Before the FEDERAL COMMUNICATIONS COMMISSION Washington, DC COMMENTS OF THE SATELLITE INDUSTRY ASSOCIATION

Transcription

1 Before the FEDERAL COMMUNICATIONS COMMISSION Washington, DC In the Matter of Amendment of the Commission s Rules with Regard to Commercial Operations in the MHz Band ) ) ) GN Docket No ) ) To: The Commission COMMENTS OF THE SATELLITE INDUSTRY ASSOCIATION July 14, 2014 Patricia Cooper President Satellite Industry Association th Street, N.W., Suite 1001 Washington, D.C (202)

2 SUMMARY SIA and its members strongly support the goal of enhancing efficient spectrum use, and we have decades of practical experience in the balancing act that comes with spectrum sharing whether with terrestrial Fixed Services or with other satellite operators using the same spectrum. The framework set forth in the Notice, however, is heavily skewed in favor of new entry at the expense of existing critical satellite services in the conventional and extended C-band. The Commission must correct this imbalance by protecting satellite operations and preserving their continued ability to grow and develop. In order to prevent proposed CBRS operations from creating harmful interference to in-band FSS earth stations, the Commission must adopt and enforce protection criteria derived from ITU standards. A technical annex to SIA s comments prepared by RKF Engineering demonstrates that the appropriate I/N values are -13 db for long-term interference and -1.3 db for short-term interference. Based on these values, RKF has calculated single-entry protection areas surrounding the in-band FSS earth stations. Excluding CBRS operations within these geographic areas would be a good start to protect these earth stations. However, a high density of CBRS operations outside of these single-entry protection areas could cause, in the aggregate, the I/N interference thresholds to be exceeded. As a result, the Commission would need to impose constraints on the density of CBRS deployments, build significant margins into these protection areas, and/or recalculate the protection areas in the future as the density of CBRS deployments increases to ensure that aggregate interference limits are not exceeded. The Notice asks whether in-band protection zones can be reduced or eliminated by using the SAS to dynamically manage interference, but that will require database capabilities whose feasibility has not been demonstrated. In particular, the SAS would need to be able to monitor and recalculate aggregate interference in real time from dozens, hundreds, or even i

3 thousands of transmitting CBRS devices in the vicinity of any given earth station. Propagation modeling will be extremely complex as well. Once it performs the necessary calculations, the SAS would also need to be able to address any exceedances of the aggregate interference criteria by identifying terminals that are significant contributors to the exceedance and requiring them to immediately shut down or reduce power. Regardless of whether the SAS is enforcing protection zones or performing more complicated interference management, its capabilities will need to be thoroughly analyzed and validated in real-world conditions prior to implementation. Furthermore, security of the SAS and its communications with devices are of the utmost importance to prevent circumvention of the Commission s regulatory framework that could lead to harmful interference. To prevent harmful adjacent-band interference to FSS operations, including thousands of conventional C-band earth stations, a combination of separation distances and outof-band emissions limits will be needed. As the Notice recognizes, the OOBE level is directly relevant to the necessary separation distances between CBRS devices and FSS earth stations. Accordingly, if the Commission seeks to permit CBRS devices to operate in closer proximity to potentially affected FSS earth stations, it must adopt a stricter OOBE limit to prevent interference. Fundamental fairness requires the Commission to reconsider its decision to freeze 3.5 GHz FSS earth station deployment. If true spectrum sharing is possible, both the FSS and the CBRS should have the opportunity to continue to grow and develop. The freeze strands investment and deprives satellite operators of the necessary flexibility to adapt to changes in demand or other circumstances that may require relocation or addition of an earth station facility. ii

4 Finally, the Commission must abandon the idea that the framework developed here to address the specific characteristics of the 3.5 GHz band can be duplicated in other spectrum, which necessarily will have different usage and operational characteristics. In particular, the Commission s decisions here should not drive U.S. positions internationally for the MHz band, nor should the Commission extend the CBRS regulatory framework to the MHz band. iii

5 TABLE OF CONTENTS SUMMARY...i I. INTRODUCTION...2 II. PROTECTION AREAS WILL BE NEEDED TO PREVENT INTERFERENCE TO IN-BAND FSS EARTH STATIONS UNLESS A HIGHLY SOPHISTICATED SAS IS DEVELOPED...3 A. Interference Criteria Should Be Derived from ITU Recommendations...4 B. In-Band FSS Earth Stations Can Be Protected by Using an SAS to Enforce Geographic Protection Areas...6 C. Significant Obstacles Exist to Development of an SAS Capable of Managing Interference if CBRS Operations Are Permitted within Protection Areas Extremely complex SAS functionalities would be required Robust enforcement mechanisms would be needed...11 D. The SAS and its Security Must Be Rigorously Tested and Validated...13 III. SEPARATION DISTANCES AND OUT-OF-BAND EMISSION LIMITS WILL BE NEEDED TO PREVENT HARMFUL ADJACENT BAND INTERFERENCE...15 IV. FUTURE FSS EARTH STATIONS IN MHz MUST BE ALLOWED ON A PRIMARY BASIS...19 V. THE COMMISSION SHOULD NOT ASSUME THAT THE SHARING APPROACH FOR THE 3.5 GHz BAND CAN BE USED IN OTHER SPECTRUM...21 VI. CONCLUSION...22 iv

6 Before the FEDERAL COMMUNICATIONS COMMISSION Washington, DC In the Matter of Amendment of the Commission s Rules with Regard to Commercial Operations in the MHz Band ) ) ) GN Docket No ) ) To: The Commission COMMENTS OF THE SATELLITE INDUSTRY ASSOCIATION The Satellite Industry Association ( SIA ) hereby responds to the Commission s Further Notice of Proposed Rulemaking in the above-captioned proceeding, which seeks additional input regarding the feasibility of new terrestrial services in the MHz band ( 3.5 GHz band ). 1 As discussed below, SIA is very concerned that the proposed Citizens Broadband Radio Service ( CBRS ) will seriously adversely affect satellite operations in extended and conventional C-band spectrum. 2 Because satellite services in these bands are critical elements of the national communications infrastructure, we urge the Commission to proceed with extreme caution before authorizing a new service that could disrupt existing satellite networks or impede their future growth and development. 1 Amendment of the Commission s Rules with Regard to Commercial Operations in the MHz Band, Further Notice of Proposed Rulemaking and Order, GN Docket No , FCC (rel. Apr. 23, 2014) ( Notice ). 2 The conventional C-band refers to downlink (space-to-earth) spectrum at MHz and uplink (Earth-to-space) spectrum at MHz. The adjacent frequencies, including the MHz downlink (space-to-earth) spectrum and MHz uplink (Earth-tospace) spectrum, are referred to as the extended C-band.

