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Cognitive radio is a promising technology proposed to solve the scarcity of the radio spectrum by opportunistically allocating the idle channels of the licensed users to unlicensed ones. The effectiveness of the cognitive radio is highly dependent on fair and efficient management of the access to the unused portion of the frequency channels, which is performed by the media access control layer. Therefore, any malicious activities disrupting operation of this layer result in significant performance degradation of the cognitive radio networks. As a result, it is necessary to understand functions of the media access control layer of the cognitive radio and analyze the impacts of possible attacks these functions might encounter. This paper provides an overview of different attacks that target the media access control layer of cognitive radio and analyzes them based on this layer's functions. In addition, the paper describes and compares recent defense strategies related to each attack.

In wireless regional area networks (WRAN's), spectrum sensing (SS) is one of the vital functions who detects primary users (PU) licensed signal for cognitive radios. In this paper, an improved-two stage detection (improved-TSD) technique for spectrum sensing has been proposed. In improved-TSD technique, two detectors (energy detector with single adaptive threshold (ED_SAT) and energy detector with two adaptive thresholds (ED_TAT)) work simultaneously, and then based on the decision of both detectors final decision has been takes place by decision device (DD) using OR-rules. Detectors have adaptive thresholds, ED_SAT has single adaptive threshold and ED_TAT has two adaptive thresholds. Thresholds depend on noise variance ( σ ω 2 ), and noise variance value changes according to noise signal. Due to this, the values of thresholds also change. Therefore, the thresholds are adaptive thresholds. Graphical results confirm that proposed improved-TSD technique improves detection performance and outperforms the multiple-ED and ED with adaptive double thresholds detector-2013 (MED and ED-ADT-2013), energy detection technique for adaptive spectrum sensing-2015 (EDT-ASS-2015), ED and ED-ADT detector-2015, and conventional-ED by 1.4%, 10.4%, 0.5% and 31.3% at −10 dB signal-to-noise ratio (SNR) respectively. Further, in terms of sensing time the presented scheme yields smaller sensing time frame than EDT-ASS-2015 SS scheme, ED and ED-ADT detector-2015, and multiple-ED and ED-ADT detector-2013 i.e. 0.5 ms, 1.7 ms and 2.4 ms at −20 dB SNR. It is further found that cooperative SS (CSS) with improved-TSD beats hierarchical with quantization-2012 by 11.5% in terms of detection performance at −11 dB SNR, and meanwhile, it detects PU signal at −19.5 dB SNR level.

In this work, a cognitive Wireless Regional Area Network (WRAN) technology-based sensor network for agricultural monitoring is proposed. In WRAN technology, a Consumer Premise Equipment (CPE) and a base station communicate through incumbent channels opportunistically without causing any harmful interference to incumbent operations. Because CPE in IEEE 802.22 WRAN is considered as a fixed device, CPE with sensing capability is suitable for wireless sensor network environment in agriculture monitoring where there is no need for node mobility. The proposed network model consists of terrestrial and underground networks. In terrestrial network, CPEs employ Time Division Multiple Access (TDMA) technique with the purpose of sensing environmental data such as temperature, pressure, etc. and transmitting them to the base station. In the underground network, underground sensor nodes use Carrier Sense Multiple Access (CSMA) technique with the aim of sensing underground data such as humidity, soil mineral, etc. and transmitting them to the base station via cluster heads. After obtaining the analytical model of the proposed network, the simulation model of the network is carried out using Riverbed Modeler. The graphical results prove the validity and applicability of the proposed network in terms of throughput and energy consumption without any spectrum cost for agricultural monitoring in rural areas. (c) 2020 Elsevier Inc. All rights reserved. WOS:000571497400008 2-s2.0-85087276669

IEEE 802.22 WRAN standard does not specify algorithm for selecting operating channel from backup channel list and prioritizing the backup and candidate channels. Because all the channels in the backup and candidate channels list are not with the same properties, selecting channels randomly from the list may decrease the networks performance. We propose an approach of ranking channel according to behavior of primary users on the channel and RSSI value. It utilizes fuzzy-logic-based algorithm for prioritizing channels in the backup and candidate channels list. Performances of the networks with fuzzy-logic-based channel selection and random channel selection are compared.

