NTIA Comments on Authorization and Use of Software Defined Radios

Docket Number: 
ET Docket No. 00-47
Date: 
March 21, 2001

 

Before the
FEDERAL COMMUNICATIONS COMMISSION
Washington, DC 20554

 

In the Matter of                             )
                                                     )
Authorization and Use of Software )
Defined Radios                              ) ET Docket No. 00-47
                                                     )
                                                     )
 

 

COMMENTS OF THE NATIONAL TELECOMMUNICATIONS
AND INFORMATION ADMINISTRATION

 

John F. Sopko                                    Kathy D. Smith
Acting Assistant Secretary for             Chief Counsel
Communications and Information

William Hatch
Associate Administrator
Office of Spectrum Management

Edward Drocella
Electronics Engineer
Office of Spectrum Management
National Telecommunications and
Information Administration
U.S. Department of Commerce
Room 4713
1401 Constitution Avenue, N.W.
Washington, DC 20230
(202) 482-1816
 

March 21, 2001


Table of Contents

Section
I. INTRODUCTION

II. APPROVAL OF SDR HARDWARE AND SOFTWARE COMBINATIONS
SHOULD INCLUDE ANY MODIFICATIONS PERMITTED UNDER THE
PROPOSED NEW CLASS III PERMISSIVE CHANGES

III. INDUSTRY PROTOCOLS SHOULD BE DEVELOPED TO PREVENT
THE UNAUTHORIZED MODIFICATION OF SOFTWARE THAT CONTROLS
THE OPERATING FREQUENCY, POWER LEVEL, AND MODULATION
OF AN SDR

IV. THE COMMISSION SHOULD PERFORM THE APPROVAL OF SDR
EQUIPMENT FOR A PERIOD OF AT LEAST TWO YEARS

V. CLARIFICATION IS NECESSARY ON WHERE THE CURRENT AUTHORIZED EMISSION CHARACTERISTICS WILL RESIDE IN THE ELECTRONIC
LABELING OF AN SDR

VI. A CAREFUL ASSESSMENT IS NECESSARY OF ALL POSSIBLE INTERFERENCE SCENARIOS INVOLVING SDR TECHNOLOGY THAT IS CAPABLE OF OPERATING OVER INCREASINGLY WIDER FREQUENCY RANGES

VII. THE LABELING REQUIREMENTS FOR SDR SHOULD BE EXPANDED TO
ALLOW TRACEABILITY OF SOFTWARE MODIFICATIONS

VIII. AS CURRENTLY WRITTEN THE NEWLY PROPOSED SECTION 2.1043(b)(3)
IS OPEN TO MULTIPLE INTERPRETATIONS

IX. THE NEWLY PROPOSED PARAGRAPH IN SECTION 2.932 ADDRESSING MODIFICATION OF EQUIPMENT SHOULD BE REWORDED TO MINIMIZE
AMBIGUITY

X. REGULATORY RESPONSIBILITIES FOR GOVERNMENT SDR CAPABLE OF
CIVILIAN FUNCTIONS NEEDS TO BE ADDRESSED BY NTIA AND THE COMMISSION

XI. CONCLUSION


COMMENTS OF THE NATIONAL TELECOMMUNICATIONS
AND INFORMATION ADMINISTRATION

The National Telecommunications and Information Administration (NTIA), an Executive Branch agency within the Department of Commerce, is the President's principal adviser on domestic and international telecommunications policy, including policies relating to the Nation's economic and technological advancement in telecommunications. Accordingly, NTIA makes recommendations regarding telecommunications policies and presents Executive Branch views on telecommunications matters to the Congress, the Federal Communications Commission (Commission), and the public. NTIA, through the Office of Spectrum Management, is also responsible for managing the Federal Government's use of the radio frequency spectrum. NTIA submits the following Comments in response to the Commission's Notice of Proposed Rulemaking in the above-captioned proceeding.(1)

I. INTRODUCTION

Wireless technology advances promise to make radios based on Software Defined Radio (SDR) technologies more prevalent within the Federal and non-Federal communications infrastructure. New technologies such as SDR emerge in the private sector, or within the Federal Government, where necessary research and development initiatives are undertaken to more adequately define the limits and capabilities of the technology. In turn, this has lead to the adoption of market driven technical standards for the new technology. Traditionally, the Commission has favored such a developmental approach to new radio technological advances and NTIA and the Federal agencies believe that this course of action is prudent in the case of SDR.

