Presentation by
Dale N. Hatfield at the
Radio Regulation Summit:
Defining Out-of-Band Operating Rules
Silicon Flatirons Center for
Law, Technology, and Entrepreneurship
Boulder
September 8 - 9, 2009

• Welcome
• Purpose of Summit
• Agenda
• Review of Ground Rules
• Introductions
• Preliminary Remarks

• 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
Source: IEEE P1900
Far From Band Edge

• Cochannel Interference
Interfering or Undesired
Signal
Desired Signal
Transmitter A
Transmitter B
Both Transmitter A and Transmitter B are operating on the same channel causing cochannel interference if the geographic spacing is not sufficient

• Practical Radio Propagation Models
– Site General Model

• Practical Radio Propagation Models
– Site Specific Model

• Adjacent Channel Interference
Output Signal
Power
Idealized “Perfect” Filter
100%
Actual Filter
50%
Lower
Adjacent
Channel
Desired
Channel
Upper
Adjacent
Channel
Frequency

• Adjacent Channel Interference – “Near-Far”
Problem
Desired Signal
Undesired Signal on
Adjacent Channel
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

• Transmitter Emission and Receiver
Selectivity Characteristics
Sample Transmitter
Emission 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)

• Out of Band Interference
– Filtering (Band vs. Channel Selection)
Channel (“IF”) Filter
Band (“Front-end”)
Filter)
Lower Adjacent
Band
Desired
Band
Far Out of Band Interference Types:
Intermodulation
Desensitization/Overload
Upper Adjacent
Band
Frequency

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

• 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

• 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

• 800 MHz Rebanding
• S-DARS – WCS Interference
• AWS-3 Interference

FCC Spectrum Allocation of 800 MHz Band * - Prior to Rebanding
- SMR (80 channels)
INCLUDES NEXTEL
- Business/SMR (50 channels)
INCLUDES NEXTEL
- Industrial/SMR (50 channels)
INCLUDES NEXTEL
-
Public Safety (70 channels) )*
Up-Link
806
TV
Broadcast
Ch. 60-69
General Category
INCLUDES NEXTEL
B/ILT & SMALL
NO. OF PUBLIC
SAFETY
809.75
816
Upper 200 SMR
(NEXTEL)
821 824 825
NPSPAC CELLULAR
[7.5 MHz] [12.5 MHz] [10 MHz] [6 MHz]
851 854.75
861 866 869 870
Down-Link
Source: APCO/Gurss
Interference Concerns:
Nextel Adjacent Channel Interference to Public Safety
Intermodulation Interference
(Nextel GC, Interleaved, Upper 200, & Cellular A Block)

• S-DARS and WCS Spectrum
2305
WCS
2320
Sat.
S-DARS
Ter.
Sat.
Sat.
S-DARS
Ter.
Sat.
2332.5
2345
WCS
2360
AT
2370 MHz
Interference Concerns
S-DAR Terrestrial Tx (Repeaters)

WCS Receivers
WCS Mobile Tx

S-DARS Mobile Rx
WCS Base/Mobile Tx

AT Systems
AT = Aeronautical Telemetry (2370 -2395 MHz)

• AWS-3 Interference to AWS-1 (Or Not)
Base Tx
Mobile Rx
Base Tx/Rx
Mobile Tx/Rx
2110
Paired with
1710-1755
AWS-1 (FDD)
2155
AWS-3 (TDD) MSS
2180 Frequency (MHz)
Potential Interference Concerns:
AWS-3 Mobile Tx  AWS-1 Mobile Rx (Spillover/OBE)
AWS-3 Mobile Tx  AWS-1 Mobile Rx (Overload/Desensitization
AWS-1 Base Tx  AWS-3 Base Rx

• Mobile Satellite Service (MSS) Ancillary
Terrestrial Component (ATC) Interference to GPS/GNSS
1525
MSS (Down)
1559
GPS
1575.42
GPS L1 Signal
1610 1626.5
MSS (Up)
1660.5
Interference Concerns:
MSS ATC Interference

GPS Rx

• Military Radar Interference with 4.9 GHz
Public Safety
RA = Radio Astronomy
Military Radar Public Safety Primary
4920 4940
Note: RA is also allocated 4940-4990 on a secondary basis
Interference Concerns:
Military Radar

Public Safety Systems
4990
RA
5000

• 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?

• Potential Discussion Points
– FCC resolved the issue by:
• Separating non-cellular (high-power, high elevation, noiselimited systems) from cellular (low-power, low elevation, interference limited systems) into different, discrete spectrum blocks
• Prohibited the deployment of cellular systems in the noncellular block
– Established basis for resolving interference cases
• Defined the environment in which protection would be provided to non-cellular licensees (as described above)

• 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

Dale N. Hatfield
Executive Director
Silicon Flatirons Center for Law, Technology, and Entrepreneurship
University of Colorado at Boulder
401 UCB - Office 404
Boulder, CO 80309
Direct Dial: 303-492-6648
Email: dale.hatfield@colorado.edu
or dale.hatfield@ieee.org