Cognitive radio applications for enhanced spectrum efficiency

Growing demand of reliable and affordable wireless connectivity requires alternative solutions and television white space (TVWS) provides that opportunity. However, the biggest challenge in TV spectrum re-use is to allocate best channels for secondary user while maintaining good Quality of Service (QoS). Allocation of Secondary User (SU) channels with less interference to Primary User (PU) is still a challenge not only to academia research communities but to industry as well. We studied the spectrum selection method of geo-location database (GLDB) that provides certainty in selecting available white space spectrum in the geographical area of request. The Internet Engineering Task Force (IETF) developed a standard communication protocol between the GLDB and white space devices (WSD) in order to establish reliable communication method for WSD. In this paper, a protocol to access white space (PAWS) method combined with analytical hierarchy process (AHP) is proposed for best channel selection from the GLDB. MATLAB simulation platform was used to test the performance of the proposed technique. The results show that the algorithm using proposed AHP based method (with deterministic queuing model within WSD) selects the best operating channel based on a better global priority vector (GPV). The numerical results show that the proposed selection technique is capable of selecting the best channels that satisfy the QoS for SUs profiles as compared to existing techniques.

In this paper, we investigate how to acquire spectrum information for accessing the available TV white space quickly. It is known that the load of secondary device can be reduced by utilizing geolocation database. A channel allocation algorithm based on geo-location and positioning accuracy is proposed by using geo-location database in order to further reduce the secondary device's load and sensing cost. Based on the geo-location and positioning accuracy of white space devices (WSDs), the proposed algorithm first allocates the available channels to the WSD which locates outside the keepout region of TV stations. Then, it allocates the channels to the WSDs within the scope of protection of TV station, and in this case the WSD has to sense the allocated channels to determine whether they are idle using the energy detection algorithm. Detailed simulations show that the proposed algorithm effectively reduces the sensing costs and information feedback overhead, and improves the throughput and spectrum efficiency of the whole system.

TV White Spaces technology is a means of allowing wireless devices to opportunistically use locally-available TV channels (TV White Spaces), enabled by a geolocation database. The geolocation database informs the device of which channels can be used at a given location, and in the UK/EU case, which transmission powers (EIRPs) can be used on each channel based on the technical characteristics of the device, given an assumed interference limit and protection margin at the edge of the primary service coverage area(s). The UK regulator, Ofcom, has initiated a large-scale Pilot of TV White Spaces technology and devices. The ICT-ACROPOLIS Network of Excellence, teaming up with the ICT-SOLDER project and others, is running an extensive series of trials under this effort. The purpose of these trials is to test a number of aspects of white space technology, including the white space device and geolocation database interactions, the validity of the channel availability/powers calculations by the database and associated interference effects on primary services., and the performances of the white spaces devices, among others. An additional key purpose is to undertake a number of research investigations such as into aggregation of TV White Space resources with conventional (licensed/unlicensed) resources, secondary coexistence issues and means to mitigate such issues, and primary coexistence issues under challenging deployment geometries, among others. This paper describes our trials, their intentions and characteristics, objectives, and some early observations.

We propose a novel information market for TV white space networks, where white space databases sell the information regarding the TV channel quality to unlicensed white space devices (WSDs). Different from the traditional spectrum market, the information market demonstrates the positive network externality, as more WSDs purchasing the information from a database will increase the value of the database's information to each of its buyers. We study an oligopoly information market, where two competitive databases compete to sell their information to WSDs, and WSDs decide whether and from which database to purchase the information. Specifically, we first derive the WSD's optimal purchasing behavior under fixed information prices, and show how the market share of each database dynamically evolves over time. We then characterize the market equilibrium, where no WSD has an incentive to change its purchasing behavior. Our analysis indicates that given the prices of databases, there may be multiple market equilibria, and which one actually emerges depends on the initial market shares of both databases. We further show that some equilibria are stable, in the sense that a small fluctuation on the equilibrium will drive the market back to the equilibrium, while some equilibria are not.

Advent of TV white space digitization has released frequencies from 470 MHz to 790 MHz to be utilized opportunistically. The secondary user can utilize these so called TV spaces in the absence of primary users. The most important challenge for this coexistence is mutual interference. While the strong TV stations can completely saturate the receiver of the cognitive radio (CR), the cognitive radio spurious tones can disturb other primary users and white space devices. The aim of this paper is to address the challenges for enabling cognitive radio applications in WLAN and LTE. In this process, architectural considerations for the design of cognitive radio front ends are discussed. With high-IF converters, faster and flexible implementation of CR enabled WLAN and LTE are shown. The effectiveness of the architecture is shown by evaluating the CR front ends for compliance of standards namely 802.11b/g (WLAN) and 3GPP TS 36.101 (LTE).

