Consulting Report FOLLOW-ON SHARING STUDY ON EFFECTS OF INTERNATIONAL MOBILE TELECOMMUNICATIONS-ADVANCED SYSTEMS ON C-BAND EARTH STATIONS

Transcription

1 Consulting Report FOLLOW-ON SHARING STUDY ON EFFECTS OF INTERNATIONAL MOBILE TELECOMMUNICATIONS-ADVANCED SYSTEMS ON C-BAND EARTH STATIONS Prepared for: North American Broadcasters Association ESO September 2013 Use and Disclosure of Data Approved for public release Prepared by: Mark Gowans Jason Greene Alion Science and Technology Electromagnetic Solutions Operation 306 Sentinel Drive, Suite 300 Annapolis Junction, Maryland 20701

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3 EXECUTIVE SUMMARY World Radiocommunication Conference (WRC) 2015 Agenda Item (AI) 1.1 proposes the consideration of additional spectrum allocations to the mobile service on a primary basis and identification of additional frequency bands for International Mobile Telecommunications (IMT) and related regulatory provisions, to facilitate the development of terrestrial mobile broadband applications, in accordance with Resolution 233 (WRC12). International Telecommunication Union Radiocommunication Sector (ITU-R) Working Party 5D (WP5D) has been tasked with identifying suitable bands for IMT. The MHz frequency band has been identified as a suitable band by ITU-R WP5D. This frequency band is allocated for use by the fixed satellite service ( FSS ) in the space-to-earth direction. As part of the WRC 2015 process, Joint Task Group (JTG) is responsible for conducting the necessary sharing studies. Incumbent users of this C-band spectrum, represented by the North American Broadcasters Association (NABA), currently utilize this spectrum for satellite downlink of video and television broadcast programming content in North America. In support of NABA, there is a need for analysis that assesses potential interference that may be caused by IMT into the fixed satellite service operating in the spaceto-earth direction in the 3400 MHz to 4200 MHz frequency band. In July 2013, ITU-R WP5D presented a document to JTG listing the characteristics of terrestrial IMT-Advanced (IMT-A) systems to be used in the performance of frequency sharing studies (Reference 3). Alion Science and Technology Corporation (Alion) was contracted by NABA to perform a sharing study on the effects of IMT-A sharing on the fixed satellite service in the MHz frequency band using the IMT-A system characteristics documented by WP5D. Alion is a leader in the field of spectrum management with over 70 years of experience and a multitude of tools in place to provide spectrum services in the areas of planning, management, modeling and simulation, measurements and testing, consultation, and electromagnetic compatibility (EMC) design. At the request of NABA, two main analysis tasks were proposed for the study. Task 1 was an update of the previous analysis using an updated IMT base station antenna model and IMT-A parameters as provided by WP5D to the JTG in Document /236. Macro and small cell base station deployment scenarios were analyzed individually, rather than as combined layers of deployment scenarios. Task 2 consisted of investigating the use of a guard band for the adjacent-band analysis. This investigation parameterized the size of the IMT-A device guard band in the adjacent-band analysis, resulting in required separation distance as a function of guard band size. ESO

4 Both in-band and adjacent-band cases including short- and long-term interference criteria were evaluated, as well as non-linear effects. Consideration of the suitability of this band as a possible candidate band should take into account the results and conclusions of this sharing study. The conclusion of this study was that sharing the band from 3400 MHz to 4200 MHz is not feasible due to the size of the needed exclusion zones, and the large number of C-Band earth stations that would need to be protected. For the in-band case, the required protection distances were dependent on the type of base station scenario with the macro cell cases requiring the largest exclusion zones. Similarly, for the adjacent band case, IMT-A system use will create unacceptable restrictions to avoid radio-frequency interference or large-signal interactions with C-band earth stations for macro cell base station scenarios. For the small cell scenarios, the size of the exclusion zones was smaller, but still large enough to make sharing of the adjacent band not feasible. ESO