In March 2000, the Commission issued a Notice of Inquiry (NOI) on SDRs.(2) The SDR NOI sought comments in four broad areas related to SDR technology: 1) the state of technology, 2) improving interoperability between radio services, 3) improving spectrum efficiency and spectrum sharing, and 4) the equipment approval process. The SDR Notice of Proposed Rulemaking (SDR NPRM) summarizes the comments submitted in response to the NOI and proposes certain changes to the equipment authorization rules for SDRs.

NTIA applauds the Commission for its efforts in advancing SDR technology. In the SDR NPRM the Commission proposes to define SDR as a new class of equipment and allow manufacturers to make changes in the frequency, power, and modulation of such equipment without the normal requirement to file a new authorization request. While NTIA and the Federal agencies recognize and support the inherent flexibility afforded to the commercial sector by such rule changes, we remain concerned that without appropriate safeguards, this flexibility may lead to unauthorized spectrum usage. Given the Federal Government's reliance on spectrum to support functions such as safety of life communications and navigation, NTIA supports establishing requirements prohibiting manufacturers from knowingly marketing software that would cause a SDR to operate in violation of the Commission's rules. NTIA offers the following comments to specific issues raised in the SDR NPRM that NTIA believes will likely have a direct and significant impact on the future needs and operations of Federal radiocommunication systems.

II. APPROVAL OF SDR HARDWARE AND SOFTWARE COMBINATIONS SHOULD INCLUDE ANY MODIFICATIONS PERMITTED UNDER THE PROPOSED NEW CLASS III PERMISSIVE CHANGES

The Commission has proposed that each combination of hardware and software that an SDR can support should be tested as part of the equipment approval process.(3) NTIA agrees with the Commission, that this is the most effective way at this time to ensure that equipment complies with the technical standards in the rules to prevent interference to other radio services.(4) NTIA continues to believe that separate hardware and software approval would only be workable if a consistent predictable connection between the software object (computer program) operating on a given digital signal processing platform and the hardware object can be established.(5) NTIA also agrees with the Commission that testing each hardware and software combination that can be used in an SDR should be no more burdensome than the current process which requires testing each mode in which a radio operates.(6)

The Commission has proposed that changes in frequency, power, and modulation type of an SDR could be authorized as a new class of permissive change, designated as Class III.(7) The Commission also proposes that the Class III permissive change may only be made to equipment in which no hardware changes have been made from the originally approved device.(8) NTIA does not object to establishing this new class of permissive change for SDRs as proposed by the Commission. However, NTIA does believe that, in order to verify that after the modifications authorized under a Class III permissive change, the SDR still remains compliant with the Commission's operating and service rules (e.g., authorized frequency bands and power levels), the combination of the hardware and the software modification must be reauthorized. This view is supported in the comments submitted by Motorola(9), and reply comments submitted by the SDR Forum.(10) Both commenters recommend that when additional modes are added to already authorized equipment, the resulting combination of hardware and software should be re-authorized. NTIA believes that this will ensure that SDR equipment complies with the technical standards that are necessary to prevent interference to other radio services.

For some SDRs numerous software waveform applications from the original manufacturer and third parties could be available. This could also result in various combinations of software existing on SDRs. NTIA believes that the proposed rules are not clear as to whether all possible combinations of installed software need to be tested or if it is sufficient to test each waveform separately. NTIA also believes that it is unclear whether the Class III permissive change would address the situation when software is removed from a SDR.