7 I. INTRODUCTION SIA has consistently emphasized the need to ensure that essential Fixed Satellite Service ( FSS ) operations throughout the C-band are protected from harmful interference. 3 In discussing the protection of incumbent services, most comments to date have focused on the coprimary federal allocation used for Department of Defense radar systems. Although commenters recognize the requirement to protect FSS earth stations, very few proponents of the CBRS have addressed the practical feasibility of ensuring that CBRS operations do not interfere with FSS earth stations operating in the 3.5 GHz band or the thousands of conventional C-band terminals deployed nationwide. The Notice recognizes the importance of these interference concerns and seeks further input regarding measures that will be necessary to prevent disruption of FSS networks if the Commission proceeds with its proposals to introduce the CBRS in the 3.5 GHz band. 4 In these comments, SIA supplements its previous showings regarding the potential for harmful interference from CBRS systems to in-band FSS earth stations and the risks that out-of-band emissions ( OOBE ) from CBRS operations will interfere with satellite operations in the adjacent band, including conventional C-band FSS earth stations. SIA has also retained an engineering firm, RKF Engineering ( RKF ), and its report, which provides analysis of in-band and adjacent-band interference issues, is attached hereto as Appendix A. 3 See Comments of the Satellite Industry Association filed Feb. 20, 2013 ( SIA February 2013 Comments ); Reply Comments of the Satellite Industry Association filed Apr. 5, 2013 ( SIA April 2013 Reply Comments ); SIA Written Ex Parte Presentation filed Aug. 20, 2013 ( SIA August 2013 Ex Parte ); Comments of the Satellite Industry Association on Licensing Models and Technical Requirements filed Dec. 5, 2013 ( SIA December 2013 Comments ); Reply Comments of the Satellite Industry Association on Licensing Models and Technical Requirements filed Dec. 5, 2013 ( SIA December 2013 Reply Comments ); SIA Written Ex Parte Presentation filed Feb. 1, 2014 ( SIA February 2014 Ex Parte ). 4 Notice at

8 SIA also observes that the large number of questions posed with respect to protection areas and the effectiveness of interference mitigation measures necessitates a go-slow approach to the prospect of CBRS. In particular, SIA urges the Commission not to proceed at this juncture with any incorporation of the MHz frequency band into the regulatory scheme proposed in the Notice. 5 II. PROTECTION AREAS WILL BE NEEDED TO PREVENT INTERFERENCE TO IN-BAND FSS EARTH STATIONS UNLESS A HIGHLY SOPHISTICATED SAS IS DEVELOPED The Commission and the record support protecting FSS earth stations receiving signals from space in the same frequency bands as transmitting Citizen Broadband Service Devices ( CBSDs ) from harmful interference. 6 In this regard, the Notice seeks comment on whether geographic protection areas are necessary, and if so, the size of such areas. 7 In addition, the Notice invites input regarding what criteria need to be taken into account in a Spectrum Access System ( SAS ) that would ensure FSS earth stations are protected while simultaneously maximizing the areas available for CBRS operations. 8 All commenters that have submitted technical analyses in the record to date have shown that separation distances will be necessary to ensure adequate protection of in-band FSS earth station operations. 9 The differences among the parties lie in what constitutes adequate protection, i.e. the protection criteria, and how to determine whether the criteria have been met. 5 Notice at See, e.g., Notice at 19 & 150; Google Written Ex Parte Presentation filed Sept. 3, 2013 ( Google September 2013 Ex Parte ) at 1. 7 Notice at Id. at See, e.g., SIA August 2013 Ex Parte, SIA February 2014 Ex Parte; Google September 2013 Ex Parte. 3

9 SIA demonstrates below that the appropriate protection criterion is an interference-to-noise ratio ( I/N ) based on International Telecommunication Union ( ITU ) standards. Using that ratio, and taking into account both FSS earth station and CBRS system characteristics and deployment scenarios, a received power limit can be calculated that must not be exceeded by the equivalent power flux density ( EPFD ) at the FSS earth station from any single CBRS transmitter and from all CBRS transmitters combined. RKF has calculated the required geographic protection areas surrounding the sites of FSS earth stations within which CBRS devices would need to be excluded to meet the single-entry interference criteria. The Commission asks whether an SAS could be used to reduce or eliminate protection areas. However, the feasibility and cost-effectiveness of a database that would be capable of the highly complex, real-time calculations of aggregate interference levels necessary to ensure that FSS interference protection levels are not exceeded has not been proven. A. Interference Criteria Should Be Derived from ITU Recommendations The Notice seeks comment on the feasibility of protecting in-band FSS earth stations using technical metrics relating to CBRS operations. For example, the Commission asks whether a model could be developed to apply an aggregate power flux density ( pfd ) level, 10 or whether other parameters such as CBSD field strength could be used. 11 SIA supports use of I/N criteria in ITU Recommendations for the protection of FSS earth stations. From these I/N criteria, a received power limit at the FSS earth station can be calculated, taking into account the FSS earth station and CBRS system characteristics and deployment scenarios. In turn, whether this received power limit is exceeded should be determined by using an aggregate EPFD calculation methodology. An aggregate limit is 10 Notice at Id. at

