Extended Cyclostationary Signatures for OFDM in the Presence of Hardware Imperfections

Frequenz ◽  
2012 ◽  
Vol 66 (9-10) ◽  
Author(s):  
Johannes Schmitz ◽  
Milan Zivkovic ◽  
Rudolf Mathar
Keyword(s):  
Cognitive Radio ◽  
Sampling Rate ◽  
Modulation Scheme ◽  
Ofdm Systems ◽  
Simulation Environment ◽  
Signal Parameter ◽  
Major Drawback ◽  
Signature Detection ◽  
Cyclostationary Detection ◽  
Evaluation Platform

AbstractCyclostationary signatures have been shown to be an effective method for OFDM network synchronization and Cognitive Radio coordination. In this article, an extended method that utilizes cyclostationary signatures for signal parameter identification of OFDM-based Cognitive Radio nodes is presented. The scenario, implemented on a GNU Radio based evaluation platform, shows how different signal parameters, e.g. carrier frequency, occupied bandwidth and the used modulation scheme can be identified at the receiver side using the described approach. A major drawback of cyclostationary detection in OFDM systems is its sensitivity to frequency offset and sampling rate mismatches between oscillators at the transmitter and the receiver. An analytical model that characterizes this impairments is derived, followed by a discussion of implementation issues and the performance evaluation of proposed cyclostationary signature detection, both in a simulation environment and through RF experiments.

scholarly journals An Efficient Adaptive Technique with Low Complexity for Reducing PAPR in OFDM-Based Cognitive Radio

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Hefdhallah Sakran ◽  
Omar Nasr ◽  
Mona Shokair
Keyword(s):  
Cognitive Radio ◽  
Orthogonal Frequency Division Multiplexing ◽  
Average Power ◽  
Low Complexity ◽  
Papr Reduction ◽  
Modulation Scheme ◽  
Ofdm Systems ◽  
Cpu Time ◽  
Reduction Techniques ◽  
Selective Mapping

Cognitive radio (CR) is considered nowadays as a strong candidate solution for the spectrum scarcity problem. On standards level, many cognitive radio standards have chosen Non-Contiguous Orthogonal Frequency Division Multiplexing (NC-OFDM) as their modulation scheme. Similar to OFDM, NC-OFDM suffers from the problem of having a high Peak to Average Power Ratio (PAPR). If not solved, either the transmitted signal will be distorted, which will cause interference to primary (licensed) users, or the effeciency of the power amplifier will be seriously degraded. The effect of the PAPR problem in NC-OFDM based cognitive radio networks is worse than normal OFDM systems. In this paper, we propose enhanced techniques to reduce the PAPR in NC-OFDM systems. We start by showing that combining two standard PAPR reduction techniques (interleaver-based and selective mapping) results in a lower PAPR than using them individually. Then, an “adaptive number of interleavers” will be proposed that achieves the same performance of conventional interleaver-based PAPR reduction while reducing the CPU time by 41.3%. Finally, adaptive joint interleaver with selective mapping is presented, and we show that it gives the same performance as conventional interleaver-based technique, with reduction in CPU time by a factor of 50.1%.

scholarly journals An Active and Passive Reputation Method for Secure Wideband Spectrum Sensing Based on Blockchain

Electronics ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 1346
Author(s):  
Xinyu Xie ◽  
Zhuhua Hu ◽  
Min Chen ◽  
Yaochi Zhao ◽  
Yong Bai
Keyword(s):  
Cognitive Radio ◽  
Spectrum Sensing ◽  
Cognitive Radio Networks ◽  
Cooperative Spectrum Sensing ◽  
Sampling Rate ◽  
Radio Networks ◽  
Single Node ◽  
Decision Algorithm ◽  
Collusion Attacks ◽  
Wideband Spectrum Sensing

Spectrum is a kind of non-reproducible scarce strategic resource. A secure wideband spectrum sensing technology provides the possibility for the next generation of ultra-dense, ultra-large-capacity communications to realize the shared utilization of spectrum resources. However, for the open collaborative sensing in cognitive radio networks, the collusion attacks of malicious users greatly affect the accuracy of the sensing results and the security of the entire network. To address this problem, this paper proposes a weighted fusion decision algorithm by using the blockchain technology. The proposed algorithm divides the single-node reputation into active reputation and passive reputation. Through the proposed token threshold concept, the active reputation is set to increase the malicious cost of the node; the passive reputation of the node is determined according to the historical data and recent performance of the blockchain. The final node weight is obtained by considering both kinds of reputation. The proposed scheme can build a trust-free platform for the cognitive radio collaborative networks. Compared with the traditional equal-gain combination algorithm and the centralized sensing algorithm based on the beta reputation system, the simulation results show that the proposed algorithm can obtain reliable sensing results with a lower number of assistants and sampling rate, and can effectively resist malicious users’ collusion attacks. Therefore, the security and the accuracy of cooperative spectrum sensing can be significantly improved in cognitive radio networks.

scholarly journals Frequency Domain based Digital Down Conversion Architecture for Software Defined Radio and Cognitive Radio

2018 ◽  
Vol 7 (2.16) ◽  
pp. 88 ◽  
Author(s):  
Latha Sahukar ◽  
Dr M. Madhavi Latha
Keyword(s):  
Cognitive Radio ◽  
Frequency Domain ◽  
Software Defined Radio ◽  
Sampling Rate ◽  
Complex Multiplication ◽  
Clock Rate ◽  
Direct Rotation ◽  
Digital Down Conversion ◽  
Frequency Domain Filtering ◽  
Down Conversion

This paper presents a sampling rate digital down converter that is totally based on frequency domain processing. The proposed DDC is targeted for Software Defined Radio and Cognitive Radio architectures. The proposed architecture is based on replacement of the complex multiplication with direct rotation of the spectrum. Different aspects of frequency domain filtering are also discussed. The Xilinx Virtex-6 family FPGA, XC6VLX240T is used for the implementation and synthesis of the proposed FFT-IFFT based architecture. The overlapping in time domain at the output of the IFFT block is avoided using overlap and add method. In terms area, highly optimized implementation is observed in the proposed architecture when compared to the conventional DDC. The synthesis results have shown that the developed core works at a maximum clock rate of 250 MHz and at the same time  occupies  only 10% of the slices of  FPGA. 

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