scholarly journals Estimation and equalization strategies for fiber-wireless communications in a multiuser CDMA environment

2021 ◽  
Author(s):  
Stephen Z. Pinter
Keyword(s):  
Signal To Noise Ratio ◽  
Multiple Access Interference ◽  
Wireless Channel ◽  
Decision Feedback ◽  
Optical Channel ◽  
Channel Noise ◽  
Training Sequences ◽  
Nonlinear Channels ◽  
Linear And Nonlinear ◽  
Pn Sequences

Two major issues associated with fiber-wireless technology are the nonlinear distortion of the optical link and the multipath dispersion of the wireless channel. In order to limit the effects of these distortions, estimation, and subsequently equalization of the concatenated fiber-wireless channel needs to be done. This thesis addresses three scenarios in this regard, they are: uplink estimation using pseudonoise (PN) sequences, downlink estimation using Walsh codes, and uplink equalization using a decision feedback equalizer (DFE) and series reversion, all in the presence of both wireless and optical channel noise. The training sequences used in the identification are practically feasible. These training sequences have white noise-like properties which effectively decouples the identification of the linear and nonlinear channels. Correlation analysis is then applied to identify both systems. Furthermore, we propose an algorithm to mitigate the adverse effect of multiple access interference (MAI). Numerical evaluations show a good estimation of both the linear and nonlinear systems with 10 users for the uplink and 54 users for the downlink, both with a signal-to-noise ratio (SNR) of 25 dB. Chip error rate (CER) simulations show that the proposed MAI mitigation algorithm leaves only small residual MAI.

scholarly journals Estimation and equalization strategies for fiber-wireless communications in a multiuser CDMA environment

2021 ◽  
Author(s):  
Stephen Z. Pinter
Keyword(s):  
Signal To Noise Ratio ◽  
Multiple Access Interference ◽  
Wireless Channel ◽  
Decision Feedback ◽  
Optical Channel ◽  
Channel Noise ◽  
Training Sequences ◽  
Nonlinear Channels ◽  
Linear And Nonlinear ◽  
Pn Sequences

Two major issues associated with fiber-wireless technology are the nonlinear distortion of the optical link and the multipath dispersion of the wireless channel. In order to limit the effects of these distortions, estimation, and subsequently equalization of the concatenated fiber-wireless channel needs to be done. This thesis addresses three scenarios in this regard, they are: uplink estimation using pseudonoise (PN) sequences, downlink estimation using Walsh codes, and uplink equalization using a decision feedback equalizer (DFE) and series reversion, all in the presence of both wireless and optical channel noise. The training sequences used in the identification are practically feasible. These training sequences have white noise-like properties which effectively decouples the identification of the linear and nonlinear channels. Correlation analysis is then applied to identify both systems. Furthermore, we propose an algorithm to mitigate the adverse effect of multiple access interference (MAI). Numerical evaluations show a good estimation of both the linear and nonlinear systems with 10 users for the uplink and 54 users for the downlink, both with a signal-to-noise ratio (SNR) of 25 dB. Chip error rate (CER) simulations show that the proposed MAI mitigation algorithm leaves only small residual MAI.

scholarly journals Performance Investigation of Channel Noise Effect in Data Transmission Medium Using Signal to Noise Ratio (SNR)

2018 ◽  
Vol 11 (2) ◽  
pp. 419
Author(s):  
Gebremedhn Wubet Wagaye
Keyword(s):  
Bit Error Rate ◽  
Error Rate ◽  
Data Transmission ◽  
Signal To Noise Ratio ◽  
Main Idea ◽  
Wireless Channel ◽  
Channel Noise ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Wrong Interpretation

<p>The noise introduced in the channel obviously affects the bit error rate of the communication system and this has direct impact in the security. Here the main problem is that the receiver terminal decoding techniques can lead to wrong interpretation even if the Bit Error Rate (BER) is acceptable. So the main idea here is to introduce high values of Signal to Noise Ratio (SNR) that can improve the bit error rate which exists due to the noise introduced in the wireless channel.</p>

