Introduction and OverviewIntroduction and OverviewPresentation by

Dale N. Hatfieldat the

Radio Regulation Summit:

Defining Out-of-Band Operating RulesSilicon Flatirons Center for

Law, Technology, and Entrepreneurship

Boulder

September 8 - 9, 2009

Welcome and Introduction

• Welcome

• Purpose of Summit

• Agenda

• Review of Ground Rules

• Introductions

• Preliminary Remarks

Outline• Welcome and Introduction• Types of Interference• Drawing Geographic Boundaries• Drawing Frequency Boundaries• Out of Band Interference• Drawing Time Boundaries• Introduction of Case Studies

– 800 MHz Rebanding

– AWS-3

– SDARS – WCS

• Other Interference Cases

Types of Interference

In Band Out of Band

Cochannel Adjacent Channel Near Band Edge Far From Band Edge

Types of Interference (Potential “Trespass”)

Source: IEEE P1900

Drawing Geographic Boundaries

Desired Signal

Interfering or UndesiredSignal

Transmitter A

Transmitter B

Both Transmitter A and Transmitter Bare operating on the same channel causingcochannel interference if the geographic spacing is not sufficient

• Cochannel Interference

Drawing Geographic Boundaries• Practical Radio Propagation Models

– Site General Model

Drawing Geographic Boundaries• Practical Radio Propagation Models

– Site Specific Model

Drawing Frequency Boundaries• Adjacent Channel Interference

Lower AdjacentChannel

Output SignalPower

100%

50%

Upper AdjacentChannel

FrequencyDesiredChannel

Idealized “Perfect” Filter

Actual Filter

Drawing Frequency Boundaries

Undesired Signal on Adjacent Channel

Desired Signal

Transmitter A

Transmitter B

Transmitter A and Transmitter B are operating on channels adjacent in frequency; when the receiver is far from the desired transmitter and very close to the undesired transmitter, adjacent channel interference is exacerbated

• Adjacent Channel Interference – “Near-Far” Problem

Drawing Frequency Boundaries

• Transmitter Emission and Receiver Selectivity Characteristics

Sample TransmitterEmission Mask

Note that the FCC does not regulate receiver characteristics even though in some sense it is the receivers that “consume” spectrum; poor receiver front end selectivity, adjacent channel selectivity, intermodulation performance etc. can produce very inefficient use of the resource (See NOI in ET Docket No. 03-65, In the Matter of Interference Immunity Performance Specifications for Radio Receivers, Rel. 3/24/03)

Drawing Frequency Boundaries• Out of Band Interference

– Filtering (Band vs. Channel Selection)

Frequency

Band (“Front-end”)Filter)

Channel (“IF”) Filter

Lower AdjacentBand

DesiredBand

Upper AdjacentBand

Far Out of Band Interference Types:IntermodulationDesensitization/Overload

Drawing Time Boundaries

• Sharing Spectrum in Time

Time

ChannelOccupancy

Examples:AM Broadcasting – “Daytime Only Stations”Time Sharing of Radio Paging Channels (Historical)Time Division Multiple Access (TDMA)Dynamic Spectrum Assignment

Observations Regarding AdjacentBand Interference Issues

• Compared to Co-channel Interference, Adjacent Band (Both Near Band Edge and Far from Band Edge) Issues Are More Apt to be Problematical Because: – Interference can occur at any location within the geographic

service area, not just at the edges

– The actual or perceived risk or consequences of interference may be asymmetrical

– The architectures and technologies may be vastly different

– The number of players or stakeholders involved may be much larger and involve the general public directly

Observations

• Compared to Co-channel Interference, Adjacent Band Issues Are More Apt to be Problematical Because (Cont’d):– Providers in adjacent band are more likely to have very

different perspectives, incentives and even cultures – e.g., public safety entities versus commercial entities

– Receiver performance plays an especially important and complex role in adjacent channel/adjacent band interference issues and are not only not regulated, but sometimes outside the control of the service provider

– Our case studies tend to confirm that hypothesis and that is reason for focusing special attention on the topic in this Summit

Introduction of Case Studies

• 800 MHz Rebanding

• S-DARS – WCS Interference

• AWS-3 Interference

FCC Spectrum Allocationof 800 MHz Band * - Prior to Rebanding

TVBroadcastCh. 60-69

General Category

INCLUDES NEXTEL B/ILT & SMALL

NO. OF PUBLIC SAFETY

Upper 200 SMR(NEXTEL)

