https://urgentcomm.com/wp-content/themes/ucm_child/assets/images/logo/footer-new-logo.png
  • Home
  • News
  • Multimedia
    • Back
    • Multimedia
    • Video
    • Podcasts
    • Galleries
    • IWCE’s Video Showcase
    • Product Guides
  • Commentary
    • Back
    • Commentary
    • Urgent Matters
    • View From The Top
    • All Things IWCE
    • Legal Matters
  • Resources
    • Back
    • Resources
    • Webinars
    • White Papers
    • Reprints & Reuse
  • IWCE
    • Back
    • IWCE
    • Conference
    • Special Events
    • Exhibitor Listings
    • Premier Partners
    • Floor Plan
    • Exhibiting Information
    • Register for IWCE
  • About Us
    • Back
    • About Us
    • Contact Us
    • Advertise
    • Terms of Service
    • Privacy Statement
    • Cookie Policy
  • Related Sites
    • Back
    • American City & County
    • IWCE
    • Light Reading
    • IOT World Today
    • Mission Critical Technologies
    • TU-Auto
  • In the field
    • Back
    • In the field
    • Broadband Push-to-X
    • Internet of Things
    • Project 25
    • Public-Safety Broadband/FirstNet
    • Virtual/Augmented Reality
    • Land Mobile Radio
    • Long Term Evolution (LTE)
    • Applications
    • Drones/Robots
    • IoT/Smart X
    • Software
    • Subscriber Devices
    • Video
  • Call Center/Command
    • Back
    • Call Center/Command
    • Artificial Intelligence
    • NG911
    • Alerting Systems
    • Analytics
    • Dispatch/Call-taking
    • Incident Command/Situational Awareness
    • Tracking, Monitoring & Control
  • Network Tech
    • Back
    • Network Tech
    • Interoperability
    • LMR 100
    • LMR 200
    • Backhaul
    • Deployables
    • Power
    • Tower & Site
    • Wireless Networks
    • Coverage/Interference
    • Security
    • System Design
    • System Installation
    • System Operation
    • Test & Measurement
  • Operations
    • Back
    • Operations
    • Critical Infrastructure
    • Enterprise
    • Federal Government/Military
    • Public Safety
    • State & Local Government
    • Training
  • Regulations
    • Back
    • Regulations
    • Narrowbanding
    • T-Band
    • Rebanding
    • TV White Spaces
    • None
    • Funding
    • Policy
    • Regional Coordination
    • Standards
  • Organizations
    • Back
    • Organizations
    • AASHTO
    • APCO
    • DHS
    • DMR Association
    • ETA
    • EWA
    • FCC
    • IWCE
    • NASEMSO
    • NATE
    • NXDN Forum
    • NENA
    • NIST/PSCR
    • NPSTC
    • NTIA/FirstNet
    • P25 TIG
    • TETRA + CCA
    • UTC
Urgent Communications
  • NEWSLETTER
  • Home
  • News
  • Multimedia
    • Back
    • Video
    • Podcasts
    • Omdia Crit Comms Circle Podcast
    • Galleries
    • IWCE’s Video Showcase
    • Product Guides
  • Commentary
    • Back
    • All Things IWCE
    • Urgent Matters
    • View From The Top
    • Legal Matters
  • Resources
    • Back
    • Webinars
    • White Papers
    • Reprints & Reuse
    • UC eZines
    • Sponsored content
  • IWCE
    • Back
    • Conference
    • Why Attend
    • Exhibitor Listing
    • Floor Plan
    • Exhibiting Information
    • Join the Event Mailing List
  • About Us
    • Back
    • About Us
    • Contact Us
    • Advertise
    • Cookie Policy
    • Terms of Service
    • Privacy Statement
  • Related Sites
    • Back
    • American City & County
    • IWCE
    • Light Reading
    • IOT World Today
    • TU-Auto
  • newsletter
  • In the field
    • Back
    • Internet of Things
    • Broadband Push-to-X
    • Project 25
    • Public-Safety Broadband/FirstNet
    • Virtual/Augmented Reality
    • Land Mobile Radio
    • Long Term Evolution (LTE)
    • Applications
    • Drones/Robots
    • IoT/Smart X
    • Software
    • Subscriber Devices
    • Video
  • Call Center/Command
    • Back
    • Artificial Intelligence
    • NG911
    • Alerting Systems
    • Analytics
    • Dispatch/Call-taking
    • Incident Command/Situational Awareness
    • Tracking, Monitoring & Control
  • Network Tech
    • Back
    • Cybersecurity
    • Interoperability
    • LMR 100
    • LMR 200
    • Backhaul
    • Deployables
    • Power
    • Tower & Site
    • Wireless Networks
    • Coverage/Interference
    • Security
    • System Design
    • System Installation
    • System Operation
    • Test & Measurement
  • Operations
    • Back
    • Critical Infrastructure
    • Enterprise
    • Federal Government/Military
    • Public Safety
    • State & Local Government
    • Training
  • Regulations
    • Back
    • Narrowbanding
    • T-Band
    • Rebanding
    • TV White Spaces
    • None
    • Funding
    • Policy
    • Regional Coordination
    • Standards
  • Organizations
    • Back
    • AASHTO
    • APCO
    • DHS
    • DMR Association
    • ETA
    • EWA
    • FCC
    • IWCE
    • NASEMSO
    • NATE
    • NXDN Forum
    • NENA
    • NIST/PSCR
    • NPSTC
    • NTIA/FirstNet
    • P25 TIG
    • TETRA + CCA
    • UTC
acc.com

