Before the Federal Communications Commission Washington, D.C. 20554 In the Matter of) ) Request For Declaratory Ruling on the Use ) DA 95-1854 of Digital Modulation by Multipoint ) Distribution Service and Instructional ) Television Fixed Service Stations) DECLARATORY RULING AND ORDER Adopted: July 9, 1996 Released: July 10, 1996 By the Commission: Table of Contents Paragraph I. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . 1 II. BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . 3 III. DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . 9 A. Commission Rules and Cases in Support of Authorization of Digital Modulation . . . . . . . . . . . . . . . . . . . . 9 B. Modulation Methods . . . . . . . . . . . . . . . . . . . . . 13 C. Interference Considerations . . . . . . . . . . . . . . . . 16 1. Test Procedures . . . . . . . . . . . . . . . . . . . 17 2. Interference Protection Ratios and Out-of-Band Emissions Limitations . . . . . . . . . . . . . . . . . . . 20 3. Digital Power and Related Considerations . . . . . . . 26 4. Frequency Tolerance and Use of Frequency Offset Techniques 31 5. Responsibility and Procedures for Alleviating Potential and Actual Interference . . . . . . . . . . . . . 33 D. Application of Other MDS and ITFS Technical Rules in a Digital Environment . . . . . . . . . . . . . . . . . . 38 1. Equipment Approval . . . . . . . . . . . . . . . . . . 39 2. Emission Designators . . . . . . . . . . . . . . . . . 42 3. Transmission Standards . . . . . . . . . . . . . . . . 44 4. Equipment Standards, Modulation Limits and Aural Power Limitations . . . . . . . . . . . . . . . . . . 47 5. Transmission of ITFS Call Signs . . . . . . . . . . . 48 E. Application Procedures . . . . . . . . . . . . . . . . . . . 52 F. ITFS Programming Requirements . . . . . . . . . . . . . . . 58 IV. ORDERING CLAUSES . . . . . . . . . . . . . . . . . . . . . . 59 I. INTRODUCTION 1. The Commission has before it a request for declaratory ruling filed by a coalition of 99 parties with interests in the wireless cable industry (collectively, "Petitioners"), pursuant to Section 1.2 of the Commission's Rules, 47 C.F.R.  1.2. Petitioners seek a declaratory ruling on their proposed "interim approach" to the use of digital modulation in MDS and ITFS upon application by individual MDS or ITFS entities. Petitioners request that the Commission, based on some uniform rule clarifications and waivers, avoid the need for developmental authorizations and "routinely grant" MDS and ITFS applications proposing the use of digital modulation on a non-interference basis, subject to further research and testing by the industry and the provisions of any subsequent MDS and ITFS rulemaking on digital technology. Except as noted herein, for the reasons discussed below, we grant Petitioners' request. 2. The ruling we now adopt will provide a quick and easy framework for wireless cable operators and MDS or ITFS licensees to increase their channel capacity and service offerings through the use of digital compression techniques. It will additionally enable the industry to gain experience with a broad array of digital technology and to perform further testing in order to fine tune performance measures for use of this technology in wireless cable systems. By this action, wireless cable becomes the first over-the-air terrestrial video programming service that we authorize to utilize digital transmissions. Thus, we accelerate the development of wireless cable services and advance Congress' goal of "promot[ing] competition . . . in order to secure lower prices and higher quality services for American telecommunications consumers." We also seek to promote the use of digital technology, along with its attendant benefits, by the educational community. II. BACKGROUND 3. The Commission has taken several actions in recent years to enhance the viability of the wireless cable service and foster its competitiveness with wired cable and other multichannel video programming distributors ("MVPDs"). We have explained our reasons for taking such actions: [I]n providing communications services, the public interest is better served by competition. A competitive industry framework promotes lower prices for services, provides incentives for operators to improve those services and stimulates economic growth. An essential component of competition is choice. As we recognized in our recent report to Congress, consumers in the market for video programming do not have enough choices. Although competing technologies have made major strides . . . the cable television market remains largely noncompetitive. Amendment of Parts 21 and 74 of the Commission's Rules With Regard to Filing Procedures in the Multipoint Distribution Service and in the Instructional Television Fixed Service and Implementation of Section 309(j) of the Communications Act -- Competitive Bidding, Notice of Proposed Rulemaking, 9 FCC Rcd 7665, 7666 (1994) (hereinafter MDS Auction NPRM) (footnote omitted). 4. Various factors, including insufficient channel capacity, have been blamed for the relatively low penetration of wireless cable systems, and the difficulties such systems have experienced in competing with cable television systems. In addition, wireless cable operators have been contending with increased competition from DBS providers, who are the first MVPDs to implement digital technology on a wide scale. Cable operators also plan to introduce digital technology into their major markets this year or next year. 5. While we have recognized that "the difficulty of accumulating sufficient channel capacity remains a major obstacle to many wireless cable operators," we have expressed hope that "the combination of administrative improvements in wireless cable licensing and the use of digital compression should help to alleviate this problem in the future." MDS Auction NPRM, 9 FCC Rcd at 7666-67 (footnote omitted); see First Competition Report, 9 FCC Rcd at 7488. We expect that the introduction of digital technology will enhance the service of wireless cable operators by allowing opportunities for increased channel capacity and programming choices available to consumers, sharper television pictures, a broader coverage area, and the provision of video, voice and data services that cannot be offered currently. We have additionally concluded that advances in digital technology "have the potential to exert a major influence on the structure of the market for the delivery of video programming." Second Competition Report, 11 FCC Rcd at 2143. By this ruling, we intend to permit the benefits of digital technology to be realized by ITFS licensees and their educational communities. We note that several ITFS licensees that do not lease excess channel capacity are interested in quickly implementing digital technology. See Petition at iii. Thus, the Commission's interests in fostering competition in the video programming services market and promoting the use of ITFS spectrum for educational programming will clearly be advanced by authorizing wireless cable operators to employ digital technologies. In adopting new procedures for the filing of applications for new MDS stations, we stated: The filing system and procedures we adopt herein are expected to . . . afford wireless cable operators the flexibility to . . . implement digital technologies. . . . We believe that our rules will facilitate the transition to digital transmissions. If modification of our rules become[s] necessary, we will act promptly to ensure that our rules in no way impede the digital future. MDS Auction Order, 10 FCC Rcd at 9606. See also Second Wireless Cable Reconsideration Order, 10 FCC Rcd at 7093 (discussing "the imminent transition from analog to digital transmissions for MDS stations"). 6. In light of the public interest in a competitive video programming services market, it is important to authorize wireless cable operators to use digital transmissions. We agree with Petitioners that a rulemaking proceeding for developing permanent standards for use of digital technology would be lengthy, and would be delayed by a dependence upon additional testing that has not yet been completed, thus putting the wireless cable industry at a further competitive disadvantage with respect to other video programming services, which either have already implemented digital technology or will have done so by the completion of such a proceeding. Moreover, the Petitioners requesting this ruling are comprised of MDS and ITFS licensees, wireless cable operators, equipment manufacturers, industry engineers, the Wireless Cable Association International, Inc. and other industry groups, representing a strong and rare consensus amongst significant industry participants, who often have divergent interests. Accordingly, we believe that a declaratory ruling on an interim approach to the employment of digital technology in the MDS and ITFS services is the appropriate measure at this juncture. 7. The following eight parties filed timely comments on this request for declaratory ruling: Bell Atlantic; NYNEX Corporation (NYNEX); Hammett & Edison, Inc. (Hammett), consulting engineers; ITS Corporation (ITS), an equipment manufacturer and co-signor of the Petition; Kraskin & Lessee, on behalf of several independent telephone companies; the Rural Wireless Cable Coalition (Rural Coalition); SR Telecom Inc. (SR Telecom), an equipment manufacturer; and Tarrant County Junior College District, Education Service Center Region 10 and Richardson Independent School District (Tarrant County), ITFS licensees in the Dallas-Fort Worth area. Petitioners filed a timely reply. 8. The commenters generally support the Petition and the Commission's efforts to facilitate the transition of wireless cable to digital technology. Most of the commenters believe that the transitional approach outlined in the requested ruling will increase the competitive viability of wireless cable in the MVPD marketplace by allowing operators to offer a competitive number of channels, without causing harmful interference to existing analog systems, and without the unnecessary regulatory delay of a rulemaking proceeding. III. DISCUSSION A. Commission Rules and Cases in Support of Authorization of Digital Modulation 9. Petitioners recognize that the MDS and ITFS rules contained in Parts 21 and 74 are oriented toward transmission of NTSC analog video programming signals, but they nonetheless maintain that the rules allow for a variety of modulation schemes, and that the Commission has interpreted the rules to promote such flexibility where no cochannel or adjacent channel interference will result. Petition at 3-4. See, e.g., General Electric Co., 60 RR 2d 1665 (Comm. Car. Bur. 1986) (hereinafter Comband I); General Electric Co., 61 RR 2d 143 (Mass Media Bur. 1986) (hereinafter Comband II). In particular, Petitioners refer to the similar language describing emissions in Sections 21.905 and 74.936 of the Commission's Rules. Both of these rules provide that MDS or ITFS stations will "normally" employ amplitude modulation for the transmission of the visual signal and frequency modulation for the aural signal. 