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Cognitive Radio (CR) is considered as an effective technology for alleviating the spectrum shortage problem by enabling secondary users to utilize vacant spectrum allocated to a primary user (PU). IEEE 802.22 which is the first standard based on CR is developed to increase the efficiency of TV bands. However the physical layer security of IEEE 802.22 has been studied rarely. In this paper, we propose a scheme to sense the specific primary user for dealing with Primary User Emulation (PUE) Attack which is a possible threat to wireless security. According to ATSC digital TV which is one of the important PUs, we estimate the accuracies of pilot and symbol rate as RF fingerprint (RFF), and Support Vector Data Description (SVDD) is introduced to sense the fine differences of RFF to distinguish PUE attacker from PU. The simulation results show that the proposed scheme is feasible to verify the PUE attacker at a relative high SNR level.

The main challenge in resource allocation in cognitive radio based IEEE 802.22 networks is the absence of predefined control channels. Moreover, the fleeting nature of the available spectrum also hinders the communication as the radios must relinquish the acquired channels once the primary users of those channels return. In this paper, we propose a performance metrics based data channel allocation scheme for IEEE 802.22 networks where the base station allocates interference free channels to the consumer premise equipments using a spectrum map. The base station creates the spectrum map by using the raw spectrum usage data that are shared by a small subset of consumer premise equipments. The usage data are fused at the base station using a modified version of Shepard's interpolation technique. We construct a continuous and differentiable spatial distribution of spectrum usage that the base station consults to estimate the spectrum occupancy vector at any arbitrary location in its cell. Such spectrum usage is then utilized to proactively evaluate some key network and radio performance metrics which in turn help allocating the best candidate channel to a given consumer premise equipment ensuring highest achievable performance.

In IEEE 802.22 system, the quiet period for spectrum sensing consists of a series of consecutive energy detections followed by feature detection. In this paper, an adaptive operation scheme for quiet period in the IEEE 802.22 system is proposed and its performance is investigated, where the length of sensing interval is adaptively varied depending on the number of alarms by the energy detection. The effect of intra-frame cycle length is also investigated. Numerical results show that the proposed scheme may improve the channel utilization of cognitive radio system by 5% to 20%.

Cognitive networks address the spectrum shortage problem exploiting unused chunks of the frequency spectrum, i.e. channels. With the aim to opportunistically use these channels, cognitive devices (CDs) have been defined.

We address a unique security threat that arises due to channel fragmentation (or aggregation or bonding) in dynamic spectrum access (DSA) based IEEE 802.22 networks. Typically, channel fragmentation, aggregation and bonding have been studied in the literature as a means to enhance the spectrum utilization. However, the loss of orthogonality between the spectrum bands due to channel fragmentation, aggregation or bonding can be exploited by malicious attackers to cause a cognitive service disruption. We present an analysis of such a threat. We determine the optimal transmit powers a malicious attacker transmits on each fragment, so as to create maximum service disruption. Numerical results indicate that a malicious attacker can cause up to about 16% loss in the capacity of the system as a consequence of fragmentation. Detailed analysis is presented for channel fragmentation and can be easily applied to channel aggregation and bonding. To the best of our knowledge,this is the first analysis of such cognitive service disruption threats due to fragmentation.

IEEE 802.22 is a standard for Wireless Regional Area Network (WRAN) based on cognitive radio techniques. It allows sharing of geographically unused spectrum allocated to the Television Broadcast Service, without causing harmful interference to the licensed users. An open issue in cognitive 802.22 networks is represented by the resource distribution among WRANs. The contribution of this paper is a resource sharing algorithm which assigns resources to overlapped WRANs in such a way to avoid harmful interference among them. Specifically, we propose a collision free resource sharing method which, working in a multichannel environment, aims to assign band to the coexisting WRANs, satisfying their spectrum demand and determining a fair spectrum scheduling. The novel method adapts to the continuous changes of the spectrum availability due to necessity of vacating a channel in case of the incumbent primary users or otherwise due to the addition of unused band. Moreover, the introduced allocation scheme takes into account the issue of spatial diversity, i.e. the case where some channels do not spatially cover all the WRANs. The effectiveness of the proposed multichannel resource sharing scheme is proved through simulations, and the results, compared with other methods already known in literature, show that the algorithm makes a resource assignment which satisfies the requests and improve the use of the available channels, increasing the spectral efficiency.