III. INDUSTRY PROTOCOLS SHOULD BE DEVELOPED TO PREVENT THE UNAUTHORIZED MODIFICATION OF SOFTWARE THAT CONTROLS THE OPERATING FREQUENCY, POWER LEVEL, AND MODULATION OF AN SDR

To facilitate the development of SDR technology, the Commission is proposing rule changes to streamline the equipment authorization process.(11) While NTIA does not oppose the proposed streamlined authorization procedures, the potential flexibility in modifying operating frequencies, power levels, and modulation schemes used by SDR necessitates a cautious approach. NTIA shares the Commissions's concern of "… maintaining our ability to ensure that radios are only operated on approved frequency bands."(12) and as such we endorse the Commission's conclusion that, "… a means will be necessary to avoid unauthorized modifications to software that could affect the compliance of a radio."(13) However, NTIA disagrees with the Commission's proposed approach that manufacturers must take steps to ensure that only software that is part of a hardware and software combination approved by the Commission or a Telecommunication Certification Body (TCB) can be loaded onto a SDR. NTIA continues to believe that there is a benefit to the public if industry developed protocols can be established to control unauthorized modifications to the software that controls the frequency of operation, power levels, and type of modulation of the SDR.(14) NTIA agrees with the SDR Forum, that it is imperative to ensure the software modifications affecting the interference potential of a SDR are safeguarded against unauthorized modifications.(15) NTIA recommends that the Commission, in coordination with industry representatives involved in SDR development, examine security features such as authentication protocols that could be used to prevent unauthorized modifications to the radio frequency (RF) parameters that can change the compliance or the interference potential of an SDR.

IV. THE COMMISSION SHOULD PERFORM THE APPROVAL OF SDR EQUIPMENT FOR A PERIOD OF AT LEAST TWO YEARS

The Commission has tentatively concluded that TCBs should not be permitted to certify SDRs for a period of at least six months after the effective date of final rules adopted in this proceeding.(16) NTIA remains concerned that given the early stage of development of SDR technology, existing rules or requirements may not be sufficient to ensure compatible operation of that equipment or the application of the rules may be unclear. As a result, NTIA supports the Commission's conclusion that a period be established where certain functions of the equipment approval process continue to be performed by the Commission. However, since SDR is still continuing to evolve, we do not believe the Commission's proposal of six months is a sufficient period of time. Alternatively, NTIA proposes that the Commission continue to perform the approval of SDR equipment for a period of at least two years after the effective date of final rules adopted in this proceeding. NTIA believes that this period will ensure that enough SDR variants have been examined by the Commission to verify that the current procedures and rules are sufficient.

V. CLARIFICATION IS NECESSARY ON WHERE THE CURRENT AUTHORIZED EMISSION CHARACTERISTICS WILL RESIDE IN THE ELECTRONIC LABELING OF AN SDR

The Commission has proposed that SDRs be equipped with an electronic label to display the Commission's identification number.(17) This would provide a method to re-label equipment in the field. NTIA agrees with the SDR Forum that all of the information currently displayed on the Commission's label could easily be made available on most SDR equipment on a user display screen.(18) NTIA believes that such a mechanism would allow for easy verification of authentication without requiring expensive and impractical equipment labeling. NTIA also believes that any form of electronic labeling should be visible when the power is removed from the labeled equipment (e.g., power backup). In addition, with all of the potential variations possible through combinations of hardware and software of SDRs and the flexibility of the new class of permissive changes, NTIA requests clarification on where the current authorized emission characteristics for an SDR will reside.

VI. A CAREFUL ASSESSMENT IS NECESSARY OF ALL POSSIBLE INTERFERENCE SCENARIOS INVOLVING SDR TECHNOLOGY THAT IS CAPABLE OF OPERATING OVER INCREASINGLY WIDER FREQUENCY RANGES

As discussed in Motorola's comments to the SDR NOI, the ability of SDRs to operate over a wider range of frequencies requires that the different interference scenarios must be carefully assessed between various parts of the spectrum and the services operating in that spectrum.(19) NTIA shares the concerns regarding potential interference to other services from SDRs as well as interference to SDRs from other radio services. For example, it would be extremely challenging to design a wideband, high sensitivity receiver that could tolerate the very large signals from a radar transmitter operating in the adjacent band with equivalent isotropically radiated power (EIRP) levels is excess of several megawatts. NTIA also agrees that there are numerous interference scenarios for both commercial and Federal government systems of widely varying transmitter power levels, significantly different occupied bandwidths and sensitivities to varying types of interfering signals that must be carefully analyzed.(20) These concerns regarding assessment of all interference scenarios would also be applicable to cognitive radio technology.(21)

NTIA continues to believe that receiver immunity requirements are an extremely important factor in mitigating interference to SDRs. As stated in NTIA's response to the SDR NOI, the ability of SDR receivers to implement filtering with greater adjacent band selectivity using software, that cannot be implemented using hardware, could be employed to reduce the potential for interference from adjacent band transmitters.(22) NTIA recommends that the Commission as part of this rulemaking process, examine the development of industry receiver immunity requirements for SDR receivers to reduce the potential for interference from adjacent band commercial and Federal Government transmitters.