10 required to ensure that interference from all CBSDs, including end user devices, is taken into account. The Commission should use sound, established international standards to derive the EPFD limit and the related percentage of time for which the limit is not to be exceeded. As discussed in more detail in the RKF Report, SIA used I/N criteria set forth in Recommendations ITU-R S.1432 and ITU-R SF.1006 for interference from non-primary (including adjacent band) sources and interference from co-primary sources into FSS earth stations for its analysis. 12 The Notice proposes that the CBRS be accorded primary status, 13 so SIA has assumed co-primary operations for purposes of setting the interference criteria. SIA has also pointed out, however, that not all of the interference allocation should be allocated to any single non-primary or primary service instead, where there are other primary or non-primary services in the band, the interference allowance must be apportioned among them. Because the proposals in the Notice contemplate continued co-primary use of the 3.5 GHz band by federal fixed and mobile radar systems and secondary operation of grandfathered non-federal radiolocation stations, 14 SIA has apportioned half of the total interference allowance to the new CBRS operations. 12 Recommendation ITU-R S.1432, Apportionment of the allowable error performance degradations to fixed-satellite service (FSS) hypothetical reference digital paths arising from time invariant interference for systems operating below 30 GHz (2006); Recommendation ITU-R SF.1006, Determination of the interference potential between earth stations of the fixed-satellite service and stations in the fixed service (1993). 13 Notice at Id. at

11 As discussed in the RKF Report, for in-band, co-primary FSS earth station protection, SIA established the following interference criteria: Long Term I/N=-13 db, not to be exceeded for more than 20% of the time Short Term I/N=-1.3 db, not to be exceeded for more than % of the time B. In-Band FSS Earth Stations Can Be Protected by Using an SAS to Enforce Geographic Protection Areas As the Notice discusses, one option for preventing interference to in-band FSS earth stations is to establish geographic protection areas surrounding the earth station sites. 15 This is the approach the Commission proposes to use to protect federal radar systems from harmful interference. 16 The Commission contemplates a scenario in which each SAS database has information regarding the protection areas specified to protect federal radar systems. 17 If a CBSD is located within one of those areas, the SAS would not authorize it to transmit. 18 A comparable methodology could be used to prevent CBRS transmissions from causing harmful interference to FSS earth stations, using conservative assumptions to eliminate the possibility that the received power limits at each FSS earth station could ever be exceeded. Specifically, the Commission could determine appropriate protection areas for FSS receivers based on the I/N criteria discussed above and in the attached RKF report. Within those areas, no Priority Access Licenses ( PALs ) or authorizations for Contained Access Facilities ( CAFs ) would be issued, and the SAS would be required to block transmissions by General Authorized Access ( GAA ) CBSDs located within FSS protection areas. Employing this approach could 15 Id. at Id. at Id. at 95 & Id., proposed Section

12 reduce the need for highly sophisticated functionality in the SAS, though an SAS with accurate enforcement and security measures would still be needed to ensure protection. This kind of approach, however, can yield quite large protection zones. This is because even a single CBRS transmitter could cause the I/N criteria to be exceeded, as RKF shows in its study. RKF calculated the area surrounding each of the FSS earth stations within which a single CBSD could exceed the aggregate interference limit, and these areas are depicted in Section 1.4 of the RKF Report. Because the Notice proposes a variety of terminal power levels for different CBSD usage situations, 19 RKF performed its calculations using two illustrative CBSD terminal types: a non-rural base station and a fixed point-to-point station. 20 For each station, RKF calculated the protection areas using both the long-term interference criteria and the short-term interference criteria. 21 But even these single-entry protection zones may not be enough, as the aggregate interference from a multitude of CBRS devices outside of this protection zone could cause the I/N threshold to be exceeded. In particular, RKF did an analysis of aggregate interference and determined that if CBRS deployment conforms to the projections in an ITU report, the aggregate EPFD limit would be exceeded by about 30 db even if CBRS devices are excluded from the protection areas surrounding FSS earth stations. 22 If CBRS devices become ubiquitous, then the FSS protection zones almost certainly will have to be recalculated to implement larger separation distances necessary to ensure FSS earth stations are protected against aggregate interference. This could result in previously authorized CBRS devices (now located in the newly expanded 19 Id. at RKF Report, Section Id. 22 Id., Section

13 protection zone) being instructed to shut off. If the Commission wishes to avoid this scenario, prior to authorizing CBRS operations it should articulate a set of deployment and operational constraints designed to allow the calculation of a truly adequate protection zone. Otherwise, the Commission will need to build in a significant margin to the protection zones and recalculate them in the future to account for aggregate interference. By establishing geographic protection areas around the relatively few FSS earth stations in the 3.5 GHz band, the Commission can protect primary FSS networks using an SAS with limited functionality. Provided that the SAS can accurately track the locations of CBRS devices, it will be able to preclude CBRS transmissions within the defined protection areas. In this regard, SIA has a significant concern regarding the location reporting proposal in the Notice. Specifically, SIA believes that 60 seconds is too long an interval for CBSD location reporting and especially for responding to a frequency change or shut-off command from the SAS. 23 A mobile CBSD could travel a significant distance in a 60-second interval 24 and could cause substantial interference to an FSS earth station if almost two minutes elapse between initiation of its move and the time when it is required to respond to an SAS command to terminate transmissions or switch frequencies. Much shorter time intervals must be prescribed for location updates and device response. 25 An SAS must have the capability of keeping up with rapid updates in location. 23 Notice at 63 & For example, a mobile CBSD in a car travelling at the freeway speed limit of 65 miles per hour could change its location by over a mile in one minute. 25 By way of comparison, in the satellite context, the Commission s FSS mobility rules require earth stations on vessels, vehicle-mounted earth stations, and earth stations aboard aircraft to switch off within 100 milliseconds of losing pointing accuracy towards the intended space station, in order to protect adjacent space stations from interference. See 47 C.F.R , , &