As in IEEE 802.22 proposal, the spectrum sensing technique should be capable enough to sense the primary signal with very low receiver sensitivity such as at -116 dBm. In this paper, the detection performance of an energy detector used for the spectrum sensing in cognitive radio networks is investigated under very low signal-to-noise ratio (SNR) level. The analysis focuses on the derivation of a closed-form expression for the average missed-detection probability over Rayleigh fading and Nakagami-$m$ fading channels. Subsequently, the detection threshold is optimized as minimizing the total error rate. The analysis is validated by numerical and simulation results. The sensing requirements defined in IEEE 802.22 are also discussed with numerical examples.

Due to copyright restrictions, the access to the full text of this article is only available via subscription. In this paper, we consider the shared used model in the context of IEEE 802.22 cognitive and investigate spectrum trading via auction approach. We consider two different scenarios in which the dominant risk is either associated with imperfect spectrum sensing or the uncertainties in the environment. Taking into account these risks, we propose a bidding strategy for sealed-bid first-price auction. Our numerical results demonstrate significant revenue increases in comparison to the conventional auction methods in risky environments.

In this paper, a novel channel sharing scheme for IEEE 802.22 systems is introduced and its performance is investigated. In order to minimizing the number of user to share one channel, the status of backup channels, not occupied by any adjacent users, is checked. In addition, the condition of channels occupied by neighboring users is investigated. Based on these channel statuses, the proposed channel sharing scheme selects the optimal channel, which includes a non-occupied backup channel and the channel shared by least users, in order to change the channel currently in use with other users. The simulation results illustrate that significant performance enhancement is achieved by applying the proposed channel sharing scheme to IEEE 802.22 systems.

Several recent studies have shown that Cognitive Networks (CNs) can effectively address the spectrum shortage problem in wireless networks, which is mainly caused by the increasing number of wireless services and applications operating in unlicensed channels. However, these studies fail to consider the differences between channel characteristics, i.e. they do not consider that channels are on different frequencies.In this paper, we fill this gap by providing a technique that classifies channels based on their operating frequency. We enable each cognitive device to choose the best channel depending on its traffic demand. We focus on the IEEE 802.22 physical layer in order to analyze and classify channels, and we propose the aware channel assignment algorithm for cognitive networks (Aaron). Aaron assigns channels to cognitive devices with the goal of satisfying the capacity demand of the largest number of end-users in order to maximize the throughput.We evaluate Aaron using an ad-hoc event-driven simulator for CNs. In addition we compare it with the Dumb algorithm, where cognitive devices are not able to characterize channels, and with the Upper Bound, where no packet is lost due to the channel assignment algorithm. Simulation studies demonstrate that Aaron performs considerably better than Dumb and very close to the Upper Bound.

Spectrum sensing is the key for Cognitive Radio (CR) systems such as IEEE 802.22 standard in improving the Quality of Service (QoS) of secondary user while avoiding harmful interference to primary user (PU) of the allocated spectrum. In this paper, we reviewed the traditional MF's (Matched Filter) properties and proposed a novel hybrid MF structure which is designed to perform spectrum sensing function in IEEE 802.22 standard. This structure mixes segmented MF with parallel MFs, and overcomes MF's bottleneck — frequency offset without sacrificing its advantage. We revealed some properties of this novel structure and demonstrate a case in 802.22 standard and compare it with other papers. The result shows that our novel structure has advantages over other spectrum sensing methods.

The well known noise rejection property of the cyclostationary spectrum makes it an ideal candidate for spectrum sensing in low SNR environments such as the IEEE 802.22 WRAN, which stipulates detection of primary signals at -20.8dB. In this paper, we propose two novel detector architectures that exploit cyclostationary properties: the Spectral Correlation Density (SCD), and the Magnitude Squared Coherence (MSC). Through extensive simulations, both on generated data and real world ATSC capture data, we show that our detector achieves an improvement of 2.5dB compared to existing proposals. Additionally, we compare our proposal against two popular choices for spectrum sensing in cognitive radio -- the matched filter detection and energy detection, and show the superiority of cyclostationary spectrum sensing in such low SNR environments.

Frequency Assignment is an important approach to mitigate multi-cell interference in cellular systems. In this paper, we consider frequency hopping as one possible frequency assignment approach. In particular we focus our attention on cognitive radio cellular systems as one of the very promising future access technologies, taking IEEE 802.22 as an example. While the optimal frequency assignment for such a system is conceptually straightforward as well as computationally complex, we demonstrate that usage of distributed methods leads to a significant loss of assignment efficiency. In addition, we suggest means of mitigating this adverse effect.

