The spectrum sensing problem has gained new aspects with cognitive radio and opportunistic spectrum access concepts. It is one of the most challenging issues in cognitive radio systems. In this paper, a survey of spectrum sensing methodologies for cognitive radio is presented. Various aspects of spectrum sensing problem are studied from a cognitive radio perspective and multi-dimensional spectrum sensing concept is introduced. Challenges associated with spectrum sensing are given and enabling spectrum sensing methods are reviewed. The paper explains the cooperative sensing concept and its various forms. External sensing algorithms and other alternative sensing methods are discussed. Furthermore, statistical modeling of network traffic and utilization of these models for prediction of primary user behavior is studied. Finally, sensing features of some current wireless standards are given.

A survey of spectrum sensing algorithms for cognitive radio applications

With the rapid deployment of new wireless devices and applications, the last decade has witnessed a growing demand for wireless radio spectrum. However, the fixed spectrum assignment policy becomes a bottleneck for more efficient spectrum utilization, under which a great portion of the licensed spectrum is severely under-utilized. The inefficient usage of the limited spectrum resources urges the spectrum regulatory bodies to review their policy and start to seek for innovative communication technology that can exploit the wireless spectrum in a more intelligent and flexible way. The concept of cognitive radio is proposed to address the issue of spectrum efficiency and has been receiving an increasing attention in recent years, since it equips wireless users the capability to optimally adapt their operating parameters according to the interactions with the surrounding radio environment. There have been many significant developments in the past few years on cognitive radios. This paper surveys recent advances in research related to cognitive radios. The fundamentals of cognitive radio technology, architecture of a cognitive radio network and its applications are first introduced. The existing works in spectrum sensing are reviewed, and important issues in dynamic spectrum allocation and sharing are investigated in detail.

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Advances in cognitive radio networks: A survey

In this survey paper, we characterize the learning problem in cognitive radios (CRs) and state the importance of artificial intelligence in achieving real cognitive communications systems. We review various learning problems that have been studied in the context of CRs classifying them under two main categories: Decision-making and feature classification. Decision-making is responsible for determining policies and decision rules for CRs while feature classification permits identifying and classifying different observation models. The learning algorithms encountered are categorized as either supervised or unsupervised algorithms. We describe in detail several challenging learning issues that arise in cognitive radio networks (CRNs), in particular in non-Markovian environments and decentralized networks, and present possible solution methods to address them. We discuss similarities and differences among the presented algorithms and identify the conditions under which each of the techniques may be applied.

A Survey on Machine-Learning Techniques in Cognitive Radios

Protection systems and methods provide for protecting one or more personal computers (“PCs”) and/or other intermittently or persistently network accessible devices or processes from undesirable or otherwise malicious operations of Java TN applets, ActiveX™ controls, JavaScript™ scripts, Visual Basic scripts, add-ins, downloaded/uploaded programs or other “Downloadables” or “mobile code” in whole or part. A protection engine embodiment provides for monitoring information received, determining whether received information does or is likely to include executable code, and if so, causes mobile protection code (MPC) to be transferred to and rendered operable within a destination device of the received information. An MPC embodiment further provides, within a Downloadable-destination, for initiating the Downloadable, enabling malicious Downloadable operation attempts to be received by the MPC, and causing (predetermined) corresponding operations to be executed in response to the attempts.

Malicious mobile code runtime monitoring system and methods

In order to provide meaningful data about spectrum use, occupancy measurements describing the utilization rate of a specific frequency band should be conducted over a specific area instead of a single location. This paper presents a comprehensive methodology for the measurement and analysis of spectrum occupancy. This paper surveys spectrum measurement campaigns and associated interference maps, introducing the latter as a tool for spectrum analysis and management based on measurement data. An interference map characterizes the spectrum use by defining the level of interference over an area of interest in a certain frequency band. Building on findings from practical measurement studies, guidelines for spectrum occupancy measurements are given. While many scientific spectrum occupancy measurement papers tend to be too optimistic about the significance and generality of the results, we propose a cautionary perspective on drawing strong conclusions based on the often limited amount of data gathered. The different phases of the spectrum occupancy measurement and analysis process are described and a thorough discussion of interpolation methods is provided. Means to improve the measurement accuracy are discussed, especially regarding spatial domain considerations and the impact of the sampling interval on the results. A practical example of an improved measurement system design covering all the phases of the measurement process and used at the Turku, Finland; Blacksburg, VA, USA; and Chicago, IL, USA, spectrum observatories is given. Using the improved design, more realistic spectrum occupancy data can be obtained to lay the foundation for spectrum management decisions.

