105542 Federal Register / Vol. 89, No. 248 / Friday, December 27, 2024 / Notices 

these assessments. Stock assessment 

teams will solicit advice from data 

stewards, stakeholders, and fishery 

managers knowledgeable about these 

species. 

No management actions will be 

decided by the workshop participants. 

The participants’ role will be the 

development of recommendations for 

consideration by the stock assessment 

teams assigned to conduct these 

assessments. Assessments for these 

stocks are tentatively scheduled for peer 

review during a Stock Assessment 

Review (STAR) panel on June 23–27, 

2025. The Pacific Council and the 

Pacific Council’s Scientific and 

Statistical Committee are scheduled to 

consider these draft assessments for use 

in informing management decisions at 

their September 2025 meeting in 

Spokane, Washington. 

Although nonemergency issues not 

contained in the workshop’s agenda 

may be discussed, those issues may not 

be the subject of formal action during 

this workshop. Action will be restricted 

to those issues specifically listed in this 

notice and any issues arising after 

publication of this notice that require 

emergency action under Section 305(c) 

of the Magnuson-Stevens Fishery 

Conservation and Management Act, 

provided the public has been notified of 

the intent of the workshop participants 

to take final action to address the 

emergency. 

Special Accommodations 

Requests for sign language 

interpretation or other auxiliary aids 

should be directed to Mr. Kris 

Kleinschmidt (kris.kleinschmidt@

noaa.gov; (503) 820–2412) at least 10 

days prior to the meeting date. 

Authority: 16 U.S.C 1801 et seq. 

Dated: December 19, 2024. 

Alyssa Weigers, 

Acting Deputy Director, Office of Sustainable 

Fisheries, National Marine Fisheries Service. 

[FR Doc. 2024–30786 Filed 12–26–24; 8:45 am] 

BILLING CODE 3510–22–P 

DEPARTMENT OF COMMERCE 

National Telecommunications and 

Information Administration 

[NTIA–2024–0005] 

RIN: RIN 0660–XC065 

Impact of L-Band MSS ‘Direct-toDevice’ Operations on GPS 

AGENCY: National Telecommunications 

and Information Administration, 

Department of Commerce. 

ACTION: Notice; request for comment. 

SUMMARY: The National 

Telecommunications and Information 

Administration (NTIA) is seeking 

information and public comment on the 

potential impact on the GPS L1 signal 

at 1575.42 MHz of the increasing 

deployment of mobile devices capable 

of operating on satellite systems in the 

L-band at 1610–1660.5 MHz. Under 

current FCC rules, these devices are 

permitted to operate subject to a 

substantially less restrictive out-of-band 

emission limit than similar devices 

transmitting on the same frequencies 

and connecting to terrestrial base station 

systems. NTIA is seeking public 

comment on the risk of interference 

posed by this increased deployment of 

mobile devices capable of operating on 

L-band satellite systems at 1610–1660.5 

MHz, as well as potential mitigation 

options to safeguard GPS systems while 

facilitating the potential benefits of 

direct-to-device services (D2D services). 

DATES: Written comments must be 

received on or before February 10, 2025. 

ADDRESSES: All electronic public 

comments on this action, identified by 

Regulations.gov docket number NTIA– 

2024–0005, may be submitted through 

the Federal e-Rulemaking Portal at 

https://www.regulations.gov. The docket 

established for this request for comment 

can be found at www.Regulations.gov, 

NTIA–2024–0005. To make a 

submission, click the ‘‘Comment Now!’’ 

icon, complete the required fields, and 

enter or attach your comments. 

Additional instructions can be found in 

the ‘‘Instructions’’ section below, after 

SUPPLEMENTARY INFORMATION. 

FOR FURTHER INFORMATION CONTACT: 

Please direct questions regarding this 

Request for Comment to Ashley 

Davenport at adavenport@ntia.gov with 

‘‘Impact of L-band MSS D2D Operations 

on GPS’’ in the subject line. If 

submitting comments by U.S. mail, 

please address questions to Ashley 

Davenport, National 

Telecommunications and Information 

Administration, U.S. Department of 

Commerce, 1401 Constitution Avenue 

NW, Washington, DC 20230. Questions 

submitted via telephone should be 

directed to (202) 482–0297. Please direct 

media inquiries to NTIA’s Office of 

Public Affairs, telephone: (202) 482– 

7002; email: press@ntia.gov. 

SUPPLEMENTARY INFORMATION: 

Background 

NTIA, located within the Department 

of Commerce, is the Executive Branch 

agency that is principally responsible by 

law for advising the President on 

telecommunications and information 

policy issues and managing the federal 

use of spectrum. The Global Positioning 

System (GPS) is one such federal 

system. NTIA is beginning to see 

increasing deployment of consumer 

equipment capable of operating on 

Mobile-Satellite Service (MSS) networks 

with operations in the L-band near the 

L1 signal of the Global Positioning 

System (GPS) at 1575.42 MHz. Some of 

these devices are traditional mobile 

phones or Internet of Things (IOT) 

devices that typically operate on 

terrestrial networks in mobile bands 

outside the L-band, while others are 

being designed as lower-cost IOT or 

other devices operating primarily, if not 

exclusively, with satellites (collectively, 

D2D devices). The services enabled by 

these devices (D2D services) could 

provide substantial benefits to the 

public, including during times of 

emergency, while also supporting 

important federal government missions. 

The purpose of this Request for 

Comment is to secure public input on 

the risk of interference into GPS posed 

by wider deployment of D2D services in 

the L-band and potential mitigation 

opportunities. 

When the FCC developed MSS rules 

for the L-band, there was an expectation 

that comparatively few user devices 

would be deployed relative to 

ubiquitous terrestrial mobile handsets. 