47 C.F.R.  21.905(a) and 74.936(a). Petitioners suggest that the use of the term "normally" in both rules reflects a recognition by the Commission that modulation schemes other than NTSC may be appropriate for MDS and ITFS. Petition at 12-13 n.23. Petitioners further point out that Section 21.905(b) specifically contemplates that "[f]or purposes other than standard television transmission, different types of emissions may be authorized . . . ." See Petition at 3 n.4. In promulgating the initial rules governing the MDS service, including Section 21.905, the Commission expressed confidence that MDS licensees "will imaginatively exploit the technical possibilities of MDS." Amendment of Parts 1, 2, 21, and 43 of the Commission's Rules and Regulations to Provide for Licensing and Regulation of Common Carrier Radio Stations in the Multipoint Distribution Service, 45 FCC 2d 616, 619 (1974) (hereinafter MDS Allocation Order). Moreover, nothing in the original implementation of Section 74.936 controverts Petitioners' interpretation of that rule. Thus, we agree with Petitioners' reading of Sections 21.905 and 74.936 as allowing sufficient latitude for authorization of digital transmissions over MDS and ITFS stations. 10. Other rules applicable to MDS and ITFS in Parts 21 and 74 also permit authorization of the use of digital technology. Section 21.907(c) provides in part that "[i]n addition to the standard television transmission service . . . the licensee may offer a television service not meeting such standards if the tariff or contract clearly describes the type and quality of the service and distinguishes it from the standard service . . . ." 47 C.F.R.  21.907(c). As was explained nearly 10 years ago in a declaratory ruling authorizing the use of Comband analog compression technology for MDS transmissions, "Section (c) of 21.907 was specifically added to enable MDS carriers to use non-standard transmitters and to encourage developments such as Comband." Comband I, 60 RR 2d at 1669; see also MDS Allocation Order, 45 FCC 2d at 623-24. Furthermore, in amending Section 74.938, the Commission elaborated that "we are persuaded that ITFS operators should not be restricted to NTSC format . . . when other video standards may be better suited to their needs. . . . For these reasons, we are amending our rules to relax the technical standards for ITFS transmissions." Amendment of Part 74 of the Commission's Rules and Regulations in regard to the Instructional Television Fixed Service, 98 FCC 2d 925, 928 (1984) (hereinafter ITFS Technical Order). 11. Petitioners also cite several cases to support authorization of digital transmission under the current rules. In Comband I and Comband II, the Common Carrier Bureau and Mass Media Bureau, respectively, authorized for MDS and ITFS licensees use of Comband analog compression technology, which allows for transmission of two analog video signals on a single 6 MHz channel. The Bureaus concluded that the Comband system is consistent with Parts 21 and 74 of the Commission's Rules and approved the use of Comband, subject to application to the Commission in individual cases, where the applicant could demonstrate non-interference and where the applicant specified a type accepted Comband transmitter. The Commission later confirmed that "[t]here is nothing in our current rules to restrict use of Comband transmission by MDS or ITFS licensees, and we do intend, when possible, to accommodate the widest possible voluntary usage of this or any other technology that can achieve spectrum efficiencies of this nature." Wireless Cable Order, 5 FCC Rcd at 6417. These cases further confirm our finding that the regulatory framework in Parts 21 and 74 of the Commission's Rules governing MDS and ITFS can accommodate the use of transmission formats other than NTSC analog, including the use of digital modulation techniques. 12. SR Telecom supports the Petition provided that any subsequent rule changes facilitate, rather than impede, the provision over the MDS spectrum of digital wireless loop service, a two-way communications service. SR Telecom Comments at 4-5. In response to SR Telecom's comments, Petitioners explain that the testing underlying the Petition did not evaluate any two-way transmissions, and involved the use of modulation methods that differ significantly from the method proposed by SR Telecom. "Thus, the record is inadequate to permit a reasoned discussion of the merits of SR's wireless local loop system." Reply at 2 n.2. Petitioners suggest that the Commission invite SR Telecom to submit a detailed petition which should include test data and proposed interference standards. Id. The Commission recently reiterated that "[w]e will allow alternative uses other than wireless cable video transmission if the applicant can satisfy MDS technical rules or adequately support waivers of those rules." MDS Auction Reconsideration Order, 10 FCC Rcd at 13825. However, as Petitioners indicate, no data was submitted here for consideration of the merits of SR Telecom's proposal. Therefore, we find clarification of the use of digital wireless loop technology on MDS frequencies beyond the scope of this ruling. B. Modulation Methods 13. Petitioners request interim authorization of two types of digital modulation: Quadrature Amplitude Modulation ("QAM") and Vestigial Sideband ("VSB"). While the test data submitted in support of the Petition focuses on the specific densities of 64-QAM and 8- VSB, Petitioners also seek Commission authorization for the use of both higher and lower modulation densities of QAM and VSB, to gain experience with "a wider array of . . . modulation densities . . . before permanent rules can be adopted." Petition at 9. While supporting the Petition, NYNEX questions Petitioners' commitment to "conform . . . operation to whatever permanent rules the Commission may adopt in the future to govern digital modulation . . . ." Petition at 1-2; see NYNEX Comments at 7-8. NYNEX argues that licensees should avoid interference with other licensees as may be required by current and future rules, but should not be required to commit to a subsequent changeout in the digital technology deployed merely because the Commission adopts a different "standard" modulation technology. NYNEX explains that "[t]here are currently two competing methods of digital modulation (QAM and VSB), with perhaps others in development, which should be authorized by the Commission. Thereafter, each provider will make an election of technology by market. . . . There is no reason for the Commission to chose [sic] among competing technologies or to specify a standard' technology." NYNEX Comments at 8 (footnote omitted). NYNEX observes that while a licensee is likely to use a single technology for each market, which would make a subsequent changeout in technology particularly costly and challenging, the Commission should allow different digital modulation technologies to be deployed by different licensees in the same market, or by the same licensee in different markets. Id. at 8-9. Petitioners did not reply to these comments. 14. Though Petitioners request authorization of the use of QAM and VSB modulation, they do not ask for adoption of a "standard" technology or the exclusion of other modulation methods. In fact, Petitioners specify that they do not "mean to suggest that other modulation methods . . . cannot be employed under appropriate circumstances." Petition at 15 n.27. Petitioners add that if the proponent of another digital modulation method can demonstrate that its proposal will not cause harmful interference, there is no reason not to issue a declaratory ruling similar to that requested by Petitioners. Id. We are not now proposing to adopt one or more "standard" digital technologies. This ruling is limited to QAM and VSB. We interpret Sections 21.905, 21.907(c), 74.936, and 74.938 of the Commission's Rules as enabling us to authorize use of these digital modulation formats over MDS and ITFS stations, provided that such use will not result in harmful interference. See paras. 9-10, supra and para. 52, infra. As set forth below, based on the test results submitted by Petitioners, we agree with Petitioners that use of the VSB and QAM modulation formats up to the densities of 8-VSB and 64-QAM, together with the current MDS and ITFS interference protection criteria, would not be likely to cause harmful interference to MDS and ITFS service. 15. Petitioners also argue that using QAM and VSB "will ensure excellent interference protection no matter what densities of VSB or QAM are employed for the digital signals." Petition at 24-25; see para. 20, infra. We are persuaded that the wireless cable industry also should have an opportunity to gain practical experience with higher modulation densities, those up to 16-VSB and 256-QAM. This is consistent with our interpretation of the rules for emission types, as discussed above. However, we wish to ensure that use of higher densities will not present an increased likelihood of causing harmful interference to MDS or ITFS service. Therefore, MDS and ITFS licensees may utilize such densities provided, in their applications, they submit supplemental measurement data specific to these higher modulation levels, akin to the data provided by Petitioners in support of the Petition. See Petition at Appendix B, Rationale for Interim Implementation of Wireless Cable Digital Transmission (hereinafter Interim Implementation Report); Report on Wireless Cable Interference Testing, April 27-May 4, 1995 (hereinafter Interference Testing Report). But see para. 19, infra. We will provide additional flexibility by not prohibiting the simultaneous deployment of different authorized digital technologies in the same market by different licensees. Further, pursuant to Sections 21.905, 21.907(c), and 74.936 of the Commission's Rules, which provide for use of more than one emission type, during this interim period, licensees may alternate between analog and digital transmission systems, in order to compare their effects and make full use of available transmitting and receiving facilities. C. Interference Considerations 16. As the cornerstone of their interim proposals for digital wireless cable, Petitioners emphasize that the Commission must assure that use of digital modulation will not cause harmful electromagnetic interference to nearby analog or digital stations. See Petition at 16. Based on industry test results, Petitioners submit that use of the existing interference protection ratios for analog MDS and ITFS stations, together with a small relaxation in the currently permitted levels of out-of-channel emissions, is a conservative approach that would provide more than adequate interference protection to such stations. See id. at 21-22 and 27-28. 