VII. THE LABELING REQUIREMENTS FOR SDR SHOULD BE EXPANDED TO ALLOW TRACEABILITY OF SOFTWARE MODIFICATIONS

As currently worded in the SDR NPRM, modifications could be made to portions of a SDR's software that determine tuned frequency, modulation, and power without triggering a Class III permissive change, as long as the characteristics required to be reported to the Commission are not affected by the software modifications.(23) The purpose of such changes might be to correct defects (i.e., software bugs), implement more efficient waveform processing, or to minimize software code size. From a regulatory perspective, it is desirable to require the grantee to maintain records of such changes such that traceability exists from the certified software version to the version of software that is currently loaded on the SDR. NTIA recommends that the labeling requirements be expanded to require a means of displaying the current software version, Commission ID number, and source/manufacturer of each software module.

VIII. AS CURRENTLY WRITTEN SECTION 2.1043(b)(3) IS OPEN TO MULTIPLE INTERPRETATIONS

In the SDR NPRM Section 2.1043(b)(3) has been revised to define what constitutes a Class III permissive change.(24) NTIA believes that the use of the word "affect" in the first sentence defining the Class III change is open to multiple interpretations. Clearly modifications can be made to software that affects the frequency, modulation type, and output power without actually changing the value of these parameters. For example, upgrades to increase software code execution speed or to reduce software code size without changing the resulting software code function. To remove this potential ambiguity, NTIA recommends that the word "affect" be replaced with the word "change" in the first sentence of Section 2.1043(b)(3) so that the sentence reads: "A Class III permissive change includes modifications to the software of a software defined radio transmitter that change the frequency, modulation type, output power or maximum field strength."

IX. THE NEWLY PROPOSED PARAGRAPH IN SECTION 2.932 ADDRESSING MODIFICATION OF EQUIPMENT SHOULD BE REWORDED TO MINIMIZE AMBIGUITY

The SDR NPRM adds a new paragraph (e) to Section 2.932 of the Commission's rules that adds a new requirement that manufacturers provide controls to insure that unauthorized software changes cannot be made by the user.(25) This addresses the concern that user's might install software that could cause a SDR's transmitter technical characteristics to exceed those authorized by the Commission in the Certification grant. As currently written various interpretations to the proposed rule are possible. The Commission should consider rewording the proposed rule to minimize ambiguity.

Since an SDR may contain software modules that do not affect the RF characteristics, the wording of this new provision should be clarified to indicate that the requirement to use only Commission or TCB approved software is limited only to those components that affect the radio technical characteristics regulated by the Commission. NTIA suggests that Section 2.932(e) be reworded as follows:

The manufacturer of an SDR must develop a plan to provide assurance that software loaded onto a SDR that can be installed by the end-user will not cause operation exceeding approved limits. This software security plan may make use of technology-based safeguards such as authentication codes or more traditional approaches such as physical security and operator training and discipline. The proposed software security plan must be described in the application for equipment authorization and provide a level of protection appropriate to the radio application as determined by the Commission. This plan must provide reasonable assurance that waveform software not approved for operation on a particular SDR will not be executed.

This wording makes a distinction between waveform and other SDR software, but still requires assurance that software that is loaded onto an SDR not affect the RF characteristics. The downloading of baseband application software (e.g., JAVA applets, Active-C, etc.) associated with baseband information content would not be prohibited by this wording. The proposed rewording would also provide the applicant and the Commission broader flexibility in tailoring the software modification safeguards to the particular situation. Clearly, infrastructure equipment (e.g., base stations) under the control of a system operator should have different controls than equipment (e.g., handsets) used by members of the general public. Software configuration management and physical security should provide an adequate level of control for infrastructure equipment. Robust digital authentication techniques likely would be required to restrict the execution of unauthorized software on SDRs used by the general public. Moreover, as the use of SDR becomes more commonplace, it may be appropriate to develop protective requirements that would apply to are radio service specific.

