Due to the under-utilization problem of the allocated radio spectrum, cognitive radio (CR) communications have recently emerged as a reliable and effective solution. Among various network models, this survey paper focuses on the enabling techniques for interweave CR networks which have received great attention from standards perspective due to its reliability to achieve the required quality-of-service. Spectrum sensing provides the essential information to enable this interweave communications in which primary and secondary users are not allowed to access the medium concurrently. Several researchers have already considered various aspects to realize efficient techniques for spectrum sensing. In this direction, this survey paper provides a detailed review of the state-of-the-art related to the application of spectrum sensing in CR communications. Starting with the basic principles and the main features of interweave communications, this paper provides a classification of the main approaches based on the radio parameters. Subsequently, we review the existing spectrum sensing works applied to different categories such as narrowband sensing, narrowband spectrum monitoring, wideband sensing, cooperative sensing, practical implementation considerations for various techniques, and the recent standards that rely on the interweave network model. Furthermore, we present the latest advances related to the implementation of the legacy spectrum sensing approaches. Finally, we conclude this survey paper with some suggested open research challenges and future directions for the CR networks in next generation Internet-of-Things applications.

Advances on Spectrum Sensing for Cognitive Radio Networks: Theory and Applications

Design of a novel hybrid intercarrier interference mitigation technique through wavelet implication in an OFDM system

Kernel fuzzy c-means clustering on energy detection based cooperative spectrum sensing

This paper studies and analyzes the performance of the licensed-assisted access (LAA) scheme introduced by 3GPP in LTE Release 13, and adopted by 3GPP in LTE Release 14, which is called 3GPP LAA scheme for short. Considering the characteristics that the 3GPP LAA scheme is different from other LAA schemes and IEEE 802.11 distributed coordination function (DCF) protocol in WiFi systems, the 3GPP LAA scheme is modeled as a new two-dimensional discrete Markov model, and the collision probability and the channel occupancy utilization are further derived based on the proposed model. To more deeply analyze the performance of the 3GPP LAA scheme by comparisons, we also derive the expressions of the same performance indices for the linear backoff based LAA scheme proposed in this paper and the fixed contention window based LAA scheme mentioned in existing literatures. The simulation and numerical results prove the validity of the proposed Markov chain model, and also show that the 3GPP LAA scheme is the friendliest one to WiFi networks among the three LAA schemes, whereas its total channel occupancy utilization is the lowest when the number of LAA small base stations (SBSs) is little and that is the highest when large. However, the other two LAA schemes are still the graceful coexistence, which is defined as the scheme where the interference to WiFi users caused by LAA SBSs coexisting with them is not more than that caused by other WiFi APs replacing the LAA SBSs.

Performance Analysis of Licensed-Assisted Access to Unlicensed Spectrum in LTE Release 13

As a general and rigid mathematical tool, wavelet theory has found many applications and is constantly developing. This article reviews the development history of wavelet theory, from the construction method to the discussion of wavelet properties. Then it focuses on the design and expansion of wavelet transform. The main models and algorithms of wavelet transform are discussed. The construction of rational wavelet transform (RWT) is provided by examples emphasizing the advantages of RWT over traditional wavelet transform through a review of the literature. The combination of wavelet theory and neural networks is one of the key points of the review. The review covers the evolution of Wavelet Neural Network (WNN), the system architecture and algorithm implementation. The review of the literature indicates the advantages and a clear trend of fast development in WNN that can be combined with existing neural network algorithms. This article also introduces the categories of wavelet-based applications. The advantages of wavelet analysis are summarized in terms of application scenarios with a comparison of results. Through the review, new research challenges and gaps have been clarified, which will serve as a guide for potential wavelet-based applications and new system designs.

https://ieeexplore.ieee.org/ielx7/6287639/6514899/09785993.pdf

A Review of Wavelet Analysis and Its Applications: Challenges and Opportunities

Comparative Study of Single-user Spectrum Sensing Techniques in Cognitive Radio Networks

Orthogonal frequency division multiplexing (OFDM) is considered among the most suitable multiplexing technique for realizing high speed wireless communication in the present era. Substantially immune to frequency selective fading, high spectral efficiency and superior data rate made OFDM a preferred and popular modulation technique in 3rd generation and 4th generation mobile communication systems. The high value of peak to average power ratio (PAPR) and inter carrier interference (ICI) are the most severe bottleneck for OFDM applications to deliver high performance in communication system.
The present work portraits most of conventional and current PAPR reduction techniques through comparative study assisted by simulative analysis which foretells future research potential in wavelet based OFDM to generate more efficient system. PAPR optimization is achieved through hybridization of wavelet with clipping and companding techniques. Different modulation techniques have been analyzed (through Matlab simulation) over proposed hybrid model to observe the PAPR reduction in OFDM system.

Evolution of PAPR Reduction Techniques: A Wavelet Based OFDM Approach

Cognitive Radio is a promising solution to spectrum underutilization problem, highlighting the concept of Dynamic Spectrum Access with two primary functions of efficient radio spectrum usage and providing reliable communication whenever and wherever needed. In a Cognitive Radio Network, secondary users are allowed to use the vacant licensed spectrum. Hence secondary users need to sense the spectrum to check availability of vacant spectrum and vacate as soon as primary user arrives back. Thus, spectrum sensing plays a significant role in Cognitive Radio Networks. Cooperative spectrum sensing is of great importance as it combats shadowing multipath fading and receiver uncertainty problems. There are two important parameters in spectrum sensing: probability of detection and probability of false-alarm. Higher detection probability signifies better primary user protection. In this paper, performance has been evaluated and depicted for Energy detection based cooperative spectrum sensing through MATLAB simulations.

Performance Evaluation of Energy Detection Based Cooperative Spectrum Sensing in Cognitive Radio Network

Orthogonal frequency division multiplexing (OFDM), a very promising technique that is leading the evolution in wireless mobile communication to sideline the bandwidth scarcity issue in spectrum allocation, is severely affected by the undesirable effects of the frequency offset error, which generates inter carrier interference (ICI) due to the Doppler shift and local oscillator frequency synchronization errors. There are many ICI cancellation techniques available in the literature, such as self-cancellation (SC), maximum likelihood estimation (MLE), and windowing, but they present a tradeoff between bandwidth redundancy and system complexity. In this study, a new energy-efficient, bandwidth-effective technique is proposed to mitigate ICI through cyclic prefix (CP) reuse at the receiver end. Unlike SC and MLE where the whole OFDM symbol data is transmitted in duplicate to create redundancy at the transmitter end, the proposed technique uses the CP data (which is only 20% of the total symbol bandwidth) to estimate the channel, and it produces similar results with a huge bandwidth saving. The simulation results show that the proposed technique has a significant improvement in error performance, and a comparative analysis demonstrates the substantial improvement in energy efficiency with high bandwidth gain. Therefore, it outperforms the legacy ICI cancellation schemes under consideration.

Sandeep Sarowa

Papers

Design of a novel hybrid intercarrier interference mitigation technique through wavelet implication in an OFDM system

Comparative Study of Single-user Spectrum Sensing Techniques in Cognitive Radio Networks

Evolution of PAPR Reduction Techniques: A Wavelet Based OFDM Approach

Performance Evaluation of Energy Detection Based Cooperative Spectrum Sensing in Cognitive Radio Network

A novel energy-efficient ICI cancellation technique for bandwidth improvements through cyclic prefix reuse in an OFDM system