5 INTRODUCTION World Radiocommunication Conference (WRC) 2015 Agenda Item (AI) 1.1 proposes the consideration of additional spectrum allocations to the mobile service on a primary basis and identification of additional frequency bands for International Mobile Telecommunications (IMT) and related regulatory provisions, to facilitate the development of terrestrial mobile broadband applications, in accordance with Resolution 233 (WRC12). International Telecommunication Union Radiocommunication Sector (ITU-R) Working Party 5D (WP5D) has been tasked with identifying suitable bands for IMT. The MHz frequency band has been identified as a suitable band by ITU-R WP5D. This frequency band is allocated for use by the fixed satellite service ( FSS ) in the space-to-earth direction. As part of the WRC 2015 process, Joint Task Group (JTG) is responsible for conducting the necessary sharing studies. The North American Broadcasters Association (NABA) currently utilizes this spectrum for satellite downlink of video and television broadcast programming content in North America. In support of NABA, there is a need for analysis that assesses potential interference that may be caused by IMT into the fixed satellite service operating in the space-to-earth direction in the 3400 MHz to 4200 MHz frequency band. Alion Science and Technology Corporation (Alion) was contracted by NABA to perform an analysis of potential interference caused by IMT-Advanced (IMT-A) systems into the fixed satellite service operating transmission links in the space-to-earth direction in the MHz frequency band. Alion is a leader in the field of spectrum management with over 70 years of experience and a multitude of tools in place to provide spectrum services in the areas of planning, management, modeling and simulation, measurements and testing, consultation, and electromagnetic compatibility (EMC) design. In April 2013, Alion conducted an analysis of the effects of the small cell broadband deployments proposed in Notice of Proposed Rulemaking (NPRM) Federal Communications Commission (FCC) on the domestics satellite (DOMSAT) fixed satellite service users in the space-to-earth standard C- Band. 1 In July 2013, Alion conducted a sharing study on the effects of IMT-A systems on C-Band Earth stations. 2 1 Lloyd Apirian, Mark Gowans, Jason Greene, Effects of the Proposed Citizens Broadband Service to C-Band DOMSAT Earth Stations, Alion Science and Technology Corporation, Consulting Report ESO v3, April Lloyd Apirian, Mark Gowans, Maurice Winn, Sharing Study on the Effects of International Mobile Telecommunications- Advanced Systems on C-Band Earth Stations, Alion Science and Technology Corporation, Consulting Report ESO , July ESO

6 In July 2013, ITU-R WP5D presented a document to JTG listing the characteristics of terrestrial IMT-A systems to be used in the performance of frequency sharing studies. 3 OBJECTIVE The objective of this analysis was to analyze the effects of IMT-A sharing on the space-to-earth transmission links of the fixed satellite service in the MHz frequency band. SYSTEM DESCRIPTIONS C-Band earth stations in the 3700 MHz to 4200 MHz band that operate in North America and IMT-A systems are described in this section. C-Band FSS Receiving Earth Stations A search of United States Federal Communications Commission (FCC) database records indicated that approximately 5000 earth stations are licensed in the MHz band 4 in the United States. Since receive-only systems are not required to be licensed, there are additional, but largely unknown, numbers of unlicensed earth stations. For example, as of December 2005, there were approximately 122,000 receive-only earth stations that received programming from the Public Broadcasting System (PBS), a provider of public television programming in the United States, on the MHz band. There are more than 1,300 earth stations that are registered for this band in the Industry Canada database. In addition to these, there are currently over 1,700 unregistered cable head-ends operating in Canada. Figure 1 shows the deployment of C-Band earth stations in the United States. 5 3 Sharing Parameters for WRC-15 Agenda Item 1.1, ITU Radiocommunication Study Groups, Document /236-E, Working Party 5D, Liaison Statement to Joint Task Group , July 18, Frequency select performed from Federal Communications Commission (FCC) International Bureau website, March 28, Consideration of MHz as a Candidate Band for Use by IMT-Advanced, ITU Radiocommunication Study Groups, Document 8F/1163-E, North American Broadcasters Association (NABA), WRC-07 Agenda Item 1.4, January 11, ESO

7 Figure 1. C-Band earth stations in the United States This band has been in use for this service for many decades and such earth stations are ubiquitous. The earth station antenna patterns used for this study were modeled as having a sidelobe gain, in dbi, corresponding to ITU-R Recommendation S An earth station receiver system typically employs a low-noise, high-gain preamplifier at the antenna feed. The preamplifier may produce output at the same frequencies as are received in the 4-GHz band, in which case it is designated a Low-Noise Amplifier (LNA). Or, the preamplifier may incorporate a mixer which downconverts the signal to a lower frequency band near 1000 MHz (e.g., MHz), in which case it is designated a Low-Noise Block Downconverter (LNB). A third preamplifier type designated a Low-Noise Converter (LNC), downconverts frequencies from the 4-GHz band to a few hundred megahertz (e.g., MHz) output 7. 6 Reference radiation pattern of earth station antennas in the fixed-satellite service for use in coordination and interference assessment in the frequency range from 2 to 31 GHz, ITU-R Recommendation, S.465-6, January F.H. Sanders, R.L. Hinkle, and B.J. Ramsey, Analysis of Electromagnetic Compatibility Between Radar Stations and 4 GHz Fixed Satellite Earth Stations, NTIA Report , July ESO