1. Test Procedures 17. The Petition appends a report of the findings of extensive tests that have been conducted with 64-QAM and 8-VSB modulation in a closed laboratory setting using actual wireless cable equipment, as well as ITFS equipment and receiving configurations. Two basic receive installations were employed in the tests, one replicating a typical wireless cable subscriber installation and the other simulating an ITFS receive site that is not part of a wireless cable system. With each configuration, several television receivers were used, and for each combination of equipment and transmission mode, the thresholds of perceptibility of interference to pictures and sound were measured, as well as the signal ratios producing a CCIR grade 4 level of television picture impairment. Petitioners explain that CCIR grade 4 was employed for these tests to provide a conservative safety margin of interference protection. Accordingly, Petitioners conclude that the interference results discussed in the Interim Implementation Report demonstrate a level of interference protection to existing NTSC analog facilities better than the current analog-to-analog protection. Petition at 20-21. Petitioners emphasize that the tests analyzed only the susceptibility of analog MDS/ITFS reception to cochannel and adjacent channel interference caused by digital signals. Because digital signals are "more robust to interference" than are analog signals, application of the digital-to-analog protection ratios to digital-to-digital reception will even further limit the likelihood of interference. Petition at 21- 22; see Interim Implementation Report at 3. 18. Based on the results of these tests, Petitioners conclude that under their requested interim parameters and rule waivers, QAM and VSB digital modulation can be implemented without causing interference to analog systems or other digital systems. Petition at 17. Petitioners maintain that following the technical proposals described below will enable the Commission to authorize the use of digital modulation techniques without requiring applicants to present information beyond the standard interference studies now required by 47 C.F.R.  21.902 and 74.903, and without the staff conducting any materially different engineering analysis than is now used to process MDS and ITFS applications. Petition at 18. Petitioners also state that the Commission should rapidly grant applications to use digital technology based on the consent of all neighboring stations, where such consent is obtained. Petition at 16. 19. Petitioners concede that as the modulation densities are increased, the susceptibility of digital receivers to interference likewise increases. Thus, Petitioners encourage the continued use of the current conservative 45 dB cochannel and 0 dB adjacent channel interference protection criteria in order to accommodate use of high modulation densities, until further testing can be completed to establish optimum digital interference criteria. Petition at 22 n.38; see para. 20, infra. While we believe that the current interference protection criteria are sufficiently conservative, we specify that we will not provide additional interference protection for digital systems with higher modulation densities. 2. Interference Protection Ratios and Out-of-Band Emissions Limitations 20. Petitioners first propose the continued employment of the current 45 dB cochannel and 0 dB adjacent channel D/U signal strength ratios as interim interference protection criteria, while awaiting the results of further testing from which to develop recommendations for permanent protection ratios. Petitioners assert that the tests conducted verify that these interference criteria, when applied to a digital-to-analog interference situation, will yield a picture quality better than the picture currently delivered when these criteria are applied to an analog-to-analog interference situation. Petition at 24. The tests also showed that the degradation in aural distortion and stereo separation caused by 0 dB adjacent channel operation is "insignificant" in a digital-to-analog interference situation. Id. Petitioners additionally maintain that adhering to the current interference criteria as an interim step will allow an easy fall-back to analog transmission if such a change becomes necessary. Id. 21. Petitioners further request relaxation of the limitations on out-of-band emissions (spectral mask), found in Sections 21.908(b) and 74.936(b) of the Commission's Rules, as these limitations relate to digital emissions. Specifically, Petitioners seek out-of-band emission limitations of: 38 dB attenuation relative to the licensed average power level at the channel edges, constant slope attenuation from that level to 60 dB attenuation at 3 MHz above the upper and below the lower channel edge, and 60 dB attenuation below the licensed average power level at all other frequencies. Petition at 26. Petitioners contend that application of the current analog spectral mask to digital use during the interim period both would be unnecessarily restrictive and could be very costly to wireless cable operators; for example, requiring the use of expensive filtering. Petitioners report that the tests underlying the Petition demonstrate that even when the spectral mask is loosened, as proposed, a digital station is less likely to cause adjacent channel interference than an analog station meeting the existing mask. Id. at 27. Therefore, Petitioners assert that a "blanket waiver" of Sections 21.908(b) and 74.936(b) for digital transmitters will benefit the "public interest in rapid, low-cost introduction of digital technology" in that it "will allow much of the installed base of analog transmission equipment to be converted rapidly and inexpensively to digital usage without sacrificing interference protection standards." Id. at 27-28. 22. We have reviewed the test results submitted with the Petition and are satisfied that retaining the current 45 dB cochannel and 0 dB adjacent channel D/U signal strength protection ratios will enable us as an interim step to authorize the use of the QAM and VSB digital modulation formats requested by Petitioners without harmful interference to analog MDS and ITFS service. See paras. 14-15 and note 39, supra. In view of the results obtained in connection with the Commission's Digital Television proceeding, we are also confident that harmful interference will not occur among digital MDS and ITFS stations. See Final Report and Recommendations of the Advisory Committee on Advanced Television Service (November 28, 1995). 23. Generally, unless there is an interference agreement between the affected parties, applicants must protect the 56.33 km (35 mile) service areas of MDS "incumbent" stations, those authorized or proposed on or before September 18, 1995. Such interference protection must also be afforded to previously authorized or proposed service areas of ITFS stations. In expanding the protected service areas of ITFS stations and MDS incumbent stations, we recognized that there would be situations in which two expanded service areas would overlap. Accordingly, we adopted a limited exception to the 56.33 km (35 mile) protected service area definition to govern modification applications of MDS incumbents, where two protected service areas overlap. See Second Wireless Cable Reconsideration Order, 10 FCC Rcd at 7083-84. In such cases, applicants are allowed to request waiver of the protection criteria in Section 21.902 of the Commission's Rules. The waiver submission must demonstrate that the facilities proposed in the modification application will not increase the size of the geographic area predicted to receive interference, nor be predicted to cause harmful interference to any new portion of the other station's protected area. 24. Consistent with use of our existing interference criteria, the limited exception described in para. 23, supra, will also apply to modification applications of MDS incumbents seeking use of digital technology. We note that the same physical situation will be encountered by "ITFS incumbents" whose facilities were either authorized or proposed on or before September 18, 1995. The vast majority of these licensees are part of wireless cable systems, having identical facilities to those of the MDS licensees in the same systems. Therefore, in order to facilitate the introduction of digital technology on all of the channels in a wireless cable system, during the interim period, ITFS incumbent licensees applying for digital authority may, when applicable, request waiver of the interference criteria in Section 74.903 of the Commission's Rules based on the limited exception described above. This will further our goal of "enhancing the compatibility for the wireless cable operator who uses ITFS and MDS channels." Second Wireless Cable Reconsideration Order, 10 FCC Rcd at 7079. This matter will be revisited in a future rulemaking proceeding on use of digital technology in the MDS and ITFS services. 