Rebanding


An introduction to 4.9 GHz

An introduction to 4.9 GHz

Starting in 2003, the federal government has made available 50 MHz of new radio spectrum between 4.940 MHz and 4.990 MHz for public-safety use. This spectrum
  • Written by Urgent Communications Administrator
  • 1st January 2007

Starting in 2003, the federal government has made available 50 MHz of new radio spectrum between 4.940 MHz and 4.990 MHz for public-safety use. This spectrum is designated for fixed and mobile broadband wireless services. Communications in this band must support the protection of life, health or property, with proposed uses including wireless local area networks, or WLANs; mobile data; video security; voice over IP, or VoIP; and ad hoc networks.

Although permanent point-to-point fixed installations are allowed with certain restrictions, the main purpose of the band is for temporary point-to-point links and mobile operations, which take priority over permanent fixed installations. This article provides a basic primer for navigating the 4.9 GHz airwaves.

Prior to 2003, the 4.9 GHz band (4.940 GHz to 4.990 GHz) in the U.S. was allocated to federal government fixed and mobile services. The band was used for fixed services such as conventional point-to-point microwave, tactical radio relay, high-power tropospheric scatter systems, and for mobile services such as control of remote piloted vehicles, video and data telemetry links, target drone control links, fleet defense systems and tethered aerostat systems.

In 1999, the 4.9 GHz band was transferred from federal government use to non-government use in accordance with the provisions of the Omnibus Budget Reconciliation Act. In 2000, the FCC released a Notice of Proposed Rulemaking that suggested allocating the 4.9 GHz band to non-government fixed and mobile services, excluding aeronautical mobile service, on a co-primary basis, and allowing for flexible use of the band. The FCC also tentatively decided not to designate the band exclusively for public-safety use. However, many local government entities and national public-safety associations argued that public safety urgently needed this spectrum for broadband wireless services. In its second Report and Order (R&O), the commission reversed itself and reserved the 4.9 GHz band exclusively for public safety [1].

The FCC issued a third R&O in May 2003 that defined additional rules for eligibility and use of the 4.9 GHz band, and for the first time allowed public-safety agencies to apply for and receive licenses to operate in the band [2]. FCC rules governing the 4.9 GHz band are found in Part 90, Title 47 of the Code of Federal Regulations [3]. Sections of Part 90 relevant to the 4.9 GHz band include the following: Part 90.523 defines who is eligible to hold a 4.9 GHz license; Part 90.1213 defines the channelization of the band; Part 90.1215 defines the power limits for radios operating in the band; and Part 90.210 defines the emission masks for the band.

The FCC allows channels to be aggregated to channel bandwidths of 1, 5, 10, 15, or 20 MHz. The maximum channel size is 20 MHz. FCC channels are listed in Table 1.

An emission mask defines how much spectrum the signal may occupy. Today, the FCC authorizes two masks for use in the 4.9 GHz band: Emission mask L for low-power devices and emission mask M for high-power devices. The M mask provides better adjacent channel protection and was adopted first.