TV white space is a general term for the geographical redundancies in the TV broadcast bands. The re-use of TV white space is of current interest due to the change to digital transmission in many parts of the world. This has led to the biggest re-structuring of the TV bands since their creation. The bands represent a prime section of spectrum, which currently has some geographical white space. This paper attempts to quantify the number of bands available in the south-west of the UK where digital switch over is now complete. It is shown that, in high and flat terrain, there is little spectrum free. This suggests that limiting access to this spectrum to large scale protocols, such as IEEE 802.22, would be inefficient in the UK. In areas of more complex terrain the number of bands increases significantly allowing short-range, local links.

In IEEE 802.22 WRAN networks, spectrum sharing among different cells is an important problem. Aiming at efficiently solving the spectrum sharing problem, a dynamic channel auction scheme is proposed in this paper. Based on auction theory in microeconomics, the proposed algorithm models the spectrum sharing as an auction problem which includes one auctioneer base station and multiple bidder base stations. Simulation results show that our algorithm obtains higher spectrum utilization and higher auction benefit, and guarantees no interference between competitive WRAN base stations.

This paper follows IEEE 802.22 proposed coexistence beacon protocol (CBP), the mechanism carry the information of dynamic resource renting and offering to solve the problem of spectrum sharing for inter-BS (Base Station) coexistence mechanism. Due to high flexibility and low complexity, fuzzy rules based on empirical laws can dynamically adjust parameters to control the radio resources. The fuzzy logic control (FLC) spectrum sharing for Inter-BS coexistence mechanism is chosen to make effective utilization of resources in IEEE 802.22 WRAN. The proposed scheme considers three kinds of traffic, voice, video and data respectively. The simulation results reveal that the proposed scheme can meet the goals of the dynamic spectrum sharing to improve resource utilization and fairness.

This paper introduces the implementation of IEEE 802.22 Wireless Regional Area Network (WRAN) for broadband internet access in rural areas. It highlights the advantage of implementing such technology and feasibility to co-exist with Digital Video Broadcasting – Terrestrial (DVB-T) in Malaysia. It adopts a model to determine the maximum number of WRAN base stations (BSs) by analyzing its co-channel interference between the BSs. The analysis shown that maximum WRAN BSs that could co-exist is 8 to 19 BSs outside the protection contour of the DVB-T BS. Coverage areas of 30 – 100 km will also feasible to co-exist. By implementing the IEEE 802.22 WRAN, the digital divide can be narrowed and broadband penetration would be increased.

IEEE 802.22 is the first worldwide Wireless Regional Area Networks (WRAN) standard based on cognitive radios (CR). In IEEE 802.22 WRAN, if a wireless microphone appears in any TV channel, the whole channel should be cleaned. 802.22 WRAN devices probably need to fractionally use the first adjacent channel for improving spectrum efficiency while ensuring no harmful interference is caused to the wireless microphone nearby. To determine the appropriate portion of the TV channel that WRAN can utilize, we firstly need to know the frequency location of wireless microphone. In this paper, we propose a two step DFT filter bank (TS-DFTFB) enhanced with an adaptive threshold method to detect the wireless microphone (WM). Comparing with conventional single step DFTFB, the TS-DFTFB method has low complexity while the detection precision is equal to single step DFTFB under the same condition. And with an adaptive method, the threshold can be kept very close to the noise power, which can increase the detection probability especially in the condition of low SNR.

Distributed Cognitive Radio Network (CRN) topology is described in IEEE 802.22 standard which is the first worldwide standard operating in TV bandwidth of wireless regional area. Spectrum sensing is conducted at distributed customer premise equipment (CPE). Cooperative sensing between CPEs is widely used to obtain more accurate spectrum sensing results. However, Byzantine failures can happen when some CPEs are attacked inside the CRN. A robust Byzantine security model can be built on MAC layer of base station (BS) by using published data fusion algorithm -Weighted Sequential Probability Ratio Test (WSPRT) to assist making a decision as to whether a licensed channel is occupied by other primary users or not. In this paper different sets of simulations are run for evaluating the performance of the WSPRT algorithm in terms of correct sensing rate, miss detection rate and number of samples comparing with other three algorithms for binary hypothesis test, namely, "And", "Or" and "Majority". Simulation results also show the different performance metrics under two types of attack patterns. From the results of simulations WSPRT is shown to have better performance than the other three algorithms.