Therefore, the out-of-band emission 

(OOBE) limit for L-band devices 

operating in the MSS is substantially 

more relaxed (by more than 30 dB) than 

the requirement later developed for user 

devices that would communicate with 

terrestrial base stations in the L-band. 

The stricter OOBE limit for devices 

operating with terrestrial base stations 

was based in large part on the 

expectation that there would be a much 

larger number of such devices. The wide 

deployment of devices subject to the 

MSS limit thus presents an unexpected 

increase in the risk of interference to 

nearby GPS receivers. Attached hereto is 

a technical analysis conducted by the 

U.S. Department of Transportation, in 

conjunction with other U.S. 

Government departments and agencies, 

that more fully describes the basis for 

concern. 

NTIA and other U.S. Government 

departments and agencies are cognizant 

that the initial business case for satellite 

operation of the new devices appears to 

focus on situations in which the user is 

outdoors and terrestrial wireless service 

is unavailable and that these situations 

will often arise in areas with less 

intensive GPS use for critical service. 

The extent to which this is the case and 

will continue to be the case in the future 

remains unclear, as is the extent to 

which the delivery of such a service 


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might involve the devices transmitting 

in the L-band at other times. We seek to 

understand these issues and their 

connection to interference risks. 

One of the situations of greatest 

concern involves the use of such a 

device while on an airplane given the 

proximity of the device to GPS receivers 

and the importance of those receivers to 

aircraft navigation systems. We seek 

information on this scenario, in 

particular, and on the need for 

mitigation options that go beyond the 

existing regulatory prohibition against 

operating the device on an airplane and 

corresponding labeling requirements. 

Request for Comments 

Through this Request for Comment, 

we hope to gather information on the 

following issues and questions. These 

questions are not exhaustive, and 

commenters are invited to provide input 

on relevant questions not asked below. 

Commenters are not required to respond 

to all questions. When responding to 

one or more of the questions below, 

please note in the text of your response 

the number of the question to which 

you are responding. Commenters should 

include a page number on each page of 

their submissions. Commenters are 

welcome to provide specific actionable 

proposals, rationales, and relevant facts. 

All comments received are a part of 

the public record and will generally be 

posted to Regulations.gov without 

change. All personal identifying 

information (e.g., name, address) 

voluntarily submitted by the commenter 

may be publicly accessible. Anyone 

submitting business confidential 

information should clearly identify any 

business confidential portion of a 

comment at the time of submission, file 

a statement justifying nondisclosure and 

referring to the specific legal authority 

claimed, and provide a non-confidential 

version of the submission. 

For comments submitted 

electronically containing business 

confidential information, the file name 

of the business confidential version 

should begin with the characters ‘‘BC.’’ 

Any page containing business 

confidential information must be clearly 

marked ‘‘BUSINESS CONFIDENTIAL’’ 

on the top of that page. The 

corresponding non-confidential version 

of those comments must be clearly 

marked ‘‘PUBLIC.’’ The file name of the 

non-confidential version should begin 

with the character ‘‘P.’’ Any 

submissions with file names that do not 

begin with either a ‘‘BC’’ or a ‘‘P’’ will 

be assumed to be public and will be 

made publicly available through https:// 

www.regulations.gov. 

Questions 

1. We seek further information from 

parties deploying or planning to deploy 

D2D service in the L-band regarding: 

a. the actual out-of-band emissions of 

the devices; 

b. the potential for limiting those 

emissions further; 

c. the typical duration and frequency 

of occurrence of L-band transmissions 

supporting D2D services (including any 

automatic transmissions); 

d. expected geographic deployment 

patterns based on initial offerings of 

D2D services, as well as planned and/ 

or potential service expansions (for 

example, to what extent might they 

operate indoors as well as outdoors or 

in areas where terrestrial wireless 

service is also available); 

e. any other information relevant to an 

evaluation of the likelihood that an Lband device will cause harmful 

interference to a nearby GPS receiver; 

f. the ability to limit or preclude 

satellite operations to and from a device 

when terrestrial service is available, 

including incidental transmissions; 

g. the ability to limit L-band 

operations and attempted operations 

when on an airplane or near other 

critical GPS receivers (including 

information about the effectiveness of 

‘‘airplane mode’’ or other similar 

settings); 

h. the options for educating users 

regarding the risks of operating near 

critical GPS receivers, including onscreen warnings and the likely 

effectiveness of these options; and 

i. any other mitigations that might 

reduce the risk of harmful interference 

to a nearby GPS receiver. 

2. We seek information from GPS 

manufacturers and users regarding: 

a. any documented instances of 

harmful interference from MSS L-band 

devices; 

b. their concerns regarding the 

increased probability of harmful 

interference; and 

c. any mitigations that might be 

effective in reducing the risk of harmful 

interference while minimizing impacts 

on MSS service delivery. 

3. We seek information on industry 

standards and performance 

improvements achieved by the GPS 

industry over the past ten years to selfprotect the various categories of GPS 

receivers to minimize receiver blocking 

and overload. 

a. Information on separation distances 

due to receiver selectivity, compared 

with the separation distances shown in 

the DoT technical analysis due to MSS 

L-band mobile earth station out-of-bandemissions (OOBE). 

b. GPS receiver overload limits (i.e., 

GPS receiver input power tolerance 

thresholds and separation distance(s)) 

from MSS mobile earth station 

operations from Globalstar, Inmarsat, 

etc., in the vicinity of different 

categories of GPS receivers. 

4. We seek comment on the 

Department of Transportation technical 

analysis. Parties should feel free to 

submit any alternative technical 

analysis. 

Sean Conway, 

Deputy Chief Counsel, National 

Telecommunications and Information 

Administration. 

