Search

Wide-area communication systems using TV white space (TVWS) are promising technologies capable of full-coverage and cost-effective vehicular and transportation communications owing to their excellent propagation characteristics. IEEE 802.22 was developed as a TVWS-based fixed communication standard to support a wide coverage area of 10–30 km. To cope with the various applications in mobile communication, the transmission performance needs to be enhanced and evaluated. Thus, it becomes necessary to develop an experimental platform to enable the flexible implementation of transmitter and receiver algorithms. In this regard, we propose a software-defined radio (SDR)-based evaluation platform enabling the bench testing of physical layer (PHY) performance for highly mobile IEEE 802.22 communication systems. Using this platform, radio frequency signals can be transmitted and received using reconfigurable hardware and software, with the received baseband signals being recorded and stored by the SDR device. The stored data were post-processed using a MATLAB-based program to evaluate the transmission performance. The performance achieved by SDR-based evaluation system is similar to computer simulations, thereby demonstrating the feasibility of highly mobile IEEE 802.22 communication systems. Moreover, the proposed evaluation platform is available for future field experiments to encourage the development and evaluation of novel PHY algorithms.

During the design and development of a reliable transceiver, its performance and robustness are evaluated using channel models that simulate the propagation channel characteristics in a real-world environment. In the case of wide-area communication systems in rural areas such as those based on TV white spaces, long delay multipath fading is one of the dominant factors impairing communication quality, and it is important to apply realistic multipath fading channel models in various application scenarios. Therefore, it is necessary to develop channel measurement and modeling systems that adaptively obtain channel factors and reflect multipath propagation characteristics in various wide-area communication environments. In this study, we developed a flexible channel measurement and modeling prototype applicable to mobile IEEE 802.22-based wide-area communication systems, which can be simply implemented by using programmable hardware and software. The prototype includes a new channel modeling framework that applies an improved double exponential slope model to extract the essential factors of multipath propagation characteristics. To validate the developed prototype, a fading emulator is applied to it to measure the raw data used for modeling. As a result, the multipath fading characteristics measured with the prototype were successfully modeled and reproduced by the proposed channel modeling framework with a high fitness of root mean square delay spread distribution. The derived bit error rate characteristics agreed better with the simulation results compared to the conventional channel model.

The continuous growth of demand experienced by wireless networks creates a spectrum availability challenge. Cognitive radio (CR) is a promising solution capable of overcoming spectrum scarcity. It is an intelligent radio technology that may be programmed and dynamically configured to avoid interference and congestion in cognitive radio networks (CRN). Spectrum sensing (SS) is a cognitive radio life cycle task aiming to detect spectrum holes. A number of innovative approaches are devised to monitor the spectrum and to determine when these holes are present. The purpose of this survey is to investigate some of these schemes which are constructed based on machine learning concepts and principles. In addition, this review aims to present a general classification of these machine learningbased schemes

The IEEE 802.22 standard targets rural and sparsely populated regions exploiting television white space (TVWS) technology. In these regions, there are fewer mobile users per density and end-user traffic is light. Hence, there is a need to adopt traffic aware algorithm leveraging on the end-user nonuniform traffic attributes and in essence, promote spectrum efficiency in the TVWS spectrum-management regime. This paper investigates a mechanism to encourage spectrum sharing during low end-user traffic regime motivated by financial inducement. Since incumbent coexistence has been achieved using market models, it is tractable to apply market-assisted spectrum sharing models to address self-coexistence issues in TVWS networks. The purpose of this paper is to use the market model to promote self-coexistence in TVWS networks in the uplink self-frequency reuse. Toward this goal, this paper proposes discounted spectrum price game-based resource allocation in a competitive environment (D-GRACE). Specifically, D-GRACE is a transmit power reduction strategy motivated by financial incentives during light TVWS end-user traffic. When compared with an existing non-market-inspired TVWS self-coexistence resource allocation algorithm under the same scenario, D-GRACE exhibited superior power savings of about 20% and converged after five iterations.