The L mask is nearly identical to the mask defined in the IEEE 802.11 standards. It was chosen to let public-safety agencies and equipment vendors exploit the economies of scale created by existing 5 GHz commercial off-the-shelf devices, thereby reducing costs and time to market. Both emission masks are plotted for 10 MHz in Figure 1 on the proceeding page.

Higher-power devices will of course extend the range and reliability of 4.9 GHz networks, so from that perspective, emission mask M is preferred.

Emission mask, transmitter power and effective isotropic radiated power (EIRP) are tightly coupled in the FCC rules. Part 90.1215 creates a relatively complicated set of power limitations that we will summarize here.

Part 90.1215 limits both transmitter power and EIRP. The power limits for low- and high-power devices are listed in Table 2. Note that within each category, the power density (dBm/MHz) is the same, regardless of channel bandwidth. The power-density limit for low-power devices is 7 dBm /MHz, while the power-density limit for high-power devices is 20 dBm/MHz.

EIRP is the product of transmitter power and antenna gain (relative to isotropic radiated power). Assuming that the receiving station is operating in the main lobe of the transmitting antenna, EIRP determines the power received, not the transmitter power. For example, a 30 dBm transmitter operating with a 10 dBi antenna has an EIRP of 40 dBm, but a 27 dBm transmitter operating with a 13 dBi antenna also has an EIRP of 40 dBm — both systems will result in the same receive power if the receiving station is in the main lobe of the transmitting antenna.

Both low- and high-power devices may use omnidirectional or directional antennas with gains up to 9 dBi at maximum transmitter power.

Low-power devices may use directional antennas with gain greater than 9 dBi if both transmitter power and power spectral density are reduced decibel-for-decibel by the amount the directional antenna gain exceeds 9 dBi.

High-power devices used for point-to-point or point-to-multipoint operation (fixed or temporary) may use directional antennas with gain up to 26 dBi at maximum authorized power. However, directional antenna gain may exceed 26 dBi if both transmitter power and power spectral density are reduced decibel-for-decibel by the amount the directional antenna gain exceeds 26 dBi.

EIRP limits for directional antenna systems are summarized in Table 3.

The emission mask was a contentious issue in 2003 and 2004. Emission mask M — also known as the “tight” mask — originally was the sole emission mask authorized. But neither IEEE 802.11a or 802.11j radios could meet this emission mask, so there was no industry-standard 4.9 MHz product available to public-safety agencies.

Consequently, the National Public Safety Telecommunications Council (NPSTC) and other agencies filed comments with the FCC objecting to the original emissions mask on the grounds it would preclude the use of industry-standard 802.11 radios and would result in expensive, proprietary devices that would stifle innovation. The FCC relented and eventually adopted two masks for 4.9 GHz, the original M mask for high-power devices and the L mask for low-power devices, in November 2004 [3].

Thus, the prohibition on the 802.11a mask has been lifted, but the power limitations of the “loose” L mask create an incentive to use tight mask devices.

At the time of this writing, some manufacturers are developing or have fielded devices that are 802.11 standard-compliant and meet the tight mask, so the original problem may soon be overcome.


Jay Jacobsmeyer is president of Pericle Communications Co., a consulting engineering firm located in Colorado Springs, Colo. He holds bachelor’s and master’s degrees in Electrical Engineering from Virginia Tech and Cornell University, respectively, and has more than 25 years experience as a radio frequency engineer.

References:

  1. Second Report and Order and Further Notice of Proposed Rule Making, “In the Matter of the 4.9 GHz Band Transferred from Federal Government Use,” WT Docket 00-32, Adopted February 14, 2002.

  2. Memorandum Opinion and Order & Third Report and Order, “In the Matter of the 4.9 GHz Band Transferred from Federal Government Use,” WT Docket 00-32, Adopted April 23, 2003.

  3. Title 47 of the U.S. Code of Federal Regulations, Part 15, Part 90, October 1, 2005.

Acknowledgement:

Much of the content for this article was originally developed for the Colorado 4.9 GHz Project, an NTIA-funded study under the direction of the Parker Fire Protection District (Daniel Qualman, Chief).