Spectrum Occupancy Measurements: A Survey and Use of Interference Maps

This invention generally relates to methods, apparatus and computer program code for
secure communication links, in particular where accountability is required. A method of initialising a secure communications link between a first data processing
system and a second data processing system using a first token comprising a first key
and associated first request data is described. The method comprises: generating at said
first system a first message comprising said first token and first authentication data
generated by operating on at least one of said first key and said first request data with a
secret key of said first system; encrypting said first message using a key known to both
said first and said second data processing systems to form an encrypted first message;
and sending said encrypted first message from said first system to said second system to
initialize said secure communications link. The method is particularly useful for establishing chains of accountability in systems
where trust is delegated.

Methods and apparatus for secure data communication links

The reconfigurable software radio concept has been an active research topic for many years. This was driven initially by military requirements for flexibility, but more recently by the commercial pressure to take advantage of economies of scale, reductions in maintenance costs and more efficient utilisation of spectrum. Therefore, initial projects looking at this concept have focussed on the technology for providing multi-mode and software reconfigurable terminals. The Transparently Reconfigurable Ubiquitous Terminal (TRUST) project differs in that it examines the user requirements in order to identify the frameworks and systems that are needed to support software reconfigurable radios from the users' perspective. The primary goal of the TRUST project is to realise the user potential of reconfigurable radio systems, which will provide network connectivity and services when and where they are required. The project will achieve this through a four-step process: (1) understand the users' requirements from their perspective of the system: "the terminal" (2) translate these users' requirements into technology requirements (3) advance the terminal and network technologies through research and innovation (4) validate, promote and disseminate these advancements and technologies.

IST-TRUST: a perspective on the reconfiguration of future mobile terminals using software download

The Project Authorization Request (PAR) for the IEEE P1900.4 Working Group (WG), under the IEEE Standards Coordinating Committee 41 (SCC41) was approved in December 2006, leading to this WG being officially launched in February 2007 [1]. The scope of this standard is to devise a functional architecture comprising building blocks to enable coordinated network-device distributed decision making, with the goal of aiding the optimization of radio resource usage, including spectrum access control, in heterogeneous wireless access networks. This paper introduces the activities and work under progress in IEEE P1900.4, including its scope and purpose in Sects. 1 and 2, the reference usage scenarios where the standard would be applicable in Sect. 4, and its current system architecture in Sect. 5.

https://www.jstage.jst.go.jp/article/transcom/E91.B/1/E91.B_1_2/_pdf

Introduction to IEEE P1900.4 Activities

One of the prime goals of a reconfigurable terminal is that it shall work on a great range of systems and standards. Amongst the many features that are required to support this inter-system roaming is the ability to detect, discover or identify alternative systems. Having located alternative systems, the terminal then needs the ability to connect to them and also monitor them in order to determine how viable the level of service offered by each one is. This paper is an introductory study of the problems that a software defined radio (SDR) terminal will face during its initial power-on in a geographical area where no a priori information about the available networks is provided to the terminal.

Blind radio access technology discovery and monitoring for software defined radio communication systems: problems and techniques

The invention provides a method of sharing the searching burden for discovering available services in a wireless network. Terminals within the network carry out searches of part of the available spectrum and communicate information between each other to establish a database of collective information.

Gary Clemo

Papers

Methods and apparatus for secure data communication links

IST-TRUST: a perspective on the reconfiguration of future mobile terminals using software download

Introduction to IEEE P1900.4 Activities

Blind radio access technology discovery and monitoring for software defined radio communication systems: problems and techniques

Distributed network discovery