Radio Frequency Spectrum and Regulation

“Cognitive Radio Communications and Networks: Principles and Practice”By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)

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Chapter 2

Radio Frequency Spectrum and Regulation


The Basics

An understanding of the actual physics behind the layers of interactions in cognitive radio environments Provides a valuable basis for

understanding the rest of the topic!


Characteristics ofElectromagnetic Waves Radiate (stone in a pond) / light bulb Decrease in intensity with distance

(R2 Rule) from point of origin Can travel in straight line (lens /

laser) Can be Reflected, Refracted, Diffused,

Scattered and Absorbed


Electromagnetic Spectrum

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Photograph of the output of a prism on a table


PropagationReceived Power is inverselyProportional to Distance fromThe Transmitter(radius) Squared – the R2 Rule!


Reflection / Refraction

Velocity 1 Interfacei i

rVelocity 2Velocity 2 r


Diffraction - Absorption -Scattering

IncidentIncident Incident


Characteristics ofElectromagnetic Waves

Radiate (stone in a pond) Can travel in straight line (lens / laser) Decrease in Intensity with distance from

point of origin Can be Reflected, Refracted, Diffused,

Scattered, and Absorbed Even more exciting, waves can and do all

these things at the same time and based on mobility, dynamically change as well!


Reflection / Refraction

Velocity 1 Interfacei i

rVelocity 2Velocity 2 r

Velocity 1

Incident Ray

Interference

Source


Electromagnetic spectrum

Our FocusVisible Light

X-rays Ultraviolet Infrared Microwaves Radio

0.000000010.0000010.0001 0.01 1.0 100 10,000

Wavelength (in cm)

High Frequency

Short Wavelength

Low Frequency

Long Wavelength


Wavelength = Speed of Light / Frequency– or –

= c / f

for WiFi – 802.11b/g, f =~ 2.4 GHz and c = ~300,000 km / sec, therefore,

=~300,000 / 2,400,000 = 12.5 cm (~ 4.9”)

For low band cellular, f = 900 MHz – therefore300,000 / 900,000 = 33.3 cm (~13”)

Frequency and Wavelengths



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Cognitive Radio Challenges Interference! Co-existence Interoperability Complexity International Standards &

Regulations Power …


Regulatory Issues for Cognitive Access Should a Regulator Allow Cognitive

Access? Deciding not to allow it (and hence do

nothing). Enabling existing license holders to

allow cognitive access into their own bands if they chose to.

Licensing cognitive access to particular bands.

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Regulatory Issues for Cognitive Access Exempting cognitive equipment from the

need for licensing with appropriate restrictions on when, where and how they might operate.

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Regulatory Issues for Cognitive Access How to Determine the Rules of Entry If the regulator has decided to allow

cognitive access to a particular band, the next step in to set the rules of entry.

Rules ensure a very low probability of interference to the incumbent users of the band while at the same time placing the minimum possible restrictions on the cognitive device

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Regulatory Issues for Cognitive Access The incumbents will be seeking the

maximum level of protection Will seek out situations where the

“hidden node” problem or other signal modification issues are most extreme.

Even setting an appropriate level of probability of interference occurring can be fraught with difficulties.

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Regulatory Issues for Cognitive Access Even setting an appropriate level of

probability of interference occurring can be fraught with difficulties Many other rules are also needed

including: Maximum inband power Out-of-band power limits Bandwidth Transmit power control Sensing periodicity

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Regulatory Issues for Cognitive Access Regulatory Implications of Different

Methods of Cognition Geographical Databases Access to a database listing the

frequencies allowed to secondary use at each location.

Beacon Reception Transmission of a signal from some

appropriate infrastructure providing information on which frequencies are available for cognitive use 20


Regulatory Issues for Cognitive Access Geographical Databases To what accuracy should the device

know its location? Who will maintain the database? What availability is needed for the

database? How will devices download updated

versions of the database? What about dynamic use of spectrum?