The continuous growth of demand experienced by wireless networks creates a spectrum availability challenge. Cognitive radio (CR) is a promising solution capable of overcoming spectrum scarcity. It is an intelligent radio technology that may be programmed and dynamically configured to avoid interference and congestion in cognitive radio networks (CRN). Spectrum sensing (SS) is a cognitive radio life cycle task aiming to detect spectrum holes. A number of innovative approaches are devised to monitor the spectrum and to determine when these holes are present. The purpose of this survey is to investigate some of these schemes which are constructed based on machine learning concepts and principles. In addition, this review aims to present a general classification of these machine learning-based schemes. [ABSTRACT FROM AUTHOR]

Wireless communication channels are highly prone to interference in addition to the presence of additive white Gaussian noise (AWGN). Stochastic gradient (SG)-based non-parametric maximum likelihood (NPML) estimator, gives better channel estimates in the presence of Gaussian mixture (AWGN plus interference) noise processes, for subsequent use by the channel equalizer. However, for sparse channels, the SG-NPML-based channel estimator requires large iterations to converge. In this paper, we propose a natural gradient (NG)-based channel estimator for sparse channel estimation in the presence of high interference. We propose a generalized pth order warping transformation on channel coefficients space and then calculate the Riemannian metric tensor, thereby resulting in faster convergence in interference limited channels. The proposed algorithm is applied for IEEE 802.22 (based on orthogonal frequency division multiplexing) channel estimation in the presence of interference. Extensive simulations and experimental results show that the proposed NG-based algorithm converges faster than SG-NPML for the same mean squared error (MSE) floor with similar computational complexity per iteration as an SG-NPML algorithm. We also present convergence analysis of proposed NG-NPML algorithm in the presence of Gaussian mixture noise and derive an analytical expression for the steady-state MSE.

With rapid increase in new applications and services, there is huge demand for internet bandwidth. Several researchers around the world have found that, majority of licensed bands (mostly terrestrial TV band) are either unused or underused. These underutilized bands allocated for TV transmission are known as TV white space (TVWS). For effective utilization of TVWS, the IEEE 802.22 is proposed. The IEEE 802.22 wireless regional area network (WRAN) is the latest standard for effective utilization of TV bands. This standard is based on orthogonal frequency division multiplexing with various modulation techniques to provide different data rates. In this paper, an implementation framework for physical layer of IEEE 802.22 WRAN standard for normal mode is demonstrated and analyzed. This transceiver is implemented using the National Instruments Laboratory Virtual Instrument Engineering Workbench programming software on the National Instruments universal software radio peripheral 2952R. We have also analyzed different blocks of IEEE 802.22 based on their execution time, and identify the critical blocks of IEEE 802.22 that should be optimized for real-time applications for commercial product development and field deployments. We have also highlighted the difference between theoretical and practical performance of the considered error control codes for IEEE 802.22 specified block size. Additionally, various covariance based spectrum sensing methods are also analyzed for real-world environment. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A two-hop wireless regional area network (WRAN) providing monitoring services operating in Television White Space (TVWS), i.e., IEEE P802.22b, may employ a great number of subscriber customer-premises equipments (S-CPEs) possibly without mains power supply, leading to requirement of cost-effective and power-saving design. This paper proposes a framework of cooperative spectrum sensing (CSS) and an energy/bandwidth saving CSS scheme to P802.22b. In each round of sensing, S-CPEs with SNRs lower than a predefined threshold are excluded from reporting sensing results. Numerical results show that the fused missed-detection probability and false alarmprobability could remainmeeting sensing requirements, and the overall fused error probability changes very little. With 10 S-CPEs, it is possible to save more than 40% of the energy/bandwidth on a Rayleigh channel. The principle proposed can apply to other advanced sensing technologies capable of detecting primary signals with low average SNR.

Ensuring self-coexistence among IEEE 802.22 networks is a challenging problem owing to opportunistic access of incumbent-free radio resources by users in co-located networks. In this study, we propose a fully-distributed non-cooperative approach to ensure self-coexistence in downlink channels of IEEE 802.22 networks. We formulate the self-coexistence problem as a mixed-integer non-linear optimization problem for maximizing the network data rate, which is an NP-hard one. This work explores a sub-optimal solution by dividing the optimization problem into downlink channel allocation and power assignment sub-problems. Considering fairness, quality of service and minimum interference for customer-premises-equipment, we also develop a greedy algorithm for channel allocation and a non-cooperative game-theoretic framework for near-optimal power allocation. The base stations of networks are treated as players in a game, where they try to increase spectrum utilization by controlling power and reaching a Nash equilibrium point. We further develop a utility function for the game to increase the data rate by minimizing the transmission power and, subsequently, the interference from neighboring networks. A theoretical proof of the uniqueness and existence of the Nash equilibrium has been presented. Performance improvements in terms of data-rate with a degree of fairness compared to a cooperative branch-and-bound-based algorithm and a non-cooperative greedy approach have been shown through simulation studies. [ABSTRACT FROM AUTHOR]