8 The purpose of a front-end preamplifier is to provide high sensitivity to a weak input signal (which requires that the noise figure of the preamplifier be low) and to produce an output with enough gain to compensate for both the line loss between the antenna and the receiver and the self-generated noise of the receiver. To achieve this functionality, 4-GHz front-end preamplifiers are typically designed to operate with noise figures of about db (noise temperatures of about K) and gain values of about db. Ideally, the frequency response range of such a preamplifier would be the same as the assigned operational band of the receiver (i.e., MHz). If the frequency response of an amplifier is wider than the allocated band of the receiver, then the likelihood of overloading an earth station preamplifier by emissions from transmitters outside the receiver band is increased (Sanders et al). This study analyzes LNBs, the most common preamplifier type used in this band. Figures 2 and 3 show typical LNA and LNB gain and noise figure characteristics (Sanders et al). It is readily seen that the gain characteristics extend far beyond the nominal MHz band. A direct waveguide connection from the antenna to the LNA or LNB is generally used. Figure 2. Typical LNA gain and noise figure (measured) ESO

9 Figure 3. Typical LNB gain and noise figure (measured) The satellite signals have a 3-dB bandwidth of 36 MHz in a 40 MHz channel. This study was concerned with one digital TV distribution signal per channel; multiple carriers with smaller bandwidths and other uses of the channels may be more susceptible to interference, but were not analyzed here. It is noted that many of the earth station antennas cannot physically accept a filter between the feed and the amplifier, such as those with multibeam feeds. These multibeam antennas may be more susceptible to radio-frequency interference (RFI). For those that do use front-end radio-frequency (RF) filters, the filter model MFC 13961W was taken as representative. Measured spectral response characteristics are shown in Figure Downloaded from Microwave Filter Company, Inc website, March ESO

10 Figure 4. C-Band earth station front-end filter characteristics Table 1 summarizes the C-Band earth station characteristics used in this study. ESO

11 Frequency Table 1. C-Band FSS receiving earth station technical characteristics Parameter Data Data Source 3-dB Intermediate Frequency (IF) bandwidth Earth station antenna radiation patterns Noise temperature (including the contributions of the antenna, feed and LNA/LNB referred to the input of the LNA/LNB receiver) Earth station off-axis gain (toward the local horizon) Antenna height AGL* Short-term and longterm maximum permissible interference level Apportionment of the interference 3720 MHz (Band = MHz) Typical North American Usage 36 MHz/channel ITU-R M dbi Mainbeam (calculated for 2.5-meter antenna) 32-25Log10(θ) for 1 <θ 48-10dBi for θ > K Elevation Angle Off-Axis Gain (dbi) 3 meters Table 2 of ITU-R M.2109 (and per S.465) Table 2 of ITU-R M Table 2 of ITU-R M.2109 (and per S.465) Long-term: In-band: I/N = 10 db, 20% of any month (or I/N = 12.2 db, 100% of worst month) Adjacent-band: I/N = 20 db, 100% of the time Short-term: I/N = 1.3 db which may be exceeded up to % time (single-entry) 50% of the interference to the earth station receiver will be allocated to IMT-Advanced systems (will reduce I/N thresholds by 3 db) This 50% apportionment will apply to the long-term Section 6.1 of ITU-R M.2109 Most clearly stated in Section and of ITU-R M.2109 (Recommendations ITU-R S , ITU-R SF and ITU-R SF ) ITU-R S and Section 7.3 of Document JTG / Sharing Studies between IMT-Advanced Systems and Geostationary Satellite Networks in the Fixed-Satellite Service in the and MHz Frequency Bands, ITU-R, M.2109, Maximum Allowable Values of Interference from Terrestrial Radio Links to Systems in the Fixed-Satellite Service Employing 8-Bit PCM Encoded Telephony and Sharing the Same Frequency Bands, ITU-R SF.558, July 1, Determination of the Interference Potential between Earth Stations of the Fixed-Satellite Service and Stations in the Fixed Service, ITU-R SF.1006, April Considerations on Suitability of MHz, MHz, and MHz Bands for Possible Identification for IMT, if Appropriate, ITU Radiocommunication Study Groups, Document /133-E, Working Party 4A, Liaison Statement to Joint Task Group , WRC-15 Agenda Item 1.1, May 28, ESO

12 Parameter Data Data Source in-band and adjacent-band analyses. For the shortterm and large-signal analyses, 100% of the interference will be allocated to IMT-Advanced systems. System noise power dbm Calculated Cable/feed loss 0 db Assumed LNB gain 63 db Typical 1-dB gain compression point Third-order intercept * AGL: Above ground level 2 dbm (at LNB output) 15 dbm (at LNB output) CA2511 specification sheet 13 CA2511 specification sheet International Mobile Telecommunications-Advanced System Technical Characteristics IMT-A, also known as 4G network systems, are mobile systems that include new capabilities that go beyond those of IMT Such systems provide access to a wide range of telecommunication services including advanced mobile services, supported by mobile and fixed networks, which are increasingly packet-based. IMT-A includes the operation of a communications network on an Internet Protocol (IP)-based, packet switched network mechanism. It includes support for mobile, fixed, Worldwide Interoperability for Microwave Access (WiMAX), personal, and other major network types. IMT-A is geared toward providing high-speed connectivity to moving and fixed clients with speeds from 100 Mbps to 1 Gbps, respectively. It also includes global support, connectivity, and roaming services for mobile devices/users; seamless delivery of high-quality multimedia applications and backward support and compatibility. For this follow-on study, sharing was analyzed using the IMT-A system characteristics from Table 2 that WP5D has provided to JTG in Document / Isolated, Low Noise Block Down Converter, CA2511, Downloaded from CAP Wireless, Inc website, May ESO