Avoiding collision among contending customer premise equipments (CPEs) attempting to associate with a base station (BS) in a wireless regional area network (WRAN) is a challenging issue. The collision probability is highly dependent upon the size of the initial contention window and the number of contending CPEs. To reduce the collision probability among CPEs in order to start the ranging process in an IEEE 802.22 network, the BS needs to adjust the initial contention window size. This paper provides an analytical framework to estimate the ranging request collision probability depending upon the size of the initial contention window and the number of CPEs attempting to join the IEEE WRAN cell. The accuracy of the estimated curve is analyzed for various numbers of contention CPEs on the basis of the relative errors. The numerical results confirm that the approximation works reasonably well for finding the ranging request collision probability for any number of contention CPEs at a particular value of initial contention window size. Moreover, this approximation provides the threshold size for a contention window to start the initial ranging process for any number of CPEs in an IEEE 802.22 network.

The primary objective of IEEE 802.22 standard is to determine vacant spectrum bands available in Digital Television channel (DTV) and to utilize them for wireless rural broadband connectivity. Cognitive Radio aims at maximizing the utilization of the limited radio bandwidth while accommodating the increasing number of services and applications in Wireless networks. For cognitive radio networks to operate efficiently, Secondary Users (SU) should be able to exploit radio spectrum that is unused by the primary user. A critical component of cognitive radio is thus spectrum sensing. The secondary user should sense the spectrum efficiently, utilize the opportunities for transmission, and vacate the channel once primary user reoccupies it. In this paper, we propose approaches for cooperative spectrum sensing as per the IEEE 802.22 standard. This paper describes several simulation scenarios that can be used to evaluate spectrum sensing by single SU unit (local sensing) and multiple SUs in a cooperative setup. The detection accuracy and performance of the proposed algorithms are described using performance metrics called probability of detection and probability of false-alarm through extensive simulations using Matlab.

The development of the IEEE 802.22 standard is aimed at providing broadband access in rural areas by effectively utilizing the unused TV band, provided no harmful interference is caused to the incumbent operation. The motivation behind TV band selection is of having lower frequencies compared to other licensed bands, which, therefore, results in lower propagation path loss. Due to this quality, the spectral power density of the radio signal reduces slowly, which results in a high coverage area. Further, it has been observed that many TV channels largely remain unoccupied, as most households and businesses rely on cable and satellite TV services. This is the first international standard for a wireless regional area network (WRAN) based on cognitive radio technologies. This standard provides both PHY and MAC layer functionalities in an infrastructure based network for communication between customer premise equipments (CPEs) through a base station (BS). The Spectrum Manager is the central part of the BS, which plays a significant role in maintaining spectrum availability information, channel selection, channel management, scheduling quiet periods for spectrum sensing, accessing to the database and implementing IEEE 802.22 policies. A WRAN can particularly accommodate up to 512 CPEs in a cell. Contention may occur during initial ranging, periodic ranging, bandwidth request and urgent coexistence situation notification. The medium access control (MAC) incorporates several schemes to control contention between CPEs within a cell and overlapping cells sharing the same channel. A CPE has to make decision to resolve collisions in the upstream direction. In the case of initial ranging and periodic ranging, code division multiple access (CDMA) is employed to resolve collisions. For bandwidth and UCS notification, either a CDMA or exponential time backoff approach can be applied for collision resolution. This paper presents the analytical framework to evaluate the number of active CPEs in a cognitive radio network. It is important to note that when the arrival rate becomes equal to the service rate, the active CPEs curve attains a constant value. Further, the active CPEs length is highly dependent on service rate. The different special cases have been addressed and the effectiveness of the proposed framework has been validated through various evaluation results.

