The NTIA Preliminary Report discussed the 1710-1850 MHz band as four separate band segments: 1710-1755, 1755-1761, 1761-1842, and 1842-1850 MHz. The 1710-1755 MHz band segment was proposed for reallocation to the private sector on a mixed use basis. The 1761-1842 MHz band segment was excluded from reallocation because it is used by Air Force to operate the Space-Ground Link Subsystem (SGLS). The SGLS has 20 discrete factory preset uplink frequencies throughout the 1761-1842 MHz band segment that provide tracking, telemetry, and control for all military satellites.[EN 2] Over 90 satellites, both geostationary and non-geostationary, are supported by SGLS. In addition to the five fixed SGLS site locations, DOD has transportable SGLS-compatible earth stations that are used to provide additional coverage for launch and on-orbit operations.[EN 3]

In addition to SGLS, DOD also uses this band segment for Air Combat Training Systems (ACTS) such as, Air Force's Air Combat Maneuvering Instrumentation (ACMI) and Navy's Air Combat Maneuvering Range (ACMR) and Tactical Aircrew Combat Training System (TACTS). The ACMI, ACMR, and TACTS all employ factory preset frequencies in 1761-1842 MHz that are used to transmit information to and from training aircraft. Training support systems such as these are key elements in the military's efforts to provide realistic simulation and pilot training in a peacetime environment.[EN 4] As stated in Section 4, NTIA reaffirms its decision not to include the 1761-1842 MHz band segment in the reallocated spectrum.

As shown in Figure D-1, two band segments remain for consideration: 1755-1761 MHz (6 MHz) and 1842-1850 MHz (8 MHz). The Preliminary Report states that a guard band must exist around the 1761-1842 MHz band segment to provide adequate interference protection for both Federal satellite command and control and combat training systems; and PCS (or other adjacent-band users).[EN 5] The question remains as to how wide the guard band should be to protect Federal and non-Federal operations. Transmitter and receiver characteristics (power, antenna gain, emission spectrum, and receiver selectivity) as well as projected PCS transmitter and receiver characteristics will be used to estimate the guard band requirements around the 1761-1842 MHz band segment.

**FIGURE D-1:** 1710-1850 MHz Band Breakdown.

============================================================================ TABLE D-1: Caracteristics of Fixed Microwave Systems in 1755-1850 MHz Band ============================================================================ Transmitter Bandwidth 1-8 MHz Transmitter Power 3 Watts Antenna Gain 28 dBi ============================================================================Interference from Fixed Microwave Transmitters to Low-Orbiting SGLS Satellite Receivers In this analysis a 1.8 meter parabolic antenna with a mainbeam gain of 28 dBi and a beamwidth of 8 degrees will be used to represent the fixed microwave transmitter in the 1755-1850 MHz band. Since an omnidirectional antenna is assumed for the SGLS satellite receiver, coupling will depend on the mainbeam and sidelobe characteristics of the fixed microwave antenna.

If the fixed microwave transmitters are randomly distributed regarding geographic position as well as azimuth pointing angle, then the number of mainbeam couplings that can occur will be the number of emitters contained in the annular ring of the SGLS low-orbiting satellite footprint where it can be viewed at elevation angles between 0 and 4 degrees. The percent of the area that the annular ring occupies, of the entire footprint, times the number of fixed transmitters, will give the number of mainbeam couplings that can occur. The area of the annular ring and the area of the SGLS low-orbiting satellite footprint are calculated as follows:

where

R is the radius of the earth, and H is the satellite altitude.

The ratio of the area of the annular ring and the satellite footprint is calculated as follows:

From the above calculation, two percent of the 492 transmitters can intersect the SGLS low-orbiting satellite with their mainbeam. Because of the random azimuth pointing angles, only

will be likely to do so. Therefore, the probability of intersecting the SGLS low-orbiting satellite receiver with a single fixed microwave transmitter antenna mainbeam is low; the probability of multiple intersections is very low. Consequently, for analysis purposes, a single mainbeam coupling will be considered.

