scholarly journals Cooperative relay beamforming in IDMA communication networks

2018 ◽  
Vol 69 (4) ◽  
pp. 300-304
Author(s):  
Aasheesh Shukla ◽  
Vishal Goyal ◽  
Puneet Mishra ◽  
Vinay Kumar Deolia
Keyword(s):  
Communication Networks ◽  
Multiple Access ◽  
Multiple Access Interference ◽  
Spatial Diversity ◽  
Communication Strategy ◽  
New Combination ◽  
Beam Forming ◽  
Problem Solver ◽  
Cooperative Relay ◽  
Performance Improvements

Abstract In this paper, a new combination of Interleave division multiple access (IDMA) and spatial diversity offered by cooperative relay aided distributed beam forming is proposed. In the offered scheme communication strategy consists two steps. All users broadcast their message to relays in the first step and then relays amplifies and forward the information to the desired destination. IDMA, which is popular non-orthogonal multiple access (NOMA) technique is used to combat the effect of multiple access interference (MAI) at relay as well as destination nodes. Each relay processed the signal to maintain the QoS of destination. The goal of this work is to find the appropriate beam forming weights by minimising the transmit power and without compromising the QoS in terms of SINR. However power minimization is not the convex problem, so semi-definite relaxation is used to modify the problem in to semi-definite programming (SDP) problem and the conventional SDP problem solver CVX is used for solution. The numerical explanation and simulation experiment of the proposed scheme shows the performance improvements in terms of bit error rate.

Research on TD-SCDMA System Based on Joint Detection and Smart Antenna Technology

2012 ◽  
Vol 459 ◽  
pp. 624-627
Author(s):  
Hong He ◽  
Dan Li ◽  
Tong Yang ◽  
Lin He
Keyword(s):  
Channel Estimation ◽  
Multiple Access ◽  
High Speed ◽  
Smart Antenna ◽  
Multiple Access Interference ◽  
Beam Forming ◽  
Joint Detection ◽  
Real Time Control ◽  
Time Control ◽  
Simulation Results

Channel estimation of TD-SCDMA is inaccurate if Joint Detection is separately used in anti-interference progress, and when the number of users or channels increases, amount of calculation is large, real-time control is hard to implement too; if Smart Antenna is only adopted, the formed beam which points to the user is likely to interfere other users. Especially for high-speed mobile users, beam forming bias exists. To solve this problem, combination of Joint Detection and Smart Antenna is proposed in the paper. Simulation results show that the combination not only improves capacity of system remarkably but also eliminate the multiple access interference (MAI)

scholarly journals Spatial Diversity for CDMA RoFSO Links over M Turbulence Channels with Nonzero Boresight Pointing Errors

Computation ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 55
Author(s):  
Michalis Ninos ◽  
Hector Nistazakis
Keyword(s):  
Performance Improvement ◽  
Multiple Access ◽  
Nonlinear Distortion ◽  
Multiple Access Interference ◽  
Spatial Diversity ◽  
Atmospheric Conditions ◽  
Reverse Link ◽  
Pointing Errors ◽  
Link Performance ◽  
Average Bit Error Rate

A CDMA RoFSO link with receivers’ spatial diversity is studied. Turbulence-induced fading, modeled by the M(alaga) distribution, is considered that hamper the FSO link performance along with the nonzero boresight pointing errors effect. Novel, analytical closed-form expressions are extracted for the estimation of the average bit-error-rate and the outage probability of the CDMA RoFSO system for both directions of the forward and the reverse link. The numerical results show clearly the performance improvement of using spatial diversity, even in the most adverse atmospheric conditions with strong and saturated atmospheric turbulence with enhanced misalignment. Also, the effects of nonlinear distortion, multiple access interference and clipping noise aggravate the performance of the link, where cases with large number of users are taken into account.

scholarly journals A New Code Family for QS-CDMA Visible Light Communication Systems