25. We are also persuaded by Petitioners' arguments for interim waiver of the emissions limitations of Sections 21.908(b) and 74.936(b). When we considered the MDS and ITFS spectral mask in 1990, we originally proposed a constant slope attenuation from the emission level at the channel edges to 60 dB attenuation at 3 MHz above the upper and below the lower channel edge, and Petitioners essentially reiterate that proposal here. While we eventually adopted the more restrictive current spectral mask, we did so, as Petitioners point out, based on tests utilizing NTSC analog transmissions. We find, based on the digital test results submitted by Petitioners, that we may allow Petitioners' proposed spectral mask as an interim measure without sacrificing adjacent channel interference protection. Acceptable levels of out- of-band emissions shall reference the average transmitter output power. See para. 27 and note 54, infra. We also clarify that the relative power of out-of-band emissions shall be measured with 100 kHz resolution bandwidth. As we have recently articulated, "[t]o maximize spectrum efficiency . . . the shape of the emission mask [must] be designed to permit reasonable and practical information transfer without excessively expensive filtering requirements. At the same time, out-of-band emission limits must be judiciously selected to provide acceptable adjacent channel protection." Replacement of Part 90 by Part 88 to Revise the Private Land Mobile Radio Services and Modify the Policies Governing Them and Examination of Exclusivity and Frequency Assignment Policies of the Private Land Mobile Radio Services, 10 FCC Rcd 10076, 10117 (1995). Petitioners' proposed interim spectral mask will facilitate the swift, low-cost introduction of digital technology to wireless cable, by allowing the use of existing transmission equipment without the significant costs and delays associated with equipment upgrades. In this manner, the public interest is fulfilled, while at the same time, adequate adjacent channel interference protection is provided. 3. Digital Power and Related Considerations 26. A major difference between analog and digital transmission systems is the measure used to describe the transmitted power. For NTSC analog signals, the chosen measure is the envelope power at the peak of the synchronizing pulses of the television video signal ("peak visual power"), which does not change appreciably during the course of normal station operations. NTSC peak visual power is commonly thought of as a transmitter parameter; however, it also determines the power radiated from a transmitting antenna, one measure of which is the effective isotropically radiated power ("EIRP"). Digital signals based on VSB or QAM modulation are different from NTSC signals. Except for a pilot carrier frequency in the VSB format, the digital signal waveform resembles random electrical noise, with many closely spaced irregular peaks at different levels evenly distributed above and below some average value, a value generally not affected by the modulating video signal. Therefore, digital signals are normally characterized by the "average" power in a 6 MHz digital channel, and calculations and/or measurements are made of average transmitter power, average EIRP, and average signal strength. In MDS and ITFS interference studies, a station's EIRP is entered into the free space propagation formula to predict levels of desired and undesired signal strengths, which in turn comprise the D/U interference protection ratios. The interim D/U protection ratios proposed by Petitioners are based on measurements of the peak NTSC visual power of the "desired" analog signal and the average power of the "undesired" digital signal, an established practice according to Petitioners: This results in comparing apples and oranges.' So long as the measurements are always made in the same way and the degree of acceptable interference is established using corresponding values, this is not a problem. Thus acceptable interference from digital-into-analog or from analog-into-digital is expressed in decibels based upon the peak of one and the average of the other. This is the industry norm for describing such relationships. Interim Implementation Report at 2. Accordingly, Petitioners ask the Commission to clarify that all digital power measurements and values in the MDS and ITFS services be defined as average power levels. Petition at 20 n.32. 27. We agree that average power, as described above, is a suitable measure for digital transmissions, and is the most suitable for purposes of this interim ruling, in that it was a measured variable in the testing in support of the Petitioner's interference protection proposals. Thus, we determine here that interim digital authorizations for MDS and ITFS stations will specify average values for EIRP, and that emissions in the spectral mask will reference the average power in a 6 MHz bandwidth measured at the output of the digital transmitter. Moreover, for purposes of this ruling, all other relevant signal propagation measures and parameters for digitally transmitted signals will reflect the use of average power; e.g., power flux density, received power, and electric field strength. As suggested in the Interim Implementation Report, we will authorize digital transmissions with an average power level (EIRP) equal to the peak visual power (EIRP) of analog transmissions from the same facility. Generally, applicants may seek an EIRP for their digital facilities up to the EIRP limits now permitted in our rules for analog transmissions. An MDS or ITFS applicant proposing to use an omni-directional transmitting antenna may request authority to operate digitally with an EIRP (average) of up to 2,000 watts, based on compliance with the interim standards and procedures for interference protection, spectral mask, and spectral energy dispersion. See para. 30, infra. This policy will facilitate the use of existing equipment (e.g., portions of an analog transmitter) and the rapid introduction of digital wireless cable systems into the competitive marketplace. 28. As a practical matter, in order to control the undesired effects of large amplitude peaks in a digital signal, "it will be necessary to back off' the power output by as much as 6-7 dB (to a level of 20-25 per cent of the rated analog power output)." Interim Implementation Report at 14. According to Petitioners, some stations may find it necessary to temporarily operate with reduced power until they begin to operate with fully digital transmitters; thus, Petitioners request that the Commission permit licensees to operate at less than authorized power during the interim period. Section 21.107(c) provides that transmitter power must be maintained "as near as practicable" to the power specified in the station authorization, and Section 74.951(f) states that a formal application is required for a change in operating power. 47 C.F.R.  21.107(c) and 74.591(f). Petitioners explain that a licensee may need to operate at reduced power: (1) to eliminate distortion otherwise caused by irregular power peaks in the digital signal; (2) to achieve the required 45 dB D/U protection ratio with respect to a closely-spaced station that had been licensed through consent or through the use of frequency offset techniques; or (3) because its existing transmitter equipment is incapable of meeting even the relaxed limitations on out-of-band emissions proposed by Petitioners. Petition at 28-29. Generally permitting licensees converting to digital technology to operate at reduced power on an interim basis will, Petitioners assert, avert a flood of individual requests for special temporary authority. This, in turn, will add an element of certainty, reduce Commission staff workload, and expedite the deployment of digital technology in the wireless cable industry. Petition at 30. 29. We are persuaded by Petitioners' justification of their request for operation at reduced power by licensees employing digital modulation during this interim period. We note that our rules contemplate operation at reduced power where necessary to avoid harmful interference. See, e.g., 47 C.F.R.  74.903(a) ("Interference may also be controlled through . . . use of the minimum power required to provide the needed service."). See also Second Wireless Cable Reconsideration Order, 10 FCC Rcd at 7084 ("There are a number of engineering techniques which can be used [by an MDS applicant], singularly or in combination, to avoid or eliminate the potential for harmful interference. Examples of such techniques include . . . decrease of transmitter power . . . ."). Interpreting Sections 21.107(c) and 74.951(f) to the extent of permitting, without application to the Commission, operation at less than authorized power will expedite introduction of digital technology in the wireless cable industry, as described by Petitioners. Although MDS licensees may operate with reduced power without notifying the Commission, licensees are cautioned that interference protection will be based on the authorized EIRP. 30. While we agree with the specification of average power for digital transmissions, we are concerned that the power spectrum of digital signals be properly shaped to produce an average power that is meaningful for controlling interference; i.e., that the power spectral density be uniform across the digital channel. To achieve this uniformity, the digital signal input must be suitably randomized before being modulated, in order to avoid "symbol patterns" (clustering of high energy symbols) that cause significant power peaks in the digital spectral waveform, which in turn increases the potential for cochannel interference. Accordingly, we believe it is necessary to stipulate interim measures for ensuring that adequate energy dispersal will be provided at all times for digitally modulated signals, including times when no data (input signal) is applied to the transmitter. The means of energy dispersal shall insure substantially uniform power spectral density across the occupied bandwidth (within the 3 dB power points) of the signal, except for the spectral region of any system pilot carrier used, when averaged over both relatively long and short periods. Such energy dispersal may be accomplished through the use of data randomization by scrambling the digital signal input with a pseudo random binary sequence ("PRBS") generated from a polynomial randomizer. Other methods of energy dispersal are possible. However, no segment of the bandwidth of the transmitter output signal, other than at the pilot frequency, shall be above the energy level expected for uniform dispersal. When transmitting a VSB signal, a small in-phase pilot carrier may be added to the data signal. As another safeguard against interference, we stipulate that the level of the pilot carrier be at least 11.3 dB below the average signal power. We believe that these additional measures are necessary during the interim period covered by this ruling; particularly, in view of our permitted use of transmission equipment that has not been type accepted for digital operation. In this regard, we will require licensees of stations that will operate transmitters not type accepted for digital use to test the in-channel power dispersal, pilot carrier level and level of out-of-band emissions, and certify compliance with the above provisions. Testing of the power dispersion at the output of such transmitters shall be made both with and without the presence of a digital input signal to the transmitter. A statement certifying compliance with the above provisions, accompanying the licensee's certification or notification to the Commission that construction of the station has been completed, will be a necessary condition for obtaining digital operating authority. See para. 41, infra. 