The main emphasis of the dynamic spectrum access 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, a set of policy-based components, tightly integrated with the accredited kernel on the radio, avoids potentially harmful interference caused by a malfunctioning device. The policy conformance and enforcement components ensure that a radio does not violate policies, which define regulatory and other stakeholders' goals and requirements, and which are encoded in an abstract, declarative language^[6].

Policy-system architecture is based on several key areas that involve both the policy author and the software-defined radio. The core components are depicted in Figure 3 and Table 1.

The DSA software is provided to the radio manufacturers as compiled code. The code is implemented in the software-defined radio (SDR) as a new waveform. The software-defined radio does not require any hardware modifications to operate.

While the policy enforcer, policy manager and policy conformance reasoner are loaded onto the SDR radio, the policy-authoring tools (policy administrators, system strategy reasoner) are loaded into a server attached to the network. The policy authorer uses the GUI and policy software to create and push the policies down to the radio.

Military exercises and campaigns create an environment of constrained and highly coordinated access to spectrum. Technologies like policy-based DSA will increase flexibility and timeliness of mission planning. Troop radios are enabled by policy to find available frequencies for communication when impacted by intentional or unintentional frequency interference. To control the operating parameters of the software-defined radios, the local or regional spectrum manager establishes the policies. Beyond handheld radios, DSA technology enables greater control over unmanned systems by closing long-link ranges and adapting to the changing RF environment without disrupting communications. The impact is greater use of small UAVs and tactical robots to improve surveillance and keep soldiers out of dangerous situations.

SSC has been awarded a grant from the National Institute of Justice (NIJ) to develop and demonstrate a multiband cognitive radio system that will help optimize spectrum access for public safety agencies. This project focuses on creating a spectrum management subsystem on radio networks that control the individual radios with spectrum access “policies” that allow better use of available spectrum frequencies. This subsystem, called cognitive radio access and management (CRAM), will lead to the creation and dissemination of a wide range of spectrum access and priority rules, including trusted security measures to avoid unauthorized access and operations. It will also provide for logging of transmissions to monitor usage and quickly remedy interference. This is one of the first steps at providing a dynamic spectrum environment needed during rapid deployment situations where multiple government agencies are responding to a situation.

Access to spectrum is an immediate problem for military and public safety users. After the 700 MHz auction, access to needed blocks of spectrum will require adoption of new communications tools to harvest existing spectrum. Dynamic spectrum access technology is available now to provide the critical link through a wireless software suite comprising policy-based rules and database engines that drive algorithms for frequency agility and cognitive decision-making. The entire suite enables an environment for users to adopt DSA and begin to address spectrum challenges and enable innovation and growth in wireless solutions.

1. M. Zeltser, F. Morser, P. Long and F. Box, “White Paper: Spectrum Depletion Analysis,” The MITRE Corp. MITRE MP 03W0000068, April 2003, [online] available at http://www.mitrecaasd.org/library/documents/MP03W68.pdf.

2. Presidential Memorandum, June 5, 2003, “Spectrum Policy for the 21st Century,” [online] available at http://www.ntia.doc.gov/osmhome/spectrumreform/execMemoMay2003.htm.

3. M. McHenry and D. McCloskey, “Multiband, Multilocation Spectrum Occupancy Measurements,” Proc. Intl. Symposium on Advanced Radio Tech., Boulder, CO, March 7-9, 2006, pp. 167-175.

4. M. McHenry, “Dynamic Spectrum Sharing,” presentation to the Northern Virginia chapter of IEEE Comsoc, Jan. 25, 2005, [online] available at http://www.sharedspectrum.com/?section=presentations.

5. F. Seelig “A Description of the August 2006 XG Demonstrations at A.P. Hill,” IEEE DySPAN 2007, Dublin, Ireland, April 2007.

6. F. Perich, “Policy-based Network Management for NeXt Generation Spectrum Access Control,” IEEE DySPAN 2007, Dublin, Ireland, April 2007.

Salvador D'Itri is director of sales and marketing for Shared Spectrum Company in Vienna, VA. He has more than 15 years experience in strategic marketing, business development and product management for MVNO and tier 1 network service and software application providers. He has focused on new market launches in multimode wireless communications and innovative last-mile network solutions. He is an appointed member of the Cable and Information Technology Commission for Arlington County, VA. D'Itri received a M.A. in telecommunications from George Mason University and B.S. in accounting and computer systems from Robert Morris College in Pittsburgh.

Mark A. McHenry is founder and CEO of Shared Spectrum, and has 22 years experience as an innovative engineer. He was a co-founder of San Diego Research Center, Inc., a wireless research and development company. Previously, he was a program manager at the Defense Advanced Research Projects Agency (DARPA), where he managed multiple programs. He has worked as an engineer at SRI International, Northrop Advanced Systems, McDonnell Douglas Astronautics, Hughes Aircraft and Ford Aerospace. McHenry received the Office of Secretary of Defense Award for Outstanding Achievement in 1997 and the Office of Secretary of Defense Award for Exceptional Public Service Award in 2000. McHenry obtained a B.S. in engineering and applied science from the California Institute of Technology, an M.S. in EE from the University of Colorado, and a Ph.D. in EE from Stanford University.

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