X. REGULATORY RESPONSIBILITIES FOR GOVERNMENT SDR CAPABLE OF CIVILIAN FUNCTIONS NEEDS TO BE ADDRESSED BY NTIA AND THE COMMISSION

The Department of Defense (DoD) is developing the Joint Tactical Radio System (JTRS) architecture.(26) Presently, JTRS is undergoing spectrum certification for legacy military waveforms. In the future, submission of other civilian waveforms (e.g., cellular and personal communication service (PCS)) will be included. For the military waveforms the JTRS radio would not be subject to the Commission's rules and regulations. However, if the JTRS radios were to include civilian waveforms for public safety purposes, then the JTRS radios and software would have to comply with the Commission's rules.(27)

Limited precedent exists for the approval of radios that can operate in Government and non-Government spectrum. NTIA and the Commission need to review the regulatory rules to determine if changes are necessary to address this issue.

XI. CONCLUSION

As described in the SDR NPRM, the Commission has proposed to streamline the equipment authorization procedures for SDR. Specifically, the Commission proposes to define SDRs as a new class of equipment and allow manufacturers to make changes in the operating frequency, power levels, and types of modulation without the normal requirement to file a new authorization request. While NTIA recognizes and supports the inherent flexibility offered to the commercial sector by such rule changes, we remain concerned that without appropriate safeguards, this flexibility may lead to unauthorized spectrum usage. NTIA urges the Commission to consider carefully the issues raised in these comments in an effort to develop a workable arrangement that would continue to advance the development of SDR technology.

For the foregoing reasons, NTIA submits these comments.

Respectfully submitted,

John F. Sopko                                    Kathy D. Smith
Acting Assistant Secretary for             Chief Counsel
Communications and Information
                                                          National Telecommunications and
William Hatch                                     Information Administration
Associate Administrator                      U.S. Department of Commerce
Office of Spectrum Management
Room 4713
1401 Constitution Avenue, N.W.
Washington, DC 20230
Edward Drocella (202) 482-1816
Electronics Engineer
Office of Spectrum Management
 

March 21, 2001



ENDNOTES:

1. Authorization and Use of Software Defined Radios, Notice of Proposed Rulemaking, ET Docket No. 00-47, FCC 00430 (rel. Dec. 8, 2000) (hereinafter "SDR NPRM").

2. Inquiry Regarding Software Defined Radios, Notice of Inquiry, ET Docket No. 00-47, FCC 00-103 (rel. March 21, 2000).

3. SDR NPRM at ¶ 18.

4. Id.

5. Comments of the National Telecommunications and Information Administration (NTIA Comments), ET Docket No. 00-47, at 20 (June 16, 2000).

6. SDR NPRM at ¶ 18.

7. Id. at 25.

8. Id.

9. Comments of Motorola Inc. (Motorola Comments), ET Docket No. 00-47, at 33 (June 14, 2000).

10. Reply Comments of the Software Defined Radio Forum (SDR Forum Reply Comments), ET Docket No. 00-47, at 17 (July 14, 2000).

11. SDR NPRM at ¶ 19.

12. Id. at ¶ 20.

13. Id. at ¶ 31.

14. NTIA Comments at 26.

15. SDR Forum Reply Comments at 6.

16. SDR NPRM at ¶ 33.

17. Id. at ¶ 29.

18. SDR Forum Reply Comments at 5.

19. Motorola Comments at 30.

20. Id.

21. Cognitive radio is a particular extension of software radio that employs model-based reasoning about users, multimedia content, and communications context.

22. NTIA Comments, at 17.

23. SDR NPRM at ¶ 25.

24. SDR NPRM Appendix A at 2.

25. Id.

26. See Joint Tactical Radio System (JTRS), available at http://www.jtrs.sarda.army.mil.

27. The March 23, 1998 JTRS Operational Requirements Document includes requirements for public safety and cellular/PCS waveforms.