IEEE 802.22 is a cognitive radio-based Wireless Regional Area Network (WRAN) standard that allows opportunistic access to idle or underutilized sub-900 MHz TV bands by unlicensed (secondary) networks. Though most of the standard has been laid out, there is still no consensus on the channel access policies for the uncoordinated secondary networks. Hence, the possibility of interference always exists. Moreover, in the absence of any control channel, the problem of establishing a connection becomes even more challenging, more so in the presence of hidden incumbents. In this paper, we address the above-mentioned self-coexistence problem among the IEEE 802.22 networks and provide novel solutions to improve the IEEE 802.22 air-interface. We use an interference-aware graph-theoretic technique and propose Utility Graph Coloring (UGC) for allocating spectrum to different IEEE 802.22 base stations such that they can coexist with the least interference, thereby maximizing the system spectrum utilization. We also consider allocation fairness among the networks in terms of minimal fairness, proportional fairness, and complete fairness. With the spectrum allocated to the IEEE 802.22 networks, we propose enhancements to the IEEE 802.22 MAC layer to maximize spectrum usage efficiency. In particular, we make use of aggregation and fragmentation of channel carriers, dynamic multiple broadcast messages, and aggressive contention resolution. Through simulation experiments, we show how the proposed techniques can increase the spectral efficiency and spectrum utilization, and still maintain fairness. We show that the spectral efficiency obtained with UGC is more than three times compared to the existing standard. The average number of collisions among the IEEE 802.22 enabled devices is significantly reduced, resulting in low connection setup delay, enhanced system performance, and higher spectrum allocation for data transmissions.

The developing IEEE 802.22 standard will allow broadband access to be provided in sparsely populated areas by using cognitive radio techniques with operations on a non-interfering basis over television broadcast bands. Such non-interfering basis operation will increase the efficiency of utilisation of that spectrum, and provide large economic and societal benefits. However, the security mechanisms supported by IEEE 802.22 security sub-layer are insufficient to ensure robust security due to the fact that the designers of the standard attempted to reuse the security sub-layer designed for IEEE 802.16 networks, which does not consider the unique security features from IEEE 802.22 networks. This paper proposes a location-based authentication protocol for IEEE 802.22, which can be integrated with the extensible authentication protocol. The proposed protocol uses location information as a key factor to be authenticated each other. Furthermore, it could provide the privacy and confidentiality.

Wireless broadband technologies provide ubiquitous broadband access to wireless users, enabling services that were available only to wireline users. In this paper, we summarize emerging wireless broadband access technologies, ranging from WLANs to satellite communications. We explain the latest standards in the IEEE 802.11 and IEEE 802.16 families in detail. The MAC layer mechanisms of IEEE 802.11e, 802.11n, and 802.11s standards are explained as well as the point-to-multipoint and Mesh modes of IEEE 802.16. The recent mobility amendment to the WiMAX family, IEEE 802.16e, is also described. Though the earliest versions of some of these technologies date back to 1996 (such as IEEE 802.11) and some are obsolete (such as HiperLAN), they have been included in this survey for the sake of completeness. Wireless technologies can be categorized based on their coverage areas. IEEE 802.11 and ETSI HiperLAN standards are considered for wireless access in local areas. IEEE 802.16 and 802.22, ETSI HiperACCESS and HiperMAN, WiBro, and HAP technologies can be used to provide service in metropolitan areas. Lastly, IEEE 802.20 and satellite systems provide service as wide area networks. Since the aim of this survey is to summarize wireless broadband technologies for data services, technologies such as Wireless USB are excluded. 3G and 4G systems have also been excluded since they are covered in detail in [C. Smith, D. Collins, 3G Wireless Networks, second ed., McGraw-Hill Osborne Media, 2006; S.G. Glisic, Advanced Wireless Networks: 4G Technologies, Wiley Publishing, 2005].