13 Table 2. IMT-Advanced macro and small cell base station parameters Parameter Macro suburban Macro urban Small cell urban Data Source Cell radius / Deployment density Intersite distance 0.6 km 0.3 km 3 per urban macro cell Table D of Document JTG / km 0.9 km 0.3 km Calculated Antenna height 25 m 20 m 6 m Sectorization 3 sectors 3 sectors 1 sector Downtilt 6 10 NA Antenna pattern Recommendation ITU-R F.1336, Annex 10 (see Antenna Pattern section) k a = 0.7 k p = 0.7 k h = 0.7 k v = 0.3 Horizontal 3 db beamwidth: 65 Vertical 3 db beamwidth: determined from the horizontal beamwidth by equations in Recommendation ITU-R F (Assumed peak sidelobe option for single-entry analysis and average sidelobe option for aggregate analysis) Feeder loss 3 db 3 db NA Maximum base station antenna gain Base station power/sector EIRP 18 dbi 18 dbi 5 dbi 61 dbm (Single-entry) 58 dbm (Aggregate) 61 dbm (Single-entry) 58 dbm (Aggregate) Recommendation ITU-R F.1336 omni-directional 29 dbm (Single-entry) 26 dbm (Aggregate) Table D of Document JTG /236 Table D of Document JTG /236 Table D of Document JTG /236 ITU-R F.1336 (Annex 10 Revision) 14 Table D of Document JTG /236 Table D of Document JTG /236 Table D of Document JTG /236 Frequency MHz (Adjacent-band analysis) MHz (In-band analysis) Assumed and in accordance with ITU RR 14 Reference radiation patterns of omnidirectional, sectoral and other antennas in point-to-multipoint systems for use in sharing studies in the frequency range from [X] MHz to about 70 GHz, ITU Radiocommunication Study Groups, Document 5C/TEMP/106, Annex 12 to Working Party 5C Chairman s Report, June 4, ESO

14 Parameter Macro suburban Macro urban Small cell urban Data Source Bandwidth 10 MHz Table D of Document JTG /236 Adjacent Channel Leakage Power Ratio (ACLR) Offset ACLR Limit 1 st Adjacent channel 45 db 2 nd Adjacent channel 50 db 3 rd Adjacent channel and above 66 db Table 6 of ITU-R M.2109 Among the IMT-A deployment scenarios that were suggested by WP5D, the small cell suburban and small cell indoor deployment scenarios were not analyzed. The small cell suburban deployment scenario would not further bound the protection distance results. It was expected that the protection distance requirements for the small cell suburban deployment scenario would be greater than the requirements for small cell urban deployment scenario but smaller than those for the macro cell deployment scenarios. An indoor small cell deployment scenario was not analyzed because it is unclear as to how indoor-only operations can be practically enforced, as no regulatory enforcement mechanism exists on an international basis. Moreover, since the suggested 20 db building penetration loss cannot be depended upon, the required protection distances would be similar to those of the small cell urban deployment scenario. Given that IMT systems would not be limited to indoor use only, the impact of outdoor deployment provides the more constraining scenario that should be used by administrations basis for decision making under this Agenda Item. ESO

15 ANALYSIS This analysis consisted of performing a sharing study to evaluate the potential interference caused by IMT-A systems operating in the MHz band to FSS receiving earth stations. Sharing was analyzed using the IMT-A system characteristics in the WP5D document provided to JTG The study considered single-entry and aggregate interference effects of macro suburban and urban, in addition to small cell broadband deployments in the frequency range from 3400 MHz to 4200 MHz to Fixed Satellite Service (FSS) users. In-band and adjacent-band interactions were considered. The sharing studies summarized in ITU-R M.2109, in most cases, used the propagation model described in ITU-R P The current version of this propagation model (ITU-R P ) was incorporated into the analysis model for this study. Since this propagation model includes the effects of terrain, a representative location with moderate terrain characteristics was used for this analysis. For this analysis, only base stations were modeled. As shown in Table 2, the macro and small cell deployments were assumed to be a time-division duplex (TDD) scenarios for both the adjacent-band and in-band analyses. Other potential deployment techniques, such as frequency-division duplex (FDD), could be the subject of future studies, as may be required. Following is an outline of the areas investigated in the analysis: In-band - Small-signal Aggregate and single-entry Three scenario deployments Long-term and short-term interference thresholds Four C-Band earth station antenna elevation pointing angles With intermediate-frequency (IF) filtering-only - Large-signal, LNB overdrive Single-entry Four C-Band earth station antenna off-axis angles With and without RF filtering Adjacent-band - Small-signal Aggregate and single-entry Three scenario deployments Long-term and short-term interference thresholds Four C-Band earth station antenna elevation pointing angles ESO

