TV White Space Networks Research Articles

MINE GOLD to Deliver Green Cognitive Communications

Geo-location database-assisted TV white space network reduces the need for energy-intensive processes (such as spectrum sensing), and hence can achieve green cognitive communication effectively. The success of such a network relies on a proper business model that provides incentives for all parties involved. In this paper, we propose a Model of INformation markEt for GeO-Location Database (MINE GOLD), which enables databases to sell spectrum information to unlicensed white space devices (WSDs) for profit. Specifically, we focus on an oligopoly information market with multiple databases, and study the interactions among databases and WSDs using a two-stage hierarchical model. In Stage I, databases compete to sell information to WSDs by optimizing their information prices. In Stage II, each WSD decides whether and from which database to purchase the information, to maximize his benefit of using the TV white space. We first characterize how the WSDs’ purchasing behaviors dynamically evolve, and what is the equilibrium point under fixed information prices from the databases. We then analyze how the system parameters and the databases’ pricing decisions affect the market equilibrium, and what is the equilibrium of the database price competition. Our numerical results show that, perhaps counter-intuitively, the databases’ aggregate revenue is not monotonic with the number of databases. Moreover, numerical results show that a large degree of positive network externality would improve the databases’ revenues and the system performance.

Capacity Considerations for Secondary Networks in TV White Space

The so-called “TV white spaces” (TVWS)—representing unused TV channels in any given location as the result of the transition to digital broadcasting—is designated for unlicensed use [1] , [2] , [3] by the US Federal Communications Commission (FCC). This presents significant new opportunities within the context of emerging 4G networks for developing new wireless access technologies that meet the goals of the US National Broadband Plan [4] (notably true broadband access for an increasing fraction of the population). There are multiple challenges in realizing this goal; the most fundamental being the fact that the available WS capacity is currently not accurately known, since it depends on a multiplicity of factors—including system parameters of existing incumbents (broadcasters), propagation characteristics of local terrain as well as FCC rules. In this paper, we explore the capacity of white space networks by developing a detailed model that includes all the major variables, and is cognizant of FCC regulations that provide constraints on incumbent protection. Real terrain information and propagation models for the primary broadcaster and adjacent channel interference from TV transmitters are included to estimate their impact on achievable WS capacity. The model is later used to explore various trade-offs between network capacity and system parameters and suggests possible amendments to FCC’s incumbent protection rules in the favor of furthering white space capacity.

Improved Distributed Cooperative Spectrum Sensing (DCSS) For Cognitive Radio Adhoc Network

Cooperation among cognitive radios for spectrum sensing is deemed essential for environments with deep shadows. In this paper, we study cooperative spectrum sensing for cognitive radio ad hoc networks where there is no fusion center to aggregate the information from various secondary users. We propose a novel consensus-inspired cooperative sensing scheme based on linear iterations that is fully distributed and low-cost. In addition, the trade-offs on the number of consensus iterations are explored for scenarios with different shadow fading characteristics. Furthermore, we model Insistent Spectrum Sensing Data Falsification (ISSDF) attack aimed at consensus-based iterative schemes and show its destructive effect on the cooperation performance which accordingly results in reduced spectrum efficiency and increased interference with primary users. We propose a trust management scheme to mitigate these attacks and evaluate the performance improvement through extensive Monte Carlo simulations for large-scale cognitive radio ad hoc networks in TV white space. Our proposed trust management reduces the harm of a set of collusive ISSDF attackers up to two orders of magnitude in terms of missed-detection and false alarm error rates. Moreover, in a hostile environment, integration of trust management into cooperative schemes considerably relaxes the sensitivity requirements on the cognitive radio devices.

Spectrum Reservation Contract Design in TV White Space Networks

In this paper, we study a broker-based TV white space market, where unlicensed white space devices (WSDs) purchase white space spectrum from TV licensees via a third-party geo-location database (DB), which serves as a spectrum broker, reserving spectrum from TV licensees and then reselling the reserved spectrum to WSDs. We propose a contract-theoretic framework for the database's spectrum reservation under demand stochasticity and information asymmetry. In such a framework, the database offers a set of contract items in the form of reservation amount and the corresponding payment, and each WSD chooses the best contract item based on its private information. We systematically study the optimal reservation contract design (that maximizes the database's expected profit) under two different risk-bearing schemes: DB-bearing-risk and WSD-bearing-risk, depending on who (the database or the WSDs) will bear the risk of over reservation. Counter-intuitively, we show that the optimal contract under DB-bearing-risk leads to a higher profit for the database and a higher total network profit.

Business modeling for TV white space networks

Database-assisted TV white space network is a promising paradigm of dynamic spectrum sharing, and can effectively improve spectrum utilization and alleviate spectrum scarcity via centralized control of TV white space databases residing in the cloud. In this article, we discuss business modeling for a database-assisted TV white space network, which is very important for wide commercialization of this promising technology. Motivated by several recent business practices, we propose and study two types of different business models: spectrum market and information market. In the spectrum market model, spectrum licensees, through spectrum brokers acted by databases, lease the underutilized (licensed) TV channels to unlicensed wireless devices for secondary utilization. In the information market model, databases sell the advanced information regarding (unlicensed) TV channels to unlicensed wireless devices in order to enhance the secondary spectrum utilization performance. We outline the corresponding trading mechanism details for both market models, and evaluate the feasibility and performance of both models through theoretical and numerical studies. Numerical results indicate that both the database operator’s profit and the total network profit can be significantly improved under properly designed trading mechanisms.