Data communication networks are a vital component of any modern society. They are used extensively in numerous applications, including financial transactions, social interactions, education, national security and commerce. In particular, both wired and wireless devices are capable of performing a plethora of advanced functions that support a range of services, such as voice telephony, web browsing, streaming multimedia and data transfer [1]. With the rapid evolution of microelectronics, wireless transceivers are becoming more versatile, powerful and portable. In the wireless technology the major issue is the issue of spectrum utilization. The utilization of spectrum has increased to its maximum level. To tackle this issue the technology named cognitive radio was introduced to the rescue. The cognitive radio is an emerging technology that facilitate dynamic spectrum access in wireless networks. The cognitive radio is capable of expediently using the obtainable portions of a licensed spectrum to improve the application performance for unlicensed users. The opportunistic access of the accessible channels in the wireless environment requires dynamic channel assignment to efficiently utilize the available resources while minimizing the interference in the network. In this paper we are focusing the different traffic types such video and voice. In the voice we have different codec and in the video application we have different model types from which we need to choose the best for the optimum results. [ABSTRACT FROM AUTHOR]

This paper deals with a symbiotic radar, defined as a passive radar that is an integral part of a communication network. The symbiotic radar is integrated with an IEEE 802.22 Wireless Regional Area Network and linked with the base station. It can work as a purely passive radar or, and this is the novelty in the system, can use the base station to suggest the best customer premise equipment that should be scheduled for transmission to improve tracking performance. This paper defines a cognitive passive tracking algorithm that exploits the feedback information contained in the target state prediction to improve the performance while preserving the communication capabilities of the complete network. [ABSTRACT FROM PUBLISHER]

Este artigo apresenta um resumo sobre o padrão IEEE 802.22 para redes regionais sem fi o baseadas em rádio cognitivo. Essas redes foram, originalmente, criadas com o objetivo de prover serviço de banda larga a regiões rurais. O IEEE 802.22 reutiliza o espectro alocado para os canais de televisão sem prejudicar signifi cativamente os receptores licenciados de TV. Para isso, usa apenas canais vagos ou temporariamente ociosos. O rádio cognitivo utiliza técnicas para detectar a atividade do espectro, tendo parâmetros de reconfi gurar suas características de transmissão/recepção conforme a disponibilidade encontrada

As the first standard for cognitive radio networks, IEEE 802.22 wireless regional area networks (WRANs) exploit television white spaces. Secondary networks have to preserve primary network communications and to coexist with other secondary networks. To support self-coexistence in the IEEE 802.22 WRANs, two spectrum access methods are provided; namely, spectrum etiquette and on-demand frame contention (ODFC). The IEEE 802.22 base stations conduct the spectrum etiquette if there is an exclusively available channel; otherwise, it performs ODFC. ODFC enables the base stations to share the operating channel. However, in ODFC, contention success or failure depends on a random number generator without other considerations and contention destination is randomly selected regardless of the traffic at the destination. This paper proposes a novel frame contention strategy called highly successful frame contention (HSFC). The outstanding features of HSFC are: (1) the contention source chooses the idlest base station as the contention destination (2) the contention source with more users has a higher probability to win the frame contention, and (3) the contention destination takes its own traffic condition into consideration when processing the contention request. The performance evaluation showed that the proposed HSFC increases contention success probability and throughput remarkably compared to the conventional ODFC. [ABSTRACT FROM AUTHOR]

As cooperative spectrum sensing improves the detection probability, the multiple-input multiple-output (MIMO) system spatially transmits multiple copy of data independently to improve capacity and the IEEE 802.22 wireless regional area network standard aims to utilize the digital video broadcasting-terrestrial (DVB-T) bands opportunistically for data communication to the rural area, we consider a cooperative MIMO based reporting system where the cognitive radio users forward the DVB-T signal to the fusion center (FC) using time division multiple access. The network is operating over AWGN sensing channel and the reporting channel experiences an independent and identically distributed Rayleigh, Rician fading. We arrive an expression for average detection probability at FC for maximum ratio combining scheme. We consider the FC has the prior knowledge about the reporting channel. We analyze the system performance under various MIMO scenarios through Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