As Digital Television Broadcasting spreads over the world, existing (and more) TV channels can be distributed in less spectrum in the spectrum traditionally allocated to TV broadcasting. This freed spectrum is also referred to as the "Digital Dividend" and its use has been debated around the world. In addition, there is also a debate about the potential use of the "white space" within the TV-bands. This is due to the sparse frequency planning with large interference margins, which is typical in wide area broadcasting. Various technical approaches using Opportunistic Spectrum Access (OSA) have been proposed for unlicensed "white space" access to the TV bands. Most of previous studies have focused on spectrum sensing, i.e. detecting "free channels", where secondary users, utilizing White Space Devices (WSD) could avoid causing harmful interference to the TV receivers. However, interference caused by WSD is not only limited to co-channel interference. In particular, in short-range scenarios, the adjacent channel interference is an equally severe problem. Assessing the feasibility of WSDs in short-range indoor scenarios, taking more interference mechanisms into account is the objective of this paper. An Indoor home scenario with Cable, Rooftop antenna and Set-top antenna reception of DVB-T, has been analyzed. The spectrum reuse opportunities for WSDs have been determined, using the number of channels where it is possible to transmit without causing harmful interference to DVB-T receivers as performance measure. Simulation results show that the number of available channels for indoor unlicensed white space transmission appears to be significant in most of the studied scenarios.

One of the many standards developed recently for television white space operation is the IEEE 802.11af wireless LAN in TV white space. This white space device as a secondary user (SU) must not cause damaging interference to an incumbent primary user(PU) such as the ISDB-T digital TV service and even to an existing Analog TV Broadcast. To ensure interference-free coexistence, a keep-out distance, d <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</inf> , between the white space device (WSD) transmitter and the PU within the licensed TV service contour should be strictly observed. However, it is important that this d <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</inf> must neither be overestimated nor underestimated. In this paper, co-channel d <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</inf> between IEEE S02.11af and the ISDB – T DTV and Analog service contours using primarily ITU-R P.1546-6 and ITU–R P.1411-9 recommendations was computed and compared for the eleven analog and digital channels operating in Cebu province, Philippines. Experimental tests conducted show that analog and digital TV broadcast channels are aptly protected from co-channel interference emanating from IEEE 802.11af secondary white space devices operating within its service contour. Interestingly, the study also shows that a pair of IEEE 802.11af devices can establish connectivity within the ITU-R P.1546-based keep-out distance without causing interference to ATV and DTV services.

in television white space networks, secondary users are mandatory to query an accredited geo-location spectrum database (GSDB) in order to determine the vacant channels or white spaces. The recent developments of the Protocol to Access White Spaces (PAWS) by the Internet Engineering Task Force (IETF) have proposed to standardize communication between the GSDB and white space devices. To enable efficient sharing of spectrum, white spaces devices (WSDs) and their related restrictions, the mechanism or channel selection remain open issues in research. In this paper, we proposed use of PAWS and JavaScript Object Notation (JSON) to address the communication between the GSDB and WSDs to enable optimal channel selection decisions in the set-top box making it a smart set-top box.

TV White Spaces (TVWS) has taken a major step forward with the UK regulator Ofcom initiating a pilot of the technology and associated procedures in the UK, and TVWS rules being harmonized at the European level. This paper considers some aspects of our trial within the Ofcom TV White Spaces Pilot, namely, investigation of aggregation in TVWS and the deployment and testing of IEEE 802.11 white space devices that are capable of aggregating up to 4 TV channels, contiguously or non-contiguously. Our trial is the only deployment of these devices, developed at InterDigital in the USA, within the Ofcom TV White Spaces Pilot. This paper discusses the specifics of the InterDigital devices, including their design and capabilities. Further, results are presented highlighting what is possible in TVWS through contiguous aggregation. These results are achieved through per-channel allowed EIRP and capacity analyses based on feedback from a TVWS database within the Ofcom Pilot, using TVWS functionality developed at King's College London. Additional results outline the added benefit of optimal non-contiguous aggregation. Finally, this paper performs a like-for-like comparison of the performance of the InterDigital devices against what is theoretically possible in TVWS through capacity analyses using feedback from the TVWS database.

The television white space (TVWS) spectrum presents a promising opportunity to extend wireless broadband access, particularly in rural, underserved, and hard-to-reach communities. To leverage this potential, low-power radio communication equipment must efficiently utilise the TVWS spectrum on a secondary basis while ensuring strict compliance with regulatory requirements to prevent harmful interference to primary services. This paper presents a comparative performance analysis of TVWS radio equipment from three original equipment manufacturers (OEMs). The equipment under test was identified to reflect each OEM, as follows: OEM 1 and OEM 2 from South Korea and OEM 3 from the USA. We evaluated their performance in two real-world field scenarios, namely outdoor short-distance and outdoor long-distance. The evaluation was based on the following key metrics: (i) spectrum utilisation efficiency (SUE), (ii) received signal strength (RSS), (iii) downlink throughput, and (iv) connectivity to the Geo-Location Spectrum Database (GLSD) in compliance with the South African TVWS regulatory framework. The overall preliminary experimental results indicate that in both scenarios, white space devices (WSDs) based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11af Standard demonstrated better performance than those based on the 3rd Generation Partnership Project Long-Term Evolution-Advanced (3GPP LTE-A) Standard in terms of the SUE, downlink throughput, and RSS metrics. All WSDs under test demonstrated sufficient compliance with the regulatory requirement metric.