Tags: content Policy Rebanding

Most Recent


  • An introduction to 4.9 GHz
    Newscan: Cyberattacks on DoE national labs draw lawmaker scrutiny
    Web Roundup Items from other news organizations Cyberattacks on DoE national labs draw lawmaker scrutiny Blinken postpones trip to Beijing after Chinese spy balloon spotted over U.S., officials say To protect satellites, secure your networks, chief of space ops says Ransomware offlines Arizona’s largest school district Mending the fabric: FCC says to file broadband-location challenges […]
  • Phishers trick Microsoft into granting them 'verified' Cloud Partner status
    Late last year, a group of threat actors managed to obtain “verified publisher” status through the Microsoft Cloud Partner Program (MCPP). This allowed them to surpass levels of brand impersonation ordinarily seen in phishing campaigns, as they distributed malicious applications bolstered by a verified blue badge only ever given to trusted vendors and service providers in […]
  • Automakers against stampede to BEV dominance
    When the president of the world’s biggest carmaker talks, people listen. So, when Toyota President Akio Toyoda said, in September of last year, that bans on ICE cars within 10 to 15 years  will be “rather difficult to achieve” because EVs “are just going to take longer than the media would like us to believe,” […]
  • FCC nominee Gigi Sohn headed for third Senate hearing
    President Biden’s nominee for FCC Commissioner Gigi Sohn will is expected to sit through a third hearing in the US Senate sometime in the coming weeks. That means that, in addition to being on track to become the first openly LGBTQ+ Commissioner for the FCC, Sohn will also make history as the first person to endure three […]

Leave a comment Cancel reply

To leave a comment login with your Urgent Comms account:

Log in with your Urgent Comms account

Or alternatively provide your name, email address below:

Your email address will not be published. Required fields are marked *

Related Content

  • FCC closes book on 800 MHz rebanding after almost 17 years
  • Transition Administrator notifies FCC of 800 MHz rebanding completion
  • An introduction to 4.9 GHz
    Newscan: Sprint tells FCC only two licensees have not completed 800 MHz rebanding process
  • 800 MHz rebanding work nears completion, could be finished in less than a year, according to FCC official

Commentary


How 5G is making cities safer, smarter, and more efficient

26th January 2023

3GPP moves Release 18 freeze date to March 2024

18th January 2023

Do smart cities make safer cities?

  • 1
6th January 2023
view all

Events


UC Ezines


IWCE 2019 Wrap Up

13th May 2019
view all

Twitter


UrgentComm

Newscan: Cyberattacks on DoE national labs draw lawmaker scrutiny dlvr.it/Shvpw3

3rd February 2023
UrgentComm

The shine begins to wear off 5G private wireless dlvr.it/Shth0P

3rd February 2023
UrgentComm

Phishers trick Microsoft into granting them ‘verified’ Cloud Partner status dlvr.it/Shqngn

2nd February 2023
UrgentComm

Shapeshifting robot can morph from a liquid to a solid dlvr.it/Shqk9K

2nd February 2023
UrgentComm

Automakers against stampede to BEV dominance dlvr.it/ShpX08

2nd February 2023
UrgentComm

FCC nominee Gigi Sohn headed for third Senate hearing dlvr.it/ShpDcZ

1st February 2023
UrgentComm

Sign up to learn how to successfully manage your Motorola ASTRO® 25 System: spr.ly/60143j8fp https://t.co/XcxiUwzN27

1st February 2023
UrgentComm

Hytera parent cites financial health, but unable to make royalty payment to Motorola Solutions dlvr.it/ShlrlM

1st February 2023

Newsletter

Sign up for UrgentComm’s newsletters to receive regular news and information updates about Communications and Technology.

Expert Commentary

Learn from experts about the latest technology in automation, machine-learning, big data and cybersecurity.

Business Media

Find the latest videos and media from the market leaders.

Media Kit and Advertising

Want to reach our digital and print audiences? Learn more here.

DISCOVER MORE FROM INFORMA TECH

  • American City & County
  • IWCE
  • Light Reading
  • IOT World Today
  • Mission Critical Technologies
  • TU-Auto

WORKING WITH US

  • About Us
  • Contact Us
  • Events
  • Careers

FOLLOW Urgent Comms ON SOCIAL

  • Privacy
  • CCPA: “Do Not Sell My Data”
  • Cookie Policy
  • Terms
Copyright © 2023 Informa PLC. Informa PLC is registered in England and Wales with company number 8860726 whose registered and Head office is 5 Howick Place, London, SW1P 1WG.