In the mainbeam case the elevation angle is near zero degrees, and the slant range to the satellite (250 km orbit) is 1,979 km. For the remaining 491 fixed microwave transmitters, coupling will be in the sidelobe region of the fixed microwave antenna pattern. If the representative elevation angle to the satellite from these transmitters is 45 degrees, the slant range is 415 km. The total interference power density at the SGLS low-orbiting satellite receiver is calculated by

where Io is the interference power density at the SGLS low-orbit satellite receiver (dBW/Hz); SPD is the fixed microwave power spectral density (dBW/Hz); GT is the fixed microwave transmitter antenna gain (dBi); n is the number of fixed microwave transmitters; LFS is the free space path loss (dB); GR is the SGLS receiver antenna gain (dBi).For a 5 MHz emission bandwidth, the spectral power density is -62.2 dBW/Hz. Using the parameters in TABLE D-1 and the previous calculations, the interference power density at the SGLS low-orbit satellite receiver from fixed microwave transmitters is

It should be noted that a Monte Carlo simulation of the interference to low-orbiting satellites in the 2025-2110 MHz band from fixed microwave emissions reaches a very similar estimate of the interference power density.[EN 6]

Interference from Fixed Microwave Transmitters to Geostationary SGLS Satellite Receivers Elevation angles to the SGLS geostationary satellites from fixed microwave transmitters range from 15 to 45 degrees. Using the sidelobe pattern for fixed microwave antennas, the gain in the direction of the SGLS geostationary satellite receiver for this range of elevation angles is

where G(Theta) is the off-axis antenna gain (dBi); Theta is the fixed microwave elevation angle (degrees); D is the diameter of the fixed microwave antenna (m); Lambda is the wavelength (m).Using an antenna diameter of 1.8 meters and a frequency of 1755 MHz, the off-axis antenna gains for elevation angles of 15 and 45 degrees are:

The slant range to a geostationary SGLS satellite at elevation angles of 15 and 45 degrees is 40,277 km and 37,627 km respectively. These slant ranges correspond to a free space path loss of approximately 189 dB. For analysis purposes it is assumed that half of the 492 fixed microwave transmitters are at each extreme of elevation angle to the SGLS geostationary satellite. Using the equation stated earlier, the interference power density at the SGLS geostationay satellite receiver from fixed microwave transmitters is given below:

Impact to SGLS Satellite Receiver from Fixed Microwave Transmitters Since fixed microwave systems operated by the FPAs and certain safety-of-life stations will continue to operate indefinitely in the 1755-1850 MHz band segment, their contribution must be included in the total interference power density calculation for the SGLS satellite receivers. From the preceding discussion the interference levels from the existing fixed microwave transmitters are: -185 dBW/Hz (low-orbiting satellites) and -215 dBW/Hz (geostationary satellites). When interference from the proposed terrestrial mobile service are on this order, the total interference power density at the SGLS satellite receiver will be increased by 3 dB to take into account the existing interference from fixed microwave transmitters.[EN 7]

==================================================================================== TABLE D-2: Estimated Parameters For Terrestrial Mobile And Personal Stations ==================================================================================== Base and Mobile Stations Personal Stations ------------------------------------------------------------------------------------ Transmitter ------------------------------------------------------------------------------------ Transmitter e.i.r.p. 10 W base, 1 W mobile 3 mW indoor, 20 mW outdoor Bandwidth per Channel 25 kHz 50 kHz Traffic Density 582 E/km^2 25000 E/km^2 Assumed Bandwidth 140 MHz 140MHz Estimated e.i.r.p. Density -104 dBW/m^2/Hz -123 dBW/m^2/Hz ------------------------------------------------------------------------------------ Receiver ------------------------------------------------------------------------------------ Interference Threshold -117 dBm indoor stations -119 dBm outdoor stations ====================================================================================The parameters shown in TABLE D-2 were taken from ITU-R Rec. 687-1. The e.i.r.p. densities given in TABLE D-2 represent a worst-case scenario insofar as they correspond to a mature system in an urban environment operating at its peak traffic load. The e.i.r.p densities for rural areas will be much less than those given in TABLE D-2. The e.i.r.p. densities are derived from the number of terminals per km^2 area and the power for each category of station (e.g., mobile or personal).