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 of Multi-User Transmitter Pre-Processing Assisted Multi-Cell IDMA System for Downlink Transmission

2015 ◽  
Vol 14 (03) ◽  
pp. 1550030 ◽  
Author(s):  
B. Partibane ◽  
V. Nagarajan ◽  
K. S. Vishvaksenan ◽  
R. Kalidoss
Keyword(s):  
Multiple Access ◽  
Signal To Noise Ratio ◽  
Minimum Mean Square Error ◽  
Multiple Access Interference ◽  
Base Station ◽  
Least Square ◽  
Complex Signal ◽  
Delay Spread ◽  
Downlink Transmission ◽  
Mmse Detector

In this paper, we present the performance of multi-user transmitter pre-processing (MUTP) assisted coded-interleave division multiple access (IDMA) system over correlated frequency-selective channels for downlink communication. We realize MUTP using singular value decomposition (SVD) technique, which exploits the channel state information (CSI) of all the active users that is acquired via feedback channels. We consider the MUTP technique to alleviate the effects of co-channel interference (CCI) and multiple access interference (MAI). To be specific, we estimate the CSI using least square error (LSE) algorithm at each of the mobile stations (MSs) and perform vector quantization using Lloyd's algorithm, and feedback the bits that represents the quantized magnitudes and phases to the base station (BS) through the dedicated low rate noisy channel. Finally we recover the quantized bits at the BS to formulate the pre-processing matrix. The performance of MUTP aided IDMA systems are evaluated for five types of delay spread distributions pertaining to long-term evolution (LTE) and Stanford University Interim (SUI) channel models. We also compare the performance of MUTP with minimum mean square error (MMSE) detector for the coded IDMA system. The considered TP scheme alleviates the effects of CCI with less complex signal detection at the MSs when compared to MMSE detector. Further, our simulation results reveal that SVD-based MUTP assisted coded IDMA system outperforms the MMSE detector in terms of achievable bit error rate (BER) with low signal-to-noise ratio (SNR) requirement by mitigating the effects of CCI and MAI.

scholarly journals INTELLIGENT DETECTION AND CLASSIFICATION OF MICROCALCIFICATION IN COMPRESSED MAMMOGRAM IMAGE

2015 ◽  
Vol 34 (3) ◽  
pp. 183 ◽  
Author(s):  
Benjamin Joseph ◽  
Baskaran Ramachandran ◽  
Priyadharshini Muthukrishnan
Keyword(s):  
Probabilistic Neural Network ◽  
Signal To Noise Ratio ◽  
Model Performance ◽  
High Sensitivity ◽  
Processing Technique ◽  
Set Partitioning ◽  
Experimental Result ◽  
Channel Noise ◽  
Bit Rate ◽  
Mammogram Image

The main contribution of this article is introducing an intelligent classifier to distinguish between benign and malignant areas of micro-calcification in companded mammogram image which is not proved or addressed elsewhere. This method does not require any manual processing technique for classification, thus it can be assimilated for identifying benign and malignant areas in intelligent way. Moreover it gives good classification responses for compressed mammogram image. The goal of the proposed method is twofold: one is to preserve the details in Region of Interest (ROI) at low bit rate without affecting the diagnostic related information and second is to classify and segment the micro-calcification area in reconstructed mammogram image with high accuracy. The prime contribution of this work is that details of ROI and Non-ROI regions extracted using multi-wavelet transform are coded at variable bit rate using proposed Region Based Set Partitioning in Hierarchical Trees (RBSPIHT) before storing or transmitting the image. Image reconstructed during retrieval or at the receiving end is preprocessed to remove the channel noise and to enhance the diagnostic contrast information. Then the preprocessed image is classified as normal or abnormal (benign or malignant) using Probabilistic neural network. Segmentation of cancerous region is done using Fuzzy C-means Clustering (FCC) algorithm and the cancerous area is computed. The experimental result shows that the proposed model performance is good at achieving high sensitivity of 97.27%, specificity of 94.38% at an average compression rate and Peak Signal to Noise Ratio (PSNR) of 0.5bpp and 58dB respectively.