14 C. Significant Obstacles Exist to Development of an SAS Capable of Managing Interference if CBRS Operations Are Permitted within Protection Areas The Notice seeks comment regarding whether geographic protection areas around FSS earth stations can be minimized or eliminated if detailed information regarding earth station and CBRS device characteristics, topographical features, and other relevant variables is incorporated into the SAS. 26 However, the Commission also recognizes that if the SAS is to be relied on to prevent interference among users of the 3.5 GHz band, it needs to have capabilities that go well beyond those developed for the TV white spaces database. 27 Based on the record, SIA has serious doubts regarding whether existing technology can support the development of a reliable and secure SAS database capable of performing the necessary complex, real-time calculations required to prevent CBRS operations from exceeding an aggregate EPFD limit if those operations are allowed within FSS earth station protection areas. The Commission cannot depend on the SAS to manage interference without clear evidence that doing so would be practically feasible and cost-effective. 1. Extremely complex SAS functionalities would be required As SIA has previously observed, the aggregate power emitted by CBSDs at an FSS earth station receiver will be a function of multiple factors: (i) the EIRP density of each CBSD transmitter in the direction of the FSS earth station receiver (which in turn depends on the CBSD s maximum EIRP density and its antenna pattern and orientation); (ii) the FSS earth station s receive gain in the direction of each CBSD transmitter (which depends on the FSS earth station receiver s antenna pattern and orientation); (iii) the distance between the FSS earth station receiver and each CBSD transmitter; and (iv) the intervening terrain between each CBSD 26 Id. at Id. at 6 & 94. 9

15 transmitter and the FSS earth station receiver. 28 SIA has acknowledged that it is theoretically possible for an SAS database to ensure protection of an FSS earth station by using detailed data regarding the operational characteristics of the CBRS transmissions and the earth station receiver to calculate the aggregate interference and instructing individual CBSDs either to not transmit on that frequency or to reduce power as necessary to meet prescribed interference limits. 29 However, as the RKF Report explains, this is an extremely complicated calculation that will have to be updated constantly in real time to account for a broad variety of changing circumstances. For example, the simple fact that the Commission proposes to permit mobile operation of CBRS devices exponentially increases the complexity of the SAS s task. A change in position of any individual transmitting CBRS device affects all four factors listed above that are essential to determining compliance with the interference criteria. The SAS therefore would need to be able to monitor and recalculate aggregate interference levels from dozens, hundreds, or even thousands of transmitting CBRS devices in the vicinity of any given earth station. As discussed above, SIA opposes the Commission s proposal to allow 60 seconds between CBSD location reports and for response to a command from the SAS because a moving CBSD could cause substantial interference to an FSS earth station in those intervals. In addition to responding to changes in any single CBRS device location, the SAS would have to dynamically deal with the fact that the number and location of active CBSDs in the vicinity of an FSS earth station will be changing, as terminals initiate and terminate transmissions. Other challenges to ensuring that the SAS can successfully calculate the interference environment are equally significant. Propagation will be non-line-of-sight 28 SIA February 2013 Comments at See SIA February 2014 Ex Parte at

16 ( NLOS ), which means a rapidly changing multi-path environment. Particularly in urban areas, it would be extremely difficult (and expensive) to maintain detailed and up-to-date terrain databases that reflect the constantly changing landscape due to construction and other factors. Furthermore, most propagation models are two-dimensional, but it will be necessary to take into account the multipath in three dimensions to model NLOS environments. It will be important to investigate the accuracy of proposed modeling approaches, as the variation in propagation loss can be quite large even in small geographic areas. In addition, these models cannot be expected to include up-to-date clutter, given construction and other changes to the landscape that would have to be kept up-to-date. Furthermore, the discussion above focuses only on the calculations needed to prevent interference from CBRS operations into FSS earth stations. Under the framework proposed in the Notice, however, the SAS also will be tasked with managing interference among categories of CBRS users PALs and GAA operations, including CAFs. Thus, the SAS would need to be capable of simultaneously handling real-time interference management computations both between CBRS and FSS and among multiple CBRS users with different priority levels. 2. Robust enforcement mechanisms would be needed Assuming that an SAS could be designed to receive and process the voluminous amount of dynamic information and perform the sophisticated calculations required to determine compliance with aggregate interference limits, it would also need to be able to respond immediately and effectively if an interference issue arises. The Notice recognizes that proposed CBRS operations in a multi-tier priority framework raise new and unique enforcement issues: Managing real time interactions between a large number of potential Priority Access Licensees and GAA Users while ensuring that Incumbent Users are protected from harmful 11

17 interference could present novel enforcement challenges for the Commission to address. 30 SIA agrees with this characterization, and we have concerns regarding how these challenges can be addressed. At the most basic level, if an SAS determines that CBRS operations near an earth station are causing the aggregate interference limit to be exceeded, it is unclear how an SAS would be able to determine which CBRS terminals must be shut down and if this determination will be based on transmitted powers levels or a CBSD s tier level. The Commission must also make clear that PALs and CAFs must protect earth stations to the same extent as GAA users do, and that this will be enforced through the SAS. Enforcement of the protection criteria against PALs and CAFs will likely be complex. In the case of CAFs, for example, it is unclear how the SAS will enforce the indoor-only restriction. 31 Furthermore, SIA has previously observed that the licensing of PALs and CAFs near FSS earth stations raises the possibility of conflict between the expectations of CBRS users that hold priority or CAF licenses and the protection afforded incumbent FSS earth station operators. 32 As a prophylactic matter, the Commission should not issue PALs or CAF licenses anywhere near an FSS earth station to minimize the risk that PAL/CAF auction winners are disappointed if unable to operate satisfactorily due to their proximity to an FSS earth station license. Two other aspects of the proposals in the Notice raise issues relating to assuring interference protection measures would be reliably enforced. First, as discussed above, SIA opposes use of a 60-second interval for CBSD location reporting and command response. 30 Notice at Id. at See SIA December 2013 Comments at 3-5; SIA December 2013 Reply Comments at

18 Instead, those intervals must be much shorter. Second, SIA cautions that the Commission s suggestion that requiring CBSDs to report the signal environment can help monitor and prevent interference 33 is unwarranted with respect to FSS. As SIA has previously explained, spectrum sensing cannot tell the SAS whether FSS spectrum is in use at a particular location because FSS operations in this spectrum are receive only. 34 Even if a sensor could detect the signal from a satellite in the geostationary arc, that information would not tell the SAS whether an earth station nearby was attempting to receive the signal. Accordingly, the Commission cannot rely on spectrum sensing performed by CBSDs to buttress measures to prevent interference to FSS earth stations from CBRS operations. D. The SAS and its Security Must Be Rigorously Tested and Validated Regardless of whether the SAS is used simply to implement protection zones surrounding FSS earth station locations or is tasked with the more complex function of managing aggregate interference from multiple CBRS devices, the SAS cannot be implemented until it is subjected to thorough analysis and real-world validation. This will necessitate testing of a broad variety of interference scenarios to determine whether the SAS proves to be reliably capable of managing CBRS operations and preventing harmful interference to FSS earth stations. The RKF Report describes the validation steps that would be needed to ensure that the SAS in fact is able to protect FSS earth stations from disruption. 35 Assuming an SAS could be created with the necessary functionality, all CBRS devices must then be required to check with the SAS database before transmitting. The Notice 33 Id. at SIA February 2013 Comments at 15-16; SIA April 2013 Reply Comments at RKF Report, Section 3. 13