To facilitate sharing, an allocation of 10% of the total interference budget to external interference sources is used. ITU-R Rec. 687-1 specifies a level of -117 dBm for indoor personal stations and a level of -119 dBm for outdoor personal stations.[EN 10] These values are shown in TABLE D-2 and represent maximum permissible interference levels that can be received by personal stations without significantly degrading the quality of the service provided. ITU-R Rec. 687-1 did not specify an interference threshold for the base stations.

=========================================================== TABLE D-3: Nominal SGLS Characteristics =========================================================== Earth Station Transmitter ----------------------------------------------------------- Frequency 1763.721 - 1839.795 MHz Output Power Fixed SGLS Stations: 2 - 7 kW Transportable SGLS Stations: 250W - 1 kW Bandwidth 4 MHz with subcarriers Antenna Gain Mainbeam 41 dBi Sidelobe 23 dBi ----------------------------------------------------------- Satellite Receiver ----------------------------------------------------------- Selectivity -3 dB 3.9 MHz -20 dB 7.1 MHz -60 dB 14.2 MHz Antenna Gain 0 dBi ===========================================================The sidelobe antenna gain given in TABLE D-3 is calculated based on the procedures specified in the International Telecommunication Union (ITU) Radio Regulations Appendix 29 for an elevation angle of 3 degrees.

A0 = 2ã(re)^2 (Beta-1)/ and Beta = 1+h/re where re is the radius of the Earth (6378 km); h is the altitude of the satellite.For example, the total area visible from a low-orbiting satellite at an altitude of 250 km is 9.6x106 km^2. The mobile and personal stations are assumed to be uniformly distributed over the field-of-view of the satellite. The amount of interference power received at the satellite due to stations within a spherical area bounded by ë1 and ë2 elevation angles is proportional to the e.i.r.p., station density, the spherical area, the transmitter antenna gain, the square of the range to the satellite, and the gain of the satellite receiving antenna.[EN 13] The ratio of the station distribution to the total visibility area is given by:

A/A0 = (Beta/(Beta-1))(cos(Theta2)-cos(Theta1)) and Thetai = cos-1((1/Beta)cos(ëi))-ëiThe range to the satellite Rs is given by

Rs= re(Beta)(sin(Thetai)/cos(ëi))Using the above equations it was determined that approximately 14% of the total-visibility interference will be caused by terrestrial stations located between 0 and 5 degrees elevation angle and radiating isotropically (à). The area of the spherical region bounded by elevation angles between 0 and 5 degrees is 44% of the total visibility area(A).[EN 14] These values will be used to calculate the aggregate interference power density.

The aggregate interference power density at the output of the satellite receiving antenna caused by the emissions from the terrestrial mobile and portable stations operating in the field-of-view of a low-orbiting satellite is given by [EN 15]

Io = Rho + 10LogA + 10Log(Lambda^2/4ã) + GR - 10Logà - 10Log(4ã) - 20LogRs - FDR - L where Io is the total interference power density from a given spherical area (dBW/Hz); Rho is the aggregate e.i.r.p. density (dBW/m^2/Hz); A is the field of view within the range of elevation angles (0 to 5 degrees); Lanbda is the wavelength (m); GR is the antenna gain of the satellite receiving antenna (dBi); à is the fraction of the total-visibility interference contributed by mobile and portable stations operating within the range of elevation angles (e.g., 0 to 5 degrees); Rs is the range to the satellite (km); FDR is the frequency dependent rejection (dB); L is the building penetration, shadow loss, and urban/rural loss (dB).A document used in the development of ITU-R Rec. 687-1 specifies that building penetration loss, shadowing loss, the relative deployment of urban systems compared to suburban and rural systems, and the relative maturity of the systems will reduce the total interference power density by 20 to 40 dB.[EN 16] A conservative value of 20 dB will be used in this analysis.

