Each frequency range or band offers its advantages and inconveniences, mainly in terms of:

1. Coverage (also sometimes a factor of Penetration Distance)

Lower frequencies offer more Coverage and better Penetration Distance. This can be important when deploying in cities where the cost of leasing real estate to install cellphone towers is a factor, and where good building penetration distance is required.

2. Data Throughput

Higher frequencies offer better Data Throughput and lower latencies. This can be important when cellphone companies want to offer new high bandwidth low-latency services, especially in metropolitan areas, such as multiple simultaneous video streams (imagine assistant a sports event in a stadium and the cellphone company offers you the ability to get multiple video angles of the actions that you're witnessing live)

So cellphone companies often bid high prices for the more sought-after bands, especially those in the mid-band (FR1) range. Let me give you an overview of most of the more popular radio frequency (RF) ranges or bands used for 5G.

The C-band is a designation by the Institute of Electrical and Electronics Engineers (IEEE) for a portion of the electromagnetic spectrum in the microwave range of frequencies ranging from 4.0 to 8.0 GHz. However, the U.S. FCC designated 3.7–4.2 GHz as C-band, differing from the IEEE's designation. In the rest of this article, I will refer to the U.S. C-band since that's the band where most of the contentious issues arise and it's the commonly used designation for the spectrum causing some of the issues.

The US C-band is used for many satellite communications transmissions, some Wi-Fi devices, some cordless telephones, as well as some Radar and weather radar systems. The communications C-band was actually the first frequency band that was allocated for commercial telecommunications via satellites. The same frequencies were already in use for terrestrial microwave radio relay chains.

Nearly all C-band communication satellites use the band of frequencies from 3.7 to 4.2 GHz for their downlinks, and the band of frequencies from 5.925 to 6.425 GHz for their uplinks.

Note that by using the band from 3.7 to 4.0 GHz, this C-band overlaps somewhat with the IEEE S band for radars.

The C-band communication satellites typically have 24 radio transponders spaced 20 MHz apart, but with the adjacent transponders on opposite polarizations such that transponders on the same polarization are always 40 MHz apart. Of this 40 MHz, each transponder utilizes about 36 MHz. (The unused 4.0 MHz between the pairs of transponders acts as "guard bands" for the likely case of imperfections in the microwave electronics.)

One use of the C-band is for satellite communication, whether for full-time satellite television networks or raw satellite feeds, although subscription programming also exists. This use contrasts with direct-broadcast satellite, which is a completely closed system used to deliver subscription programming to small satellite dishes that are connected with proprietary receiving equipment.

The satellite communications portion of the C-band is highly associated with television receive-only satellite reception systems, commonly called "big dish" systems, since small receiving antennas are not optimal for C band. Typical antenna sizes on C-band-capable systems range from 6 to 12 feet (1.8 to 3.5 meters) on consumer satellite dishes, although larger ones also can be used. For satellite communications, the microwave frequencies of the C band perform better under adverse weather conditions in comparison with the Ku band (11.2–14.5 GHz), microwave frequencies used by other communication satellites.[4] Rain fade – the collective name for the negative effects of adverse weather conditions on transmission – is mostly a consequence of precipitation and moisture in the air.

The US C-band also includes the 5.8 GHz ISM band between 5.725 and 5.875 GHz, which is used for medical and industrial heating applications and many unlicensed short-range microwave communication systems, such as cordless phones, baby monitors, and keyless entry systems for vehicles. The C-band frequencies of 5.4 GHz band [5.15 to 5.35 GHz, 5.47 to 5.725 GHz, or 5.725 to 5.875 GHz, depending on the region of the world] are used for IEEE 802.11a Wi-Fi wireless computer networks.

As part of the Trump administration’s 5G FAST Plan, in March 2018, the MOBILE NOW Act directed the U.S. FCC to evaluate the feasibility of commercial wireless deployments in the C-Band which was until then was used by satellite operations. By repacking existing satellite operations into the upper 200 megahertz of the band (and reserving the 20 MHz between 3980–4000 MHz as a guard band and not available for auction), the Commission makes 280 MHz of spectrum available for flexible use throughout the contiguous United States, and does so in a manner that ensures the continuous and uninterrupted delivery of services currently offered in the band.

