scholarly journals Design and Simulation of parallel CDMA System Based on 3D-Hadamard Transform

2013 ◽  
Vol 6 (4) ◽  
pp. 45-69
Author(s):  
Ali T. Shaheen
Keyword(s):  
Fading Channels ◽  
Spectral Efficiency ◽  
Hadamard Matrix ◽  
Additive White Gaussian Noise ◽  
Mapping Technique ◽  
Cdma System ◽  
Data Mapping ◽  
Two Dimensional ◽  
And Performance ◽  
Code Division Multiple

Future wireless systems aim to provide higher transmission data rates, improved spectral efficiency and greater capacity. In this paper a spectral efficient two dimensional (2-D) parallel code division multiple access (CDMA) system is proposed for generating and transmitting (2-D CDMA) symbols through 2-D Inter-Symbol Interference (ISI) channel to increase the transmission speed. The 3D-Hadamard matrix is used to generate the 2-D spreading codes required to spread the two-dimensional data for each user row wise and column wise. The quadrature amplitude modulation (QAM) is used as a data mapping technique due to the increased spectral efficiency offered. The new structure simulated using MATLAB and a comparison of performance for serial one-dimensional (1-D) CDMA and parallel (2-D) CDMA is made under Additive White Gaussian Noise (AWGN), flat fading and multi-path selective fading channels conditions. It is found that 2-D CDMA has better speed and performance than serial 1-D CDMA.

scholarly journals A Radon Slantlet Transforms Based OFDM System Design and Performance Simulation under Different Channel Conditions

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Abbas Hasan Kattoush
Keyword(s):  
Radon Transform ◽  
Spectral Efficiency ◽  
Fading Channel ◽  
Orthogonal Frequency Division Multiplexing ◽  
Additive White Gaussian Noise ◽  
Mapping Technique ◽  
Intercarrier Interference ◽  
Ofdm Systems ◽  
Ofdm System ◽  
Channel Parameters

Due to its good orthogonality, slantlet transform (SLT) is used in orthogonal frequency division multiplexing (OFDM) systems to reduce intersymbol interference (ISI) and intercarrier interference (ICI). This eliminates the need for cyclic prefix (CP) and increases the spectral efficiency of the design. Finite Radon transform (FRAT) mapper has the ability to increase orthogonality of subcarriers, is nonsensitive to channel parameters variations, and has a small constellation energy compared with conventional fast-Fourier-transform- (FFT-) based OFDM. It is also able to work as a good interleaver, which significantly reduces the bit error rate (BER). In this paper both FRAT mapping technique and SLT modulator are implemented in a new design of an OFDM system. The new structure was tested and compared with conventional FFT-based OFDM, Radon transform-based OFDM, and SLT-based OFDM for additive white Gaussian noise (AWGN) channel, flat fading channel (FFC), and multipath selective fading channel (SFC). Simulation tests were generated for different channel parameters values. The obtained results showed that the proposed system has increased the spectral efficiency, reduced ISI and ICI, and improved BER performance compared with other systems.

scholarly journals Improvement of BER performance in MIMO–CDMA systems by using initial–phase optimized gold codes

2013 ◽  
Vol 64 (1) ◽  
pp. 38-43 ◽  
Author(s):  
Ibrahim Develi ◽  
Meryem Filiz
Keyword(s):  
Fading Channels ◽  
Interference Cancellation ◽  
Initial Phase ◽  
Multiple Input Multiple Output ◽  
Cdma System ◽  
Gold Codes ◽  
Output Code ◽  
Input Multiple Output ◽  
Code Division Multiple ◽  
Ber Performance

This paper describes a new approach to improve the bit error rate (BER) performance of a multiple-input multiple-output code-division multiple-access (MIMO-CDMA) system over quasi-static Rayleigh fading channels. The system considered employs robust space-time successive interference cancellation detectors and initial-phase optimized Gold codes for the improvement. The results clearly indicate that the use of initial-phase optimized Gold codes can significantly improve the BER performance of the system compared to the performance of a multiuser MIMO-CDMA system with conventional nonoptimized Gold codes. Furthermore, this performance improvement is achieved without any increase in system complexity.

scholarly journals Two approaches to multiuser detection over fading channels

Doklady BGUIR ◽  
2021 ◽  
Vol 19 (1) ◽  
pp. 11-20
Author(s):  
V. P. Tuzlukov
Keyword(s):  
Antenna Array ◽  
Fading Channels ◽  
Multiuser Detection ◽  
Antenna Arrays ◽  
Additive White Gaussian Noise ◽  
Antenna Element ◽  
Blind Adaptive ◽  
Receiving Antenna ◽  
Downlink Channels ◽  
Code Division Multiple