We study the capacity of a single-hop wireless cell comprised of M fixed directional antennas concentrically arranged around a common axis and each reusing the same channel. The premise for this architecture is that co-channel interference between the fixed directional beams can be identified and reported, allowing joint conflict-free scheduling, i.e., it becomes possible to compute the schedule over all the M sectors together. We are primarily interested in studying the capacity gains that can be realized as a function of the number of sectors, the parameters of the directional antennas and other system parameters. Our analytical and numerical results yield several useful engineering insights on the selection of antenna parameters, the impact of node placement, and the impact of physical layer parameters. This study demonstrates how Space Division Multiple Access (SDMA) can yield excellent capacity provided inter-cell co-channel coexistence is achieved. Such coexistence techniques are now being considered for cognitive radio TV White Space systems and by evolving standards such as the IEEE 802.16h. Accepted version

Cognitive radios are efficient techniques to improve the utilization of the spectrum. Spectrum sensing is the key functionality to improve the spectrum efficiency and avoid harmful interference to the licensed users. By exploiting the spatial diversity of the different secondary users, cooperative sensing can achieve better sensing performance compared to the local sensing, thereby, receiving much attention recently. However, in large scale cognitive radio networks, such as Wireless Regional Area Network (WRAN) defined by IEEE 802.22, the secondary users may have quite different sensing SNRs due to the different pass loss and other environment parameters. How to efficiently transmit and fuse the sensing data of cooperative sensing in large scale cognitive radios have not been fully studied yet. This paper presents a sequential sensing data transmission and fusion approach for large scale cognitive radios to minimize the average sensing time by dividing the users into different sets according to their SNR parameters. The analytical and simulation results both show that the proposed approach not only decreases the sensing time but also certifies the accuracy of detection.

The cognitive radio enabled IEEE 802.22 wireless regional area network (WRAN) is designed to opportunistically utilize the unused or under-utilized TV bands. However, due to the lack of proactive security protocols and proper interaction policies among the secondary networks themselves, the IEEE 802.22 networks are vulnerable to various denial-of-service (DoS) threats. In this paper, we study the impact of coordinated DoS attacks on IEEE 802.22 networks from the malicious nodes' perspective. Assuming that multiple malicious nodes will launch coordinated attacks, we formulate a cooperative game among the malicious nodes. The expression of the net payoff is derived and the optimal decision strategy for the malicious nodes is obtained numerically. Simulation results demonstrate that the coordinated attack approach can enhance as high as 10-15% more net payoff for the malicious nodes than the uncoordinated attack.

In IEEE 802.22 Wireless Regional Area Networks (WRANs), each Base Station (BS) solves a complex resource allocation problem of simultaneously determining the channel to reuse, power for adaptive coverage, and Consumer Premise Equipments (CPEs) to associate with, while maximizing the total downstream capacity of CPEs. Although joint power and channel allocation is a classical problem, resource allocation in WRANs faces two unique challenges that has not yet been addressed: (1) the presence of small-scale incumbents such as wireless microphones (WMs), and (2) asymmetric interference patterns between BSs using omnidirectional antennas and CPEs using directional antennas. In this paper, we capture this asymmetry in upstream/downstream communications to propose an accurate and realistic WRAN-WM coexistence model that increases spatial reuse of TV spectrum while protecting small-scale incumbents. Based on the proposed model, we formulate the resource allocation problem as a mixed-integer nonlinear programming (MINLP) which is NP-hard. To solve the problem in real-time, we propose a suboptimal algorithm based on the Genetic Algorithm (GA), and extend the basic GA algorithm to a fully-distributed GA algorithm (dGA) that distributes computational cost over the network and achieves scalability via local cooperation between neighboring BSs. Using extensive simulation, the proposed dGA is shown to perform as good as 99.4- 99.8% of the optimal solution, while reducing the computational cost significantly.

The speed and accuracy of spectrum sensing techniques are essential factors in the performance of cognitive radio networks. The limitations imposed by computational complexity and limited monitoring time window impede the success of spectrum sensing operation performed by cognitive radio nodes. Compressive sensing technique is viewed as a novel approach to solve scalability problems in some signal processing operations. One popular application of compressed sensing is sizable image recovery. This technique can be used in spectrum sensing applications to reduce the barriers of current spectrum sensing computational requirements. The success of this technique will result in faster sensing operations, less complex sensing modules, or wider spectrum sensing capabilities. The coming IEEE 802.22 air interface standard aims to provide wireless services in wireless regional area network using TV spectrum white spaces. This standard is considered as the first standard that is based on cognitive radio approach. Spectrum sensing is a critical functionality that needs to be performed by 802.22 compliant devices. While, the standard does not specify any spectrum sensing method, it requires the sensing operation to be performed within timing and accuracy constraints. This work in progress is investigating the feasibility of using one of the compressive sensing techniques named Fast Fourier Sampling to detect wireless microphone signals for IEEE 802.22 air interface.