Analysis of Potential Interference to 

GPS/GNSS From Emerging L-Band MSS 

D2D and IoT Services November 25, 

2024 

1 Overview 

This paper assesses the potential 

impact of emerging L-band mobile 

satellite service (MSS) direct-to-device 

(D2D) and Internet of Things (IoT) 

services on Global Positioning System 

(GPS)/Global Navigation Satellite 

System (GNSS) receivers that are to 

receive interference protection in the 

1559–1610 MHz Radionavigation 

Satellite Service (RNSS) allocation. The 

analysis considers only the emissions 

from terrestrial devices (e.g., D2D 

handsets and IoT equipment) up to the 

L-band MSS satellites. The main finding 

of this initial analysis as detailed in this 

paper is that emissions from L-band 

MSS D2D and IoT user equipment 

operating at 1610–1660.5 MHz, 

operating in compliance with the 

Federal Communications Commission 

(FCC) rules can result in interference to 

GPS/GNSS receivers operating in the 

1559–1610 MHz RNSS band. The risks 

of interference to GPS/GNSS from Lband MSS Mobile Earth Stations (MES) 

are growing rapidly as D2D and IoT 

services are increasingly included in 

high-volume, daily-use consumer and 

industrial products (e.g., Apple phones 

and tablets). 

Within this paper, MSS emissions in 

the 1559–1610 MHz RNSS band are 

hereafter referred to as out-of-band 

emissions (OOBE). Both OOBE and the 

fundamental transmissions in the 1610– 

1660.5 MHz MSS band are considered. 

The OOBE results apply to all L-band 

MSS operators. The fundamental 

transmission analysis in this paper was 

performed using available data for 

Ligado’s specific uplink frequency 

bands of 1627.5–1637.5 MHz and 

1646.5–1656.5 MHz. Results for other 

operators are not provided in the paper 

but are expected to be worse for 


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1https://www.ecfr.gov/current/title-47/chapter-I/ 

subchapter-B/part-25. 

2See, for example, ITU–R M.1903, https://

www.itu.int/dms_pubrec/itu-r/rec/m/R-RECM.1903-1-201909-I!!PDF-E.pdf. Five of 11 GNSS 

receiver types characterized in this 

recommendation have a system noise temperature 

of 513K, which equates to a ¥201.5 dBW/Hz noise 

floor. This level, ¥201.5 dBW/Hz, is also a 

standard noise floor assumption for certified GNSS 

equipment on aircraft; see, e.g., RTCA DO–235C. 

3See Section 4.1.3.1 of the Department of 

Transportation (DOT)’s Global Positioning System 

(GPS) Adjacent Band Compatibility Assessment 

Final Report, https://rosap.ntl.bts.gov/view/dot/ 

35535. Vertically polarized emissions for the D2D 

or IoT device is assumed. 

operators using frequencies closer to the 

RNSS band. 

FCC rules for L-band MSS mobile 

Earth stations that are applicable to 

emerging D2D and IoT services are 

summarized in Appendix A. A scenario 

in which MSS D2D equipment is 

operated onboard a commercial aircraft 

is presented in Appendix B. 

2 Impact Assessments 

2.1 Emissions in the GNSS Band 

2.1.1 D2D Handset and IoT Device 

Emissions 

D2D handset or IoT device emissions 

that fall within the 1559—1610 MHz 

RNSS allocation can cause degradation 

to GNSS receiver signal-to-noise-density 

(C/N0). The FCC rules for satellite 

services, contained within Part 25 of 

Title 47 of the Code of Federal 

Regulations (47 CFR part 25),1 include 

requirements applicable to D2D handset 

or IoT device emissions. 47 CFR 25.216, 

in particular, requires that the effective 

isotropic radiated power (EIRP) levels of 

MES with assigned frequencies within 

1610 and 1660.5 MHz ‘‘. . . shall not 

exceed¥70 dBW/MHz, averaged over 

any 2 millisecond active transmission 

interval, in the band 1559–1605 MHz.’’ 

Assuming a GNSS receiver noise floor 

of ¥201.5 dBW/Hz,2 Table 1 provides 

the separation distances needed to limit 

GNSS receiver C/N0 degradation to 1, 3, 

6, and 10 dB assuming an isotropic 

receive antenna, free space path loss, 

and assuming a 3 dB polarization loss 

for linearly polarized transmissions 

being received by a right-hand circularly 

polarized antenna. 

TABLE 1—C/N0 DEGRADATION VS SEPARATION DISTANCE—GNSS RECEIVER WITH ISOTROPIC RECEIVE ANTENNA

Degradation to C/N0 (dB) 

Received interference 

level 

(dBW/Hz) 

Required separation 

(m) 

1 ............................................................................................................................................... ¥207.4 79.1 

3 ............................................................................................................................................... ¥201.5 40.3 

6 ............................................................................................................................................... ¥196.8 23.3 

10 ............................................................................................................................................. ¥192.0 13.4 

Using a model for the relative antenna 

gain pattern of a GNSS high precision 

receiver (HPR) towards a vertically 

polarized source at 1575.42 MHz 3 and 

assuming a maximum boresight gain of 

+3 dBic, Figure 1 shows the area around 

a single D2D device where the receiver 

could experience a 1, 3, or 10 dB C/N0 

degradation. The plot assumes the D2D 

or IoT device is 2 m above the ground 

and that free space path loss conditions 

exist. 