In this paper, two different receiver structures to multiuser detection that are appropriate for the code-division multiple-access systems with antenna arrays in fading channels are investigated and compared. We analyze and compare the performance of the two different multiuser detection structures for uplink or downlink channels. The number of elements of receiving antenna array may be limited in the downlink channel due to the small size of receivers. We assume a synchronous system, but it can be easily extended to an asynchronous system. The first approach is based on the distributed decorrelator where the signal decorrelation is performed by each receiving antenna element independently and decorrelated outputs are combined according to the maximum ratio. The second approach is the central decorrelator where the signal decorrelation is performed once collectively on the outputs from all elements of receiving antenna array. Both decorrelators provide the same performance in the additive white Gaussian noise channels. The distributed decorrelator provides the better performance in flat fading channels. We employ the decorrelator to demonstrate our results. The results discussed in the present paper can be extended to other configurations such as the blind adaptive space-time multiuser detection.

Two Dimensional Tunable Optical-CDMA System

2016 ◽  
Vol 4 (1) ◽  
pp. 125
Author(s):  
Rajesh Yadav Yadav ◽  
Gurjit Kaur Kaur
Keyword(s):  
Prime Number ◽  
Code Division Multiple Access ◽  
Optical Signal ◽  
Optical Cdma ◽  
Cdma System ◽  
Two Dimensional ◽  
Eye Diagram ◽  
Optical Delay ◽  
Code Division Multiple ◽  
Multiple Access System

<p>In this work an experimental demonstration is proposed to implement the synchronous optical code division multiple access system using two dimensional wavelength hopping and time spreading optical prime code is presented. An optical CDMA system is configured on latest version of optisystem by optiwave for the 20 users (Prime Number = 5) connected in a network operating at a bit rate 10 Gbps each. Tunability is achieved by using a MATLAB based delay selector which serves as the source of control signal for optical delay lines. The encoded optical signal of each user has been assigned a particular mode. The resulting optical signal is then transmitted over parabolic index multimode optical fiber. The received signal can successfully be retrieved at the decoder, when the encoder and decoder are configured for the same user. The performance of Optical CDMA system is evaluated in terms of the autocorrelation and cross correlation function, BER, Q factor, eye diagram and compared with 1D code for a given prime number. </p>

ROBUST JPEG2000 IMAGE TRANSMISSION THROUGH LOW SNR MULTI-CARRIER CDMA SYSTEM IN FREQUENCY-SELECTIVE RAYLEIGH FADING CHANNELS: A PERFORMANCE STUDY

2011 ◽  
Vol 09 (02) ◽  
pp. 283-303 ◽  
Author(s):  
KATHIYAIAH THIYAGU ◽  
T. H. OH
Keyword(s):  
Fading Channels ◽  
Signal To Noise Ratio ◽  
Image Transmission ◽  
Multipath Fading ◽  
Cdma System ◽  
Performance Study ◽  
Compression Technique ◽  
Multipath Fading Channel ◽  
Low Snr ◽  
Code Division Multiple

The demand for high data rate transmission is ever increasing every day. Multi-carrier code division multiple access (MC-CDMA) system is considered as the forerunner and advancement in the mobile communication system. In this paper, two types of JPEG2000 lossily-compressed test images are transmitted through an MC-CDMA channel in low SNR (as low as 4 dB) environment and their quality are evaluated objectively by using peak signal-to-noise ratio (PSNR) and root mean square error (RMSE). The test images are all compressed from ratio of 10 : 1 up to 70 : 1 and the system involves multi-user image transmission in near real-time low SNR (±5 dB). It is found that JPEG2000 image compression technique that applies wavelet transform performed quite well in the low SNR multipath fading channel — as low as 4 dB, and this looks promising for future applications.

scholarly journals Simulation and Analysis of MC-CDMA System under AWGN and Rayleigh Fading Channel

2013 ◽  
Vol 6 (2) ◽  
pp. 336-342
Author(s):  
Bhavana Kulhare ◽  
Dr. Poonam Sinha
Keyword(s):  
Fading Channel ◽  
Rayleigh Fading ◽  
Additive White Gaussian Noise ◽  
Standard Technique ◽  
Multipath Fading ◽  
Rayleigh Fading Channel ◽  
Complete Analysis ◽  
Cdma System ◽  
Spectrum Utilization ◽  
Code Division Multiple

This paper presents a detailed analysis of Multicarrier Code Division Multiple Access (MC-CDMA) system over Additive White Gaussian Noise (AWGN) and Rayleigh Fading Channel with analysisof the effects of different number of sub-carriers and multiuser scenarios and at the end a comparison with standard technique is also performed. The complete analysis is performed by simulating the mathematical model of the MC-CDMA system with various combinations of sub-carriers, number of users, SNR, path gains and path delays etc. the simulation results shows that the MC-CDMA is an effective way to overcome the multipath fading losses and spectrum utilization with relatively simple system architecture.

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