4. Use of Frequency Offset Techniques and Frequency Tolerance 31. With respect to frequency tolerance, Petitioners state that 47 C.F.R.  21.101 and 74.961 can and should continue to apply, but that for some types of digital signals, there is no carrier frequency to measure. Petition at 33. Petitioners additionally maintain that frequency offset techniques are of no utility in reducing interference caused by a station employing digital modulation. Petitioners cite our recent acknowledgement that: We are especially concerned about the imminent transition from analog to digital transmissions for MDS stations and the effect of frequency offset transmitters on that transition. . . . [I]t is possible that our authorization of an involuntary frequency offset may frustrate the subsequent conversion of [a] particular MDS station to digital compression technology. This is not a desirable result. Second Wireless Cable Reconsideration Order, 10 FCC Rcd at 7093; see Petition at 29 n.53. Thus, Petitioners request that the Commission "reiterate" that it will not mandate frequency offset operations for stations utilizing digital modulation, despite the provisions of Sections 21.905(c) and 74.961(c) of the Commission's Rules that MDS or ITFS licensees may be required to use frequency offset to avoid or minimize interference. Petition at 29 n.53. 32. We concur that frequency tolerance is not relevant to the digital modulation systems involved herein, with the exception of the pilot carrier frequency in VSB systems. Testing of the 8-VSB modulation in connection with our advanced digital television proceeding has discovered that the "beating" of the pilot carrier and visual carrier frequency of a lower adjacent NTSC channel can introduce interference in the adjacent NTSC channel. This effect can be mitigated by precisely controlling the difference (offset) between the two frequencies. Accordingly, we believe that there may be some utility in frequency offset operation involving VSB digital transmissions. However, in this ruling, we will not mandate either a frequency offset or a tolerance for the 8-VSB pilot carrier. In view of the nature of the collocated adjacent channel stations that comprise wireless cable systems, this is a matter best left for now to the control of system operators. Thus, also keeping in mind our pronounced concerns that involuntary frequency offset may in fact frustrate the ability of an MDS or ITFS station to convert to digital transmissions, we grant, on an interim basis, Petitioners' request that we not mandate frequency offset operations for stations utilizing digital modulation, subject to the outcome of any future rulemaking proceeding. See Second Wireless Cable Reconsideration Order, 10 FCC Rcd at 7093. Nonetheless, we encourage the inclusion of pilot carrier offset studies in the additional program of testing to be conducted by those in the wireless cable industry, looking toward the adoption of permanent rules for digital systems. 5. Responsibility and Procedures for Alleviating Potential and Actual Interference 33. While Hammett generally supports the Petition, it raises as an issue Petitioners' treatment of existing wireless cable stations that have engineered their systems, on the basis of frequency offsets, to allow cochannel D/U signal ratios of less than the 45 dB which is required for nonoffset operation. Specifically, Hammett is concerned about the statement that "a station that provides less than 45 dB D/U to a co-channel station will have to reduce power in order to convert to digital technology, absent successful coordination." Petition at 29 n.53. Hammett requests that Petitioners clarify which station, the analog station or the station electing to switch to digital modulation, would be the candidate for a power reduction. See Hammett Comments at 2. Moreover, in a case where two cochannel analog stations have engineered their systems to less than 45 dB D/U ratios through frequency offsets and both wish to convert to digital operations, mutual reductions in power would not be helpful, because that would leave the D/U ratio unchanged. Hammett again questions which station should be the one to reduce power, and states that apparently, "the only solution in such cases would be for each licensee to give up half of its channels, so that the remaining channels can be afforded D/U ratios of 45 dB or better." Hammett Comments at 2-3. Assuming these two interference concerns can be adequately addressed, Hammett fully supports the Petition. 34. In their reply, Petitioners indicate that the language referenced by Hammett is not intended to force a station that is remaining analog to reduce power. Reply at 4-5. Instead, they affirm that under their proposed interim standards, "it is the station that desires to convert to digital technology that will have to reduce power to provide a 45 dB D/U [ratio] to the existing analog facility, absent agreement among the parties." Id. at 5. In response to Hammett's second situation where two closely-spaced stations both wish to convert to digital operations, Petitioners state that Hammett's solution is one possible approach, but suggest that "the parties could also logically agree to convert to digital technology in tandem and retain their existing power levels." Id. Petitioners also maintain that the Commission should permit licensees to mutually agree to convert to digital technology, even if the 45 dB D/U standard cannot be met. Id. at 6. As acknowledged by Petitioners, in the absence of an agreement between the parties in such situations, resolution of the issue would depend upon the final digital-to-digital interference protection standards to be developed in a future rulemaking proceeding. Although Petitioners believe that "closely-spaced digital systems will be able to operate with D/U ratios below 45 dB and still provide subscribers with signal quality no worse than that afforded in an analog environment under the 45 dB D/U standard," Petitioners reiterate that further testing, at higher modulation densities, will be required before the Commission can adopt the final interference protection standards. Id. at 5-6. 35. Similar to Hammett, Tarrant County generally supports the Petition, but it urges the Commission to establish a mechanism to ensure that ITFS and MDS licensees are protected from actual interference caused by digital transmissions. Tarrant County asserts that where actual interference occurs, the digital operator must be required to remove the interference immediately, at its own cost. See Tarrant County Comments at 2-3. In its reply, Petitioners contend that the Commission should apply its current policies regarding actual interference to ITFS and MDS signals, whether the interfering signal is from analog or digital transmissions, because digital transmissions are no more likely to cause harmful interference than analog transmissions. Petitioners add that Tarrant County has given no reason to believe that the Commission's current policies in this regard are inadequate. See Reply at 7 n.14. 36. We believe that our current rules provide adequate mechanisms to deal with the potential for harmful interference, as well as actual interference. Section 21.902 of the Commission's Rules provides that MDS applicants, conditional licensees and licensees are expected to "cooperate fully" in attempting to resolve problems of potential interference before bringing them to the attention of the Commission, and are required to "[c]ooperate fully and in good faith" to resolve interference problems. 47 C.F.R.  21.902(a) and (b)(2). Section 74.903 likewise provides that existing licensees and prospective applicants are expected to "cooperate fully" in attempting to resolve problems of potential interference before bringing them to the attention of the Commission. 47 C.F.R.  74.903(c); see 47 C.F.R.  74.903(d) and (e). As Petitioners articulate, "given the paucity of complaints of actual interference that the Commission has been called upon to resolve over the years, it appears that the existing policies work well." Reply at 7 n.14. In addition, we have declared with respect to MDS stations and ITFS facilities being leased or used for non-ITFS purposes, that if a station causes harmful interference within the protected service area of another existing station and the interference is not de minimis, "we will require the offending station to cease operations until the interference is eradicated. The station alleging that it is being interfered with will be required to make a clear and convincing showing that the interference is occurring." Amendment of Parts 21, 74 and 94 of the Commission's Rules and Regulations with regard to the technical requirements applicable to the Multipoint Distribution Service, the Instructional Fixed Television Service and the Private Operational-Fixed Microwave Service (OFS), 98 FCC 2d 68, 93 (1984). See id. at 92-93. 