scholarly journals Wavelet based multicarrier CDMA system

2019 ◽  
Vol 9 (4) ◽  
pp. 3051
Author(s):  
Nasser Hamad ◽  
Maen Takruri ◽  
Mahdi Barhoush
Keyword(s):  
Fading Channels ◽  
Orthogonal Frequency Division Multiplexing ◽  
Driving Forces ◽  
Multipath Propagation ◽  
Discrete Wavelet ◽  
Multicarrier Cdma ◽  
Service Levels ◽  
High Data ◽  
Modulation Techniques ◽  
User Capacity

Emerging demands for high data rate services, high user capacity and low power consumption systems are the key driving forces behind the continued technology evolution in wireless communications. Multicarrier Modulation techniques support variety of services requiring different data rates and different QoS (quality of service) levels. Multicarrier CDMA is a wireless communication system that can be seen as a combination of direct sequence CDMA and Orthogonal Frequency Division Multiplexing techniques. The main benefits of this system are its robustness to inter symbol interference and multipath propagation in fading channels. This paper studies and simulates the Discrete Wavelet Transform based Multicarrier CDMA and compares it with the  Discrete Fourier Transform based one using different number of sub carriers, and different modulation techniques. The results shows that the Wavelet based system outperforms the Fourier based one since it has lower bit error rate BER performance, lower peak to verage power ratio PAPR and higher user capacity.

BER Improvement in OFDM Systems Using Wavelet Transform Based on Kalman Filter

2020 ◽  
pp. 102-124
Author(s):  
Sajjan Singh
Keyword(s):  
Kalman Filter ◽  
Wavelet Transform ◽  
Fading Channels ◽  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
High Speed ◽  
Performance Enhancement ◽  
Average Power ◽  
Discrete Wavelet ◽  
Rate Analysis

Orthogonal frequency division multiplexing (OFDM) is an efficient method of data transmission for high speed communication systems over multipath fading channels. However, the peak-to-average power ratio (PAPR) is a major drawback of multicarrier transmission systems such as OFDM is the high sensitivity of frequency offset. The bit error rate analysis (BER) of discrete wavelet transform (DWT)-OFDM system is compared with conventional fast Fourier transform (FFT)-OFDMA system in order to ensure that wavelet transform based OFDMA transmission gives better improvement to combat ICI than FFT-based OFDMA transmission and hence improvement in BER. Wavelet transform is applied together with OFDM technology in order to improve performance enhancement. In the proposed system, a Kalman filter has been used in order to improve BER by minimizing the effect of ICI and noise. The obtained results from the proposed system simulation showed acceptable BER performance at standard SNR.

scholarly journals Discrete Multiwavelet Critical-Sampling Transform-Based OFDM System over Rayleigh Fading Channels

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Sameer A. Dawood ◽  
F. Malek ◽  
M. S. Anuar ◽  
Suha Q. Hadi
Keyword(s):  
Fading Channels ◽  
Mobile Communications ◽  
Orthogonal Frequency Division Multiplexing ◽  
Discrete Wavelet ◽  
Ofdm Systems ◽  
Ofdm System ◽  
Time Frequency ◽  
Wireless Mobile Communications ◽  
Time Frequency Localization ◽  
Multiwavelet Transform

Discrete multiwavelet critical-sampling transform (DMWCST) has been proposed instead of fast Fourier transform (FFT) in the realization of the orthogonal frequency division multiplexing (OFDM) system. The proposed structure further reduces the level of interference and improves the bandwidth efficiency through the elimination of the cyclic prefix due to the good orthogonality and time-frequency localization properties of the multiwavelet transform. The proposed system was simulated using MATLAB to allow various parameters of the system to be varied and tested. The performance of DMWCST-based OFDM (DMWCST-OFDM) was compared with that of the discrete wavelet transform-based OFDM (DWT-OFDM) and the traditional FFT-based OFDM (FFT-OFDM) over flat fading and frequency-selective fading channels. Results obtained indicate that the performance of the proposed DMWCST-OFDM system achieves significant improvement compared to those of DWT-OFDM and FFT-OFDM systems. DMWCST improves the performance of the OFDM system by a factor of 1.5–2.5 dB and 13–15.5 dB compared with the DWT and FFT, respectively. Therefore the proposed system offers higher data rate in wireless mobile communications.

scholarly journals Indoor optical wireless MIMO-OFDM system

2014 ◽  
Vol 17 (1) ◽  
pp. 5-16
Author(s):  
Khoa Le Dang ◽  
Tung Thanh Vu ◽  
Tu Thanh Nguyen ◽  
Phuong Huu Nguyen
Keyword(s):  
Fading Channels ◽  
Electromagnetic Interference ◽  
Orthogonal Frequency Division Multiplexing ◽  
High Speed ◽  
Optical Wireless ◽  
Error Vector Magnitude ◽  
Ofdm System ◽  
High Data ◽  
Mimo Ofdm ◽  
Vector Magnitude

Indoor optical wireless systems have attracted attention, because they allow high-speed transmission without electromagnetic interference. Multi Input Multi Output (MIMO) techniques are very promising in providing high data rate or providing performance over fading channels. Orthogonal frequency division multiplexing (OFDM) can send multiple high speed signals by using orthogonal carrier frequencies. In this paper, we propose an optical wireless MIMO-OFDM system to achieve better performance. The signal of each optical transmit antenna is detected by using zero forcing (ZF) algorithm. We use the error vector magnitude (EVM) to predict BER performance. The analysis of bit error rate (BER) shows that the proposed system achieve better performance transmission than OMIMO system when transmitting the signal over reflection channels.