16 With IF filtering-only, and with combined IF and RF filtering Aggregate guard band analysis - Large-signal, LNB overdrive Single-entry Three scenario deployments Four C-Band earth station antenna off-axis angles With and without RF filtering Guard band analysis Mutual Coupling Characterization Frequency-dependent rejection (FDR) is the mutual coupling between the interferer (source) and receiver (victim). In other words, FDR is a measure of the rejection produced by the receiver selectivity curve to unwanted transmitter emission spectra. FDR was used in the computation of received interference levels. More information on FDR can be obtained from Recommendation ITU-R SM Transmitter emission spectrum and receiver selectivity characteristics are usually available from ITU Recommendations or Reports, manufacturer specifications, or measured data. For this analysis, IMT-A transmitter emissions were modeled using the Adjacent-Channel Leakage Power Ratio (ACLR) specification documented in ITU-R M The C-Band earth station receiver IF selectivity characteristic was assumed. Using these emission and selectivity curves, FDR was calculated to estimate the received energy. The interference level at the receiver is a function of the gains and losses the interference signal will incur between the source and the victim, and is expressed by: I = P t + G t + G r L b (d) FDR( f ) dbm where: P t G t : G r : L b (d): FDR( f ): where: Equation (1) = interferer transmitter power (dbm) = gain of interferer antenna in direction of receiver (dbi) = gain of receiver antenna in direction of interferer (dbi) = transmission propagation loss for a separation distance d between interferer and receiver (db) = frequency dependent rejection (db) f = f t f r ESO

17 where: f t : f r : = interferer tuned (center) frequency = receiver tuned (center) frequency. and FDR( f ) 10 log 0 P( f ) 0 P( f )df H ( f + f ) 2 df db where: P(f) : H(f) : = power spectral density of the interfering signal equivalent IF = frequency response of the receiver Equation (2) Replacing I in Equation 1 with the interference threshold criteria (I th ) and rearranging terms yields, L b (d) = P t + G t + G r FDR( f ) I th db Equation (3) Determination of d, such that Equation 3 is valid, then determines the required protection distance. The IMT-A system spectrum was modeled assuming a 9-MHz, 0 db bandwidth, dropping to the ACLR1 value (Table 2) at the band edge, to ACLR2 at 10 MHz from the band edge, and to ACLR3 at 20 MHz from the band edge and beyond (forming a stair-step pattern when plotted). For the C-Band earth station receiver, RF filtering was obtained from measurements (Figure 4). The IF selectivity was modeled based on the C-Band earth station receiver 3-dB channel bandwidth of 36 MHz, and channel width of 40 MHz. It was assumed that, at the edges of the channel, the IF selectivity would be 60 db. Outside the channel a 20 db per decade roll-off was assumed for the filtering. FDR computations were performed using numerical integration techniques and software. Figure 5 presents the data curves used for the IMT-A system emissions and the C-Band earth station receiver selectivity. ESO

18 Figure 5. Input data and mutual coupling results Apportionment of Interference The apportionment of the allowable interference to the C-Band earth station receiver from the IMT-A systems was considered in this analysis as discussed in ITU-R M It was assumed for this study that 50% of the interference to the C-Band earth station receiver was allocated to IMT-A systems. This 50% apportionment applied to the in-band and adjacent-band analyses for which the long-term interference criteria applied. 15 For the cases in which the short-term interference criteria were applicable, and also for the large-signal analysis, 100% of the interference was allocated to IMT-A systems. For the cases in which 50% apportionment applied, I/N thresholds were reduced by 3 db. Following is some additional information on interference apportionment and justification for consideration in this analysis. 15 The apportionment of the long-term interference protection criteria applied in the analysis is consistent with the guidance provided by Working Party 4A in Section 7.3 of Document /133. ESO