Despite the shortage of available frequency spectrum, recent studies have shown that the actual usage of the allocated spectrum is scarce. The IEEE is developing the 802.22 standard for spectral reuse in TV bands that uses cognitive radio (CR) technology. One of the essential and challenging features of CR is spectrum sensing. This paper proposes a novel spectrum sensing algorithm using spectral covariance of the received signal. The proposed spectral covariance sensing (SCS) algorithm exploits different statistical correlations of the signal and noise in the frequency domain. Test statistics are computed from the covariance matrix of spectrogram and compared with the decision threshold. Detection performance is theoretically analyzed and verified through extensive simulation according to the IEEE 802.22 requirements. We show that SCS achieved 3dB better sensitivity to pilot location detector with the same sensing time. It is also shown that SCS is very robust to the noise uncertainty, which is one of the critical performance measures of spectrum sensing. The results of the paper suggest that SCS is an efficient and viable sensing scheme for IEEE 802.22 systems.

We present an analytical model that enables throughput evaluation of Opportunistic Spectrum Orthogonal Frequency Division Multiple Access (OS-OFDMA) networks. The core feature of the model, based on a discrete time Markov chain, is the consideration of different channel and subchannel allocation strategies under different Primary and Secondary user types, traffic and priority levels. The analytical model also assesses the impact of different spectrum sensing strategies on the throughput of OS-OFDMA network. The analysis applies to the IEEE 802.22 standard, to evaluate the impact of two-stage spectrum sensing strategy and varying temporal activity of wireless microphones on the IEEE 802.22 throughput. Our study suggests that OS-OFDMA with subchannel notching and channel bonding could provide almost ten times higher throughput compared with the design without those options, when the activity and density of wireless microphones is very high. Furthermore, we confirm that OS-OFDMA implementation without subchannel notching, used in the IEEE 802.22, is able to support real-time and non-real-time quality of service classes, provided that wireless microphones temporal activity is moderate (with approximately one wireless microphone per 3,000 inhabitants with light urban population density and short duty cycles). Finally, two-stage spectrum sensing option improves OS-OFDMA throughput, provided that the length of spectrum sensing at every stage is optimized using our model.

Different from the MAC of IEEE 802.11, the application of IEEE 802.22 suffers the uncertain spectrum and frequency width, which can not ensure the access of mobile users to be valid. To solve the problem, in this paper, we modify the CSMA/CA mechanism in order to make it suit the Cognitive Radio environments, in which the spectrum can be effectively used. We validate the modification by numerical analysis.

The main application of Cognitive Radio (CR) is for the broadband wireless access in the rural areas which demand adequate data rate and multi user support. IEEE 802.22 , the first standard evolved for CR suggests Orthogonal Frequency Division Multiple Access (OFDMA) as the physical layer technique. In this paper wavelet packet based multi carrier multiple access scheme is proposed which can be an equally promising candidate for high data rate multi user CR applications. The performance of the proposed system is evaluated using standard wavelet bases and is compared with OFDMA.

Cognitive radio based IEEE 802.22 wireless regional area networks have been proposed to harness the highly underutilized sub 900 MHz TV bands. In such networks, both base stations and the consumer premise equipments (CPEs) continuously perform spectrum sensing and transmit only on those channels which are not being used by the primary incumbents. In this paper, we propose a heuristic for an efficient channel allocation by a base station to the CPEs in that cell. Due to the lack of dedicated control channels, the BS and CPEs within a cell go through a process of exchanging control messages on free channels. The benefit of such sharing of their mutual spectrum usage helps the base station make informed decisions on the allocation of uplink and downlink channels to CPEs. This, in turn, guarantees no interference to and from the primary licensed incumbents. For validation of the proposed allocation scheme, we conducted simulation experiments. The results show how the proposed scheme ensures allocation to almost all the CPEs in a cell and how the nature of allocation is dependent on the total number of channels scanned, probability of getting a free channel and number of CPEs in the cell.

Prime design goals for next-generation wireless networks to support emerging applications are spectral efficiency and low operational cost. Among a gamut of technical solutions, cognitive approaches have long been perceived as a catalyst for the above goals by facilitating the coexistence of primary and secondary users by means of efficient dynamic spectrum management. While most available techniques today are essentially opportunistic in nature, a truly cognitive device needs to exhibit a certain degree of intelligence to draw optimum decisions based on prior observations and anticipated actions. Said intelligence however, comes along with high complexity and poor convergence, which currently prevents any viable deployment of cognitive networks. We thus introduce an emerging and largely unexplored concept of docitive networks, where nodes effectively teach other nodes with the prime aims of reducing cognitive complexity, speeding up the learning process, and drawing better and more reliable decisions. To this end, we review some important concepts borrowed from the machine learning community for both centralized and decentralized systems, in order to position the emerging docitive with known cognitive approaches. Finally, we validate introduced concepts in the context of a primary digital television system dynamically coexisting with IEEE 802.22 secondary networks. For this scenario, we demonstrate the superiority of various unprecedented docitive over known opportunistic/cognitive algorithms.