Figure 1. Impact on HPR Due to Ø70 

dBW/MHz Emissions in 1559–1605 MHz 

The required lateral separations to 

keep a high precision GNSS receiver C/ 

N0 degradation with the modeled 

antenna below 1, 3, or 10 dB shown in 

Figure 1 are slightly less than the results 

for a receiver with isotropic receive 

antenna in Table 1. This observation can 

be explained by the fact that a typical 

HPR antenna may have a gain towards 

a vertically polarized source at the 

horizon that is below 0 dBi. The results 

for other GPS/GNSS receiver classes are 

slightly worse (i.e., requiring additional 

separation for the same C/N0 

degradation) since their noise floors are 

similar to HPR devices but they 


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4https://docs.fcc.gov/public/attachments/FCC20-48A1.pdf. 

typically have higher antenna gain at 

low elevation angles (see Table 2). 

Sample calculations for the separation 

distances in Tables 1 and 2 are provided 

in Appendix C. 

TABLE 2—SEPARATION DISTANCES FROM D2D HANDSET OR IOT DEVICE NECESSARY TO LIMIT C/N0 DEGRADATION FOR

VARIOUS GPS/GNSS RECEIVER CLASSES

GPS/GNSS receiver class Noise floor, N0 

(dBW/Hz) * 

Required separation to limit C/N0 

degradation to 1, 3, and 10 dB 

(m) ** 

High precision (HPR) ......................................................................... ¥201.5 ....................................... 52.2 (1 dB), 27.5 (3 dB), 10.1 (10 dB) 

General Location/Navigation (GLN) ................................................... ¥200.5 ....................................... 59.6 (1 dB), 31.0 (3 dB), 10.9 (10 dB) 

Cellular (CEL) .................................................................................... ¥200.5 to ¥201.5 ..................... 99.8 to 112.0 (1 dB), 50.9 to 57.1 (3 

dB), 16.9 to 19.0 (10 dB) 

Certified Aviation *** or General Aviation (GAV) ............................... ¥201.5 ....................................... 66.7 (1 dB), 34.6 (3 dB), 12.2 (10 dB) 

* Based upon receiver system noise temperature values in ITU–R M.1903. 

** Using representative antenna gain patterns for each receiver class from https://rosap.ntl.bts.gov/view/dot/35535, and assuming the transmit 

antenna is at 2 m height above ground. 

*** See Appendix B for an assessment of a scenario in which the D2D equipment is operated by a passenger on a commercial aircraft. 

A lower emission limit would reduce 

the impact area. For instance, Figure 2 

shows the impacted area for HPR GNSS 

devices if the EIRP emissions in 1559– 

1605 MHz were reduced to ¥105 dBW/ 

MHz (as required for Ligado ancillary 

terrestrial component [ATC] handset 

transmissions per the April 2020 FCC 

Order and Authorization 4). 

Figure 2. Impact on HPR due to Ø105 

dBW/MHz Emissions in 1559–1605 MHz 

For a GNSS device with an isotropic 

receive antenna and –201.5 dBW/Hz 

noise floor, Figure 3 presents required 

separation distances for 1, 3, 6, and 10 

dB C/N0 degradations as a function of 

D2D and IOT device emission levels in 

1559–1605 MHz. 


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5See https://rosap.ntl.bts.gov/view/dot/34708 and 

https://rosap.ntl.bts.gov/view/dot/34710. 

Figure 3. Required Separation Distance 

vs D2D Emissions in 1559–1610 MHz To 

Limit GNSS Receiver C/N0 Degradation 

To 1, 3, 6, or 10 dB 

The above results are similar to those 

provided to DOT GPS ABC Workshops 

by Greenwood Telecommunications 

Consultants LLC5. Greenwood 

additionally examined the impacts of 

multiple transmitters in the referenced 

presentations and recommended ¥105 

dBW/MHz as a Ligado mobile device 

EIRP limit in 1559–1605 MHz. 

2.2 Emissions in the Adjacent Band— 

Fundamental Emissions 

2.2.1 D2D Handset and IoT Emissions 

D2D handsets and IoT devices may 

operate with many center frequencies 

and at various power levels within the 

1610–1660.5 MHz MSS band. In this 

section, one example is provided 

applicable to Ligado D2D operations. As 

noted earlier in Section 1, other L-band 

MSS operators are providing D2D/IoT 

services using frequencies closer to the 

1559–1610 MHz RNSS band and may 

also utilize higher uplink transmit 

power levels. These services could 

therefore have a potentially greater 

impact on GPS/GNSS. 

Again, as just one example of D2D/IoT 

operations, Ligado D2D handsets are 

expected to have a maximum EIRP of 23 

dBm, use vertical polarization, and only 

operate in the 1627.5–1637.5 MHz and 

1646.5–1656.5 MHz bands. These are 

the same emission characteristics as 

Ligado ATC handsets. 

Extensive results for the impact of 

vertically-polarized, 23 dBm handset 

emissions at 1630 MHz are presented in 

Appendix I of the DOT GPS ABC 

Assessment Final Report (see footnote 3 

for a hyperlink to this report). Some of 

these results, for the most sensitive 

device within each receiver class, are 

reproduced below. In these figures 

‘‘ITM’’ corresponds to a 1 dB CNR 

degradation, ‘‘LOLL’’ corresponds to 

loss of lock on low-elevation angle 

satellites, and ‘‘LOLH’’ corresponds to 

loss of lock on high elevation angle (i.e., 

all) satellites. GLN = ‘‘General Location/ 

Navigation’’ and TIM = ‘‘Timing’’ GNSS 

devices. 


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6https://docs.fcc.gov/public/attachments/DOC392372A1.pdf. 