The FCC started a proceeding in May 2018 and adopted the C-band Report and Order authorizing flexible use of the 3.7-3.98 GHz band in March 2020 to reform the use of the 3.7-4.2 GHz band (FCC adopted rules).

Satellite companies agreed to vacate their holdings in exchange for accelerated payments from an FCC Auction, a relocation process to be finalized by December 2023. The prospective bidders will pay holders for their spectrum rights so they can deploy next generation wireless services like 5G, a more valuable use. The FCC was hoping to sell more than 5,000 new flexible-use overlay licenses for C-band spectrum in the 3.7–3.98 GHz frequency. 

Since then, the FAA also issued aircraft-model-specific Airworthiness Notifications and ADs to reduce the risk to other critical aircraft systems that was not previously covered by the generic AD 2021-23-12 or 2021-23-13.

• On 2022-01-14, FAA required operators of  Boeing 787s to take additional precautions when landing on wet or snowy runways at airports where 5G C-band service is deployed. During the two-week delay in deploying new 5G service, safety experts determined that 5G interference with the aircraft’s radio altimeter could prevent engine and braking systems from transitioning to landing mode, which could prevent an aircraft from stopping on the runway. The Airworthiness Notification requires crews to be aware of this risk and to adopt specific safety procedures when landing on these runways. The directive affects 137 aircraft in the United States and 1,010 worldwide. 

• On 2022-01-25, FAA issued an AD prohibiting Boeing B747-8, 747-8F and 777 airplanes from landing at airports where 5G interference could occur. Link to Airworthiness Directive (AD). The AD does not apply to landings at airports where the FAA determined the aircraft altimeters are safe and reliable in the 5G C-band environment. It also does not apply to airports where 5G isn’t deployed. The FAA issued the AD because many systems on Boeing 747-8, 747-8F and 777 aircraft rely on the altimeter, including autothrottle, ground proximity warning, thrust reversers and Traffic Collision Avoidance System. The AD affects approximately 336 airplanes in the United States and 1,714 worldwide. Compliance time is within two days of the effective date of the AD.  

• Many others...

RTCA Special Committee SC-239 and EUROCAE Working Group WG-119 started working jointly to address minimum performance requirements for radio altimeters when subjected to RF interferences, considering the ongoing deployments of 5G and other broadband technologies. The original work plan was to completely re-write the MOPS document (including the addition of new RF interference requirements and test procedures) and to release the entire DO-155A/ED-30A MOPS update by December 2022. Since the immediate need by industry and regulators are the RF interference requirements & associated tests, the work plan has been revised to first release a new DO-XXX/ED-XXX document “Technical Standard on RF Interference Environment for Radar Altimeters” in December 2022, followed by the DO-155A/ED-30A MOPS revision in December 2023. 

In addition, a new joint RTCA Special Committee SC-242 and EUROCAE Working Group WG-124 has been initiated. The WG is intended to provide guidance to ensure that the radio frequency characteristics of aeronautical Communications, Navigation and Surveillance (CNS) systems use the spectrum efficiently while respecting the necessary safety margins. The guidance is intended to facilitate any future evaluation of compatibility with other systems and ensure that the usage of the allocated spectrum is as efficient as possible, fully taking into account the specificities of aeronautical CNS systems. The deliverables are envisaged to be referenced by EASA, FAA, other CAAs, ICAO, and national/international spectrum regulators, as appropriate, in guidance material for aviation systems.

On June 17th 2022, the FAA issued a statement with a major update:

"Key stakeholders in the aviation and wireless industries have identified a series of steps that will continue to protect commercial air travel from disruption by 5G C-band interference while also enabling Verizon and AT&T to enhance service around certain airports.

“We believe we have identified a path that will continue to enable aviation and G C-band wireless to safely co-exist,” said Acting FAA Administrator Billy Nolen. “We appreciate the willingness of Verizon and AT&T to continue this important and productive collaboration with the aviation industry.”

The phased approach requires operators of regional aircraft with radio altimeters most susceptible to interference to retrofit them with radio frequency filters by the end of 2022. This work has already begun and will continue on an expedited basis.

At the same time, the FAA worked with the wireless companies to identify airports around which their service can be enhanced with the least risk of disrupting flight schedules.

During initial negotiations in January, the wireless companies offered to keep mitigations in place until July 5, 2022, while they worked with the FAA to better understand the effects of 5G C-band signals on sensitive aviation instruments.