19 proposes to require CBSDs to be capable of communicating with the SAS, 36 but not end user CBRS devices. Instead, the Notice suggests that end user devices would be authorized to transmit by a CBSD, and that this would be sufficient to prevent unauthorized operation of end user devices. 37 SIA questions this conclusion. How can the Commission be sure that an end user device is operating consistent with the instructions from the SAS if it is not communicating with the SAS, only with a CBSD? SIA objects to the proposal to rely on a daisy-chain approach to authorizing transmissions by user devices instead, such devices should receive their instructions directly from the SAS, like other CBSDs. The Commission rightly recognizes the crucial importance of ensuring that the SAS itself and its communications with devices are secure. 38 This will require measures to prevent SAS spoofing i.e., making sure that a fake SAS database cannot be substituted for the real SAS database (either by the user or a malicious third party) to shut down transmissions or authorize transmissions that should not be allowed. In addition, experience in the U-NII spectrum with interference into federal weather radar systems has highlighted the long-term issues that arise when devices in the hands of users can be modified without authorization. 39 This is not a theoretical concern, as demonstrated by the prevalent practice of jailbreaking iphones and other ios devices in order to modify their functionality. Here, the risks of security breaches at the SAS database level could have much broader negative effects, including 36 Notice at Id. at Id. at See, e.g, Revision of Part 15 of the Commission s Rules to Permit Unlicensed National Information Infrastructure (U-NII) Devices in the 5 GHz Band, First Report and Order, FCC (rel. Apr. 1, 2014) at 12 (after multi-year investigation, interference to federal radar system was determined to have been caused by devices that had been illegally modified and operated at high power levels in elevated locations ). 14

20 impacting national security, since the SAS may contain sensitive government information regarding primary Department of Defense ( DOD ) radar operations. The record demonstrates that significant questions remain regarding the technical and economic feasibility of the proposed SAS and the necessary security features. 40 These questions must be conclusively addressed before the Commission concludes that the SAS can be relied on to prevent interference to in-band FSS earth stations. III. SEPARATION DISTANCES AND OUT-OF-BAND EMISSION LIMITS WILL BE NEEDED TO PREVENT HARMFUL ADJACENT BAND INTERFERENCE All parties that have submitted technical studies have shown a need to protect adjacent band FSS earth stations from CBSD emissions, including Google a prominent proponent of SAS-managed small cells in the MHz band. 41 As both SIA (and Google) have shown, the dominant adjacent band interference problem is the out-of-band emissions ( OOBE ) of the CBSD transmitters i.e., the unwanted energy that is emitted by such transmitters outside of their assigned band and in the band in which an FSS receiver is operating. 42 Receive filters on the FSS earth station antenna cannot help with this mode of interference because such filters are designed to reject only energy outside of the wanted FSS receive band. 43 SIA proposes that the Commission address potential interference into conventional C-band FSS earth stations through a combination of separation distances and 40 See, e.g., SIA April 2013 Reply Comments at & n.77 (citing comments raising concerns about the risks of unauthorized modification of devices and the security and reliability of the SAS). 41 Google September 2013 Ex Parte, Declaration of Dr. Preston Marshall at See id., Declaration of Dr. Preston Marshall at 16; SIA February 2014 Ex Parte at SIA February 2014 Ex Parte at

21 OOBE limits. As discussed above, because of the technical complexities involved, it is not clear that it is practical given existing technology to rely on an SAS to manage in-band interference, and managing out-of-band interference will be just as, if not more, difficult. Most significantly, in contrast to the 37 FSS earth stations currently licensed to operate in the 3.5 GHz band, there are thousands of licensed FSS earth stations in the conventional C-band ( MHz) geographically distributed throughout the country. 44 Dozens of new earth station licenses are granted each year, and dozens more existing licenses are modified. 45 Furthermore, C-band receive-only antennas are generally not required to be licensed or registered at all. 46 The SAS would have to be capable of protecting these conventional C-band earth stations as well by performing real-time calculations required to prevent CBRS operations from exceeding the aggregate interference limits into these earth stations. SIA has previously demonstrated that the separation distances necessary to protect adjacent-band FSS earth stations from interference caused by CBRS transmissions, while smaller than for in-band interference, can still be significant. 47 Separation distances can be reduced by adopting a stricter OOBE limit for all CBSD equipment. Presumably, all CBSD terminals would use the same RF filter to meet the OOBE limit. For protection from OOBE, SIA used an interference protection standard of 1% delta T/T or an I/N of -20 db from ITU Recommendation S.1432, which is the amount of allowable interference into an FSS earth station receiver reserved 44 See, e.g., SIA February 2013 Comments at For example, a search of IBFS indicates that more than 40 new conventional C-band earth station licenses have been granted since July 1, 2013, and more than 100 C-band earth station modification applications have been granted during that time. 46 See 47 C.F.R (b) (FSS receive-only earth stations may be registered ). 47 SIA August 2013 Ex Parte at