Comparison of various channel equalization techniques in OFDM system using different digital modulations

2016 ◽  
Vol 3 (3) ◽  
pp. 634 ◽  
Author(s):  
Pratima Manhas ◽  
M.K. Soni
Keyword(s):  
Fading Channels ◽  
Orthogonal Frequency Division Multiplexing ◽  
Signal To Noise Ratio ◽  
Multipath Fading ◽  
Ofdm System ◽  
Multipath Fading Channels ◽  
Estimation Algorithms ◽  
High Data ◽  
Data Rates ◽  
High Data Rates

<p>The nature of future wireless applications requires high data rates and for this OFDM technique is used. OFDM stands for orthogonal frequency division multiplexing and is a type of multi-carrier transmission where all the subcarriers are orthogonal to each other. At high data rates, the channel distortion to the data is very important and it is somewhat impossible to recover the transmitted data with a simple receiver. So a complex receiver structure is needed which uses computationally expensive equalization and channel estimation algorithms to estimate the channel. These estimations can be used within the received data to recover the originally transmitted data. OFDM can simplify the equalization problem by changing the frequency-selective channel into a flat channel. The radio channels in mobile radio systems are usually multipath fading channels that results in intersymbol interference (ISI) in the received signal. To remove ISI from the signal, many kind of equalizers can be used. The need for equalizers arises from the fact that the channel has amplitude and phase dispersion which results in the interference of the transmitted signals with one another which is known as ISI .So, to solve this problem equalizers are designed. Equalizer is intend to work in such a way that Bit Error Rate (BER) should be low and Signal-to-Noise Ratio (SNR) should be high. An equalizer within a receiver compensates for the average range of expected channel amplitude and delay characteristics. This paper deals with the various equalization techniques (LMS, RLS and CMA) used for OFDM system .A comparative analysis of different equalization technique in terms of BER is done using MATLAB Simulink.</p>

scholarly journals Study of Modulation Schemes over a Multipath Fading Channels

2021 ◽  
Vol 7 (10) ◽  
pp. 34-39
Author(s):  
Karthik Kumar Vaigandla, Allanki Sanyasi Rao and Kallepelli Srikanth
Keyword(s):  
Wireless Communication ◽  
Fading Channels ◽  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Wireless Channels ◽  
Multipath Fading ◽  
Rician Fading ◽  
Multipath Fading Channels ◽  
High Data ◽  
Modulation Schemes

Communications systems concerted over wireless channels depend on the environment. Communications system can be more reliable and efficient by properly analyzing wireless channels. Today's most important features are a high data rate and reliable performance to exploiting viable networks during this new information age. The channel is not time-invariant in wireless communication, so the received signal exhibits amplitude, phase, and angle variations due to multipath fading. Increasing data rates and reducing bandwidth make Orthogonal Frequency Division Multiplexing (OFDM) an important component of wireless communication systems. The OFDM technique uses many carriers very efficiently. With this scheme, interference is robustly reduced, and fading scenarios are easily accommodated. Analyzing digital modulation schemes requires evaluating link performance with fading channels. The paper compares channel performance over varying fading environments using a variety of modulation schemes. We study the BER and SNR properties of the AWGN, Rician fading and Rayleigh fading channels modulated with BPSK, QPSK, and M-ary QAM.

scholarly journals Design and Performance Analysis of OFDM and FBMC Modulation Techniques

2017 ◽  
Vol 17 (2) ◽  
pp. 30-34 ◽  
Author(s):  
Arun Kumar ◽  
Shikha Bharti
Keyword(s):  
Mobile Communication ◽  
Orthogonal Frequency Division Multiplexing ◽  
Signal To Noise Ratio ◽  
Spectrum Utilization ◽  
High Data ◽  
Fifth Generation ◽  
Modulation Techniques ◽  
Data Consumption ◽  
And Performance ◽  
Selection Of