37. Thus, we find that Petitioners present satisfactory approaches for resolving Hammett's first concern and those concerns expressed by Tarrant County. As for the situation where two closely-spaced stations, which operate on the basis of frequency offset, both seek to convert to digital operations, Hammett and Petitioners have proposed three solutions involving agreement between the two parties. We believe, in the interest of fostering a clear, market- based solution, that for the interim period governed by this ruling, any conflict resulting from this type of situation must be resolved by agreement between the two parties, or we will grant neither party the authority to modify its operations to employ digital technology. This approach will maintain an environment free of harmful interference until we have the opportunity to adopt the final interference protection standards applicable to the use of digital technology in the MDS and ITFS services. D. Application of Other MDS and ITFS Technical Rules in a Digital Environment 38. Petitioners argue that while there is flexibility in our current rules for authorization of the use of digital technology, the rules nevertheless remain focused on NTSC transmissions, and there are instances where the use of digital technology does not comport with these rules. Consequently, Petitioners maintain that the Commission should clarify how it will apply certain of these rules in the digital environment, and permit "deviations" from any rules designed solely to address NTSC issues, which are "inherently unsuitable for application to the use of digital technology." Petition at 30. 1. Equipment Approval 39. Petitioners request that the Commission provide manufacturers an opportunity to secure type acceptance for digital transmitters that comply with the relaxed out-of-band emissions limitations proposed by Petitioners. They also request that manufacturers be offered the option of obtaining digital type acceptance for "earlier designs that are already installed in analog systems," but where a manufacturer does not do so, the Commission should afford the affected MDS or ITFS licensee a vehicle for utilizing its existing transmitters, without meeting the type acceptance requirement under 47 C.F.R.  21.907(c). Petition at 32. Petitioners propose that the Commission allow use of existing analog transmitters adapted for digital transmission, but that have not received digital type acceptance, to operate at reduced power and/or with appropriate filtering, if necessary, in order to comply with the interim spectral mask sought by Petitioners. Petitioners further suggest that absent type acceptance, the licensee should be required to submit a "proof-of-performance at the time of construction" of the digital system, demonstrating compliance with the interim spectral mask. Petition at 32-33. 40. Parts 21 and 74 of the Commission's Rules require that all MDS and ITFS transmitters be type accepted. See 47 C.F.R.  21.120, 21.907(c), 74.938 and 74.952. For manufacturers who seek to secure digital type acceptance for newly-designed or modified transmitters that comply with the interim spectral mask approved above, upon an appropriate showing the Commission will grant type acceptance based on the conditions of waiver described in this ruling. See 47 C.F.R.  2.915(a) and (b). We intend to reevaluate digital type acceptance issues in a future rulemaking proceeding on digital modulation for the MDS and ITFS services. At the present time, given the public and industry interest in expediting the employment of digital technology, notwithstanding the type acceptance requirements in Parts 21 and 74, we also will allow MDS and ITFS licensees to use existing analog equipment modified for digital transmissions that comply with the interim spectral mask approved above, without obtaining digital type acceptance, subject to certain conditions incorporating Petitioners' "proof- of-performance" proposal. Approval of the use of newly-designed digital transmitting equipment will still be subject to type acceptance procedures pursuant to Parts 2, 21 and 74 of the Commission's Rules. 41. Under this scheme, after the Commission staff grants a licensee's application to employ digital technology, the licensee will incorporate a digital component (e.g., modulator or exciter) into its existing base of transmission equipment, and perform on-site tests (measurements) at the transmitter output to determine compliance with the interim spectral mask, as well as power level and energy dispersal strictures discussed above. See paras. 21, 25 and 27-30, supra. The licensee may rely on tests performed by the equipment manufacturer or by a test laboratory confirming compliance with the interim spectral mask for a specific combination of digital modulator and amplifiers. The licensee will then certify to the Commission, at the time it certifies or notifies the Commission that construction of the station has been completed, that these tests have been performed, the transmissions meet the interim spectral mask, the maximum EIRP of its facility does not exceed the authorized EIRP, and the transmissions comply with the spectral energy dispersal requirements. Test results must be furnished to the Commission upon request. Thus, in furtherance only of the scheme delineated herein, we waive the requirements, contained in Subpart J of Part 2 of the Commission's Rules, pertaining to issuance of equipment authorizations prior to operation, though we will allow manufacturers to seek type acceptance of existing analog equipment modified for digital transmissions under the technical guidelines described above in this ruling. Furthermore, any other rules in Parts 2, 21 and 74 containing requirements for type acceptance and applicable to analog MDS or ITFS transmissions are waived for existing analog equipment modified for digital transmissions. These waivers, as well as the testing and statement-of-performance process set forth above and additionally described below, will be effective until final rules are adopted in the future. 2. Emission Designators 42. Petitioners state that MDS and ITFS stations using digital modulation "will likely employ" emission designators of 6M00D7W for QAM and 6M00C7W for VSB. Petition at 13 n.23. ITS believes that both applicants and equipment manufacturers who must seek type acceptance of transmitting equipment would benefit from standardized emission designators, and posits that 6M00D1W for QAM and 6M00C1W for VSB may be more accurate. ITS suggests that a "1," signifying a single channel of digital information, would be more correct than a "7," which is generally reserved for multiple channels of unrelated digital information. ITS Comments at 1-2. In its reply, Petitioners agree with ITS that it would be beneficial for the Commission to clarify its policy regarding emission designators and to apply that policy uniformly. However, Petitioners contend that the issue of which emission designator is appropriate to QAM and VSB systems has no bearing on the issues addressed in the Petition, and that the results of the testing conducted for the Petition and the conclusions from that testing remain valid. See Reply at 3-4. 43. We agree with ITS and Petitioners that standardization of emission designators would be beneficial in eliminating confusion. Emission designators are governed by Section 2.201 of the Commission's Rules, 47 C.F.R.  2.201. Section 2.201(d) provides that use of a "1," as suggested by ITS, indicates that the signal modulating the carrier is a "single channel containing quantized or digital information without the use of a modulating sub-carrier, excluding time- division multiplex." 47 C.F.R.  2.201(d) (emphasis added). We envision that the modulating signal will contain a time division multiplex of video, audio, and data signals from two or more sources. Therefore, the more appropriate emission designators are 6M00D7W for QAM and 6M00C7W for VSB. Where necessary, applications may be amended to change the emission designator to bring it into conformance with those specified herein, and we will treat these changes as minor amendments. See paras. 55-57, infra. 3. Transmission standards 44. Petitioners request that despite the mandates of 47 C.F.R.  21.907 that all MDS licensees equip their facilities for NTSC transmission capability, the Commission not require MDS licensees to offer NTSC service if the operator using the station elects and receives authorization to transmit digitally. Petition at 31. When the Commission promulgated this rule as part of the original rules governing MDS, NTSC transmission capability was retained as a safeguard against other transmission standards that might prove lacking in quality. See MDS Allocation Order, 45 FCC 2d at 624. We acknowledge that the technology upon which the standards adopted in 1974 were based has changed substantially, and we recognize that digital will likely be the primary transmission method for video programming for the foreseeable future. In further recognition of the tested and proven quality of the digital modulation formats which Petitioners seek to utilize, we find that waiver of Section 21.907 does not undermine the rule's purpose. In addition, compliance with Section 21.907 for licensees who transmit digitally places unnecessary burdens on such licensees. Cf. note 77, infra (MDS station identification requirements removed where burdens on licensees outweighed benefits). Accordingly, we will not require MDS licensees who utilize digital transmissions to equip their facilities for NTSC transmission capability. Section 21.907 is hereby waived to the extent indicated in this paragraph. For the same reasons, we also waive Section 74.950(f)(1) to the extent it requires ITFS translators and boosters relaying digital signals to be designed so that the electrical characteristics of an NTSC signal introduced into the input terminals will not be significantly altered, except as to frequency and amplitude, by passage through the translator or booster. 47 C.F.R.  74.950(f)(1). 45. Tarrant County maintains that "for at least the near term" licensees should be permitted to (1) flexibly employ digital operations on one or more, but not necessarily all, of their authorized channels; (2) freely switch from analog to digital and digital to analog modulation among channels and on the same channel; and (3) freely utilize digital technology to transmit other modulations in addition to those advanced in the Petition, such as " high definition'" or "digital data broadcasting in the NTSC blanking intervals." Tarrant County Comments at 3-4. Petitioners agree that the flexibility sought by Tarrant County is appropriate at least for the time being, and they assert that the Petition contemplated that sort of flexibility. See Reply at 7. However, Petitioners note that to the extent the technologies mentioned by Tarrant County do not employ QAM or VSB, Tarrant County "should be required to demonstrate that its digital proposal will not cause harmful electromagnetic interference to nearby stations." Id. at n.15. 