improved quality of service (QoS) and better support for simultaneous transmission of video surveillance, comms and sensor data by reducing the impact of multiple access interference (MAI). The MW-ZCC code’s power of two code-weight properties provide enhanced support for the needed service differentiation provisioning. The performance of this novel code has been studied by simulations. This investigation revealed that for a minimum allowable bit error rate of 10−3, 10−9 and 10−12 when supporting triple-play services (sensing, datacomms and video surveillance, respectively), the proposed WON-OCDMA using MW-ZCC codes could support up to 32 simultaneous services over transmission distances up to 32 km in the presence of moderate atmospheric turbulence.

A Novel Technique to Detect Code for SAC-OCDMA System

2018 ◽  
Vol 39 (2) ◽  
pp. 215-221 ◽  
Author(s):  
Manisha Bharti ◽  
Manoj Kumar ◽  
Ajay K. Sharma
Keyword(s):  
Multiple Access ◽  
Optical Power ◽  
Multiple Access Interference ◽  
Spectral Amplitude ◽  
Main Task ◽  
Received Power ◽  
Performance Deterioration ◽  
Spectral Amplitude Coding ◽  
Code Division Multiple ◽  
Detection Schemes

AbstractThe main task of optical code division multiple access (OCDMA) system is the detection of code used by a user in presence of multiple access interference (MAI). In this paper, new method of detection known as XOR subtraction detection for spectral amplitude coding OCDMA (SAC-OCDMA) based on double weight codes has been proposed and presented. As MAI is the main source of performance deterioration in OCDMA system, therefore, SAC technique is used in this paper to eliminate the effect of MAI up to a large extent. A comparative analysis is then made between the proposed scheme and other conventional detection schemes used like complimentary subtraction detection, AND subtraction detection and NAND subtraction detection. The system performance is characterized by Q-factor, BER and received optical power (ROP) with respect to input laser power and fiber length. The theoretical and simulation investigations reveal that the proposed detection technique provides better quality factor, security and received power in comparison to other conventional techniques. The wide opening of eye in case of proposed technique also proves its robustness.

Performance Analysis of Spectral Amplitude Coding Optical Code Division Multiple Access System using Modified Double Weight Codes with Adomian Decomposition Method

2018 ◽  
Vol 39 (4) ◽  
pp. 459-462 ◽  
Author(s):  
Monika Rani ◽  
Harbax Singh Bhatti ◽  
Vikramjeet Singh
Keyword(s):  
Code Division Multiple Access ◽  
Multiple Access ◽  
Decomposition Method ◽  
Adomian Decomposition Method ◽  
Multiple Access Interference ◽  
Spectral Amplitude ◽  
Adomian Decomposition ◽  
Spectral Amplitude Coding ◽  
Code Division Multiple ◽  
Multiple Access System

Abstract In this manuscript, we have analyzed a Spectral Amplitude Coding-Optical Code Division Multiple Access (SAC-OCDMA) System. The system performance is enhanced by reducing the effect of Multiple Access Interference (MAI) using uniform Fiber Bragg Gratings (FBGs) encoders and decoders at central office and subscriber’s end. The results are verified through a mathematical model and Modified Double Weight (MDW) codes for the proposed system using Adomian Decomposition Method (ADM). Further, we have demonstrated SAC-OCDMA system for transmission of 40 Gbps data rate up to a distance of 80 km by increasing the number of FBGs. The proposed system has been analyzed in terms of distance, bit error rate (BER) and Quality Factor.

scholarly journals Incremental gradient algorithm for multiuser detection in multi-carrier DS-CDMA system under modulation schemes

2018 ◽  
Vol 7 (2.6) ◽  
pp. 311
Author(s):  
Sumitra N. Motade ◽  
Anju V. Kulkarni
Keyword(s):  
Spread Spectrum ◽  
Multiple Access ◽  
Minimum Mean Square Error ◽  
Multiple Access Interference ◽  
Gradient Algorithm ◽  
Channel Noise ◽  
Cdma System ◽  
Communication Performance ◽  
Optimum Performance ◽  
Code Division Multiple

Nowadays, Multicarrier Direct sequence code division multiple access (MC DS-CDMA) systems are used in mobile communication. Performance of these systems are limited by multiple access interference (MAI) created by spread-spectrum users in the channel as well as background channel noise. This paper proposes an incremental gradient descent (IGD) multi-user detection (MUD) for MC DS-CDMA system that can achieve near-optimum performance while the number of users is linear in its implementation complexity.  The IGD algorithm make an effort to perform optimum MUD by updating one user's bit decision each iteration in the best way. This algorithm accelerates the gradient algorithm convergence by averaging. When a minimum mean square error (MMSE) MUD is employed to initialize the proposed algorithm, in all cases tested the gradient search converges to a solution with optimum performance. Further, the iterative tests denote that the proposed IGD algorithm provides significant performance for cases where other suboptimum algorithms perform poorly. Simulation compares the proposed IGD algorithm with the conventional detectors. 

Performance Analysis of 2-D Prime Codes Encoded Optical CDMA System

2019 ◽  
Vol 40 (4) ◽  
pp. 463-472
Author(s):  
Ankita Rani ◽  
Deepak Kedia
Keyword(s):  
Multiple Access ◽  
Electrical Power ◽  
Multiple Access Interference ◽  
Optical Cdma ◽  
Wavelength Division ◽  
High Data ◽  
Construction Methods ◽  
Data Rates ◽  
Improved Performance ◽  
Code Division Multiple

Abstract Optical code division multiple access (OCDMA) system provides highly secured transmission in addition to its capabilities to support asynchronous transmission and soft blocking. Two-dimensional OCDMA codes are chosen in this paper due to their high cardinality, good spectral efficiency and flexibility in their construction methods against direct sequence codes. This paper focuses on study of impact of multiple access interference (MAI) at high data rates for 2-D prime codesbased OCDMA system. It is shown that how the change in number of simultaneous users affects the transmission quality. Further, performance of the system is analysed in terms of bit error rate, received electrical power and eye openings. In addition, this paper also shows a comparative analysis of 2-D codes-based OCDMA system and wavelength division multiple access (WDMA) system in order to justify the improved performance of the proposed system. It is observed that the performance of 2-D OCDMA system is much better than WDMA system in terms of quality as well as security.

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