A 50 MHz-1 GHz low-noise amplifier circuit with high linearity for IEEE 802.22 wireless regional area network is presented. It was implemented without any inductor and offers a differential output for balun use. Noise canceling and linearity boosting techniques were combined to improve the amplifier performance in such a way that they can be separately optimized. Linearity was improved using diode-connected transistors. The amplifier was implemented in a 130 nm CMOS process in a compact 136 μm × 71 μm area. Simulations are presented for post-layout schematics for two classes of design: one for best linearity, another for best noise figure (NF). When optimized for best linearity, simulation results achieve a voltage gain >23.7 dB (power gain >19.1 dB), a NF <3.6 dB over the entire band (with 2.4 dB min figure), an input third-order intercept point (IIP3) >3.3 dBm (7.6 dBm max.) and an input power reflection coefficient S <−16 dB. When optimized for best NF, it achieves a voltage gain >24.7 dB (power gain >19.8 dB), a NF <2 dB over the entire band, an IIP3 >−0.3 dBm and an S <−11 dB. Monte Carlo simulation results confirm low sensitivity to process variations. Also a low sensitivity to temperature within the range −55 to 125 °C was observed for Gain, NF and S11. Power consumption is 18 mW under a 1.2 V supply. [ABSTRACT FROM AUTHOR]

Copyright of Arab Gulf Journal of Scientific Research is the property of Arabian Gulf University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The search for a method of utilizing the scarce spectrum in an efficient manner is an active area of research in both academic and industrial communities. IEEE 802.22 is a standard for wireless regional area network (WRAN) based on cognitive radio (CR) that operates over underutilized portions of TV bands (54-862MHz). Time division duplex (TDD)-based WRAN cells have such advantages as dynamic traffic allocation, traffic asymmetry to users and ease of spectrum allocation. However, these cells suffer from severe cross time slot (CTS) interference when the frames of the cells are not synchronized with adjacent WRAN cells. In this paper, we evaluate the location-based duplex (LBD) scheme for eliminating the CTS interference. The proposed LBD system is much more flexible and efficient in providing asymmetric data service and eliminating CTS interference by exploiting the advantages of both TDD and frequency division duplex (FDD) schemes. We also compare the performance of LBD systems with virtual cell concepts. Furthermore, our simulation results reveal that LBD-based systems outperform the virtual cell approach in terms of the low signal-to-interference (SIR) ratio requirement by mitigating the effects of CTS. [ABSTRACT FROM AUTHOR]

Topics include an intensification of the digital crime wave that began in late 2013; technology companies supporting an inexpensive wireless technology that could bring Internet access to poor and remote areas; Intel developing a small, energy-efficient chip that could enable ultrathin mobile devices; a new approach that lets huge robot swarms self-assemble into complex shapes; scientists using visible light for car-to-car communications; NATO preparing to approve a mutual cyberattack defense pact; systems that secretly track cell phone owners' movements becoming increasingly popular; NASA developing tumbling robotic cubes for exploring asteroids; ransomware being found on Android phones for the first time; researchers naming the most hackable cars; and a list of US colleges providing computer-science graduates with the greatest earning potential. [ABSTRACT FROM PUBLISHER]

The recent emergence of the cognitive radio standard IEEE 802.22 is finally empowering network operators with a new platform for their abundant services. Likewise previous wireless standards, where the modeling helped in a better understanding of the concepts and played an important role in extending the outreach of the technology and subsequent innovations, the modeling of IEEE 802.22 wireless regional area networks (WRANs) is a necessity. In this work, we accomplish this task using the theory of queues. To that end, we model the dynamics of each cognitive user, termed customer premises equipments (CPE) according to the standard terminology, with a 2-D Markov chain. Given this model, we show that a WRAN cell can be modeled as a Jackson network. We also find the probability mass function (PMF) and cumulative distribution function (CDF) of the CPE queue length, from which any higher moment can be derived. Notable is the fact that said PMF is expressed in an exact closed-form. In addition to the nodal analysis, a WRAN cell-level discussion is conducted by finding the stability condition and peer-to-peer delay. Moreover, we provide preliminary results on the resource allocation in WRANs, which is a very important area of focus and discovery for an efficient deployment and operation of future WRANs. [ABSTRACT FROM PUBLISHER]

