US Domestic Watch

The ICTS is also concerned with United States Domestic issues that can impact the availability of telemetry spectrum within the United States of America (USA). In the USA there are several bands identified for aeronautical mobile telemetry operations by the National Telecommunications and Information Administration. Each Band and threats are noted below.

Lower L-Band (1350-1390)

Current Use: In the U.S. this band is critical for time space positioning information data transmission/data linkage.

Spectrum Threat(s): Cellular Interference. While the band is currently not perceived as threatened, it is on several target lists due to its proximity to other “low band” spectrum. There is a concern that that TSPI data links (ARDS, CRIIS, 1350-1390 MHz)) may be affected by adjacent channel interference from cellular operation below 1350 Mhz. This is a watch item for test and training ranges that rely on GPS-based TSPI I instrumentation as the susceptibility of the TSPI data link operations to LTE interference is unknown as this time. Efforts to access this susceptibility, and necessary protection criteria, are needed to analyze this threat.

L-Band (1435-1525 MHz)

Current Use: Allocated for manned AMT in the U.S. This is the primary mother-AMT band in the U.S. and is used for AMT by a number of other administrations as well.

Spectrum Threat(s); Int’l Mobile Telecommunications. The ITU Radio Regulations give AMT priority over IMT in 1435-1535 MHz in Region 2 (North and South America). It remains high on the list of encroachment concerns for ICTS as it resides in the low band “sweet spot” for RF propagation characteristics for international mobile communications. While the ITU regulations are clear, the threat to AMT protection criteria and assignments is real and constant in the World Radiocommunication Conference discussions. ITU Recommendations M. 1459 and 2116 are relevant for AMT protection criteria. Ligado. The upper part of the L-band is also home to several global positioning systems (GPS). Along with AMT operations below 1525 MHz, one of these signals is potentially threatened. L1 (encrypted precision code, coarse acquisition code), at 1575.42 MHz, could receive interference from a terrestrial data link proposed by Ligado Networks (Reston, VA) in the U.S. The Federal Communication Commission (FCC) issued an Order in April 2022 granting the Ligado application for 1526-1536 MHz, 1627.5-1637.5 MHz, and 1646.5-1656.5 MHz operations for a terrestrial Internet of Things (IoT) network. A number of agencies and commercial interests filed Petitions for Reconsideration due to concerns about interference to GPS. If this IoT network is implemented, it could have significant impact on GPS dependent systems (like TSPI). In the National Defense Authorization Act (NDAA-21), Congress added language that bars use of funds by DOD to retrofit any GPS device or system in order to mitigate interference from Ligado or to contract with Ligado until such operations are shown not to cause harmful interference to DOD GPS devices. NDAA-21 also calls for an independent technical review of the FCC’s Order by National Academies of Sciences, Engineering and Medicine. This is still a very lively debate inside the U.S. Commercial Space Launch: Again, in the U.S. the FCC is considering potential allocation of other bands for commercial space launch. One commenter (Virgin Galactic) has asked for space launch allocation in 1435-1525 MHz The ICTS is monitoring this request.

Upper L-Band (1780-1850 MHz)

Current User: Allocated for manned AMT in the US.

Spectrum Threat(s): AWS-3 Auction. In 2014 the Federal Communications Commission started the process of auctioning 65 MHz of spectrum to meet the goals of the National Broadband Plan. This was the third of three auctions required for funding the FirstNet, public safety broadband network and other services. Previous auction results had raised nearly $1.6 billion of the $7 billion needed. The AWS-3 auction generated $44.9 billion. As a result, several government users were compensated to vacate the band. AMT operations, previously in the band 1755-1780 MHz, were compressed into the remaining spectrum between 1780 and 1850 MHz. The ICTS is concerned that the commercial interests are not satisfied and will return for the remainder of the band. HIBS: This band is also in discussion for ITU consideration at the next World Radio-communications Conference (WRC). WRC-23 Agenda Item 1.4: “to consider . . . the use of high-altitude platform stations as IMT base stations (HIBS) in the mobile service in certain frequency bands below 2.7 GHz already identified for IMT, on a global or regional level [such as 1780-1850 MHz];”. Discussions on this are ongoing in several ITU-R working parties.