The cognitive networks need the flexible utilization of the spectrum and bandwidths, without impacting the licensed Users(also called Primary Users, PU). While the cognitive radio network Media Access Control (MAC) layer is required not only to provide traditional services but also to perform an entirely new function for effective using the available bandwidths for the unlicensed users called Secondary Users (SU). To solve the problem, this paper develops a new MAC scheme that allows unlicensed users adaptively select spectrum, and it supports the QoS of high priority unlicensed users. The proposed MAC protocol offers differentiated access through the SUs' parameters setting AIFS[AC], CWmin[AC], CWmax[AC]. Each AC is equipped with a transmitting queue. Simulations verify the proposed MAC scheme for cognitive networks.

Reconflgurability of transceivers for wireless communication systems such as GSM, UMTS, WiMAX and WLAN will become increasingly important. Therefore, a flexible and reliable software and hardware architecture based on the software-defined radio (SDR) paradigm is a meaningful concept. SDRs have paved the way towards cognitive radios (CR), which are based on SDRs that additionally sense their environments, track changes, and react upon their findings. A CR is an autonomous unit in a communications environment that frequently exchanges information with the networks it is able to access as well as with other CRs. A tool is required for the description and design of the multitude of concurrent processing tasks running on the CR. Petri nets are both a simple and strong solution and are recommendable to deploy them for these demands. In this manuscript, the authors present a concept for a CR as well as the hardware demonstrator realization. This demonstrator was developed by the authors and makes use of a digital signal processor (DSP) in combination with field-programmable gate arrays (FPGAs). The authors will describe the solution also in view of the recent developments of IEEE 802.22.

Although the proliferation of wireless applications operating in unlicensed spectrum bands has resulted in over-crowding, recent analysis has shown that license bands are still underutilized. Cognitive Radio is seen as the key enabling technology to address the spectrum shortage problem, opportunistically using the spectrum allocated for TV bands. In this paper, we present a novel game theoretic framework that uses the potentialities of the new IEEE 802.22 Standard to guarantee self-coexistence among Wireless Regional Area Networks. We address this problem as a channel assignment problem where each WRAN acquires a chunk of spectrum free of interference in a dynamic and distributed way. Using a novel technique to compute backoff windows, we show that the channel assignment problem can be formulated as a multi-player non-cooperative repeated potential game that converges to a Nash Equilibrium point. We consider each WRAN as a player of our game and we use two different types of utility functions to maximize the spatial reuse and minimize the interference. An extensive simulation study shows that having the interference minimization as objective is not necessarily the best solution with selfish players. ©2010 IEEE.

The primary task in any cognitive radio (CR) network is to dynamically explore the spectrum and determine spectrum band that can be used without causing interference to other users. In this paper, we propose a multistage filter banks to sense the spectrum band. Compared with the conventional filter banks, our proposed method has low complexity but high detection precision. The proposed scheme has been analyzed and tested through simulations on wireless microphone detection in IEEE 802.22 WRAN.

Currently, for rural and remote education, wireline solutions are inefficient in most remote areas due to uneconomic returns especially in sparse remote areas. But, utilizing wireless communications on rural and remote communities is forecasted to be enormous. The aim of this research is to introduce existing and suitable wireless communication technologies that could potentially provide telecommunication infrastructure, plus cognitive radio technology which include many new opportunities will be a solution to increasing users and service demands effectively on changing environments and different working conditions by solving spectrum scarcity issue and IEEE 802.22 cognitive radio based wireless regional access network (WRAN) in order to achieve educational goals. ©2009 IEEE.

The cognitive radio (CR) based IEEE 802.22 is a standard for wireless regional area networks (WRANs), which is allowed to utilize TV bands when no interference is present to incumbents (i.e. TV receivers and microphones). Compared to other existing networks, it has larger coverage range and provides broadband access in rural and remote areas with performance comparable to DSL and cable modems. It is a promising networks for future wireless communications. When multiple networks deployed by different wireless service providers overlay each other in the same area, they would have to compete to access available TV channels. When more than one WRANs accesses the same channel, the interference occurs. This will cause some given quality of service (QoS) requirements to be unsatisfied. Appropriate strategy such that finding an available channel with minimum cost is needed. In this paper, we formulate the problem as a noncooperative game and establish the Nash equilibrium. Both theoretical and experimental analysis are conducted and demonstrate that the proposed strategy can find an available channel with smaller cost than that of other strategies.

