Multicarrier Spread Spectrum Modulation Schemes and Efficient FFT Algorithms for Cognitive Radio Systems

Sundararajan, Mohandass; Govindaswamy, Umamaheswari

doi:10.3390/electronics3030419

Cited by 16 publications

(10 citation statements)

References 74 publications

(92 reference statements)

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“…Although OFDM has many advantages in the communication environments, the high peakto-average-power-ratio (PAPR) is considered the main drawback of the OFDM system [10]. The high PAPR runs the amplifiers less efficient and produces intermodulation that interferes with the adjacent channels [11].…”

Section: Introductionmentioning

confidence: 99%

Zero-Padding Techniques in OFDM Systems

Al‐Jawhar¹,

Ramli²,

Taher³

et al. 2018

IJEEI

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Although the OFDM system has been gaining importance in recent years, the high peak to average power ratio is considered the main limitation of the system. The oversampling operation in the frequency-domain plays an essential role in the PAPR calculations precisely. The main purpose of the paper to draw attention to zero-padding methods which are used to oversampled baseband OFDM signals. Moreover, to study the influence of the zero-padding methods on the accuracy of the PAPR calculations, and the spectral spreading of the OFDM signals. Simulation results show that the zero-padding method which inserts the zeros at the center of the baseband OFDM signal is better than the other zero-padding methods in terms of both accuracy PAPR calculations and spectral distribution. Electrical Engineering, College of Engineering at University of AL-Mustansiriya Baghdad, Iraq in 1998. He received his M.S. degree from Faculty of Electrical and Electronic Engineering, University Tun Hussein Onn Malaysia in 2015. He is currently working toward his Ph.D. degree at Faculty of Electrical and Electronic Engineering, University Tun Hussein Onn Malaysia. His research interests mainly focus on signal processing in communication, OFDM, PAPR reduction in Multicarrier system, 5G waveform design, and wireless network. Khairun Nidzam Ramli is a Senior Lecturer of Faculty of Electrical and Electronic Engineering at Universiti Tun Hussein Onn Malaysia (UTHM), Johor, Malaysia. He obtained his BEng in Electronic Engineering from the University of Manchester Institute of Science and Technology (UMIST), United Kingdom, in 1997, and the MEng at the Universiti Kebangsaan Malaysia (UKM), Malaysia, in 2004. He worked within the antennas and applied electromagnetic research group at University of Bradford, United Kingdom since 2007, on a number of projects, concentrating on antenna design and computational electromagnetics. Later, he obtained his PhD for research in electromagnetic analysis using hybrid computational techniques from the University of Bradford in 2011. His typical academic interests include wireless technologies, antennas, electromagnetics, and engineering computing. He is a member of the IEEE. Montadar Abas Taher received the B.

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Section: Introductionmentioning

confidence: 99%

Zero-Padding Techniques in OFDM Systems

Al‐Jawhar¹,

Ramli²,

Taher³

et al. 2018

IJEEI

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“…Ever since its introduction, the computational advantages of the FFT have made it an essential algorithm with widespread applications in science and engineering, such as communication, signal processing, image processing, bio-robotics, and intelligent maintenance [1,2,4,[7][8][9][10]. The high-speed requirements of smart maintenance systems, such as fault diagnosis in rotary machines using the spectral analysis of AE signals, necessitate a high-performance FFT processor.…”

Section: Introductionmentioning

confidence: 99%

A Pipelined FFT Processor Using an Optimal Hybrid Rotation Scheme for Complex Multiplication: Design, FPGA Implementation and Analysis

et al. 2018

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Abstract:The fast Fourier transform (FFT) is the most prevalent algorithm for the spectral analysis of acoustic emission signals acquired at ultra-high sampling rates to monitor the condition of rotary machines. The complexity and cost of the associated hardware limit the use of FFT in real-time applications. In this paper, an efficient hardware architecture for FFT implementation is proposed based on the radix-2 decimation in frequency algorithm (R2DIF) and a feedback pipelined technique (FB) that allows effective sharing of storage between the input and output data at each stage of the FFT process via shift registers. The proposed design uses an optimal hybrid rotation scheme by combining the modified coordinate rotation digital computer (m-CORDIC) algorithm and a binary encoding technique based on canonical signed digit (CSD) for replacing the complex multipliers in FFT. The m-CORDIC algorithm, with an adaptive iterative monitoring process, improves the convergence of computation, whereas the CSD algorithm optimizes the multiplication of constants using a simple shift-add method. Therefore, the proposed design does not require the large memory typically entailed by existing designs to carry out twiddle factor multiplication in large-point FFT implementations, thereby reducing its area on the chip. Moreover, the proposed pipelined FFT processor uses only distributed logic resources and does not require expensive dedicated functional blocks. Experimental results show that the proposed design outperforms existing state-of-the-art approaches in speed by about 49% and in resource utilization by around 51%, while delivering the same accuracy and utilizing less chip area.

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“…The CP in OFDM holds redundant data which decreases the spectral efficiency (Sundararajan and Govindaswamy, 2014) and it also causes high mutual interference between Primary User's due to its large frequency domain side-lobes. The total spectrum efficiency is despoiled due to the insertion of CP to each of the OFDM symbols (Absi and Kaiser, 2014).…”

Section: Problems In Ofdmmentioning

confidence: 99%

“…Multiple SUs are assigned with orthogonal spreading codes to guarantee their separability at the receiver. CR networks use the subcarrier deactivation technique, which avoids the interference between MC-CDMA based SUs and PUs (Sundararajan and Govindaswamy, 2014). Multicarrier CDMA is a combination of CDMA and OFDM.…”

Section: Mc-cdmamentioning

confidence: 99%

A Review on Cognitive Radio for Next Generation Cellular Network and its Challenges

Pandi¹,

Кумар²

2017

American Journal of Engineering and Applied Sciences

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Cognitive Radio (CR) is considered an intelligent technology. It improves the utilization of the radio spectrum. The increasing number of new devices has resulted in growing congestion of the ISM bands. FCC issued an order only permitting unlicensed users (secondary users) to operate in white space without interfering with licensed users (primary users). Cognitive Radio Networks (CRNs) provides a solution to the problem of additional spectrum requirements by utilizing the spectrum more efficiently. CR is able to sense the spectrum and share the spectrum with unlicensed users. There are number of popular spectrum sensing techniques in CR such as cyclostationary feature detection, energy detection and matched filter detection, which capture the best available spectrum. They use a spectrum dynamically in wireless communication network. A CR with multicarrier technique (OFDM and FBMC) are the next generation of advanced cellular network, which would provide better spectrum utilization and therefore have greater capacity. In this study we have described and reviewed CR technology and its numerous features that may play a very essential role in the field of next generation wireless communication networks.

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Multicarrier Spread Spectrum Modulation Schemes and Efficient FFT Algorithms for Cognitive Radio Systems

Cited by 16 publications

References 74 publications

Zero-Padding Techniques in OFDM Systems

Zero-Padding Techniques in OFDM Systems

A Pipelined FFT Processor Using an Optimal Hybrid Rotation Scheme for Complex Multiplication: Design, FPGA Implementation and Analysis

A Review on Cognitive Radio for Next Generation Cellular Network and its Challenges

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