Lower S-Band (2200-2290 MHz)

Current Use: Allocated for unmanned AMT in the US.

Spectrum Threats(s): Commercial Space Launch: In the U.S. the FCC has allocated four five-megahertz segments in 2200-2290 MHz for non-federal space launch operations on a secondary basis. This is a non-Federal allocation limited to telemetry/tracking during pre-launch testing and space launch operations. It will require coordination with the NTIA for each launch pending adoption of service rules. NTIA recommends that DoD Area Frequency Coordinators (AFCs) deconflict and approve use of the allocations. While the FCC is considering potential allocation of other bands for commercial space launch including 2025-2110 MHz and 2360-2390 MHz – about which more below – it also is considering upgrading this secondary 2200-2290 MHz non-Federal allocation to primary status; potentially a major impact to AMT operators in the U.S. The Aeronautical and Flight Test Radio Coordinating Council (AFTRCC) has been proposed to coordinate non-Federal space launch requests with the DOD AFC

Upper S Band (2360-2390 MHz)

Current Use: Allocated for manned AMT in the US.

Spectrum Threat(s): Commercial Space Launch; In the US, the FCC is considering potential allocation of several additional bands for commercial space launch – including 2360-2390 MHz .

Lower C-Band (4400-4940 MHz)

Current Use: ITU Region 2 (North/South America) allocations for AMT. U.S. Major Range and Test Facility Base (MRTFB) installations have several AMT allocations in this band.

Spectrum Threat(s): Non-Federal Use: In the U.S., AFTRCC has submitted a proposal to the FCC for a non-federal AMT allocation in this band with DoD support. AFTRCC would coordinate use of any such allocation, if approved, with DoD AFCs. R-ALT Interference: In the band below 4400-4940 MHz, there has been major controversy regarding 5G compatibility in the band 3700-3980 MHz with radar altimeters (R-Alt) operating in the band 4200-4400 MHz. An FAA Special Airworthiness Information Bulletin calls on R-Alt vendors and others to provide data on specific R-Alts; to assess the need for mitigation beyond the recommended action. Meanwhile, AT&T and Verizon have agreed to delay deployment of 5G operations in 3700-3980 MHz. WRC Threat; See associated WRC Watch item.

Middle C-Band (5091-5250 MHz) Current Use: 5091-5150 MHz is the primary AMT Band for all regions. 5150-5250 MHz is an AMT band in ITU Region 1 (Europe).

Spectrum Threat(s): ITU. 5091-5150 MHz is the only globally harmonized band allocated for aeronautical telemetry world-wide. As a relative new AMT band, it has not been widely adopted except in ITU Region 1 (France) and Region 2 (the U.S. where its use is largely limited to military installations). Global telemetry users are encouraged to make use of this AMT band. AMT use may need to co-exist with airport ground communications depending on the administration.

Upper C-Band (5925-6700)

Current Use: The ITU has identified this band for AMT in portions of ITU Region 2. Thus far, the US FCC has declined to take any action on AMT assignments in this band.

Spectrum Threat(s): Unlicensed Wi-Fi: The FCC concluded 5925-7125 MHz could be utilized for unlicensed Wi-Fi and very low power devices for high data rate applications, such as wearables, augmented-reality and virtual-reality. The band is also used by point-to-point microwave links; terrestrial microwave operators (mainly public safety and utilities) which unsuccessfully opposed the FCC’s Wi-Fi plans. While the FCC has tabled any AMT assignments/allocations in the band, DoD has studied spectrum aggregation technologies that could enhance AMT compatibility with incumbent systems.