22 for non-primary emissions. 48 But because there are other sources of adjacent band interference, only half of this interference threshold should be apportioned to CBRS out-of-band emissions, resulting in a 3 db reduction in the I/N criterion to -23 db. The Notice proposes to use a typical OOBE limit of log 10 (P) db, which is equivalent to -13 dbm/mhz, to emissions by Priority Access and GAA operations in the 3.5 GHz band outside the channel assignments and frequency authorizations made by the SAS. 49 However, the Notice also recognizes the need to protect sensitive receivers, such as FSS earth stations and DOD radar systems, that operate within and adjacent to the 3.5 GHz band. 50 The Commission notes that other mobile broadband services may be using an OOBE limit of -40 dbm/mhz and that LTE standards for PCS require adherence to an even stricter limit of -50 dbm/mhz. 51 Given the use of these limits in other contexts, the Commission proposes to require emissions below 3520 MHz and above 3680 MHz to be attenuated by -40 dbm/mhz, which is equivalent to attenuation of log 10 (P) db, 52 but asks whether the more stringent - 50 dbm/mhz limit should be adopted instead. 53 As an initial matter, SIA observes that the Commission s choice of band edges and the frequency ranges in which it proposes to impose a stricter OOBE limit (at 30 MHz beyond the band edges at 3550 MHz and 3650 MHz) do not make a great deal of sense if the goal is to protect adjacent band FSS earth station receivers operating at 3600 MHz and above. 48 Recommendation ITU-R S.1432, Apportionment of the allowable error performance degradations to fixed-satellite service (FSS) hypothetical reference digital paths arising from time invariant interference for systems operating below 30 GHz (2006). 49 Notice at Id. at Id. at Id. at 83 & proposed Section 96.38(d). 53 Id. at

23 SIA does, however, agree with the Commission s observation that a more stringent limit would enable closer proximity of neighboring service operations. 54 In other words, the stricter the relevant OOBE mask, the smaller the necessary separation distances between CBRS devices and FSS earth stations. The relationship between the OOBE limit and the single-entry separation distance necessary to protect adjacent band FSS earth stations (operating at various elevation angles) is illustrated by Figure 12 of the RKF Report. 55 For simplicity, the separation distances in that Figure were calculated based on line-of-sight between the CBSD interferer and the FSS earth station. 56 Nevertheless, the Figure graphically illustrates that, as a general matter, a much larger separation distance will be required under the log10(p) db (-13 dbm/mhz) OOBE limit than under the stricter log10(p) db (-40 dbm/mhz). If the Commission were to impose an even tighter -50 dbm/mhz limit, then the separation distances could be reduced further still. For additional realism, not only must factors like terrain be taken into account, but also the impact of aggregate interference into FSS earth stations (just as for in-band interference). There is another adjacent band interference issue namely, overload of the LNA/LNB of the FSS receiver. However, both SIA s and Google s studies show that, for any given transmit power level and OOBE mask, the separation distance necessary to protect FSS receivers from CBSD OOBEs will be greater than that needed to prevent LNA/LNB overload. 57 Thus, suggested use of filters on the earth station receiver to prevent LNA/LNB overload is a red 54 Id. at RKF Report, Section 2.2, Figure Compare SIA August 2013 Ex Parte, Table 4 (providing separation distances for the log10(p) db out-of-band mask using an analysis that takes terrain into account). 57 SIA February 2014 Ex Parte at 7; Google September 2013 Ex Parte, Declaration of Dr. Preston Marshall at 6. 18

24 herring. If separation distances and attenuation requirements necessary to prevent OOBE interference are properly calculated and enforced, then LNA/LNB overload will also be prevented. IV. FUTURE FSS EARTH STATIONS IN MHz MUST BE ALLOWED ON A PRIMARY BASIS The Notice makes it clear for the first time that the Commission is proposing that the CBRS have primary status in the MHz band in the U.S. Table of Allocations. 58 SIA s previous comments had argued that CBRS should operate on a secondary basis relative to the primary FSS, 59 and SIA continues to support that position. Nevertheless, SIA s argument that future protected FSS deployments in the MHz band should not be precluded stands whether CBRS is primary or secondary. The Notice provides no justification for limiting the primary status of FSS operations to grandfathered earth stations. 60 As SIA has shown, relegating future earth stations to secondary status would strand the substantial existing investment in 3.5 GHz space stations, harming satellite operators and their customers and shareholders. 61 Moreover, as discussed below, precluding future FSS deployment is contrary to the Commission s stated premise that FSS and CBRS can share spectrum. Furthermore, relegating future FSS operations to secondary status would unnecessarily limit the much-needed flexibility of satellite network operators. Relocation or addition of an FSS earth station is quite rare, but may be necessary in light of changed 58 Notice at See, e.g., SIA February 2013 Comments at Notice at SIA February 2013 Comments at 12 &

25 circumstances. For example, SIA member Intelsat was unable to extend its lease at an existing teleport site beyond 2013 and, prior to the lease s expiration, had to relocate a significant number of FSS antennas to a new facility. In 1998, SIA member SES suffered a landslide at one of its teleports necessitating relocation and reconstruction of various antennas at the site. In such situations, establishing a new site on a secondary basis is simply not an option, because it would put the satellite operator s communications reliability at risk. Adding a new site may also be required to respond to increased demand. The Commission s framework for implementing CBRS systems should be able to accommodate new FSS operations. As SIA has proposed, the Commission could issue PALs only in the portion of the 3.5 GHz band where there are no FSS operations. 62 Alternatively, the Commission could develop a procedure to ensure that new earth stations would not be implemented during the 1-year term of a PAL, as SIA has suggested. 63 Opportunistic GAA users have no grounds for concern if there are changes in primary networks that require modification or termination of their operations. The Commission need not be concerned that according primary status to future FSS earth stations will lead to a flood of new filings. To the contrary, the international-only restriction applicable under U.S. law will continue to limit the number of FSS earth stations that will be deployed in the MHz band given that they cannot be used for U.S. domestic service. In light of these considerations, the Commission should immediately lift the freeze on 62 SIA December 2013 Reply Comments at Id. at