46. We fully support the flexibility sought by Tarrant County in its first two proposals. Such flexibility could benefit both existing licensees and new applicants alike. However, as with SR Telecom's request for consideration of the use of wireless loop technology on MDS frequencies, no data was submitted here for evaluation of the merits of Tarrant County's third proposal regarding transmission of other digital modulations. Therefore, we find clarification of the use of other digital modulation techniques beyond the scope of this ruling. We intend, in a future rulemaking proceeding, to approach the issue of alternative uses of MDS and ITFS spectrum in a digital environment. 4. Equipment standards, Modulation Limits and Aural Power Limitations 47. Petitioners contend that the transmission equipment requirements imposed by 47 C.F.R.  21.908(a) and 74.950(a) pertaining to NTSC signal waveform and transmitter performance characteristics are "[b]y their very nature" incompatible with digital transmissions, and "should be inapplicable" in the digital environment. Petition at 31. Similarly, Petitioners maintain that the Commission should not apply 47 C.F.R.  74.970 to a station utilizing digital transmissions because the modulation parameters specified in that rule are specific to analog transmissions. Petition at 33. Petitioners likewise assert that Sections 21.904(d) and 74.935(d) of the Commission's Rules regarding aural signal power are inapplicable in the digital environment, where there are no separate aural and visual carriers. Moreover, waiving Sections 21.904(d) and 74.935(d) when digital modulation is employed is consistent with the rules' purpose, namely the reduction of the potential for harmful adjacent channel interference, because Petitioners' proposal will result in improved adjacent channel performance. Petition at 34. To the extent that Sections 21.904(d), 21.908(a), 74.935(d), 74.950(a) and 74.970 are incompatible with digital transmissions or the provisions of this ruling, those rules are hereby waived. 5. Transmission of ITFS Call Signs 48. Section 74.982(b)-(f) requires ITFS licensees to transmit their call signs periodically. 47 C.F.R.  74.982(b)-(f). Petitioners argue that compliance with this rule, once an ITFS station commences digital transmission, will be costly and will provide little, if any, public benefit. Petitioners therefore request that until permanent rules regulating the use of digital in MDS and ITFS are adopted, "the Commission should spare licensees the cost of compliance . . . by not applying the requirements of Sections 74.982(b)-(f) to ITFS facilities operating in a digital mode." Petition at 35. In the alternative, Petitioners seek clarification of whether the Commission intends for the call signs to be transmitted in analog format or digital format, and if in digital format, whether such transmission must be made over one channel or all of the channels created through use of compression. Petition at 34-35. 49. In establishing the station identification requirements of Section 74.982, the Commission described their primary purpose as showing that the operation is licensed. ITFS Allocation Order, 39 FCC at 860. The importance of showing that the station is licensed was further explained in another context as protecting stations against accusations of wrongdoing, because there was a "strong suspicion" that signals originated from an unlicensed transmitter where signals were observed but call signs were not transmitted. See Amendment of Section 74.682 of the Commission's Rules and Regulations Concerning Station Identification of Television Auxiliary Broadcast Stations, 5 FCC 2d 767, 769 (1966). In the television auxiliary broadcast station identification order, the Commission emphasized that adequate station identification "assure[s] proper enforcement of our rules and prompt relief from disruptive interference should such occur." Id. at 771. Call sign transmission also keeps the public aware of a station's identity and facilitates the reporting by members of the public of infractions, though the reporting of infractions by the public "is not the primary purpose of station identification." Id. at 769. 50. The Commission's rules currently require public services -- such as ITFS, low power TV and AM-FM-TV broadcast services -- to broadcast station identifications, while private services such as MDS and Private Operational-Fixed Microwave Service are exempt from this requirement. Although requiring transmission of station identifications may continue to benefit the enforcement process, it appears that such requirements create some burdens on licensees. In this regard, Petitioners complain about the potential costs of complying with the call sign transmission requirement once an ITFS station commences digital transmission, and they argue that "there is no evidence that the transmission of call signs by ITFS licensees has resulted in any better operating environment than is the case with respect to the MDS. It is a relatively simple matter to determine any source of harmful electrical interference without reference to a call sign." Petition at 34 n.62. In addition, keeping the public aware of a station's identity may be particularly less important with respect to the channels that are leased to a wireless cable operator, because the subscriber will know the identity of the wireless cable operator. 51. Section 74.982 was last amended in 1984, prior to adoption of most of the rules encouraging the use of excess ITFS spectrum for wireless cable video programming services. The ITFS channels that are leased to wireless cable operators arguably function as private, rather than public, services. Moreover, the burdens of requiring ITFS licensees to transmit call signs may outweigh the benefits, especially where the channels are leased to a wireless cable operator, whose identity is readily discernible and whose licensing status is readily ascertainable. For these reasons, we plan to address the wisdom of continued ITFS call sign transmission requirements in a future rulemaking proceeding. Until that time, however, we do not find a waiver of these requirements for ITFS stations employing digital technology to be appropriate. In response to Petitioners' alternative request that we clarify our ITFS call sign transmission requirements as they apply to stations utilizing digital technology, we will interpret Section 74.982(b), for the interim period governed by this ruling, as requiring ITFS stations to transmit call signs only on channels reserved for ITFS programming during the hours reserved for such programming. Until we undertake a future rulemaking on the issue, the interpretation of Section 74.982(b) set forth herein will apply, regardless of whether the ITFS station is transmitting in analog or digital. Furthermore, the call sign should be transmitted in the same modulation in which the ITFS programming is transmitted. Cf. paras. 45-46, supra (authorizing ITFS and MDS licensees to flexibly switch from analog to digital and digital to analog modulation among channels and on the same channel). E. Application Procedures 52. This Declaratory Ruling and Order clarifies the Commission's interim policies, rules and procedures pertaining to MDS licensees, conditional licensees and applicants with pending applications, as well as ITFS licensees, permittees and applicants with pending applications, who elect to transmit a QAM or VSB digital signal. It also governs the new station applications filed by MDS auction winners or BTA authorization holders, or filed for ITFS licenses in a filing window, seeking authority to transmit digitally. This ruling makes clear that each party desirous of utilizing digital transmissions must apply for such authority by filing a formal application or application amendment, and receive such authority from the Commission, prior to installing and operating digital transmission equipment. A separate application or amendment must be filed for each station for which digital authority is sought. These applications or amendments must specify use of either a type accepted digital transmitter or a digital transmitter to be approved through the testing and statement-of-performance process described above. See paras. 40-41, supra. As discussed in paras. 14-15, supra, we will grant authority to utilize such transmitters for transmission in QAM with modulation densities up to 256 or VSB modulation with densities up to 16. Digital signals must be transmitted on a non-interference basis, subject to meeting the interim spectral mask and other interim technical specifications described above. 53. To assist Commission staff in expediting the processing of these applications and amendments, each application or amendment should include a cover letter clearly indicating that the attached application or amendment requests authority to utilize digital transmissions. MDS licensees, conditional licensees or applicants must file a formal application to specify digital emissions on FCC Form 304, while ITFS licensees, permittees or applicants must do so using FCC Form 330. Pending applications in either service must be amended to specify a digital emission designator. In either case, the MDS applicant for interim digital transmission authority must, in addition to meeting all other pertinent application requirements, prepare a new or amended interference showing to demonstrate non-interference to others by the new or amended application for digital operations, and serve the showing and/or copy of the application on potentially affected parties, in accordance with Sections 21.902 and recently added 21.938(g) of the Commission's Rules, in the same manner that these rules relate to applications for analog transmissions. MDS applicants generally are not required to include the interference studies with their applications; nevertheless, applicants for interim digital transmission authority may wish to submit these studies or any other information which they feel may be helpful to the processing of their applications. While applicants for minor changes to ITFS applications or facilities normally are not required to prepare or serve interference showings, we will require during the interim period that ITFS applicants for digital authority follow the same procedures as those that we have mandated for MDS applicants, as discussed above. We will use the same approach for MDS and ITFS applicants in light of the newness of digital operations in wireless cable, as well as the fact that most ITFS stations are part of wireless cable systems. We hold that all of the waivers in this ruling, which are granted in the public interest, are conditioned upon applicants for interim digital authority complying with these interference showing requirements. In lieu of an interference showing, MDS or ITFS applicants for interim digital transmission authority may submit with their applications written statements of "no objection" from all potentially affected licensees, conditional licensees, permittees, or applicants for previously proposed stations, stating that these parties do not object to the digital operation of the MDS or ITFS station, in accordance with Sections 21.902 and 74.903 of the Commission's Rules, as applicable. 