Abstract: 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. [Copyright &y& Elsevier]

Wireless Regional Area Network is a standard named IEEE 802.22 Working Group purposed in Nov 2004. The task was to develop an air interface (i.e., PHY and MAC) based on CRs for unlicensed operation in the TV broadcast bands. For this the cognitive radio techniques are of primary importance in order to sense and measure the spectrum and detect the presence/absence of incumbent signals. There are various sensing methods to avoid the inference with the licensed users. In this paper various sensing techniques are considered and by comparing we find out which one is best suitable in WRANs [ABSTRACT FROM AUTHOR]

We present an analytical model that enables the evaluation of opportunistic spectrum orthogonal frequency division multiple-access (OS-OFDMA) networks using metrics such as blocking probability or, most importantly, throughput. 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. In addition, we consider studies of cochannel interference. The analysis is applied to the IEEE 802.22 standard to evaluate the impact of the two-stage spectrum sensing strategy and the varying temporal activity of wireless microphones on the system throughput. In addition to the analytical model, we present a set of comprehensive simulation results using NS-2 related to the delay performance of the OS-OFDMA system considered. Our study suggests that OS-OFDMA with subchannel notching and channel bonding could provide almost ten times higher throughput compared with a design without these options when the activity and density of wireless microphones are very high. Furthermore, we confirm that OS-OFDMA implementation without subchannel notching, which is used in the IEEE 802.22, can support the real-time and non-real-time quality of service classes, provided that the temporal activity of wireless microphones is moderate (with sparse wireless microphone distribution, with light urban population density and short duty cycles). Finally, the two-stage spectrum sensing option improves the OS-OFDMA throughput, provided that the length of spectrum sensing at every stage is optimized using our model. [ABSTRACT FROM PUBLISHER]

SUMMARY In IEEE 802.22 wireless regional area networks (WRAN), it is indispensable to prevent the in-use channel from interfering with incumbent services such as digital TV. To achieve this end, in this paper, we propose a dynamic frequency hopping based on rank accounting. In this method, a base station utilizes a ranking database where a rank of a channel which is used frequently is high. Each base station uses an idle channel whose rank is the highest based on the database, and hence this can reduce the number of channels which are used for the data transmission. Moreover, the proposed method performs interference avoidance processes. The proposed method does not require a strict coordination for base stations. We evaluate the performance of the proposed method with simulation. Numerical examples show that the failure probability of the channel switching for the proposed method is smaller than that for the conventional random method. It is also shown that the number of channels that are used for the data transmission can be reduced by using the proposed method. Finally, we investigate the performance of the proposed method in some situations. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A 54–862-MHz single-chip CMOS transceiver with a single LC voltage-controlled oscillator (VCO) fractional-N synthesizer is developed for TV-band white-space communications and cognitive radio applications. The transceiver is based on a single-conversion zero-IF architecture with integrated harmonic filtering capability. A combined harmonic rejection mixer and coarse RF tracking filter significantly lessens the in-band harmonic emission problem in the transmitter, as well as the harmonic mixing problem in the receiver. A fractional-N phase-locked loop (PLL) with only a single LC VCO and a wideband multimodulus local oscillator (LO) generator seamlessly covers the entire band. A wideband semi-dynamic divide-by-1.5 circuit is adopted in the LO generator to reduce the VCO tuning range requirement by 25 %. A pseudoexponential capacitor bank structure in the LC VCO substantially reduces the KVCO and fstep variations across the total band, which is beneficial for maintaining the PLL loop stability and dynamics over the wide band. The transceiver is implemented in 0.18-\mum CMOS, and operates with a single 1.8-V supply. The transmitter delivers a nominal output power of -\3 dBm, and exhibits OP1\ {dB} of > +\6.4 dBm, OIP3 of > +\15.9 dBm, and error vector magnitude (EVM) of < -\34.7 dB for 64-QAM signal. The image and carrier leakage calibration circuits suppress the leakage components below -\41 dBc across the entire band. The receiver achieves about 100-dB gain dynamic range, 3.5–6.9-dB noise figure, < -\29-dB EVM, and -\43.4/-\59.7-dBc third/fifth harmonic mixing suppression. The synthesizer and LO generator achieves the integrated phase noise < \0.8 rms degree over the entire band. [ABSTRACT FROM AUTHOR]