806 825816

851 870861 866

809.75

854.75

NPSPAC

821 824

869

- SMR (80 channels) INCLUDES NEXTEL- Business/SMR (50 channels) INCLUDES NEXTEL- Industrial/SMR (50 channels) INCLUDES NEXTEL

- Public Safety (70 channels))*

Up-Link

Down-Link

[7.5 MHz] [12.5 MHz] [10 MHz] [6 MHz]

CELLULAR

Source: APCO/Gurss

800 MHz Rebanding

Interference Concerns:Nextel Adjacent Channel Interference to Public SafetyIntermodulation Interference (Nextel GC, Interleaved, Upper 200, & Cellular A Block)

S-DARS – WCS Interference• S-DARS and WCS Spectrum

WCS Sat. Ter. Sat.S-DARS WCSSat.Ter.Sat.

S-DARS

2305 2320 2345 23602332.5 MHz

Interference ConcernsS-DAR Terrestrial Tx (Repeaters) WCS ReceiversWCS Mobile Tx S-DARS Mobile RxWCS Base/Mobile Tx AT Systems

AT

AT = Aeronautical Telemetry (2370 -2395 MHz)

2370

AWS-3 Interference • AWS-3 Interference to AWS-1 (Or Not)

AWS-1 (FDD) AWS-3 (TDD) MSS

Frequency (MHz)2110 2155 2180

Paired with1710-1755

Base TxMobile Rx

Base Tx/RxMobile Tx/Rx

Potential Interference Concerns:AWS-3 Mobile Tx AWS-1 Mobile Rx (Spillover/OBE)AWS-3 Mobile Tx AWS-1 Mobile Rx (Overload/DesensitizationAWS-1 Base Tx AWS-3 Base Rx

Other Interference Cases• Mobile Satellite Service (MSS) Ancillary

Terrestrial Component (ATC) Interference to GPS/GNSS

MSS (Down) GPS MSS (Up)

1525 1559 1610 1626.5 1660.51575.42GPS L1 Signal

Interference Concerns:MSS ATC Interference GPS Rx

Other Interference Cases

• Military Radar Interference with 4.9 GHz Public Safety

Military Radar Public Safety Primary RA

4920 4940 4990 5000

Interference Concerns:Military Radar Public Safety Systems

RA = Radio Astronomy

Note: RA is also allocated 4940-4990 on a secondary basis

800 MHz Case Study• Potential Discussion Points

– Could Public Safety’s interference rights have been defined adequately to allow cellularization of the SMR spectrum to take place or did the intermixing of the channels and basic incompatibilities between the two uses preclude such a transition as a practical matter?

– If the former, would Coasian bargaining been successful between Nextel and the Public Safety community?

– Not withstanding the fact that “zoning” (e.g., separating high power/high antenna site systems from low power, low antenna sites) reduces technical flexibility for the licensee (violates technical neutrality), is it required for pragmatic reasons?

800 MHz Case Study• Potential Discussion Points

– FCC resolved the issue by:• Separating non-cellular (high-power, high elevation, noise-

limited systems) from cellular (low-power, low elevation, interference limited systems) into different, discrete spectrum blocks

• Prohibited the deployment of cellular systems in the non-cellular block

– Established basis for resolving interference cases• Defined the environment in which protection would be

provided to non-cellular licensees (as described above)

800 MHz Case Study• Potential Discussion Points (Cont’d)

– Established basis for resolving interference cases (cont’d)

• In that environment, if the desired signal is sufficient and if the radios (victim Rx) meet minimum performance requirements and the radios still receive unacceptable interference then that interference must be resolved

• There is no protection or reduced protection if the desired signal is not sufficient or if the radios have reduced performance

– Can this approach be generalized and used in other contexts to resolve out of band interference issues?

– Challenges?

Note: Portions of this section were based upon a conversation with Steve Sharkey of Motorola

Contact Information

Dale N. HatfieldExecutive DirectorSilicon Flatirons Center for Law, Technology, and EntrepreneurshipUniversity of Colorado at Boulder401 UCB - Office 404Boulder, CO 80309Direct Dial: 303-492-6648Email: dale.hatfield@colorado.edu ordale.hatfield@ieee.org