The FDR value used in the calculation of the interference power density is the attenuation of an undesired signal power by the SGLS receiver because of on-tune and off-frequency rejection. The on-tune rejection occurs because of the limited bandwidth of a receiver with respect to the undesired terrestrial emission bandwidth. The off-frequency rejection is the rejection provided by detuning of the SGLS receiver with respect to the terrestrial transmitters. From the SGLS receiver selectivity given in TABLE D-3, a value of 23 dB corresponding to a 3.7 MHz frequency separation for the lower SGLS channel (1763.721 MHz) and approximately 40 dB corresponding to a 5 MHz frequency separation on the upper SGLS channel (1839.795 MHz) will be used in this analysis.

Using the parameters given above and a satellite altitude of 250 km, the aggregate interference power density resulting from personal and mobile terrestrial stations to a SGLS low-orbiting satellite receiver is given in TABLE D-4.

================================================================= TABLE D-4: Aggregate Interference Power Density From Terrestrial Stations to SGLS Low-orbiting Satellite Receivers ================================================================= SGLS Channel Mobile Stations Personal Stations Io (dBW/Hz) Io (dBW/Hz) ------------------------------------------------------------------ Lower -171 -190 Upper -188 -207 ==================================================================It should be noted that the values of FDR used in the calculation of Io represents a worst-case scenario insofar that it locates all of the mobile and personal stations in the first adjacent channel (minimum frequency separation) from the SGLS receiver. In a more realistic scenario, these stations will be distributed across the entire band, which will result in further reduction of the interference levels at the SGLS receiver. The FDR is one of the parameters in the determination of Io that is not already determined and is significant in determining compatibility.

The carrier power density at the SGLS receiver is given by:

Co = PT + GT + GR - 10 Log(BW) - LFS where Co is the carrier power density at the SGLS receiver (dBW/Hz); PT is the SGLS earth station transmitter power (dBm); GT is the SGLS earth station transmitter antenna gain (dBi); GR is the SGLS satellite receiver antenna gain (dBi); BW is the SGLS earth station transmitter bandwidth (Hz); LFS is the free-space path loss (dB).To compute the carrier power density at the SGLS receiver, a transmitter power of 2 kW will be used for fixed SGLS stations and a value of 250 W will be used for transportable SGLS stations. In addition, during approximately half of the time low-orbiting satellites are within range of the earth station at elevation angles of less than 10 degrees above the horizon. To compute the range, an elevation angle of between 0 and 5 degrees will be used, resulting in a range of 1720 km. This value will be used to compute the free-space path loss.

Using the equation above and the parameters in TABLE D-2, the carrier power density at the SGLS low-orbiting satellite receiver for fixed and transportable SGLS stations is given below:

Co = -155 dBW/Hz (fixed SGLS stations) Co = -165 dBW/Hz (transportable SGLS stations)The C/I ratios can now be evaluated for the fixed and transportable SGLS station receivers as follows:

C/I = Co - IoThe calculated C/I ratios for the upper and lower channels of fixed and transportable SGLS station receivers are given in TABLE D-5.

==================================================================================== TABLE D-5: Calculated C/I Ratios for Fixed and Transportable SGLS Station Receivers ==================================================================================== Mobile Stations Personal Stations SGLS Channel C/I (dB) C/I (dB) ------------------------------------------------------------------------------------ Lower Fixed SGLS Station 16 35 Transportable SGLS Station 6 25 Upper Fixed SGLS Station 33 52 Transportable SGLS Station 23 42 ====================================================================================

As stated earlier, the terrestrial mobile and personal stations are uniformly distributed over the field-of-view of the satellite. Using the previous equations, and a satellite altitude of 36,000 km, it was determined that approximately 0.57% of the total-visibility interference will be caused by terrestrial stations located between 0 and 1 degrees elevation angles and radiating isotropically. The area of the spherical region bounded by the elevation angles between 0 and 1 degrees is 2% of the total visibility area.[EN 17] The aggregate interference power density at the output of the SGLS geostationary satellite receiver caused by the emissions from mobile and personal stations is then given in TABLE D-6.