26 new earth stations in the 3.5 GHz band and make clear that future earth station deployments will be permitted on a primary basis. 64 V. THE COMMISSION SHOULD NOT ASSUME THAT THE SHARING APPROACH FOR THE 3.5 GHZ BAND CAN BE USED IN OTHER SPECTRUM Finally, SIA reiterates its concern regarding the Commission s suggestion that the 3.5 GHz band could be an innovation band and that the sharing approach developed here could be expanded to apply to other bands. 65 As SIA has previously explained, the fact that there are relatively few existing earth stations 3.5 GHz band domestically is a product of specific historical policies that have limited satellite ground facility deployment. 66 These restrictions do not apply in other parts of the C-band, in the 3.5 GHz band in other parts of the world, or in other frequency bands. 67 As a result, there is no basis for presuming that an approach developed domestically to permit the introduction of new services in the 3.5 GHz band would be workable in other bands or in other countries. In particular, any decisions that the Commission may reach in this proceeding should not serve as a basis for the position the Commission advocates that the United States take at WRC-15 for the entire MHz band. Similarly, given the uncertainties associated with ensuring that FSS earth stations are adequately protected from harmful interference due to CBRS deployment, SIA continues to oppose the Commission s suggestion that the framework set forth in the Notice should be extended to encompass the Specifically, under this proposal primary status should be available to any 3.5 GHz FSS earth station licensed or modified since the freeze was imposed. By the same logic, if the Commission ultimately decides to open up the MHz band for the CBRS, then primary status should be available to new or modified earth stations in those frequencies as well. 65 Notice at SIA February 2013 Comments at 4-7; SIA April 2013 Reply Comments at See id. 21

27 3700 MHz band. 68 Concrete, practical experience demonstrating that CBRS systems can coexist with satellite operations is needed before the CBRS concept is expanded into other bands. 69 More fundamentally, SIA questions whether the Notice s approach can legitimately be considered spectrum sharing, especially if it is dependent on freezing existing services in place for all time. If the only way the new CBRS can share with existing services is to freeze existing services, then there is an implied admission that sharing is not really possible as a practical matter. The Commission should explicitly recognize that an approach that prevents existing primary users from using the 3.5 GHz in any new locations, even where CBRS users are not present, is not spectrum sharing but a spectrum taking. VI. CONCLUSION SIA urges the Commission to take the steps outlined above to ensure that any introduction of new 3.5 GHz band services does not disrupt FSS earth station operations or limit their future growth. Furthermore, the Commission should not use the approach developed for the 3.5 GHz band as a model for other frequencies or the basis for international policy decisions. Respectfully submitted, SATELLITE INDUSTRY ASSOCIATION Dated: July 14, 2014 By: Patricia A. Cooper President th Street NW, Suite 1001 Washington, D.C (202) Notice at SIA February 2013 Comments at 18; SIA April 2013 Reply Comments at

28 RKF Engineering Solutions, LLC th St. NW, Washington, DC Phone Fax Protection of In-band FSS Earth Stations Technical Annex 1.1 In-band Interference Protection Criteria for FSS Earth Stations Both long-term and short-term interference criteria are considered when assessing the in-band interference into FSS receiver earth stations. In line with Recommendation ITU-R S.1432, the following I/N criterion is identified for use for the longterm case when assessing in-band interference into FSS receive earth stations: I/N = db This criterion corresponds to the aggregate interference from a co-primary allocation for 20% of a given month. In line with Recommendation ITU-R SF.1006, the following I/N criterion is identified for use for the short-term case when assessing single-entry in-band interference into FSS receive earth stations: I/N = -1.3 db which may be exceeded up to % of the time. For cases in which the long-term interference criterion applied, 50% of the allowable interference to the FSS earth station receiver was allocated to CBSD systems. 1 This results in a reduction of the I/N protection criterion by 3 db: I/N = db For cases in which the short-term interference criterion was applicable, 100% of the interference allowance was allocated to the CBSD system. The SAS will have to calculate the total interference power at each FSS earth station in order to determine if the I/N protection criterion is exceeded. This determination can be performed using an aggregate Effective Power Flux Density (EPFD) calculation methodology. Use of EPFD rather than PFD is preferable because the FSS earth station pointing direction is taken into account in the EPFD interference calculation. In contrast, using PFD would require using the worst-case assumption regarding the FSS earth station pointing angle (5% elevation angle). 1 This apportionment reflects the fact that there are other co-primary users in the band (e.g., Federal allocations).

29 1.2 Challenges in Protecting FSS Earth Stations The total received interference power from CBSDs at an FSS earth station receiver will be a function of: (i) the EIRP density of each CBSD transmitter in the direction of the FSS receiver (which depends on the CBSD s maximum EIRP density and the antenna pattern and orientation); (ii) the FSS receiver gain in the direction of each CBSD transmitter (which depends on the FSS receiver s antenna pattern and orientation); (iii) the distance between the FSS receiver and each CBSD transmitter; and (iv) the intervening terrain between each CBSD transmitter and the FSS receiver. In order to accurately determine whether the prescribed aggregate protection criterion is met, the following technical challenges and shortcomings have to be addressed: a. Many technical and operational characteristics of CBSDs that will significantly affect potential interference into the FSS earth stations have not been defined, including whether the CBSDs will be TDD or FDD, can use beamforming to increase terminal gain, use power control, dynamically assign traffic, etc. b. In theory, if an SAS database could calculate the aggregate interference from all CBSD transmitters in real time at a given FSS receiver location, it would be able to ensure that the aggregate CBSD transmissions will not exceed the prescribed aggregate I/N criterion by instructing individual CBSDs either to not transmit on a particular frequency or to reduce power. This is at best a very complicated calculation that will have to be updated constantly in real time to account for a broad variety of changing circumstances. Some of the modeling challenges are discussed in the paragraphs that follow. c. The SAS will have to take into account constantly changing CBSD deployments. The number and location of active CBSDs will change over time, with more significant impacts from CBSDs dynamic traffic scheduling on a frame basis (e.g. 5 msec or 10 msec frames). On each frame, the CBSD Base Stations (BS) can be communicating with different user terminals, and the user terminals may also have different resource block assignments on each frame. Modulation will be changing, and user terminals may use power control. The practical feasibility of taking into account this variation in traffic over time has not been proven. d. Another significant technical obstacle is with regards to changes in CBSD deployment and traffic variations. Conservative propagation models that include significant fade margins to account for inaccuracies and variability would be needed to ensure protection of the FSS earth stations. Propagation modeling will be non-line-of-site (NLOS), which means a rapidly changing multipath environment. Without conservative propagation models, it is not clear how the SAS deployment modeling will handle this variability. Most propagation models are two dimensional, but it will be necessary to take into account the multipath in three dimensions to model NLOS environments. It will be important to investigate the accuracy of proposed modeling approaches, as the variation in propagation loss can be quite large even in small geographic areas. In addition, these models cannot be expected to include up-to- RKF Engineering Solutions, LLC th Street NW, Washington DC Page 2