IoT devices may transmit significantly 

higher power levels. For instance, on 

April 5, 2023, the FCC granted a blanket 

license to Skylo Technologies for up to 

1,000,000 IoT devices to communicate 

to the Ligado Skyterra-1 and Inmarsat 

satellites in the 1525–1559 MHz and 

1626.5–1660.5 MHz MSS bands.6 The 

license permits EIRPs of up to 10W for 

IoT transmissions to Skyterra-1 and the 

Inmarsat MSS satellites. This EIRP limit 

is 50 times greater than the Ligado ATC 

handset EIRP limit of 200 mW and 

could impact sensitive GNSS devices at 

distances of up to almost 1 km. Each of 

the impact contour plots shown above 

would have the impacted region expand 

by a factor of 7 (since free space path 

loss falls off with distance to the 

transmitter squared and the IoT devices 

are approximately a factor of 7 squared 

more powerful than 23 dBm). 

Importantly, the impact of the 

fundamental D2D handset and IoT 

device transmissions on GPS/GNSS 

receivers varies significantly with 

receiver model. The results presented 

above apply to the most sensitive device 

of all of those tested within each 

receiver class by DOT. As detailed in 


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105548 Federal Register / Vol. 89, No. 248 / Friday, December 27, 2024 / Notices 

7See, e.g., https://www.remotesatellite.com/ 

collections/msat-tracking/ and https://satellite

phonestore.com/catalog/search?q=msat. 

8See, e.g., https://www.rei.com/product/227381/ 

motorola-defy-satellite-link. 

9https://www.govinfo.gov/content/pkg/COMPS11324/pdf/COMPS-11324.pdf. 

Appendix B of the DOT GPS ABC 

Assessment Final Report (link in 

footnote 3), for the HPR tand GLN 

receiver classes approximately a 50 dB 

difference in interference levels 

resulting in a 1 dB C/N0 degradation at 

1630 MHz was observed between the 

most and least sensitive receiver. 

3 Differences Between L-Band D2D and 

IoT Services and Historical Use of the 

Mobile Earth Stations 

There have been MSS operations in 

the L band for over two decades now. 

Given that there have been no reports of 

interference from these operations to 

GNSS during this time, a reasonable 

question is: why should the GNSS 

community be concerned with 

interference at this point in time? There 

are several reasons for concern: 

• Legacy L-band mobile earth stations 

(MESs) are expensive and sparse in 

number compared to anticipated D2D 

and IoT devices 

Æ We reviewed non-D2D/IoT 

products available from several 

prominent satellite equipment vendors,7

and L-band MES equipment are on the 

order of several hundred dollars or 

more. The equipment cost, and the 

additional costs for the required satellite 

service plan and usage fees limits the 

number of devices in use and also limits 

their operation in highly populated 

areas (where cellular communications is 

an available and cheaper option). 

Æ For comparison, D2D devices are 

anticipated to include millions of 

cellular phones that are owned and used 

on a daily basis by most U.S. citizens. 

Although D2D operations are expected 

to be mainly used when the users are 

out of cell coverage, with millions of 

devices in use it is likely that some 

transmissions will occur in populated 

areas (e.g., in cellular dead zones or 

when there is a radio propagation 

blockage in the direction of the cell 

tower). It is also possible that small D2D 

devices might be operated onboard 

aircraft (see Appendix B). 

Æ In addition to legacy MES and 

cellular phones with D2D capabilities, 

there are also emerging standalone Lband MSS D2D/IoT devices. Just one 

company, Skylo, has alone already 

received a blanket license for up to 1M 

IoT devices capable of transmitting to 

Skyterra-1. The Motorola Defy satellite 

link is a new D2D product that became 

available for purchase in the United 

States in June 2023. This device is small 

(3.4 x 2.5 x 0.5 inches), battery-powered 

(with an advertised battery life of up to 

4 days), and lightweight (2.5 ounces). It 

connects to iOS and Android 

smartphones through Bluetooth and 

enables smartphone users to send and 

receive text messages through MSS 

geostationary satellites, including those 

operated by Ligado and Viasat/Inmarsat. 

This device retails for $150 including a 

one-year service plan.8

• Most existing MES include a GPS 

tracking capability. The vendor would 

thus have a need to ensure that MES 

emissions in the 1559–1605 MHz band 

are far below the ¥70 dBW/MHz level 

permitted by 47 CFR 25.216 in order to 

protect their own equipment’s GPS 

operation. It is not clear that IoT device 

manufacturers would have the same 

incentive to achieve far better OOBE 

performance than required by the FCC 

rules, especially considering the market 

motivation to make IoT devices 

extremely low-cost. 

• The FCC rules (47 CFR 25.285) 

prohibit MES capable of transmitting in 

the 1610–1660.5 MHz band from 

operating on civil aircraft unless its use 

is approved by the FAA or pilot. Further 

25.285 requires that such MES cannot 

be ‘‘. . . sold or distributed to users 

unless it conspicuously bears the 

following warning: ‘This device must be 

turned off at all times while on board 

aircraft.’ ’’ Unfortunately, the E–LABEL 

Act permits such warnings to be made 

available to the users of electronic 

devices digitally through a screen on a 

device display.9 This digital display can 

oftentimes be difficult for users to find. 

For instance, on the iPhone 14, users 

would have to navigate to a ‘‘Legal & 

Regulatory’’ screen two levels deep 

under ‘‘Settings’’ to find the warning 

required per 47 CFR 25.285 against 

using on-board aircraft (see Figure 9). 


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Figure 9. The Warning Against Use of 

the iPhone 14 Satellite Feature on 

Aircraft is Compliant With the FCC 

Rules After the E–LABEL Act but 

Obscured Two Levels Deep in the 

Settings Menu (Settings/General/ 

Legal&Regulatory) 

4 Summary 

This paper assessed the potential 

impact of emerging L-band MSS D2D 

and IoT services on GPS/GNSS. 

