Spectrum Monitoring and Analysis
Modeling means that the machine must have some representation of the outside world to which it can respond. Models represent external influences like the user's network needs and actions, the radio spectrum and propagation environment, and the governing regulatory policy. As each of these influences changes, the radio must adjust itself to satisfy the new operating environment.
Many techniques exist to measure and model radio channels. We have successfully used a channel sounder to measure and model the radio propagation environment [Rondeau, 2004b] and methods are already available for using other, more standard radio measurement techniques [Mo, 2005]. Network and user modeling are more difficult concepts that are under investigation. The goal is to monitor the data sent by the user and use it to determine the QoS parameters the CR must provide. This is a learning domain concept that a neural network could be employed to help solve, and several of our students are investigating it. The regulatory policy modeling and interpretation will come from past efforts such as the XG project [XG]. These issues are explained in greater detail below.
Spectrum monitoring is a crucial aspect of the radio communication regulatory process. Spectrum management is an area of extreme importance and requires innovative technology to help reinvent spectrum policy. Changes in spectrum management are not only strongly suggested, as evident from the President??s Spectrum Policy Task Force [FCC, 2002], but are being actively pursued by the FCC in proceedings like Interference Temperature [FCC,2003a] and Cognitive Radio [FCC, 2003b]. Currently, spectrum is poorly allocated with much of it wasted and underused while other parts are overcrowded and congested. Cognitive radios provide important benefits realizable through aware, intelligent, and adaptive radios.
There is great motivation for Spectrum Monitoring. Spectrum is already allocated with existing standards, and the problem may not be spectrum scarcity but access to it. There is a current regulatory trend to increase sharing of spectrum where co-existence is demonstrated.
Cognitive Radio Solution to Spectrum Monitoring
There are real challenges for cognitive radio to overcome, especially when it comes to ensuring on-going channel and radio sensing and minimum network disruption in an incumbent system is detected.
Cognitive radio itself is a methodology for opportunistic utilization of uncultivated spectrum and can be categorized into two broad classes: Unlicensed cognitive radios operating in the unlicensed bands and unlicensed cognitive radios operating in the licensed bands. Each class has unique challenges to ensure successful operation.
Process of Spectrum Monitoring
Three key concepts of spectrum monitoring:
1. Validating information on legitimate users
2. Evaluating real levels of usage of the spectrum
3. Identifying areas for further use, sharing or reallocation
Classes of Spectrum Monitoring
Regulatory issues: Monitoring the compliance with the conditions in the license
Interference issues: Resolving harmful interference cases
Receiver Standards: ET Docket No. 03-65 NOI
Interference Temperature: ET Docket 03-237 NPRM/NOI
Cognitive Radio: ET Docket No. 03-108 NPRM
License-exempt Operation in the TV Broadcast Bands: ET Docket No. 04-186
Additional Spectrum for License-exempt devices below 900 MHz and in the 3 GHz Band: ET Docket No. 02-380
Channel Sounder
Artificial Intelligence Techniques
Rondeau SDR 2004
Maldonado DySPAN 2005
Rondeau TPRC 2005
Policy Based Engine
Federal Communications Commission, "Establishment of an Interference Temperature Metric to Quantify and Manage Interference and to Expand Available Unlicensed Operation in Certain Fixed, Mobile and Satellite Frequency," Rep. ET Docket No. 03-237, Nov. 2003.
FCC 2003. Facilitating Opportunities for Flexible, Efficient, and Reliable spectrum Use Employing Cognitive Radio Technologies. FCC Document ET Docket No. 03-108, Dec. 2003.
1. Monitoring band occupancy:
At the allocation stage when existing band undergoes a change of use or when a new service is introduced. To ensure that the old services have vacated the band or that any sharing arrangements are in fact working in practice.
2. Monitoring channel occupancy:
This will confirm or detect the level of use of frequency assignments in particular channels.
3. Interference investigation:
Dealing with the complaints regarding interference.
4. Compliance (routine) monitoring:
Routine monitoring to ensure or confirm that new users meet license conditions. Such a random and selective inspections are particularly effective in terms of improving and maintaining compliance levels.
5. International monitoring:
Deals with the discovering and resolving the international interference sources.
What is being monitored?
(1) Fixed monitoring and HF direction finding
(2) VHF/UHF mobile and remote monitoring
(3) AM, FM, television, and microwave monitoring
(4) satellite monitoring
Spectrum Monitoring Issues
The two main issues of spectrum monitoring are:
Spectrum Allocation Cycle
Regulatory Issues and Trends
In an effort to improve radio spectrum management and promote a more efficient use of it, the regulatory bodies are trying to adopt a new spectrum access model. This represents a paradigm shift from hardware-embedded policy implementation to dynamic software-based adaptation, which makes it harder to keep tight control!
Proceedings that are the Key Drivers
Spectrum Monitoring Applications
Dynamic Spectrum Access (DSA):
DSA is currently being considered as the prime candidate for the first practical application of cognitive radio technology. Initiated by the Darpa XG Program.
Interference Temperature (IT) Metric:
The IT model aims to create a reference interference level using real-time measurements and predictions based on the actual RF environment seen at a receiver. This resulting interference temperature would reflect the total amount of RF energy present at the receiver within the operating band at any given point in time. The transmitter would configure itself in response to this value. Initiated by FCC regulations.
DARPA XG Program
XG is trying to Develop the Technology and System Concepts to Dynamically Access Available Spectrum.
Source: DARPA XG Program
Interference Temperature
Interference Temperature (IT) is ??a measure of the RF power generated by undesired emitters plus noise sources that are present in a receiver system (I + N) per unit of bandwidth,?? or, in other words, the temperature equivalent of such RF power measured in units of ??Kelvin?? (K). IT= (I+N)/kB (ET Docket No. 03-237, Nov. 2003).
This model aims to use real-time measurements and predictions based on the actual RF environment.
CWT Solutions to Spectrum Monitoring
We have successfully used a channel sounder to measure and model the radio propagation environment and methods are already available for using other, more standard radio measurement techniques [Rondeau IMS 2004]
Includes Neural Networks and Genetic Algorithms.
Implemented as a learning domain concept which primary goal is to monitor the date sent by the user in order to determine its parameters.
Policy engine needs to provide limiting opertianol parameters and interpet poicy auotmatically whether it is a US or international policy