Based on progress achieved during a series of stakeholder roundtable meetings, the wireless companies offered Friday to continue with some level of voluntary mitigations for another year.

“We all agreed when we began these meetings that our goal was to make July 5, 2022, just another date on the calendar, and this plan makes that possible,” Nolen said.

Airlines and other operators of aircraft equipped with the affected radio altimeters must install filters or other enhancements as soon as possible.

Filters and replacement units for the mainline commercial fleet should be available on a schedule that would permit the work to be largely completed by July 2023. After that time, the wireless companies expect to operate their networks in urban areas with minimal restrictions.

The radio-altimeter manufacturers have worked at an unprecedented pace with Embraer, Boeing, Airbus and Mitsubishi Heavy Industries to develop and test filters and installation kits for these aircraft. Customers are receiving the first kits now. In most cases, the kits can be installed in a few hours at airline maintenance facilities.

Throughout this process, the FAA will work with both industries to track the pace of the radio altimeter retrofits while also working with the wireless companies to relax mitigations around key airports in carefully considered phases.

The agency also will continue to engage with the National Telecommunications and Information Administration and the Federal Communications Commission on technical issues associated with these efforts."

Just prior to the 2022-2023 holidays, a similar debacle unfolded, where the FAA was notified by telecommunications providers that 5G C-band deployments in the 3.8-3.98 GHz frequency band are expected to begin deploying at selected locations beginning January 1, 2023, earlier than the planned earliest dates of July 2023. Considering the closer proximity of this frequency range to the protected radalt band, the FAA advised aircraft manufacturers right away and asked that they use the same Variable Radius Method (AMOC V3) Spreadsheet used for the previous data submittals to support the AMOCs, but reflecting the new frequency range and incresed power levels, to determine the computed interference radius for the radalt models installed on their aircraft. For most aircraft with modern radalts, the computed interference radius jumped from less than 400ft to around 1,000ft (sometimes up to 1,2000ft)! In fact, when looking at the FAA ASIAS data (notably the publically available NASA ASRS data), you can find many incidents where pilots reported aircraft systems failing at around 1,200ft!

On May 26th 2023, FAA AD 2023-10-02 (for airplanes) and FAA AD 2023-11-07 (for helicopters) were issued & immediately effective, superseding the previous AD 2021-23-12 (for airplanes) and AD 2021-23-13 (for helicopters). They maintained the Limitations in the previous ADs, but referred to the FAA Domestic Notices in lieu of the NOTAMs until June 30th, and thereafter (July 1st 2023 onwards) implementing the Limitations only for non-radalt tolerant aircraft. 14 CFR Part 121 (Commercial) operators have until February 2024 to convert their airplanes to a radalt tolerant airplane (a.k.a. Group 4 airplane) by upgrading their radalts or installing filters, but other aircraft (like business jets operating under Part 91 or Part 135) will need to comply with the Limitations until they decide to upgrade their radalts or install filters. Most aircraft manufacturers are offering retrofit solutions to upgrade their aircraft to radalt tolerant airplanes, and most operators see the operational advantages of upgrading their aircraft to remove the severe Limitations.

In June 2018, Canada's Innovation, Science and Economic Development Canada (ISED) released Spectrum Outlook 2018 to 2022, which included plans to release spectrum that would support 5G services. The Outlook indicated that releasing the 3450–3650 MHz band (referred to as the 3500 MHz band), a key band for 5G, was a high priority. 

In Canada, contrary to the U.S.A., the Aviation industry was mostly successful in lobbying the regulators, ISED, to put in place mandatory nationwide mitigation measures to reduce the impact of 5G C-band to Aviation users.

In June 2019, ISED published the Decision on Revisions to the 3500 MHz Band to Accommodate Flexible Use and Preliminary Decisions on Changes to the 3800 MHz Band as the first step toward making this band available.

Through the release of the Policy and Licensing Framework for Spectrum in the 3500 MHz Band, ISED is setting the rules for the upcoming spectrum auction, the next step toward making this band available for 5G services.

ISED is making 200 MHz of spectrum available in the 3500 MHz band for “flexible use” licensing that allows licensees to choose the type of services they will deploy, such as mobile (5G) or fixed wireless services (e.g. Internet-to-the-home). 