If D2D or IoT devices are minimally 

compliant with 47 CFR 25.216, out-ofband emissions from single or multiple 

D2D devices could degrade GNSS 

receiver performance at distances up to 

50 m or more. Additional filtering 

cannot mitigate the problem since the 

interference is overlapping with the 

GNSS signals in frequency. 

The fundamental emissions of L-band 

MSS terminals, including MES, D2D 

and IOT devices operating in the 1610– 

1660.5 MHz band can result in impact 

to GNSS devices at considerable 

distances. In this paper, as one example, 

200 mW devices transmitting in 1627.5– 

1637.5 MHz were assessed to impact 

GPS/GNSS receivers at distances of up 

to 140 m. The FCC has authorized over 

10 million mobile devices operate in Lband with EIRP of up to 10 W and at 

frequencies closer to the 1559–1610 

MHz band. These devices could cause 

GNSS receiver degradation at distances 

exceeding 1 km. The impacted distances 

are highly variable across GNSS 

receivers, with the values cited above 

applying to the most sensitive receivers 

tested by DOT in 2016. 

Finally, the paper identifies reasons 

why emerging L-band D2D and IoT 

operations may be problematic for 

GNSS even though reliant on existing 

MSS authorizations. Importantly, the 

primary concerns raised in this paper 

are applicable to MES, D2D and IoT 

devices with connectivity to any L-band 

MSS satellites with uplinks in the 1610– 

1660.5 MHz band. Thus, these issues are 

relevant to, e.g., Inmarsat/Viasat, 

Iridium, Ligado, and Globalstar MSS 

operations. 

Appendix A. FCC L-Band MSS Mobile 

Earth Station Rules 

The FCC Rules for satellite services (47 

CFR part 25) include the following 

provisions related to L-band MSS 

operations: 

• 25.216—provides limits on mobile 

earth station emissions in the 1559– 

1610 MHz ARNS band. Per 25.216(c), 

‘‘The e.i.r.p. density of emissions from 

mobile earth stations placed in service 

after July 21, 2002 with assigned uplink 

frequencies between 1610 MHz and 

1660.5 MHz shall not exceed ¥70 dBW/ 

MHz, averaged over any 2 millisecond 

active transmission interval, in the band 

1559–1605 MHz. The e.i.r.p. of discrete 

emissions of less than 700 Hz 

bandwidth from such stations shall not 

exceed ¥80 dBW, averaged over any 2 

millisecond active transmission 

interval, in the 1559–1605 MHz band.’’ 

• 25.285—prohibits operation of 

Earth stations capable of transmitting in 

the 1.5/1.6 GHz MSS frequency bands 

on board civil aircraft ‘‘unless the 

device is installed in a manner 

approved by the Federal Aviation 

Administration or is used by the pilot or 

with the pilot’s consent’’. Further, 

portable Earth stations operating in 

these bands cannot be ‘‘. . . sold or 

distributed to users unless it 

conspicuously bears the following 

warning: ‘This device must be turned off 

at all times while on board aircraft.’ ’’ 

• 25.287—provides requirements for 

mobile Earth stations operating in the 

1530–1544 MHz and 1626.5–1645.5 

MHz bands to ensure compliance with 

Footnote 5.353A in 47 CFR 2.106 and 

US315. 

Appendix B. MSS D2D Use on 

Commercial Aircraft 

Overview 

One location that many people 

encounter that is often without cellular 

or WiFi service is when flying aboard a 

commercial aircraft. Low-cost D2D 

equipment may easily be taken aboard 

an aircraft and a passenger may operate 

this equipment (without knowing it is 

illegal to do so) in the United States 


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105550 Federal Register / Vol. 89, No. 248 / Friday, December 27, 2024 / Notices 

10See 47 CFR 25.216. 

11See, e.g., Section E.5.2 of RTCA Document DO– 

235C, ‘‘Assessment of Radio Frequency Interference 

Relevant to the GNSS L1 Frequency Band,’’ 

12See for instance https://ntrs.nasa.gov/api/ 

citations/20030067884/downloads/ 

20030067884.pdf and other NASA reports 

referenced within RTCA DO–235C. 

13See, e.g., Federal Aviation Administration 

Technical Standard Orders (TSO)–C145, –C146, 

–C161, –C196, –C204, –C205 and also International 

Civil Aviation Organization (ICAO) GNSS 

Standards and Recommended Practices (SARPs). 

Certified GPS equipment are less tolerant of 

interference during initial acquisition and are only 

required to perform this function with in-band 

interference at a level of ¥146.5 dBW/MHz. 

14Note that the International Telecommunication 

Union (ITU) recommends a 6 dB safety margin 

between permitted interference levels and 

maximum tolerable levels for safety applications of 

GNSS such as aircraft navigation. See, e.g., ITU–R 

M.1903. Application of this safety margin would 

result in a much larger, 6.5 dB, excess of 

interference in this scenario. 

from a window seat. They might do so 

for a variety of reasons, e.g., to stay in 

touch with family and friends through 

text conversations while on the flight. 

Potential for Interference 

As noted in Section 2.1.1, MSS D2D 

devices are permitted to emit broadband 

noise in the GPS L1 band with an 

effective isotropic radiated power (EIRP) 

of up to ¥70 dBW/MHz from 1559– 

1605 MHz.10 The path loss at the GPS 

L1 frequency from a vertically polarized 

antenna within a commercial aircraft to 

the right-hand circularly polarized GPS 

antenna on top of the aircraft fuselage 

can be as low as 54 dB.11 This value was 

measured by Delta Airlines for a Boeing 

737–800 aircraft. NASA, in cooperation 

with United Airlines, has measured 

values as low as 65 dB for Boeing 737 

and 747 aircraft.12 Figure 1 presents an 

example of these NASA path loss 

measurement results for a 737–200 

aircraft measured from each window 

seat and also just inside each aircraft 

door. 