AbstractResearchers have already proved that data consumption in coming years will increase by leaps and bounds, so the present technologies like 3G, OFDM (Orthogonal Frequency Division Multiplexing) cannot hold the addition of huge capacitance, data use and demand of high data-rate. Hence, on that point is a necessity of fifth generation mobile communication system (5G). Presently the rollout for 5G is going virtually everywhere in the world and among several issues; selection of better modulation techniques is seen as unitary of the significant issues in the implementation of the 5G. In this work, we designed and analyse the performance of OFDM and FBMC (Filter Band Multi Carrier) multicarrier modulation schemes on the basis of Bit Error rate (BER) and Signal to Noise Ratio (SNR). Simulation results and mathematical analysis have confirmed that the performance and spectrum utilization of FBMC is better or equivalent as compared to OFDM, which can be very useful in next generation mobile communication and Internet of Things (IOT).

scholarly journals Wavelet Transform Application Based on Matlab Simulation

2020 ◽  
Vol 36 (1) ◽  
Author(s):  
Tan Nguyen Minh ◽  
Hua-Ming Chen ◽  
Binh Duong Giap ◽  
Hoang Le Quang Nhat
Keyword(s):  
Wavelet Transform ◽  
Orthogonal Frequency Division Multiplexing ◽  
Multiple Input Multiple Output ◽  
Simulation Software ◽  
Discrete Wavelet ◽  
Matlab Simulation ◽  
Ofdm System ◽  
High Data ◽  
Input Multiple Output ◽  
Mimo Ofdm

Multiple Input Multiple Output (MIMO) and Orthogonal Frequency Division Multiplexing (OFDM) are two combined technologies to provide the spectral efficiency and high data rate required for 4G, 5G wireless systems. Discrete Wavelet Transform (DWT) is presented as an alternative for Fast Fourier Transform (FFT) since there is no necessity for Cyclic Prefix (CP) due to the overlapping properties of DWT. By a simple replacement of the FFT with DWT in MIMO OFDM system, an improvement of performances has been detected which leads to a new system scenario DWT-based MIMO-OFDM. In this thesis, such a system is simulated and the performance of Bit Error Rate (BER) is analyzed to determine the different types of wavelets in various channel condition with different modulations (4, 16, 64 -QAM). Therefore, DWT-based MIMO-OFDM in comparison with DFT-based MIMO-OFDM system was investigated using MATLAB simulation software. And besides, I would like to refer to use Neural Network algorithms to replace Wavelet transform in the next research.

scholarly journals Efficient OFDM transceiver design for VLC sys-tems in fading channel

2018 ◽  
Vol 7 (1.8) ◽  
pp. 245
Author(s):  
Jayakumari J ◽  
Rakhi K J
Keyword(s):  
Fading Channels ◽  
Bit Error Rate ◽  
Fading Channel ◽  
Visible Light Communication ◽  
Communication Security ◽  
Rf Systems ◽  
High Data ◽  
Data Rates ◽  
Simulation Results ◽  
Rich Spectrum

With the widespread effective usage of LEDs the visible light communication (VLC) system has brought out an increasing interest in the field of wireless communication recently. VLC is envisioned to be an appealing substitute to RF systems because of the advantages of LEDs such as high communication security, rich spectrum, etc. For achieving bearable inter symbol interference (ISI) and high data rates, OFDM can be employed in VLC. In this paper, the performance of VLC system with popular unipolar versions of OFDM viz. Flip-OFDM and ACO-OFDM is analyzed in fading channels. From the simulation results it is seen that the Flip-OFDM-VLC system outperforms the ACO-OFDM-VLC system in terms of bit error rate and is well suited for future 5G applications.

Mobility aware of WDM-based CMO OFDM communication system

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Saad M. Hardan ◽  
Ayad A. Abdulkafi ◽  
Saadi Hamad Thalij ◽  
Sherine S. Jumaah
Keyword(s):  
Wavelength Division Multiplexing ◽  
Orthogonal Frequency Division Multiplexing ◽  
High Speed ◽  
Light Emitting Diode ◽  
Access Point ◽  
Mobile Users ◽  
Visible Light Communications ◽  
Optical Wireless Communications ◽  
High Data ◽  
The Impact

Abstract The continued increase in several mobile applications forces to replace existing limited spectrum indoor radio frequency wireless connections with high-speed ones. Visible light communications (VLC) technology has gained prominence in the development of high data rate transmission for fifth-generation networks. In optical wireless communications, light-emitting diode (LED) transmitters are used in applications that desire mobility as LED divergence enables larger coverage. Since each VLC access point covers a small area, handovers of mobile users are inevitable. Wavelength division multiplexing (WDM) can be used in VLC systems to tackle the above issue and to meet the increasing demand for indoor connectivity with high bit rates. In this paper, a new system architecture for WDM with coded modulated optical in orthogonal frequency division multiplexing (OFDM) VLC system in conjunction with red, green, blue, and yellow (RGBY) LEDs is proposed to reduce the impact of random receiver orientation of indoor mobile users over VLC downlink channels and improves the system’s bit-error-rate (BER) performance. Simulation results show that the proposed method is not affected by the user’s mobility and hence it performs better than other approaches, in terms of BER for all scenarios and at all positions. This study reveals that using WDM-OFDM-VLC with RGBY LEDs to construct a VLC system is very promising.

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