IEEE 802.22 is the first cognitive-radio-based wireless communication standard. To manage resource sharing, IEEE 802.22 designs an interbase station (inter-BS) coexistence mechanism enabling distributed competing BSs to coexist effectively. In this IEEE 802.22 mechanism, BSs could be considered as players optimizing their own performance in a self-organizing way. Therefore, it is suitable to apply game theory to model the convergence of self-organizing behaviors. An operating point where no BS can unilaterally increase its performance describes an outcome of the inter-BS coexistence mechanism; this steady-state operating point is the well-known Nash equilibrium in game theory. In this paper, an IEEE 802.22 inter-BS coexistence issue is investigated from a game-theoretical perspective. As the IEEE 802.22 standard defines the inter-BS coexistence mechanism, we design a resource-transaction algorithm to realize IEEE 802.22 dynamic resource renting and offering (DRRO) and adaptive on-demand channel contention (AODCC) operation. We also use game theory to model and analyze the proposed algorithm. In game analysis, we first study a two-player game through a graphical method to gain insights for the solution. Afterward, we investigate a general n-player game and derive the Nash equilibrium where the resource allocation is uniquely determined. The resource allocation is efficient, as the overall system performance is maximized (allocative efficiency), and no BS can further improve its performance without impairing others (Pareto optimality). The resource allocation also achieves max-min fairness and proportional fairness. Furthermore, the proposed algorithm ensures all resource acquirers' participation without resource loss (individual rationality). It also guarantees revenue maximization of the resource provider. [ABSTRACT FROM AUTHOR]

An active resistor-capacitor low-pass filter with simultaneously programmable high-end and low-end cutoff frequencies is presented for IEEE 802.22 cognitive radio transmitter applications. Transfer function analysis shows that the integrator frequency of a dc offset cancellation block should be tuned inversely proportional to the open-loop gain to maintain the low-end cutoff frequency at a constant value. Realized in a 0.18-μm complementary metal-oxide-semiconductor, the low-end cutoff frequency is successfully tuned between 740 Hz and 10 kHz over the 30-dB gain variation. Measured results show that the gain is tuned from -16.3 to +13.9 dB, and the high-end cutoff frequency is tuned from 2.1 to 6.04 MHz, while drawing 4.5 mA from a 1.8-V supply. [ABSTRACT FROM AUTHOR]

Cognitive radio (CR) has been suggested as a method for promoting more efficient spectrum usage through the principles of spectrum sensing and dynamic spectrum management. The IEEE 802.22 working group in particular is developing a wireless regional-area network (WRAN) standard that will employ unlicensed CR devices operating on a noninterfering basis in the commercial broadcast television (TV) bands. Before such TV-band CR networks can be deployed, the maximum levels of first adjacent and taboo channel interference that a digital television (DTV) receiver can tolerate must be determined. In this context, we will first provide an overview of the IEEE 802.22 WRAN system. Afterwards, we will report on an experimental study that was undertaken to characterize IEEE 802.22 WRAN interference limits into Advanced Television Systems Committee (ATSC) based DTV receivers. Lastly, we will discuss the implications of these WRAN interference limits in terms of the maximum allowable radiated power and out-of-band emission limits that are imposed on WRAN end-user devices. [ABSTRACT FROM AUTHOR]

We propose a closed-loop multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) transmission scheme appropriate for the IEEE 802.22 wireless regional area network (WRAN) channel environments. The proposed scheme utilizes the Grassmannian beamforming and an antenna selection algorithm to main-thin bit-error-rate (BER) performance and to reduce feedback information. To further reduce the feedback information considering the channel property of the IEEE 802.22 WRAN, the proposed scheme employs an extension of the feedback period and subcarrier grouping. Simulation results in the IEEE 802.22 WRAN reference channel models indicate that the proposed MIMO-OFDM transmission scheme achieves superior BER performance and spectral efficiency than open-loop MIMO-OFDM system even considering the feedback overhead of the system. [ABSTRACT FROM AUTHOR]