Figure 1. Measured Path Loss at 1575 

MHz From Vertically Polarized 

Antenna Inside a Boeing 737–200 

Aircraft to the Top-Mounted GPS 

Antenna 

Commercial aircraft GPS avionics are 

typically certified to able to tolerate inband interference with a maximum 

power spectral density of ¥140.5 dBW/ 

MHz at the output of the passive 

antenna element while meeting all 

performance requirements after initial 

acquisition.13 The interference from 

MSS D2D equipment could be much 

higher than this maximum tolerable 

level. For instance, for the worst-case 

location in a 737–800 aircraft measured 

by Delta Airlines, the ¥70 dBW/MHz 

permissible D2D equipment EIRP level 

within 1559–1605 MHz would result in 

¥124 dBW/MHz received interference 

(16.5 dB higher than the required 

avionics tolerance). A more typical path 

loss from a window seat to the GPS 

antenna, based upon NASA’s 

measurements (see Figure 2), is on the 

order of 70 dB. D2D equipment with a 

¥70 dBW/MHz EIRP would still result 

in an excessive level of interference, 

¥140 dBW/MHz, just above the 

maximum tested level for certified 

avionics.14

Legality of Operating MSS D2D 

Equipment on Civil Aircraft 

The FCC rules (47 CFR 25.285) 

prohibit operation of MSS equipment 

capable of transmitting in the 1.5/1.6 

GHz MSS frequency bands on board 

civil aircraft ‘‘unless the device is 

installed in a manner approved by the 

Federal Aviation Administration or is 

used by the pilot or with the pilot’s 

consent’’. Further, portable Earth 

stations operating in these bands cannot 

be ‘‘. . . sold or distributed to users 

unless it conspicuously bears the 

following warning: ‘This device must be 

turned off at all times while on board 

aircraft.’ ’’ 

Unfortunately, many consumers are 

not familiar with the FCC rules. 

Furthermore, the E–LABEL Act permits 

warnings such as that required in 47 

CFR 25.285 to be made available to the 

users digitally through a screen on a 

device display. This E–LABEL provision 

makes it unlikely that the warning will 

be seen by most users. For instance, 

despite the Motorola Defy Satellite Link 

dongle being compliant with 47 CFR 

25.285, nowhere in the user manual is 

it mentioned that the equipment should 

not be operated on an aircraft. The 

manual includes a cryptic section 

entitled ‘‘Viewing the E-label’’ that 

informs the user that an ‘‘E-label’’ can 

be found under a ‘‘Settings’’ menu 

within the Bullitt Satellite Messenger 

app used to send text messages on the 

users’ smartphone. Only a user that 

bothers to look at this screen would find 

the warning shown towards the bottom 

of Figure 2. 


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Federal Register / Vol. 89, No. 248 / Friday, December 27, 2024 / Notices 105551 

Figure 2. The Warning Against Use of 

the Motorola Defy Satellite Link 

Aboard an Aircraft is Compliant With 

the FCC Rules, but Obscured in a 

Smartphone Application Settings 

Screen Unlikely To Be Noticed by Most 

Consumers 

Potential Mitigations 

Equipment Performing Better than FCC 

Rules 

The ¥70 dBW/MHz EIRP emission 

limit for broadband noise in the 1559– 

1605 MHz band is required by the FCC 

rules (47 CFR 25.216) for all L-band 

MSS transmitters including D2D 

devices. It is possible that some devices 

may perform substantially better than 

this limit. One Motorola Defy device 

that was tested for FCC equipment 

authorization appears to have 

broadband emissions that are ∼10 dB 

better than the ¥70 dBW/MHz limit 

(see Figure 3). Unfortunately, this is not 

sufficiently lower to preclude the 

concern of interference if operated 

aboard a civil aircraft described above. 

Figure 3. Measured Motorola Defy 

Satellite Link Broadband Emissions 

From 1559–1610 MHz From FCC 

Equipment Authorization Filing. Device 

Appears To Have Lower Emissions 

Than the FCC–70 dBW/MHz Limit in 

1559–1605 MHz by ∼10 dB. 

Time Duration of Emissions 

Currently available MSS D2D devices 

only permit short messages to be sent 

(e.g., ∼140 characters for the Motorola 

Defy Satellite Link). MITRE has 

obtained two Motorola devices to 

measure the time duration of emissions 

(both the fundamental within the MSS 

band and also the out-of-band emissions 

within the 1559–1610 MHz GPS/GNSS 

band). 

Noting that the use of GPS for aircraft 

navigation has some very strict 

continuity requirements, it is unlikely 

that even a short duration of emissions 

will be tolerable. For instance, for 

precision approach operations the 

International Civil Aviation 

Organization (ICAO) has adopted a 

continuity requirement that the 

probability that GPS is lost over an 

exposure period of 15 seconds must not 

exceed 8E–6. Furthermore, certified GPS 

avionics are not required to be able to 

continue to track GPS signals in the 

event that broadband interference 

exceeds ¥140.5 dBW/MHz, except if 

pulsed with pulse widths less than 125 

microseconds and duty cycle less than 

1%. Once tracking is disrupted, 

reacquisition within 20 seconds is only 

required if the receiver continues to 

track a set of satellites with good 

geometry and up to 5 minutes if not. 

Summary 

This appendix has identified a 

concern of interference from MSS D2D 

devices to GPS avionics on commercial 

aircraft. Such devices have only very 

recently become available at very low 

cost in the United States. This concern 

is currently unmitigated from such 

devices that do not operate with 

significantly lower RNSS band emission 

limits than the FCC RNSS emission 

limit contained within 47 CFR 25.216 

for L-band MSS transmitters, including 

D2D and IOT equipment. 