30 date clutter. Construction and other changes to the landscape would have to be kept up-todate. If aggregate measurements into the FSS receiver are not accurate or if worst case modeling assumptions are not used, FSS earth stations may experience interference despite SAS analysis showing the applicable interference criteria are met. It is not clear that the SAS can then measure and identify the terminals causing the highest levels of interference in a deployment of thousands of terminals. The ability of an SAS to police compliance with the aggregate I/N criterion would, of course, have to be validated (with strong security measures to prevent bypass), as discussed in Section 3 below. 1.3 Sample Receive Power Limit Calculation For any given CBSD deployment, the aggregate interference from all of the CBSDs will have to be evaluated. Given an I/N threshold and depending on both FSS earth station and CBSD system characteristics and deployment scenarios, a received power limit for the aggregate interference power from all CBSDs managed by the SAS can be calculated. For example, for an I/N = -13 db, assuming an FSS earth station receiver system noise temperature of 100 K and a CBSD bandwidth of 10MHz, we can evaluate the FSS earth station noise power N=-108.6dBm/10MHz. Therefore in this case, the aggregate interference power from all CBSDs managed by the SAS would have to be less than dBm/10MHz at the FSS receiver in order not to exceed the long-term I/N threshold of -13dB. This aggregate power may change depending on the FSS earth station and CBSD system characteristics and deployment scenarios. As described in Section 1.2, the SAS will need to manage and calculate all of these changing characteristics in real time to ensure protection of FSS receivers based on the appropriate receive power characteristics for that particular FSS earth station and CBSD deployment characteristics Single Entry CBSD Interference Simulations It is important to note that a single user could exceed the interference criteria if deployed within a certain proximity to an FSS earth station. The following analysis calculates a protection area (or contour) around each of the 37 in-band FSS receive earth stations 2 in which a single CSBD could exceed the interference criteria. If deployment of CBSDs is permitted within this protection area, the SAS will need to be capable of implementing the necessary measures (as described in discussion points a-d in Section 1.2) in order to ensure that the aggregate interference criteria is not exceeded. The protection areas were determined as described below, using the modeling assumptions of the FSS earth stations, CBSD transmitters and propagation path described in sections 1 through 3 of the Appendix. For each FSS earth station (ES) pointing direction to the GEO arc (with ES elevation angle varying from 5 East to 5 West), a contour was generated via the following methodology: 2 Per FNPRM Appendix 2, table of FSS earth stations in MHz. RKF Engineering Solutions, LLC th Street NW, Washington DC Page 3

31 o Two CBSD terminal types (a non-rural base station (BS) and a fixed point-topoint station) were modeled with EIRP densities of 30dBm/10MHz and 53 dbm/10mhz, respectively. o A single CBSD interferer was oriented at a given azimuth angle relative to the ES location. The CBSD station distance was varied relative to the ES location to find the maximum distance where the CBSD interference exceeded the interference criteria. o This calculation was repeated for every azimuth direction from the ES to produce a maximum interference contour. The protection area contour is the maximum envelope of all the above contours. The resulting contours around each FSS earth station, for single-entry interference simulation described above, are illustrated in Figures 1 and 2 for the long-term interference case (I/N=-13 db not exceeded for more than 20% of the time) and Figures 3 and 4 for the short-term interference case (I/N=-1.3 db not exceeded for more than % of the time), where the FSS earth station is at (0,0) in all figures. Figure 1: Single-Entry Protection Area Contour in km (East(right), West(left), North(top), South(bottom)) - Non-rural CBSD (BS) EIRP density = 30 dbm/10 MHz for the long-term interference case. RKF Engineering Solutions, LLC th Street NW, Washington DC Page 4

32 Figure 2: Single-Entry Protection Area Contour in km (East(right), West(left), North(top), South(bottom)) Fixed Point-to- Point CBSD EIRP density = 53 dbm/10 MHz for the long-term interference case. Figure 3: Single-Entry Protection Area Contour in km (East(right), West(left), North(top), South(bottom)) - Non-rural CBSD (BS) EIRP density = 30 dbm/10 MHz for the short-term interference case. RKF Engineering Solutions, LLC th Street NW, Washington DC Page 5

33 Figure 4: Single-Entry Protection Area Contour in km (East(right), West(left), North(top), South(bottom)) Fixed Point-to- Point CBSD EIRP density = 53 dbm/10 MHz for the short-term interference case. Figure 5 and Figure 7 show the four protection area contours around two representative FSS earth stations: #12 in Medley, FL, and # 29 in Alexandria, VA, in Google Earth. Figure 6 and Figure 8 show the size of the corresponding contours. Figure 5: Single-Entry Protection Area Contours around FSS earth station in Medley, FL (ES #12) at N, W. From innermost contour, the contours correspond to Long-term interference with CBSD EIRP density=30dbm/10 MHz (Green), Long-term interference with CBSD EIRP density= 53dBm/10 MHz (Blue), Short-term interference with CBSD EIRP density=30 dbm/10 MHz (Red filled), and Short-term interference with CBSD EIRP density=53 dbm/10 MHz (Red unfilled). RKF Engineering Solutions, LLC th Street NW, Washington DC Page 6

34 Figure 6: Protection Area Contours around FSS earth station in Medley, FL (ES # 12). Figure 7: Single-Entry Protection Area Contours around FSS earth station in Alexandria, VA (ES #29) at N, W. From innermost contour, the contours correspond to Long-term interference with CBSD EIRP density=30dbm/10 MHz (Green), Long-term interference with CBSD EIRP density=53dbm/10 MHz (Blue), Short-term interference with CBSD EIRP density=30 dbm/10 MHz (Red filled), and Short-term interference with CBSD EIRP density=53 dbm/10 MHz (Red unfilled). RKF Engineering Solutions, LLC th Street NW, Washington DC Page 7