Coexistence Decision Making for Spectrum Sharing Among Heterogeneous Wireless Systems

This paper focuses on the problem of spectrum sharing between secondary networks that access spectrum opportunistically in TV spectrum. Compared to the coexistence problem in the ISM (Industrial, Scientific and Medical) bands, the coexistence situation in TV whitespace (TVWS) is potentially more complex and challenging due to the signal propagation characteristics in TVWS and the disparity of PHY/MAC strategies employed by the systems coexisting in it. In this paper, we propose a novel decision making algorithm for a system of coexistence mechanisms, such as an IEEE 802.19.1-compliant system, that enables coexistence of dissimilar TVWS networks and devices. Our algorithm outperforms existing coexistence decision making algorithms in terms of fairness, and percentage of demand serviced.

Deployment and coverage of cognitive radio networks in TV white space

This article presents experimental and simulation results for the use of TV band devices (TVBDs) in TV white space, considering the presence of interference by incumbent services. Digital TV (DTV) services are major incumbent services currently operating in the TV bands. With DTV service, co-channel and adjacent channel deployment scenarios of TVBD networks are introduced. To safely protect the incumbent service, a minimum separation distance from the DTV protected contour, which is called the keep-out distance, is required. We estimate the keep-out distance for different ranges of TVBD transmit antenna height by using several propagation models and measurements of ultra-high-frequency signals in Korea. We also investigate the hidden node problem for the spectrum sensing operation mode of TVBDs. According to the results of these measurements, the hidden node margin should be at least 38 dB in order to protect DTV service. Finally, the service coverage reduction of TVBD networks caused by neighboring DTV service is discussed. It is shown that the service coverage of a wireless local area network system decreases about 50 percent by co-channel interference from neighboring DTV service when the field strength of the DTV received signal is 41 dBu.

Rule-based dynamic TV white space spectrum sharing services composition framework

When developing a TV White Space (TVWS) system with the available TV spectrum after digital switchover, the smooth introduction of new technologies and components has to be supported because the requirements of users change frequently in a new system. We need to provide a modular, extensible and easy to implement framework rather than building highly integrated systems. According to environment, rules, polices and users’ requirements, advanced intelligent management functionalities that can guarantee the proper configuration of devices in TVWS networks and proper load balance, have to be developed. According to different requests from users, different algorithms and components have to be used to meet the needs of the users. How, when and which algorithms and components should be combined in order to meet the requests from the users become essential problems. Based on Service Oriented Architecture, all things in the proposed system including algorithms and components can be defined as services. This paper presents a framework of rule-based dynamic TVWS services composition that can meet the above needs and combine different TVWS services to fulfil users’ requirements dynamically.

A Complete Design of Coexistence Information Service for Autonomous Decision-Making Systems in TV White Space

In this paper, we present a coexistence protocol design for a coexistence information service to provide coexistence solutions among dissimilar or independently operated autonomous decision-making networks in a wireless communication environment over, specifically but not limited to, TV white space (TVWS) frequency bands. The designed coexistence protocol for the coexistence information service has three main functionalities: (1) To collect basic information of subscribed TVWS networks; (2) To support generating neighbor lists for the TVWS networks based on the geography information and/or propagation parameters; (3) To provide necessary information for TVWS networks to make coexistence decisions. Both theoretical analysis and simulation results show that the designed coexistence information service ensures harmonious communications among dissimilar networks and is able to achieve coexistence over an area with the limited number of available channels in white space.

Enabling coexistence of multiple cognitive networks in TV white space

We address the problem of coexistence among wireless networks in TV white space. We present a standard independent framework to enable exchange of information relevant for coexistence based on two mechanisms: centralized and distributed. Both mechanisms introduce the use of multiradio cluster-head equipment (CHE) as a physical entity that acquires relevant information, identifies coexistence opportunities, and implements autonomous coexistence decisions. The major conceptual difference between them lies in the fact that the centralized mechanism utilizes coexistence database(s) as a repository for coexistence related information, where CHEs need to access before making coexistence decisions. On the other hand, the distributed mechanism utilizes a broadcast channel to distribute beacons and directly convey coexistence information between CHEs. Furthermore, we give a concise overview of the current activities in international standardization bodies toward the realization of communications in TVWS along with measures taken to provide coexistence between secondary cognitive networks.

Smart utility networks in tv white space

This article presents an overview of the background, technology, regulation, and standardization in the course of deploying smart utility networks (SUNs) in TV white space (TVWS) communications, two wireless technologies currently receiving overwhelming interest in the wireless industry and academia. They are independent to and uncorrelated with each other, but share the same mission: conserving resources and increasing efficiency. This article reviews the systems as separate technologies, and then combines them to propose a hybrid solution that draws out their respective advantages. The first part focuses on SUNs and describes the SUN usage model with typical application requirements and practical examples, followed by the latest developments in standardization initiatives with emphasis on the currently active IEEE 802.15.4g and 802.11ah groups. The second part discusses TVWS, studying and summarizing the regulations governing its usage, and then reports on the standardization bodies' responses to these regulations with a focus on IEEE 802.11af, 802.19.1, and 802.22. Finally, the third part amalgamates the SUN usage model with TVWS regulations and deployment scenarios, providing relationship mapping between the SUN components and regulation-compliant TVWS devices. Further discussions concentrate on the opportunities and challenges along the path of realizing a practical SUN in the TVWS spectrum under the current technical and regulatory conditions. Several recommendations are made from both regulatory and technical standpoints to further increase utilization of SUNs in TVWS.