2018 ◽  
Vol 3 ◽  
pp. 5-8 ◽  
Author(s):  
Mouad Addad ◽  
Ali Djebbari
Keyword(s):  
Visible Light ◽  
Communication Networks ◽  
Communication Systems ◽  
Multiple Access ◽  
Multipath Propagation ◽  
Multiple Access Interference ◽  
Visible Light Communication ◽  
Wireless Communication Networks ◽  
Strong Candidate ◽  
Code Division Multiple

Visible light communication (VLC) is a promising technology for wireless communication networks. Optical code division multiple access (OCDMA) is a strong candidate for VLC-based applications. The predominant source of bit error in OCDMA is the multiple access interference (MAI). To eliminate MAI in synchronous OCDMA, zero cross correlation (ZCC) codes have been proposed. However, synchronization problems and multipath propagation introduce relative non-zero time delays. Therefore, the zero correlation zone (ZCZ) concept was introduced. In this paper, we propose a new method for generating ZCC codes. The proposed construction can accommodate any number of users with flexible Hamming weight. The numerical results obtained show that the proposed codes significantly reduce MAI, compared to ZCC, as well as ZCZ codes.

Enhancement of reliability and security in spatial diversity FSO-CDMA wiretap channel

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Jianjia Zhang ◽  
Bing Wu ◽  
Fang Peng ◽  
Zihua Zheng ◽  
Jianhua Ji
Keyword(s):  
Free Space ◽  
Physical Layer Security ◽  
Multiple Access ◽  
Multiple Access Interference ◽  
Spatial Diversity ◽  
Physical Layer ◽  
Closed Form Expression ◽  
Free Space Optical ◽  
Wiretap Channel ◽  
Code Division Multiple

AbstractDue to atmospheric turbulence, the reliability and security of free space optical (FSO) communication will be affected seriously. In this paper, we propose a novel scheme of quasisynchronous spatial diversity free-space optical code division multiple access (FSO-CDMA) wiretap channel based on gamma-gamma distribution. Considering multiple access interference, shot noise, thermal noise and background noise, performances of bit error rate (BER) and physical-layer security are analyzed theoretically. The physical-layer security of quasisynchronous spatial diversity FSO-CDMA wiretap channel is evaluated by secrecy capacity and interception probability. Closed-form expression of interception probability is obtained. In order to compare the performances between conventional spatial diversity FSO-CDMA and the proposed scheme, Optisystem simulation is carried out. The results indicate that quasisynchronous spatial diversity FSO-CDMA scheme can improve the reliability and physical-layer security simultaneously.

Performance of Hybrid OCDMA/WDM Scheme Under DPSK and QPSK Modulation Using Spectral Direct Detection Technique for Optical Communication Networks

2018 ◽  
Vol 0 (0) ◽  
Author(s):  
N. Ahmed ◽  
M. A. Rashid
Keyword(s):  
Communication Networks ◽  
Wavelength Division Multiplexing ◽  
Optical Communication ◽  
Multiple Access ◽  
Direct Detection ◽  
Multiple Access Interference ◽  
Detection Technique ◽  
Spectral Amplitude ◽  
Modulation Formats ◽  
Code Division Multiple

AbstractThe hybrid optical code-division multiple-access over wavelength-division multiplexing (OCDMA/WDM) scheme has attractive features of supporting system reach, multi Gbps data rates, security, and robustness for optical communication networks. This paper presents the performance of such scheme under DPSK and QPSK modulation formats using spectral direct detection technique. The modified double weight (MDW) code is used as spectral amplitude coding which also acts as a signature address code for the OCDMA system. The MDW code has the advantage of reducing the multiple access interference (MAI) and enhancing the security of the proposed hybrid system. The study focuses on the comparison between the two advanced modulation techniques (DPSK, QPSK) using spectral direct detection. Simulation results show bit-error-rate (BER) ≤10–09 for up to 25 km distance at the bit rate of 1 Gbps for optical communication networks.

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.

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