This paper exhibits a methodology to achieve a system level design for Cognitive Radio (CR) receiver supporting IEEE 802.22 Standard. Based on superheterodyne receiver supporting Sub-Band Sensing, the overall radio system characteristics depicted from the IEEE 802.22 Standard specifications are dispatched through the different receiver blocks. Moreover, we developed the theoretical calculation and different techniques of system level design. Each of Radio Frequency (RF) characteristics such as noise figure (NF), gain and linearity (third order intercept point, (IIP3)) is simulated taking in account the analog-to-digital converter (ADC) full scale power constraint. On the one hand, our system level simulation results proved that the receiver architecture is capable to perform spectrum sensing and to allow communication processing. The receiver performs a total gain of 51 dB and an IIP3 of −19.8 dBm for low gain mode. It achieves 105dB as gain and 9.9 dB for noise figure for high gain mode.

In this paper, we use game theory to mitigate self-interference among cognitive radio based IEEE 802.22 networks such that these networks can efficiently co-exist. When a network experiences interference, it can adopt either one of two choices-switch to a new band hoping to find a non-interfering one, or stay with its current band hoping that the interfering network(s) will move away to a new band. We model the spectrum band switching process as an infinite horizon repeated game where the aim of each network (player) is to find a channel void of interference from it's neighboring networks incurring minimal cost. We investigate both pure and mixed strategy solution space of the game and show that pure strategy solution of the game is infeasible. Thus a mixed strategy is proposed which achieves subgame-perfect Nash Equilibrium. Simulation results reveal that using the proposed strategies, each network can find a clear channel quickly and at the same time incur a low cost.

IEEE 802.22 is the first worldwide wireless standard based on Cognitive Radio (CR) for Wireless Regional Area Networks (WRAN). Usually, Secondary Users (SUs) have to be interrupted periodically for spectrum sensing so as to avoid interference to Primary Users (PUs) operating in the licensed bands. Such interruptions of data transmission, however, impair the Quality of Service (QoS) of SUs. Dynamic Frequency Hopping (DFH) has been proposed for IEEE 802.22 system. In DFH, data transmission is performed in parallel with spectrum sensing without interruptions. In this paper, we compare this hopping mode with non-hopping one by computer simulation, the results show that although hopping mode requires a little more channels, it can reduce the collision with PUs and achieve higher ratio of valid delivery and higher throughput, thus provide enhanced QoS for SUs.

IEEE 802.22 wireless regional area network (WRAN) is an emerging cognitive radio-based system. One of the major challenges for WRANs is how to efficiently schedule both channel sensing and data transmission for multiple adjacent WRAN cells. This challenge is known as coexistence problem. In this paper, we propose four schemes that aim at reducing the coexistence-problem effect. These schemes are based on a well-known operation mode of IEEE 802.22, namely dynamic frequency hopping (DFH). The first and second schemes are based on using omni-directional antennas at the base stations (BSs), whereas the BSs in the other two schemes use directional antennas. The first scheme, coined fixed-scheduling DFH (FDFH), bases upon a fixed scheduling of working channels for adjacent WRAN cells. The second scheme, called cooperative DFH (CDFH), cooperatively selects working channels. The third scheme, namely sectoral DFH (SDFH), is proposed to reduce the coordination overhead of CDFH via dividing a WRAN cell into sectors to decrease the chances of collisions between adjacent cells. Finally, we integrate FDFH and SDFH into a new scheme, called fixed-scheduling sectoral DFH (FSDFH), which exploits the advantages of both schemes with no additional overhead. Computer simulations are used to demonstrate the performance gain of the proposed schemes.

Cognitive radios require spectrum sensing. IEEE 802.22 defines constraints on conceivable spectrum sensing techniques. In order to fulfill theses constraints on the required detection probability and allowed false alarm probability, the signal sensing requires a certain sensing time period and an appropriately adjusted decision threshold. This manuscript presents a novel dynamic spectrum sensing scheme which is based on soft outputs. The novel scheme allows the reduction of the sensing time in order to save calculation and power effort.