19 Small-Signal Analysis For the small-signal analysis, protection distances were determined using ITU-R-defined interference criteria provided in Table 1. The aggregate analysis considered a scenario of base stations located near Emory, TX. Emory was chosen as a representative location because of the surrounding moderate terrain characteristics. A location with moderate terrain characteristics was desired for this analysis rather than a location with either predominantly mountainous or predominantly flat terrain. The C-Band earth station system characteristics are given in Table 1. Each simulation was performed for C-Band earth station antenna elevation angles of 5, 10, 20, and 30. Both macro and small cell IMT-A base station scenarios were analyzed. For each deployment scenario, the base stations were spaced in a grid with the C-band earth station receiver in the center as shown in Figure 6. The IMT-A base station scenario characteristics are given in Table 2. It was assumed that there were 300 base stations in each scenario. Figure 6. IMT-A base station grid scenario ESO

20 The IMT-A system bandwidth was assumed to be 10 MHz, so the channels were spaced at 10-MHz intervals. IMT-A base stations were modeled using three-sector or omnidirectional antennas, depending on the type of scenario. For the adjacent-band analysis, it was assumed that the IMT-A base stations were transmitting using 30 channels in the frequency range of MHz. Specifically, for a given base station, each of the three base station sectors was assigned a different channel. For the in-band analysis, it was assumed that the IMT-A base stations were transmitting using 50 channels in the frequency range from 3700 MHz to 4200 MHz. IMT-A mobile stations were not modeled. The analysis was performed using a modified version of a model developed by the United States National Telecommunications and Information Administration (NTIA) for the fast-track analysis 16. Modifications included: A FDR capability Generation of base station grid scenario with tri-sector antennas Propagation model: Recommendation ITU-R P (used for this analysis) Additional antenna models including Recommendation ITU-R F (Annex 10 revision) for the base station sector antennas used for this analysis For the aggregate analysis, the frequency for each IMT-A base station was randomly selected for each model iteration from the available pool of frequencies. For the three-sector base stations, each sector was assigned a random channel. The model incrementally increases the protection distance relative to the C-Band earth station receiver and calculates the received aggregate interference power. IMT-A base stations are shut off within this protection distance. For the minimum protection distance, if the calculated aggregate interference at a C-Band earth station receiver remained below the interference threshold for a minimum of 100 model iterations, this result was reported. For the single-entry analysis, a single IMT-A base station was placed along a path relative to the earth station location, aligned with the antenna azimuth. For the adjacent-band cases, it was assumed that the IMT-A base station was tuned to the closest adjacent-band channel to the lowest C-Band earth station receiver channel. For the in-band cases, it was assumed that the IMT-A base station was co-channel with the C-Band earth station receiver. The IMT-A base station was moved along this path and a protection distance was determined based on the separation distance necessary to reduce the interference level below the interference threshold. Figure 7 shows the terrain profile for the single-entry path of the base station relative to the C-Band earth station. 16 E.F. Drocella, L. Brunson, C.T. Glass, Description of a Model to Compute the Aggregate Interference From Radio Local Area Networks Employing Dynamic Frequency Selection to Radars Operating in the 5 GHz Frequency Range, NTIA Technical Memorandum , May ESO

21 Figure 7. Terrain profile for single-entry analysis An adjacent-band aggregate analysis was also performed to investigate the use of a guard band. The guard band was made up of the difference in frequency between the high frequency channel edge of the adjacent-band base stations tuned closest to the C-Band earth station receiver channel and the low frequency channel edge of the C-Band earth station receiver. The size of guard band was varied parametrically and protection distances were determined. The analysis results are presented in Tables 3 through 8 for the following cases: Macro and small cell base station scenarios Long-term and short-term interference criteria Four C-Band earth station antenna elevation angles Adjacent-band and in-band interference C-Band earth station LNBs with IF filtering-only, and with combined IF and RF filtering Aggregate, single-entry, and aggregate with single-entry The analysis results for the use of a guard band for selected adjacent-band aggregate cases are presented in Figure 8. Results for the in-band, long-term interference threshold case with IF filtering only are presented in Table 3. The aggregate scenario includes the single-entry base station. It is positioned at the inner radius of the grid scenario and along the azimuth axis of the earth station antenna. ESO

22 Table 3. In-band, long-term interference threshold protection distances from IMT-Advanced base stations to C-Band earth stations, with IF filtering only Receiver Antenna Single-Entry Aggregate Protection Elevation Angle, Protection Distance, Distance, km degrees on Azimuth, km Macro Cell Suburban Macro Cell Urban Small Cell Urban Results for the adjacent-band, long-term interference threshold case with IF filtering only are presented in Table 4. Table 4. Adjacent-band, long-term interference threshold protection distances from IMT- Advanced base stations to C-Band earth stations, with IF filtering only Receiver Antenna Aggregate Single-Entry Protection Elevation Angle, Protection Distance, on Azimuth, km degrees Distance, km Macro Cell Suburban Macro Cell Urban Small Cell Urban Results for the adjacent-band, long-term interference threshold case with IF and RF filtering are presented in Table 5. ESO

