Shared Spectrum Company developed Dynamic Spectrum Access (DSA) technology that enables military radio communication systems to deliver robust, non-interrupted wireless connectivity to tactical networks technology. DSA allows network operators to adapt to last minute spectrum assignment planning changes as well as changes made after deployment. DSA also allows the radios to overcome even unplanned, unexpected interference sources. We present a case study of dynamic spectrum access software technical and operational integration challenges.
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Abstract - Multi-band, reconfigurable cognitive radio (CR) technology has been identified as offering key solutions to Public Safety spectrum access problems. However, CR technology invokes concerns about the ability to securely control devices with Dynamic Spectrum Access (DSA) capabilities potentially operating autonomously across multiple frequency bands. To alleviate these concerns, an end-to-end, Cognitive Radio Access Management (CRAM) subsystem is presented that focuses on secure, flexible and user-friendly policy-based control mechanisms. On one end of the subsystem, policy conformance enforcement is embedded at the edge of the CR network onto CR devices by leveraging device-understandable, XML-based rules and constraints. On the other end, user-friendly policy authoring and administration tools are available to a wide range of Public Safety stakeholders to create, disseminate, and validate policies before, during and after they are loaded and run on CR devices. Throughout the subsystem, multiple layers of reliable security measures are employed to further ensure trust that the policies are valid and work properly.
Abstract- This paper describes the Probe Spectrum Access Method. This dynamic spectrum access method can be used in the TV band to enable a system to transmit at high power levels (> 1 W) without causing harmful interference. Each “Frequency Agile Radio” (FAR) transceiver measures the background spectrum to identify potential available channels. The system uses high-processing gain probe waveforms that enable propagation measurements to be made with minimal interference to the Non-cooperative users. The system uses a modulation method to identify the FAR signal to all Non-cooperative users via on/off amplitude modulation, allowing easy resolution of interference claims. Other TV band spectrum access methods do not enable high transmit power levels (> 1 W) without causing interference to the existing users.
This paper provides a comprehensive analysis of Dynamic Spectrum Access (DSA) operational parameters in a typical “Hidden Node” scenario with wireless microphones in the TV white space situation. We consider all relevant effects and use an analysis framework that properly combines probabilistic technical factors to provide specific policy recommendations including the exclusion zone distances and the sensing-based DSA threshold detection levels.
This paper describes the Dynamic Spectrum Access radio system that was built as part of the DARPA XG Program. The DSA system’s architecture four principal components (the DSA engine; the environmental sensing (i.e., detection) subsystem; the communications (i.e., radio) subsystem; and a policy module/enforcer) are described. The DSA system’s 802.16-based radio hardware is described. One of the field tests related to Group Sensing is described. A companion paper describes the XG DSA Policy software design and field test.
Determination of Detection Thresholds to Allow Safe Operation of Television Band “White Space” Devices
The purpose of this study is to determine a range of detection thresholds at which new dynamic spectrum access (DSA) devices can safely operate in unoccupied spectrum allocated to terrestrial television (TV) broadcasting and other services (i.e., the TV “white spaces”), without causing harmful interference to other authorized operations, which include digital and analog TV stations, wireless microphones and other services. Spectrum sensing data were collected at six different locations in Northern Virginia that were strategically chosen because they were within, outside and near the edges of the predicted service contours of digital TV stations serving the Washington, D.C. and Baltimore, MD metropolitan areas.
We describe the design and report on experience fielding an end-to-end framework for declarative spectrum management of frequency agile wireless communication devices. As part of the Defense Advanced Research Projects Agency NeXt Generation communication program, we developed a distributed, policy-driven system that restricts spectrum access based on spectral, temporal and geospatial context. We report on our field framework experimentation, illustrating the capability offered to wireless systems, their command & control management, and individual radios for enforcing spectrum access policies while enabling the radios to fully utilize available spectrum in comparison to traditional, static-assignment spectrum access methods.
Shared Spectrum Company (SSC) and the U.S. Department of Defense’s Defense Advanced Research Projects Agency (DARPA) demonstrated, for the first time, a six node network of Next Generation (XG) radios capable of using spectrum over a wide range of frequencies on a secondary basis. The cognitive radios making up several formations of XG networks sensed radio signals over 225-600 MHz and adapted frequencies automatically to prevent interference to existing military and civilian radio systems. The XG networks were tested on a military test range…
Dynamic Frequency Sharing provides a mean to more efficiently allocate frequency spectrum. For this to be accomplished the ambient spectrum has to be sensed and characterized. This paper presents how energy detection can be used to differentiate signals from noise for various operating environments.
This paper describes the design and implementation of a policy-based spectrum access control framework as part of the DARPA NeXt Generation communications program. The main emphasis of the framework is to overcome two types of concerns: harmful interference caused by a malfunctioning device and harmful interference caused by a malicious user. In tandem with signal-detection-based interference-avoidance algorithms employed by software-defined radios, we design a set of policy- based components, tightly integrated with the accredited kernel on the radio, for avoiding potentially harmful interference caused by a malfunctioning device….
The Potential Value Of Decentralized Trunking As Regulartory Precedent For The Introduction Of Dynamic Spectrum Access Technology
One important way of obtaining the necessary regulatory permissions for Dynamic Spectrum Access (“DSA”) technologies from domestic government agencies and the international spectrum management community is to demonstrate that there are policy and legal precedents for their introduction. A recent precedent centers on efforts in the U.S. to allow Unlicensed National Information Infrastructure devices to operate in the 5.25- 5.35 GHz and 5.47-5.725 GHz bands without causing interference to existing radio frequency operations (government radars) through the use of Dynamic Frequency Selection (“DFS”) and Transmit Power Control (“TPC”). Another, slightly older precedent is the U.S. Federal Communications Commission’s policies and rules that permit the utilization of “decentralized trunking” in the VHF and UHF Private Land Mobile Radio (“PLMR”) service bands. Under these rules, adequate “monitoring” (a.k.a., “listen-before-talk” or “LBT”) is required in order to share spectrum under a decentralized trunking approach. This paper analyzes the potential value of this older precedent in advocating for broader regulatory acquiescence and near-term deployment of DSA technology.
Burgeoning demands for communications bandwidth stress the abilities of military and civil spectrum managers to provide needed access to spectrum resources while taking appropriate measures to avoid causing harmful interference to legacy users. Empirical analysis shows that radio frequency (RF) bandwidth is often available: measurement data indicate that while most channels are used at some times, most channels remain unused at any given time. Going forward, so- called “smart radio” technologies will be able to exploit these holes in the RF spectrum and will play a crucial role in achieving the core objectives of efficient spectrum management. The United States Defense Advanced Research Projects Agency’s (“DARPA”) NeXt Generation Communications Program (“XG”) is on the vanguard of smart radio innovations. In particular, XG technology uses automated intelligence at a system’s edges in order to navigate real-time fluctuations in spectral conditions that cannot be precisely predicted in advance. This dynamism will enable opportunistic use of intermittently available spectrum.