scholarly journals Suitable Spreading Sequences for Asynchronous MC-CDMA Systems

2018 ◽  
Vol 3 ◽  
pp. 9-13 ◽  
Author(s):  
Mouad Addad ◽  
Ali Djebbari
Keyword(s):  
Communication Systems ◽  
Multiple Access ◽  
Signal To Noise Ratio ◽  
Multiple Access Interference ◽  
High Data ◽  
Research Areas ◽  
Rate Transmission ◽  
Cdma Systems ◽  
Code Division Multiple ◽  
Spreading Sequences

In order to meet the demand of high data rate transmission with good quality maintained, the multi-carrier code division multiple access (MC-CDMA) technology is considered for the next generation wireless communication systems. However, their high crest factor (CF) is one of the major drawbacks of multi-carrier transmission systems. Thus, CF reduction is one of the most important research areas in MC-CDMA systems. In addition, asynchronous MC-CDMA suffers from the effect of multiple access interference (MAI), caused by all users active in the system. Degradation of the system’s bit error rate (BER) caused by MAI must be taken into consideration as well. The aim of this paper is to provide a comparative study on the enhancement of performance of an MC-CDMA system. The spreading sequences used in CDMA play an important role in CF and interference reduction. Hence, spreading sequences should be selected to simultaneously ensure low CF and low BER values. Therefore, the effect that correlation properties of sequences exert on CF values is investigated in this study. Furthermore, a numerical BER evaluation, as a function of the signal-to-noise ratio (SNR) and the number of users, is provided. The results obtained indicate that a trade-off between the two criteria is necessary to ensure good performance. It was concluded that zero correlation zone (ZCZ) sequences are the most suitable spreading sequences as far as the satisfaction of the above criteria is concerned.

scholarly journals Introduction of the in-orbit test and its performance for the first meteorological imager of the Communication, Ocean, and Meteorological Satellite

2014 ◽  
Vol 7 (8) ◽  
pp. 2471-2485 ◽  
Author(s):  
D. H. Kim ◽  
M. H. Ahn
Keyword(s):  
Signal To Noise Ratio ◽  
Channel Noise ◽  
Test Results ◽  
User Requirement ◽  
Spacecraft Design ◽  
A Value ◽  
Improved Performance ◽  
And Performance ◽  
Shortwave Infrared ◽  
Meteorological Satellite

Abstract. The first geostationary Earth observation satellite of Korea – the Communication, Ocean, and Meteorological Satellite (COMS) – was successfully launched on 27 June 2010. After arrival at its operational orbit, the satellite underwent an in-orbit test (IOT) that lasted for about 8 months. During the IOT period, the main payload for the weather application, the meteorological imager, went through successful tests for demonstrating its function and performance, and the test results are introduced here. The radiometric performance of the meteorological imager (MI) is tested by means of signal-to-noise ratio (SNR) for the visible channel, noise-equivalent differential temperature (NEdT) for the infrared channels, and pixel-to-pixel nonuniformity for both the visible and infrared channels. In the case of the visible channel, the SNR of all eight detectors is obtained using the ground-measured parameters with the background signals obtained in orbit. The overall performance shows a value larger than 26 at 5% albedo, exceeding the user requirement of 10 by a significant margin. Also, the relative variability of detector responsivity among the eight visible channels meets the user requirement, showing values within 10% of the user requirement. For the infrared channels, the NEdT of each detector is well within the user requirement and is comparable with or better than the legacy instruments, except for the water vapor channel, which is slightly noisier than the legacy instruments. The variability of detector responsivity of infrared channels is also below the user requirement, within 40% of the requirement, except for the shortwave infrared channel. The improved performance result is partly due to the stable and low detector temperature obtained due to spacecraft design, i.e., by installing a single solar panel on the opposite side of the MI.

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