ISED planned to auction 3450–3650 MHz band (referred to as the 3500 MHz band) spectrum with bidding to start on 2021-06-15. See https://www.ic.gc.ca/eic/site/smt-gst.nsf/eng/h_sf11519.html

On October 13th, 2020, Transport Canada Civil Aviation (TCCA)'s Standards branch sent a public letter (reference SLPB-002-20) to ISED, titled “Consultation on the Technical and Policy Framework for the 3650-4200 MHz Band and Changes to the Frequency Allocation of the 3500-3650 MHz Band”, dated 2020-10-13, RDIMS #16921882, and which stated:

“[…]

Conclusion

"There are liability concerns with 5G implementation and ISED needs to consider the seriousness of harmful interference to aircraft onboard radar altimeter equipment that may be caused by 5G telecommunications systems in the 3.7–3.98 GHz band implementation in Canada with the potential loss of lives if an Aviation accident would occur due to 5G interference with Radar Altimeter or WAIC. ISED needs to establish appropriate safety 4 measures to respect the ICAO 6 dB safety margin, by implementing specific technical requirements and mitigation measures. Frequency band selection should not be swayed by economic reasons or harmonization with the USA, rather human safety should be the priority. ISED should also consider reducing the 5G operational bandwidth in some geographical areas near airports to increase the frequency guard band with the aviation frequency band in order to ensure aviation safety.

[…]”

TCCA also released CASA 2021-08 Issue 01 on June 15th, 2021, titled "Potential Risk of Interference of 5G Signals on Radio Altimeter".

ISED published the Consultation on Amendments to SRSP-520, Technical Requirements for Fixed and/or Mobile Systems, on 2021-08-06. The Canadian aviation industry applauded ISED‘s recently proposed changes in the technical consultation which would:

• • 1. Modify outdoor antenna tilt requirements in all areas, and,

    2. Limit outdoor operations in areas immediately surrounding specific airports in order to help ensure radio altimeters are not affected by 3500 MHz operations.

An October 9th 2021 Ottawa Sun article explained that ISED has responded to Transport Canada’s recommendations curtailing deployment of 5G base stations around airports because of this concern. Canadian telecoms like Bell, Rogers, and Telus, were not very happy with the restrictions, but they took the hit like champs and amended their deployment strategy and proceeded to finalize their bids on the ISED planned to auction 3450–3650 MHz band (referred to as the 3500 MHz band) spectrum.

On November 18th, 2021, ISED issued restrictions on antenna location close to airports with CAT I/II/III approaches (they called these exclusion zones and protection zones), antenna tilt restrictions, and other operational limitations.
Consultation on Amendments to SRSP-520, Technical Requirements for Fixed and/or Mobile Systems, Including Flexible Use Broadband Systems, in the Band 3450-3650 MHz

• • Addendum to Consultation on Amendments to SRSP-520, Technical Requirements for Fixed and/or Mobile Systems, Including Flexible Use Broadband Systems, in the Band 3450-3650 MHz

  • Map of Exclusion Zones and Protection Zones (SRSP-520)

  • Decision on Amendments to SRSP-520, Technical Requirement for Fixed and/or Mobile Systems, Including Flexible Use Broadband Systems, in the Band 3450-3650 MHz

TCCA also issued an Airworthiness Directive (AD) CF-2021-52 in December 2021, adopting the FAA AD 2021-12-23. Generic AMOC issued to allow automatic TCCA acceptance of FAA Global AMOCs.  TCCA AD CF-2021-52 was superseded by TCCA AD CF-2023-46 which was issued and became effective in June 2023, and adopting the latest FAA AD 2023-10-02. Similar ADs were issued for helicopters in Canada.

In July 2023, ISED issued its Decision on SRSP-520, issue 3 and RSS-192, issue 5 which summarizes the medium-term plan to allow a safe rollout of 5G in Canada. To summarize the aircraft-related provisions: 

• Decision 1: ISED will impose exclusion and protection zones for both 3500 MHz and 3800 MHz bands that take into account OCS and adopt Transport Canada’s proposed e.i.r.p. spectral density curves around 35 airports identified in the Map of Exclusion Zones and Protection Zones (SRSP-520). In simple terms, Canadian telecom companies won't be allowed to blast high-powered high bandwidth 5G signals around airports like allowed in the US. Makes sense, right? Typical Canadian approach: let's not do something that creates useless risk. This mitigation measure will apply until January 1, 2026 (see Decision 6 on sunset date below).