23 The results can be seen to be comparable to those presented in Table 4. This is due to the similarity of the FDR curves in these two cases. Table 5. Adjacent-band, long-term interference threshold protection distances from IMT- Advanced base stations to C-Band earth stations, with IF and RF filtering Receiver Antenna Aggregate Single-Entry Protection Elevation Angle, Protection Distance, on Azimuth, km degrees Distance, km Macro Cell Suburban Macro Cell Urban Small Cell Urban Results for the in-band, short-term interference threshold case with IF filtering only are presented in Table 6. Table 6. In-band, short-term interference threshold protection distances from IMT-Advanced base stations to C-Band earth stations, with IF filtering only Receiver Antenna Single-Entry Protection Elevation Angle, degrees Distance, on Azimuth, km Macro Cell Suburban Macro Cell Urban Small Cell Urban Results for the adjacent-band, short-term interference threshold case with IF filtering only are presented in Table 7. ESO

24 Table 7. Adjacent-band, short-term interference threshold protection distances from IMT- Advanced base stations to C-Band earth stations, with IF filtering only Receiver Antenna Single-Entry Protection Elevation Angle, degrees Distance, on Azimuth, km Macro Cell Suburban Macro Cell Urban Small Cell Urban < 0.10 For the single-entry adjacent band analysis, the minimum increment along the terrain path was 0.10 km. In Tables 7 and 8, a protection distance < 0.10 km indicates that at the first base station position the received interference power was below the interference threshold. Results for the adjacent-band, short-term interference threshold case with IF and RF filtering are presented in Table 8. Table 8. Adjacent-band, short-term interference threshold protection distances from IMT- Advanced base stations to C-Band earth stations, with IF and RF filtering Receiver Antenna Single-Entry Protection Elevation Angle, degrees Distance, on Azimuth, km Macro Cell Suburban Macro Cell Urban Small Cell Urban < 0.10 ESO

25 Results for the guard band aggregate analysis are presented in Figure 8 for the macro suburban deployment scenario, which is the most constraining case. The results show the required protection distance as the guard band size is increased. The guard band size was increased by parametrically eliminating the base station 10 MHz transmit channels closest to the earth station receive channel. There is an initial decrease in the required separation distance as the guard band increases from 0 to 10 MHz, however, as the guard band increases to 20 MHz and beyond, the separation distance does not continue to decrease. The reason for this leveling in required protection distance from 20 MHz and beyond is due to the fact that the ACLR emissions specification does not continue to roll-off with additional frequency separation. It can be concluded from Figure 8 that increasing the size of the guard band beyond 20 MHz has no effect on reducing the separation distance required to protect the FSS receiving earth station, i.e. for example if the guard band were to increase from 20 MHz to100 MHz, the same separation distance would still be required to ensure protect the FSS receiving earth station from harmful interference from IMT-A systems. Figure 8. Aggregate protection distance versus guard band size ESO

26 Large-Signal Analysis Large-signal interactions were also analyzed. These interactions include gain compression and receiver intermodulation (IM). C-Band earth station systems with and without RF filters were considered. For interfering signals in the adjacent frequency band, RF filter attenuation will reduce the potential for degradation. No IF attenuation was considered for this analysis because gain compression and IM products occur prior to the IF filtering. Distances to mitigate potential gain compression using the LNB characteristics from Table 1 were determined. Also, distances to mitigate the onset of non-linear interactions as described in ITU-R M.2109, were determined. This is referred to as LNB overdrive in ITU-R M These calculations were performed using the ITU-R P propagation model. A representative terrain profile (Figure 7) was used with the 3-meter C-Band earth station antenna height and the IMT-A base station heights for each of the three cell scenarios. The input threshold level of -61 dbm for gain compression (in Tables 9 and 10) was determined using the LNB characteristics in Table 1. Specifically, the gain compression threshold at the LNB input was determined by subtracting the LNB gain of 63 db from the gain compression level at the LNB output of 2 dbm. The non-linear effects criterion in Tables 9 and 10 is the level given in ITU-R M.2109 for the onset of non-linear effects. Specifically, the LNB 1 db compression point was assumed to be -50 dbm at the LNB input. It was also assumed that the LNB would start to show non-linear behavior at an input level 10 db below this level (i.e., -60 dbm). Table 9 presents the results for gain compression and onset of non-linear interactions for co-channel interference. ESO