Appendix C. Separation Distances: 

Sample Calculations 

Table 1 assumes a GNSS receiver with 

a right-hand circularly polarized 

isotropic receive antenna and a noise 

floor, N0, of ¥201.5 dBW/Hz referenced 

to the output port of the antenna. MSS 

MES emissions are assumed to be at the 

47 CFR 25 limit of ¥70 dBW/MHz (= 

¥130 dBW/Hz) and the MES is 

assumed to use a vertically polarized 

antenna. As an example of the 

calculations resulting in the separation 

distances within Table 1, consider the 

first row. A degradation of 1 dB in C/ 

N0 results when the received 

interference power density, I0, at the 

output of the GNSS receiver antenna 

reaches a level of ¥207.4 dBW/Hz. 


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105552 Federal Register / Vol. 89, No. 248 / Friday, December 27, 2024 / Notices 

This received interference power 

density occurs at a distance, d, of 79.1 

m using free space propagation loss for 

the GNSS center frequency of 1575.42 

MHz with corresponding wavelength, l 

= 0.1903 meters: 

I0 = ¥130 dBW/Hz—20 log10(4pd/l)— 

3 = ¥207.4 dBW/Hz 

The subtraction of 3 dB in the above 

equation is to account for polarization 

mismatch loss between an assumed 

vertically polarized MSS MES signal 

and the right-hand circularly polarized 

GNSS receive antenna. 

Table 2 presents refined separation 

distance results using an average of 

representative measured GNSS receiver 

antenna gain patterns from Section 

4.1.3.1 of the Department of 

Transportation (DOT)’s Global 

Positioning System (GPS) Adjacent 

Band Compatibility (ABC) Assessment 

Final Report, https://rosap.ntl.bts.gov/ 

view/dot/35535. Vertically polarized 

emissions and a height of 2 meters for 

the MSS MES are assumed. As an 

example of the calculations, the first 

row in Table 2 assumes an HPR receiver 

with a –201.5 dBW/Hz noise floor. From 

the DOT’s ABC report, and based upon 

measurements of multiple HPR 

antennas, Figure 1 below shows a 

modeled GNSS HPR receiver antenna 

gain pattern for a vertically polarized 

source. At a lateral distance of 52.2 

meters the gain of this antenna on the 

ground towards a MSS MES at 2 m 

height is approximately –6.6 dBi. With 

this geometry, the slant range distance 

is ∼52.2 meters and the received 

interference strength is: 

I0 = ¥130 dBW/Hz—20 log10(4pd/l)— 

6.6 = ¥207.4 dBW/Hz, resulting in a 

1 dB increase over N0 (as explained 

in the footnote) 

Note that since the GNSS antenna 

gain pattern that was used in this 

instance is based upon measurements 

with a vertically polarized source, no 

further polarization mismatch 

adjustment is required. 

Figure 1. Representative HPR Antenna 

Gain Pattern Towards Vertically 

Polarized Source 


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[FR Doc. 2024–30760 Filed 12–26–24; 8:45 am] 

BILLING CODE 3510–60–P 

DEPARTMENT OF DEFENSE 

Office of the Secretary 

[Docket ID: DoD–2024–HA–0037] 

Submission for OMB Review; 

Comment Request 

AGENCY: Office of the Assistant 

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(OASD(HA)), Department of Defense 

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ACTION: 30-Day information collection 

notice. 

SUMMARY: The DoD has submitted to the 

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proposal for collection of information 

under the provisions of the Paperwork 

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DATES: Consideration will be given to all 

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PRAMain. Find this particular 

information collection by selecting 

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FOR FURTHER INFORMATION CONTACT: 

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whs.mc-alex.esd.mbx.dd-dodinformation-collections@mail.mil. 

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Average Burden per Response: 15 

minutes. 

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Needs and Uses: The DD Form 2642, 

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Services (CHAMPUS) Medical Claim 

Patient’s Request for Medical Payment’’ 

is used by TRICARE beneficiaries to 

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expenses under the TRICARE Program 

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will be used by TRICARE to determine 

beneficiary eligibility, other health 

insurance liability, certification that the 

beneficiary has the received care, and 

reimbursement for medical services 

received. 

Affected Public: Individuals or 

households. 

Frequency: On occasion. 

Respondent’s Obligation: Voluntary. 

DOD Clearance Officer: Mr. Reginald 

Lucas. 

Dated: December 18, 2024. 

Stephanie J. Bost, 

Alternate OSD Federal Register Liaison 

Officer, Department of Defense. 

[FR Doc. 2024–30889 Filed 12–26–24; 8:45 am] 

BILLING CODE 6001–FR–P 

DEPARTMENT OF DEFENSE 

Office of the Secretary 

[Docket ID: DoD–2024–OS–0139] 

Proposed Collection; Comment 

Request 

AGENCY: Washington Headquarters 

Services (WHS), Department of Defense 

(DoD). 

ACTION: 60-Day information collection 

notice. 

SUMMARY: In compliance with the 

Paperwork Reduction Act of 1995, the 

Washington Headquarters Services 

(WHS) announces a proposed public 

information collection and seeks public 

comment on the provisions thereof. 

Comments are invited on: whether the 

proposed collection of information is 

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the functions of the agency, including 

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agency’s estimate of the burden of the 

proposed information collection; ways 

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burden of the information collection on 

respondents, including through the use 

of automated collection techniques or 

other forms of information technology. 

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comments received by February 25, 

2025. 

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identified by docket number and title, 

by any of the following methods: 

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please write to Office of the Secretary of 

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Dated: December 18, 2024. 

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[FR Doc. 2024–30893 Filed 12–26–24; 8:45 am] 

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