54. Upon grant of the modified, amended or new application, a conditional licensee or licensee who specifies use of a type accepted digital transmitter may install and test the transmitter. An ITFS licensee may immediately begin to operate the transmitter upon completion of construction, while an MDS conditional licensee may begin regular operation of the transmitter upon proper submission of the FCC Form 304A, described below. Conditional licensees or licensees who specify transmitters that are not type accepted for digital transmission may activate their digital transmitters for the purpose of testing, as described in paras. 30 and 41, supra. After installation or activation of the digital transmitter, whether type accepted or not, completion of other necessary construction, and completion of any necessary testing, the MDS conditional licensee will certify completion of construction on FCC Form 304A, and the ITFS licensee will submit a letter notifying the Commission that construction has been completed. In conjunction with the filing of the FCC Form 304A or the submission of the ITFS construction notification, conditional licensees or licensees who specify a digital transmitter that is not type accepted must also provide a statement certifying that the aforementioned tests have been performed, the transmissions meet the interim spectral mask, the authorized value of EIRP is not exceeded, and the transmissions comply with the spectral energy dispersal requirements. The statement accompanying the FCC Form 304A or ITFS construction notification must also identify the name, address, telephone number, and firm or company name of the person who performed the tests. 55. Amendments to pending ITFS applications and applications to modify ITFS facilities are governed by Section 74.911 of the Commission's Rules, 47 C.F.R.  74.911. Section 74.911(a) states that an application will be considered to be one for a major change if it involves adding or changing channels, changing polarization, increasing power or transmitting antenna height by certain amounts, or relocating a facility's transmitter site by at least 10 miles. See ITFS Window Filing Order, 10 FCC Rcd at 2923-24. Applications for any other changes normally are considered to be for minor changes. 56. We do not believe that proposals to use digital transmitters need to be considered major changes under Part 74 of the Commission's Rules. Classifying such proposals as major changes would restrict their filing to filing windows. See ITFS Window Filing Order, 10 FCC Rcd at 2907-11. In addition, the proposed use of digital compression does not give an applicant for interim digital authority the right to add any new ITFS channels, as contemplated by the major change provisions of Section 74.911(a). See note 11, supra; cf. Comband II, 61 RR 2d at 146 (use of Comband analog compression does not increase the number of channels utilized). Furthermore, while a major change triggers a petition to deny period under Section 74.911(c), interested parties are provided adequate announcement of a minor change through its listing on public notice, and they may file objections pursuant to 47 C.F.R.  74.910 and 73.3587. Commission staff also retains the flexibility under Section 74.911 to reclassify any application as a major change should the circumstances warrant. Therefore, ITFS applications proposing substitution of a digital transmitter, which are filed in accordance with the procedures described above, will normally be regarded as minor changes. Cf. Comband II, 61 RR 2d at 146 (considering substitution of a Comband analog compression transmitter to be a minor change under Section 74.911). Such applications may be filed at any time and are not subject to window filing procedures. However, we still are as concerned about interference avoidance with ITFS digital operations as we are with MDS digital operations, so we are requiring performance of interference studies by ITFS applicants for interim digital transmission authority. See para. 53, supra. We intend to reexamine the classification of such applications in a future rulemaking proceeding. 57. An MDS application amendment to change the type of transmitter emission is normally considered to be a major amendment under 47 C.F.R.  21.23(c)(2)(iii). However, for purposes of this interim ruling, pursuant to 47 C.F.R.  1.3, we waive Section 21.23(c)(2)(iii) on our own motion and will consider amendments to change to digital transmission to be minor. Modifications to MDS facilities to change to digital transmission are governed by 47 C.F.R.  21.40(a). Pursuant to 47 C.F.R.  21.27(a)(1) and (5), as applicable, public notice will be given of the filing of either a formal application by a licensee or conditional licensee proposing to add or switch to digital transmission, or an amendment to a pending application for this purpose. For purposes of this interim ruling, we also waive 47 C.F.R.  21.27(c) to the extent it requires a thirty day waiting period following the issuance of a public notice listing an application to modify an MDS facility for digital operations. MDS and ITFS parties in interest will be given an opportunity to comment and to raise interference objections in accordance with Section 21.30(b) of the Commission's Rules, 47 C.F.R.  21.30(b). These rule waivers will expedite the introduction of digital technology to wireless cable under interim authority, and bring the procedures for processing such applications into conformance with the procedures pertaining to ITFS applications for interim digital authority. Moreover, there will be no detriment to the public interest resulting from these waivers, because MDS applicants for interim digital authority must comply with all interference protection and study requirements normally relevant to MDS applicants, and the testing and statement-of- performance process described above will provide further safeguards against harmful interference. F. ITFS Programming Requirements 58. Section 74.931 of the Commission's Rules describes the purpose and permissible service of ITFS stations, and also sets forth the minimum ITFS programming requirements for ITFS licensees. See 47 C.F.R.  74.931. Section 74.931(e)(9), which allows an ITFS licensee to shift its required educational programming onto fewer than its authorized number of channels via channel loading or channel mapping, specifies that an ITFS licensee who leases excess channel capacity to a wireless cable operator must provide a total average of at least 20 hours per channel per week of ITFS programming on its authorized channels. ITFS licensees in such lease arrangements also retain the right to recapture "an average of an additional 20 hours per channel per week for simultaneous programming on the number of channels for which it is authorized." 47 C.F.R.  74.931(e)(9). Petitioners ask the Commission to confirm that, at least during the interim period governed by this ruling, we will not require additional ITFS programming by licensees who expand their spectrum capacity by utilizing digital compression technology. See Petition at 35. Petitioners particularly rely on the Mass Media Bureau's decision in Comband II and urge the Commission to retain the policy announced in that case. Petitioners suggest that any interim ruling would be without prejudice to any rules that may ultimately be adopted establishing the recapture rights of ITFS licensees with respect to the increased capacity made available by digital compression. See Petition at 37. We decline in the context of this petition for declaratory ruling to impose any changes in ITFS programming requirements. Those requirements remain the same regardless of the modulation technology. We will defer consideration of any changes to our ITFS programming requirements to a future rulemaking. IV. ORDERING CLAUSES 59. Accordingly, IT IS ORDERED that under the authority contained in Section 4(i) of the Communications Act of 1934, as amended, 47 U.S.C.  154(i), and Section 554(e) of the Administrative Procedure Act, 5 U.S.C.  554(e), the Petition For Declaratory Ruling, on the use of digital modulation by Multipoint Distribution Service and Instructional Television Fixed Service Stations, IS GRANTED to the extent specified above. This Declaratory Ruling and Order shall be effective upon its release and shall remain effective until adoption of rules governing digital transmissions in MDS and ITFS in a future rulemaking proceeding. See 47 C.F.R.  1.4(b)(2) and 1.103. Nothing in this Declaratory Ruling and Order shall prejudice the outcome of such a rulemaking proceeding. 60. IT IS FURTHER ORDERED that Subpart J of Part 2 of the Commission's Rules (Sections 2.901 et seq.) pertaining to issuance of equipment authorizations prior to operation, and Sections 21.120, 21.907(c), 74.938, 74.952, and any other of the Commission's Rules in Parts 2, 21 and 74 containing requirements for type acceptance of equipment and applicable to analog MDS or ITFS transmissions, ARE WAIVED for existing analog equipment modified for digital transmissions, to the extent specified above, subject to such conditions set forth in paras. 41 and 53 in the foregoing order. 61. IT IS FURTHER ORDERED that Sections 21.23(c)(2)(iii), 21.27(c), 21.904(d), 21.907, 21.908(a) and (b), 74.935(d), 74.936(b), 74.950(a) and (f)(1), and 74.970 ARE WAIVED to the extent specified above, subject to such conditions set forth in para. 53 in the foregoing order. 62. IT IS FURTHER ORDERED that the staff of the Mass Media Bureau shall send copies of this declaratory ruling to the parties filing formal comments by certified mail, return receipt requested. FEDERAL COMMUNICATIONS COMMISSION William F. Caton Acting Secretary