• Decision 2: ISED will impose a national e.i.r.p. mask. In simple terms, Canadian telecom companies won't be allowed to blast high-powered high bandwidth 5G signals everywhere else in Canada. This mitigation measure will apply until January 1, 2026 (see Decision 6 on sunset date below).

• Decision 3: ISED will impose an airport e.i.r.p. mask around the 35 protected airports for both 3500 MHz and 3800 MHz bands in SRSP-520, issue 3, until January 1, 2026. From January 2, 2026 to December 31, 2027, this airport e.i.r.p. mask will only apply to the 3800 MHz band in former exclusion zones and in protection zones (see Decision 6 on sunset date below).

• Decision 4: ISED will not impose exclusion and protection zones around H1 classified heliports across Canada.

• With regards to advanced notice from the telecommunication industry, ISED requires 3500 MHz and 3800 MHz licensees to provide pre-operation reports 15 days prior to the operation of base stations in protection zones around protected airports. ISED will extend that requirement to include the submission of these reports directly to TC to facilitate their planning process.
  […]
  If Transport canada requires additional notifications and data beyond what is described above, they are encouraged to discuss directly with 3500 MHz and 3800 MHz licensees to obtain the information, similar to the voluntary arrangements made between the FAA and mobile operators in the US. ISED encourages licensees to collaborate with Transport canada in providing the necessary information to facilitate TC’s planning of aviation restrictions and alleviations accordingly.

• In order to strike the right balance between providing sufficient time for aircraft operators to retrofit and minimizing impact on 5G deployments in Canada, ISED will extend the sunset date by 9 months, to January 1, 2026. On this date, the national e.i.r.p. mask, exclusion zones and the height and power restrictions within the protection zones for 3500 MHz and 3800 MHz bands will be removed.
  […]
  Further, elevated MDUs are typically not authorized along airport runway paths to provide proper clearance for landing and take-off of aircraft. As such, an antenna uptilt would be even less expected in areas around airports. Nevertheless, ISED will maintain an airport e.i.r.p. mask in the area covered by the former 3800 MHz exclusion zones and in the 3800 MHz protection zones. This mask will only apply to base stations operating in the 3800 MHz band around the 35 protected airports until December 31, 2027 to provide a predicable radio frequency environment around these airports. Based on expected 5G deployment scenarios, retaining an airport e.i.r.p. power mask within the exclusion and protection zones until December 31, 2027, around these 35 protected airports, will have negligeable impact on 5G deployments in Canada.
  ISED will continue to monitor domestic and international developments on coexistence between 5G operations and radio altimeters.

• Decision 6: ISED will impose the following sunset dates:

  • As of January 1, 2026, the national e.i.r.p. mask, the exclusion zones and the height and power restrictions within the protection zones around the 35 airports in the 3500 MHz and 3800 MHz bands will be removed.

  • From January 2, 2026 to December 31, 2027, the airport e.i.r.p. mask will only apply to the 3800 MHz band base stations within the former exclusion zones and within the protection zones around the 35 airports.

  • As of January 1, 2028, all mitigation measures specified above will be removed.

• Decision 7: Due to the minimal impact of extending the majority of the mitigation measures by 9 months (January 1, 2026), and the negligeable impact of the airport e.i.r.p. mask on 5G deployments in Canada, ISED will not extend the 3500 MHz and 3800 MHz licence terms. 