We propose to use IEEE 802.22 networks as a natural interconnection between energy-constrained networks, such as sensor networks, and the Internet. In this interconnection scenario, we propose Activecast, broadcast designed as a continuation of the IEEE 802.22 broadcast on sensor networks. Activecast effectively transmits a query to all active sensors in the network. Activecast minimizes the number of retransmitted messages while maintaining high reachability. Activecast requires minimum communication overhead, yet performs very well in the presence of various environmental constrains. Activecast can also be integrated to any sleep based sensor protocol, as it does not make any assumptions on the underlying wake up scheduling protocol and wake up times/durations of the sensors. We study the properties of Activecast by analysis and simulations while also considering irregular radio coverage of sensors. [ABSTRACT FROM AUTHOR]

• Opportunistic spectrum usage based sensor network is utilized for agricultural monitoring. • Incumbent channels are exploited without any spectrum cost. • Terrestrial and underground networks are designed separately according to environmental characteristics. • The validity and applicability of the proposed network are proven with graphical results. • Agricultural monitoring with terrestrial and underground sensor networks is simulated with Riverbed Modeler. 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. [ABSTRACT FROM AUTHOR]

Cooperative (or distributed) sensing has been recognized as a viable means to enhance the incumbent signal detection by exploiting the diversity of sensors. However, it is challenging to secure such distributed sensing due mainly to the unique features of dynamic spectrum access networks—openness of low-layer protocol stacks in software-defined radio devices and the absence of interactions/coordination between primary and secondary devices. To meet this challenge, we propose an attack-tolerant distributed sensing protocol (ADSP) for DTV signal detection in IEEE 802.22 WRANs, under which sensors in close proximity are grouped as a cluster, and sensors within a cluster cooperate to safeguard the integrity of sensing. The heart of ADSP is a novel filter based on shadow-fading correlation, by which the fusion center cross-validates reports from the sensors to identify and penalize abnormal sensing reports. By realizing this correlation filter, ADSP significantly reduces the impact of an attack on the performance of distributed sensing, while incurring minimal processing and communication overheads. ADSP also guarantees the detectability requirements of 802.22 to be met even with the presence of sensing report manipulation attacks by scheduling sensing within the framework of sequential hypothesis testing. The efficacy of ADSP is validated on a realistic 2D shadow-fading field. Our extensive simulation-based study shows that ADSP reduces the false-alarm rate by 99.2 percent while achieving 97.4 percent of maximum achievable detection rate, and meets the detection requirements of IEEE 802.22 in various attack scenarios. [ABSTRACT FROM PUBLISHER]

Spectrum sensing is required for many cognitive radio applications, including spectral awareness, interoperability, and dynamic spectrum access. Any approach is highly dependent on the signal environment in which it operates. Noise, multipath channel distortion, sample-rate offsets, and center-frequency mis-estimations can make feature-based signal detection difficult. Additionally, as these values change in a dynamic environment, statically-trained classifiers cannot track the evolving class statistics. Unsupervised learning allows a cognitive radio system to evolve its classifier as the radio environment evolves, without the need for expert-annotated signal samples. While this allows improved classifier performance, previous work has demonstrated that unsupervised techniques developed without security in mind suffer from classifier manipulation through transmission of carefully crafted signals that shift decision boundaries. This paper develops countermeasures to the class manipulation attacks that mitigates their efficacy, and shows the robustness of unsupervised learning for signal classification in an evolving RF environment. [ABSTRACT FROM PUBLISHER]

In cognitive radios, in-band spectrum sensing is essential for the protection of legacy spectrum users, enabling secondary users to vacate channels immediately upon detection of primary users. For in-band sensing, it is important to meet detectability requirements, such as the maximum allowed detection latency and the probability of misdetection and false alarm. In this paper, we propose key techniques for efficient in-band sensing. We first advocate the use of clustered sensor networks, and propose a periodic in-band sensing algorithm that optimizes sensing period and sensing time to meet the detectability requirements while minimizing sensing overhead. The scheme also determines the better of energy or feature detection incurring less sensing overhead at each SNR level, and derives the threshold aRSSthreshold on the average received signal strength of a primary signal above which energy detection is preferred to feature detection. We consider two key factors affecting aRSSthreshold: noise uncertainty and inter-CRN interference. aRSSthreshold appears to lie between -114.6 dBm and -109.9 dBm with noise uncertainty ranging from 0.5 dB to 2 dB, and between -112.9 dBm and -110.5 dBm with 1-6 interfering CRNs. We also investigate how strict the detection requirement must be for efficient reuse of idle channels without incurring unnecessary channel switches due to false detection of primaries. [ABSTRACT FROM PUBLISHER]