Security in wireless networks is challenging. Security in cognitive radio networks (CRN) is even more challenging. This is because a CRN consists of cognitive radios (CR) which have many more functions and processes to account for, such as sensing, geolocation, spectrum management, access to the policy database etc. Each of these functions and processes need to be assessed for potential vulnerabilities and security mechanisms need to be provided for protection of not just the secondary users of the spectrum but also the primary users or the incumbents. This paper discusses the potential security vulnerabilities and the remediations for the same in a CRN with an example using a commercial IEEE 802.22 standard. Due to the unique characteristics of the CRs in a CRN, enhanced security mechanisms are required. The security mechanisms in CRN are divided into several security sub-layers which protect non-cognitive as well as cognitive functions of the system and the interactions between the two. This paper describes these security features as incorporated into the IEEE 802.22 standard. It is possible to apply similar security mechanisms for a military CRN.

Carrier Interferometry (CI) codes have been proposed for multi-carrier systems, e. g., Orthogonal Frequency Division Multiplex (OFDM), which achieves higher transmission rate and lower Peak to Average Power ratio (PAPR). In this paper, Non-continuous Carrier Interferometry (NCI) codes have been constructed for the non-continuous multi-carrier systems. In the cognitive radio system such as IEEE 802.22, Non-Continuous OFDM is employed to avoid interference for spectrum holes. In this scheme, all the subcarriers within the spectrum holes are activated. Otherwise, the subcarriers are deactivated. This mechanism is quite suitable to involve NCI codes and formulate the NCI-OFDM system. Simulation results show that the NCI-OFDM system enjoys a wonderful transmission rate and low PAPR compared with the traditional NC-OFDM, which confirms that the NCI-OFDM is a promising transmission scheme for broadband cognitive radio systems.

To avoid interferences, network-wide quiet periods (QPs) are usually scheduled for the purpose of channel sensing in cognitive radio (CR) networks. The recent IEEE 802.22 draft standard requires that adjacent base stations (BSs) should synchronize their QP in scheduling. However, we find that the current design is incomplete in handling the dynamic of synchronized QP. The problem is that BSs cannot handle the decreasing of synchronized QP duration. This can cause the wastage of network resources. To solve the problem, we propose a Synchronization Counter (SC)-based method in this paper. With the method, the BSs can accurately synchronize the QP when the duration varies. It makes the synchronization more accurate and thus saves the network resources. We have verified the proposed scheme with simulation and provide the performance results that reveal the basic features of network-wide QP synchronization.

An analytical formulation of the mean detection time and the distribution of the detection time of a wireless microphone (primary user) in an IEEE 802.22 wireless regional area network (WRAN) is presented. The IEEE 802.22 WRAN has a number of customer-premises equipments (CPEs) in the coverage area of its base station. Out of this number of CPEs, a number of them are within the coverage area of the microphone. All of the CPEs can be inactive or active. This is modeled by a discrete time Markov chain. If the microphone turns on or becomes active, the WRAN must be able to detect the microphone and vacates the channel within a time threshold. It is assumed that as long as one of the active CPEs, within the coverage area of the microphone, detects the microphone as active, the microphone is detected. The mean and the distribution of the detection time of the microphone are derived by modeling the detection time by an absorbing discrete time Markov chain. Numerical results corresponding to typical parameter values are presented. The tradeoffs among the number of CPEs, coverage range of the wireless microphone (primary user) and probability of detection are investigated.

In this paper, we propose two novel data fusion schemes for cooperative spectrum sensing in the IEEE 802.22 WRAN system. The data fusion structure is proper for the WRAN system due to its centralized structure, and it can provide reliable sensing performance. The proposed data fusion schemes improve the sensing reliability by utilizing confidence vector of the sensing result. Moreover, application with statistic weight on the confidence vector provides additional performance gain. The computer simulation results show that the proposed data fusion methods guarantee better sensing performance than the conventional data fusion algorithms.

IEEE 802.22 is the first wireless standard based on cognitive radio (CR) technology. It defines the air interface for a wireless regional area network (WRAN) that uses fallow segments of the TV broadcast bands. CR technology enables unlicensed users in WRANs to utilize licensed (incumbent) spectrum bands on a non-interference basis to incumbent users. The coexistence between incumbent users and unlicensed users is referred to as incumbent coexistence. On the other hand, the coexistence between unlicensed users in different WRAN cells is referred to as self-coexistence. 802.22 defines several inter-base station (BS) dynamic resource sharing mechanisms to enable overlapping cells to share spectrum. However, those mechanisms do not adequately address some of the key issues concerning incumbent and self coexistence. In this paper, we propose an inter-BS coexistence-aware spectrum sharing (CASS) protocol for overlapping 802.22 cells that takes into account coexistence requirements. We show that the proposed protocol outperforms 802.22's self-coexistence solutions using simulation results. To the best of our knowledge, the work presented here is the first systematic study of the self-coexistence problem in the context of 802.22 WRANs.