• In the proposed changes to the RSS, ISED included a spurious (unwanted) emission limit of -33 dBm/MHz in the 4200-4400 MHz band, the operating band of radio altimeters, in order to minimize the potential of harmful interference to radio altimeters.
  In addition, ISED proposed to increase the limit for indoor base stations from 33 dBm to 39 dBm TRP and proposed to revise the limit for subscriber equipment other than fixed subscriber equipment from 23 dBm/10 MHz to 30 dBm e.i.r.p. per channel bandwidth. Comments were provided on these amendments, including out-of-band emission limits of equipment and the transition period between issue 4 and issue 5 of the RSS.
  […]
  Stakeholders from the telecommunications industry which included Bell, MIG, RABC, Rogers, Sasktel and TELUS, suggested ISED should adopt a spurious emission limit of -30 dBm/MHz instead of -33 dBm/MHz. In their comments, these stakeholders highlighted that 5G base stations transmit using two polarizations while radio altimeter antennas detect only one polarization, which means that a signal received by a radio altimeter antenna from a 5G base station would be 3 dB lower in power. Therefore, they suggested that a spurious emission limit of -30 dBm/MHz for a base station, which would translate to -33 dBm/MHz for the radio altimeter, would be a more suitable limit.
  […]
  ISED recognizes that 5G equipment is designed to meet international regulatory requirements, including specifications set forth in industry standards. For instance, the 3rd Generation Partnership Project (3GPP) standard body specifies two categories of equipment that meet either a -13 dBm/MHz or -30 dBm/MHz spurious emissions limit in frequency bands above 1 GHz (as specified in TS 38.104). Equipment meeting a -30 dBm/MHz limit is typically adopted in equipment deployed in European markets to meet European regulatory requirements, while a -13 dBm/MHz limit is for North American markets to meet Canadian and US regulatory requirements.
  
  In the US, the FAA secured a voluntary agreement with the four largest mobile operators to deploy base stations with spurious emission levels of -48 dBm/MHz or less in the 4200-4400 MHz band. This -48 dBm/MHz spurious emission level includes a 6 dB aviation safety margin and an additional 6 dB margin to account for aggregate emissions from multiple base stations (see FAA NPRM, Airworthiness Directives; Various Helicopters).
  ISED notes that the agreement between the FAA and the four US mobile operators is a voluntary operational specification rather than a regulatory certification requirement mandated by the US spectrum regulator, the FCC. ISED also notes that the FCC has not adopted a more stringent spurious emission limit, as -13 dBm/MHz remains the current regulatory limit. If ISED were to adopt a limit of -48 dBm/MHz as part of the certification process for 5G base stations, it could result in a Canadian-only ecosystem, leading to higher cost of 5G services for Canadians.
  […]
  ISED reviewed its own laboratory results and radio altimeter manufacturer data, and compared it with new data shared by TC. TC’s data included margins for unit-to-unit and temperature variance. ISED found that its original ITM, described in annex A of the Consultation, sufficiently captured the performance of all radio altimeters for which ISED had data.
  ISED is of the view that an additional safety margin of 6 dB was not required in its computational analysis. The ICAO Handbook notes that a minimum 6 dB safety margin is generally required to account for risk that some factors cannot be foreseen or quantified (e.g. aggregate emissions). In its computational model, ISED made multiple additive worst-case assumptions to minimize the risk of harmful interference between 5G operations and radio altimeters. ISED did not include factors that would have improved coexistence between 5G systems and radio altimeters, such as typical digital tilt of base station which limits skyward antenna lobes (up to 3 dB), base station Time Division Duplex (TDD) duty cycle (up to 3 dB) and typical traffic load (up to 3 dB), and polarization losses (up to 3 dB). Moreover, ISED’s computational analysis model assumed that the following events would all occur at the same time: worst-case antenna coupling, spurious emissions magnitude, base station antenna pointing angle and radio altimeter loop loss factor. The omission of factors that would improve coexistence and the assumption of worst-case events occurring simultaneously provided a safety margin significantly higher than the ICAO 6 dB safety margin.

• Decision 14: ISED will adopt a spurious emission limit of -30 dBm/MHz in the 4200-4400 MHz band in RSS-192, issue 5.

• Decision 15: ISED will increase the maximum power limit for indoor base stations to 39 dBm TRP and the limit for subscriber equipment, other than fixed subscriber equipment, to 30 dBm/channel bandwidth e.i.r.p in RSS-192, issue 5.

  • These values could be revisited in future revisions of the technical standard based on the evolution of the technology.

• Decision 16: ISED will adopt a -13 dBm/MHz unwanted emission limit above 3900 MHz for outdoor equipment in RSS-192, issue 5.

• The MIG, RABC, Rogers, Sasktel and TELUS recommended that the -30 dBm/MHz limit for unwanted emissions for indoor base stations apply above 3980 MHz rather than 3910 MHz. They highlighted that the proposed recommendation would make a broad indoor base station ecosystem available to the Canadian service providers, including those designed for the US market.
  ISED agreed with the Canadian telecom providers.
  […]
  Decision 17: ISED will adopt a -30 dBm/MHz out-of-band unwanted emission limit above 3980 MHz for indoor base stations in RSS-192, issue 5.