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Regulatory Issues for Cognitive Access Beacon Reception Who provides the beacon signal? How is the information the beacon is

transmitting kept up to date, especially where the licensed services are changing rapidly?

What spectrum is used for the beacon? What technical parameters and protocols

are used by the beacon transmitter?

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Regulatory Issues for Cognitive Access Regulatory Developments to Date Most notably in November 2008 the FCC

published its Report and Order enabling cognitive access in the white space in the TV broadcast spectrum.

In July 2009 Ofcom published a statement on ”Licence-exempting Cognitive Devices Using Interleaved Spectrum”

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Regulatory Issues for Cognitive Access The FCC concluded that sensing alone

was insufficiently proven for cognitive access. Sensing alone would result in an

unacceptable risk of interference. Geographical databases were also

required.

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Spectrum Occupancy Studies

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Radio Car – circa 1927 (photo courtesy of the Institute for Telecommunications Science (ITS), NTIA, U.S. Dept. of Commerce)



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WPI team prepare for an RF spectrum measurement sweep in downtown Rochester, NY.



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A map of the forty eight locations close to I-90 between Boston, MA and Blandfield, MA over which spectrum measurements were collected in June 2009


Snapshot Studies

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Measured Spectrum Occupancy in Chicago and New York City

0.0% 25.0% 50.0% 75.0% 100.0%

PLM, Amateur, others: 30-54 MHzTV 2-6, RC: 54-88 MHz

Air traffic Control, Aero Nav: 108-138 MHzFixed Mobile, Amateur, others:138-174 MHz

TV 7-13: 174-216 MHzMaritime Mobile, Amateur, others: 216-225 MHz

Fixed Mobile, Aero, others: 225-406 MHzAmateur, Fixed, Mobile, Radiolocation, 406-470 MHz

TV 14-20: 470-512 MHzTV 21-36: 512-608 MHzTV 37-51: 608-698 MHzTV 52-69: 698-806 MHz

Cell phone and SMR: 806-902 MHzUnlicensed: 902-928 MHz

Paging, SMS, Fixed, BX Aux, and FMS: 928-906 MHzIFF, TACAN, GPS, others: 960-1240 MHz

Amateur: 1240-1300 MHzAero Radar, Military: 1300-1400 MHz

Space/Satellite, Fixed Mobile, Telemetry: 1400-1525 MHzMobile Satellite, GPS, Meteorologicial: 1525-1710 MHz

Fixed, Fixed Mobile: 1710-1850 MHzPCS, Asyn, Iso: 1850-1990 MHz

TV Aux: 1990-2110 MHzCommon Carriers, Private, MDS: 2110-2200 MHz

Space Operation, Fixed: 2200-2300 MHzAmateur, WCS, DARS: 2300-2360 MHz

Telemetry: 2360-2390 MHzU-PCS, ISM (Unlicensed): 2390-2500 MHz

ITFS, MMDS: 2500-2686 MHzSurveillance Radar: 2686-2900 MHz

Spectrum Occupancy

ChicagoNew York City


Spectrum Observatories

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IIT’s Spectrum Observatory antenna array


Spectrum Observatories

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SQUIRRELWeb spectrum measurement interface at WPI


TV Spectrum Utilization

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Spectrogram of TV channels 21 − 51 taken in Chicago 22 − 29 April 2008


Cellular Spectrum Utilization

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Spectrogram of 800 MHz cellular band in Chicago taken 17−24 April 2008


Paging Spectrum Utilization

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Wireless spectrum of 928-948 MHz in Rochester, NY on 19 June 2008.


Chapter 2 Summary Nature of the electromagnetic

spectrum with specific focus on that portion of the spectrum most useful for radio networks and communications systems

Cursory review of the early use of this spectrum has been presented

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Chapter 2 Summary Rise in national and international

regulatory bodies focused on both the allocation of the spectrum and in defining the acceptable parameters for its use

Emerging unlicensed approaches to the use of the spectrum have been examined Cognitive access approach to spectrum

utilization 35

Documents

Radio Frequency Spectrum and Regulation