OF THE THESIS Design Methodology for Backhaul and Distribution Networks Using TV White Spaces by Cyrus Gerami Thesis Directors: Narayan Mandayam and Larry Greenstein Since the FCCs approval of unlicensed use of TV white spaces, the issue of how to use these white spaces has led to innovative technologies such as cognitive radios as well as a variety of spectrum policy proposals. There have been proposals to devise alternate rules for spectrum usage citing the overly conservative restrictions on secondary transmissions to protect incumbents. In this thesis, instead, we propose to utilize white spaces for a backhaul network for internet traffic based on existing restrictions. Using the available white spaces and backhaul traffic demands in New Jersey as a case study, we evaluate the feasibility of such backhauling and present a methodology that can be used for other areas as well. Using a basic design involving fixed towers and directional antennas, our results show that the TV white spaces can be an effective medium for radio backhaul as an alternative to the costly laying of optical fiber. Although the most recent FCC ruling does not mandate protection of wireless microphones, we show that meeting the more stringent earlier FCC requirements on sensing and avoiding harm to wireless microphones would have only a minor impact on capacity. Finally, we study the aggregating of multiple data traffic flows at the nodes and show that, with proper engineering, multiple flows have but a slight effect on the need for optical fiber.

The Cognitive Radio (CR) is the key technology to deal with spectrum scarcity by allowing unlicensed CR users to coexist with existing users in licensed spectrum bands without interfering with binding communications. Cognitive technology provides the spectrum ability to be shared with licensed networks. This radio system can adjust its transmitter and recipient parameters on the basis of interaction with the current conditions in the environment. Due to this flexibility cognitive radios are exploring different types of threats and security attacks. In this paper, we focus primarily on the Primary User Emulation Attack (PUEA) which is a major attack in the cognitive radio network. PUEA is similar to a Denial-of-service attack that can seriously disrupt the spectrum sensing process and deny other legitimate secondary users to access the available spectrum. We proposed a Neyman-Pearson composite hypothesis test (NPCHT) based analytical model to study the impact of PUEA in a fading wireless communication environment. Simulation results show that the proposed techniques can substantially reduce the impact of the malicious attack on the network

Cognitive radio (CR) is ascending as an advanced technology with the aim of utilizing the unused spectrum bands in an opportunistic and dynamic way. Fixed spectrum allocation done by government based agencies leads to underutilization of resources. The segments of spectrum bands that are unused, are called “spectrum holes” or “white spaces”. The solution to this issue is provided by implementing CR technology. It allows users to determine the unused bands in spectrum, choose the suitable one (depending on availability and accessibility of the spectrum) and use them in the best way possible. Spectrum assignment plays a vital role in minimizing any possibility of interference between secondary and primary users. Because of the varying parameters of available spectrum along with the different QoS specifications of various networks, CR technology raise a range of challenges. Spectrum management functions should tackle these problems and ensure that the CR network runs smoothly. This article therefore presents a brief survey on CR networks, its architecture and other relevant functionalities like spectrum sensing, spectrum decision, spectrum sharing, and spectrum mobility.

In recent year, the most emerging and growing field of research and development is “Internet of Things” (IoT). This is due to advancement in wireless sensor network (WSN) which operate in the unlicensed industrial, scientific and medical (ISM) spectrum band. However, many wireless technologies operate in the same unlicensed spectrum, make it overcrowded and hence resulted in spectrum scarcity among those bands, the performance of WSN will degrade as their popularity increases. According to FCC report, most of the licensed spectrum is underutilized, sharing of underutilized licensed spectrum among unlicensed devices is a promising solution to the spectrum scarcity issue. Cognitive Radio (CR) is one of the capable technology that allows sensor nodes (as a Secondary Users (SUs)) to detect and use the underutilized licensed spectrum temporarily when Primary Users (PUs) not using it. With recent advances in Cognitive Radio (CR) technology, possible to apply the Dynamic Spectrum Access (DSA) model in WSNs to get access to underutilized licensed spectrum, possibly with better propagation characteristics, but as the existing protocols and algorithms developed for CRNs and WSNs are not directly applicable to CR-based WSNs and required new protocols. In this paper, we present a survey on the novel design of CR-based MAC, identify the main advantages and challenges of using CR technology, and compare the different method of improving energy efficiency. We believe that CR-WSN is the next-generation WSN. In this paper, we also discussed the open issues to motivate new research interest in this field.

Cognitive radio (CR) is one of the most important challenges in contemporary communication. Because cognitive technologies are based on matching transmission parameters to the surrounding radio environment, several practical problems related to weak signal detection must be solved. These include, e.g., uncertainty of the noise variance value, the changes of this value in time and space, limited hardware resources or time of detection. All of these factors can seriously degrade system performance. The search for practically useful solutions of the encountered difficulties is therefore very important for the successful development and implementation of CR technology. This article provides an overview and comparison of chosen blind detection methods proposed for use in CR receivers. The comparison is based on simulation results, and the methods are compared in terms of detection efficiency, time complexity and robustness to changes in transmission parameters.