27 Table 9. Large-signal protection distances for C-Band earth station without RF filtering (IMT-A base station interferers co-channel) Earth Station Antenna Off-Axis Angle, degrees Gain, dbi Gain Compression Computation (LNA Input Threshold = -61 dbm) Required Distance to Mitigate, km M.2109 Non-Linear Effects (LNA Input Threshold = -60 dbm) Required Distance to Mitigate, km Macro Cell Suburban Macro Cell Urban Small Cell Urban * For distances less than 1 km, free-space propagation loss was used Table 10 presents the results for C-Band earth systems with RF filtering and assuming immediately adjacent-channel interference (at 3695 MHz or less). Table 9. Large-signal protection distances for C-Band earth stations, with RF filtering (IMT-A base station interferers at 3695 MHz or less) Earth Station Antenna Gain Compression Computation (LNA Input Threshold = -61 dbm) M.2109 Non-Linear Effects (LNA Input Threshold = -60 dbm) Off-Axis Angle, Required Distance to Gain, dbi degrees Mitigate, km Macro Cell Suburban Macro Cell Urban Small Cell Urban * For distances less than 1 km, free-space propagation loss was used Required Distance to Mitigate, km ESO

28 The intermodulation interference effect on the earth station LNA/LNB from IMT operation was also analyzed. Under certain conditions, a non-linear device such as an amplifier can cause IM products that may cause interference. ITU-R M.2109 states that the LNB would start to show non-linear behavior at an input level about 10 db below the gain compression level. Thus, for the LNB under analysis (Table 1), the onset of IM occurs at 10 db below the gain compression level of 2 dbm, or -8 dbm at the LNB output. The onset of IM at the input of the LNB was determined by subtracting the LNB gain of 63 db from the -8 dbm output level resulting in -71 dbm at the LNB input. IM was analyzed based on the third-order intercept point, and the fact that the input/output response slope for the desired RF input is 1, while the slope for 3 rd order IM is 3. The onset of IM translated to the 3 rd order results in an IM threshold at the LNB input of dbm. This is illustrated in Figure 9. Figure 9. Intermodulation analysis Tables 11 and 12 present the results for the IM protection distances required. It is assumed that the IM source signals are not co-channel with the desired signal, but may be operating within the pass band of the LNB. ESO

29 Table 11. Intermodulation protection distances for C-Band earth stations, without RF filtering (Two IMT-A base stations in MHz) IM Protection Zone Earth Station System (LNA Input Threshold = dbm) Off-Axis Angle, degrees Antenna Gain, dbi Required Distance to Mitigate, km Macro Cell Suburban Macro Cell Urban Small Cell Urban * For distances less than 1 km, free-space propagation loss was used Table 12. Intermodulation protection distances for C-Band earth stations, with RF filtering (Assumes filtering for closest IMT-A base station channel at 3695 MHz) IM Protection Zone Earth Station System (LNA Input (1.4 db RF Filter Attenuation) Threshold = dbm) Off-Axis Angle, degrees Antenna Gain, dbi Macro Cell Suburban Macro Cell Urban Small Cell Urban * For distances less than 1 km, free-space propagation loss was used Required Distance to Mitigate, km ESO

30 CONCLUSIONS The results of the study showed that the required protection distances were dependent on the type of base station scenario with the macro cell cases requiring the largest exclusion zones. For the in-band case, the required protection distance for a macro cell deployment in a suburban environment ranges from 312 to 525 km, while a deployment in an urban environment ranges from 262 to 477 km, depending on the elevation angle of the C-band earth station receiver. The required protection distance for a small cell deployment in an urban environment ranges from 5.1 to 225 km, depending on the elevation of the C-band earth station receiver. For the adjacent band case, the deployment of IMT-A systems will create unacceptable restrictions to avoid RF interference or large-signal interactions with C-band earth stations for macro cell base station scenarios. For the small cell scenario, the size of the exclusion zones was smaller due to the fact that they have been specified to be installed lower to the ground and limited in transmit power. However, the required protection distances would still prevent small cell urban deployments over a protection area centered around a C-band earth station receiver ranging from 2.5 to over 45 sq km a result which makes sharing not feasible. The results show that an IMT implementation of any deployment scenario sterilizes large geographical areas preventing future deployment of satellite earth stations. The results also show that the use of a common representative front-end RF filter provides an insignificant decrease in the required separation distance. Moreover, inclusion of an RF filter provides little additional rejection over what is already provided by the IF selectivity of the tuner. The conclusion of this study is that sharing the band from 3400 MHz to 4200 MHz is not feasible due to the size of the needed exclusion zones (up to an area of over 865,000 sq km), and the large number of C- Band earth stations that would need to be protected. ESO

31 Distribution List for Consulting Report ESO Follow-On Sharing Study on Effects of International Mobile Telecommunications-Advanced Systems on C-Band Earth Stations External Addresses Fox Network Group/Winston Caldwell West Pico Blvd Bldg. 100/2090 Los Angeles, CA Number of Copies 5 (soft copy) Internal Addresses Alion/ESO/Mark Gowans 1 Alion/ESO/Jason Greene 1 Alion/ESO/Scott Wiley 1 Alion Library Camera Ready and PDF ESO