================================================================= TABLE D-6: Aggregate Interference Power Density From Terrestrial Stations to SGLS Geostationary Satellite Receivers ================================================================= SGLS Channel Mobile Stations Personal Stations Io (dBW/Hz) Io (dBW/Hz) ----------------------------------------------------------------- Lower -184 -204 Upper -201 -221 =================================================================Using the equation stated earlier and the parameters in TABLE D-3, the carrier power density at the SGLS geostationary satellite receiver for fixed and transportable SGLS stations is given below:

Co = -180 dBW/Hz (fixed SGLS stations) Co = -190 dBW/Hz (transportable SGLS stations)The calculated C/I ratios for the upper and lower channels of fixed and transportable SGLS stations are given in TABLE D-7.

============================================================================= TABLE D-7: Calculated C/I Ratios For Fixed And Transportable SGLS Stations ============================================================================= Mobile Stations Personal Stations SGLS Channel C/I (dB) C/I (dB) ----------------------------------------------------------------------------- Lower Fixed SGLS Station 4 24 Transportable SGLS Station -6 14 Upper Fixed SGLS Station 21 41 Transportable SGLS Station 11 31 =============================================================================

================================================== TABLE D-8: Overview of Calculated C/I Values ================================================== Lower Channel Upper Channel -------------------------------------------------- Low-Orbiting SGLS Satellites -------------------------------------------------- Fixed 16 dB 33 dB Transportable 6 dB 23 dB -------------------------------------------------- Geostationary SGLS Satellites -------------------------------------------------- Fixed 4 dB 21 dB Transportable -6 dB 11 dB ==================================================The C/I values shown in TABLE D-8 are based on a 5 MHz guard band. Given this guard band constraint, the calculated C/I values for the lower SGLS channel are below the established threshold. Hence, reallocation of the 1755-1760 MHz band segment is not possible without degrading the SGLS uplink transmissions.

The calculated C/I values for the upper SGLS channel for low-orbiting satellites exceed the threshold of 20 dB. However, for geostationary SGLS satellites, the calculated C/I for the upper channel of transportable SGLS earth stations is below the established threshold. Hence, reallocation of the 1845-1850 MHz band segment with a 5 MHz guard band would degrade uplink transmissions of transportable SGLS earth stations.

It should be noted that the actual C/I values may be greater than those shown in TABLE D-8 when factors such as receiver signal processing are taken into consideration.

The interference level at a mobile service receiver from SGLS earth station transmissions can be determined using the following equation:

I = PI + GI + GR - Lreq - FDR where I is the interference power at the terrestrial receiver (dBm); PI is the SGLS earth station transmitter power (dBm); GI is the SGLS earth station transmitter antenna gain in the direction of the terrestrial mobile receiver (dBi); GR is the antenna gain of the terrestrial mobile receiver (dBi); Lreq is the propagation loss required to preclude interference to the terrestrial receivers (dB); FDR is the frequency dependent rejection (dB).To compute the interference level at a mobile service receiver, a transmitter power of 7 kW will be used for fixed SGLS earth stations and a value of 1 kW will be used for transportable SGLS earth stations. The term GI is a function of the antenna elevation of the earth station. For the purpose of this analysis GI will be calculated using both the mainbeam and sidelobe antenna gains shown in TABLE D-3. The mainbeam gain represents the worst-case condition and will result in the maximum required distance separation to preclude interference to mobile and personal terrestrial receivers. The sidelobe antenna gain was calculated using an earth station elevation angle of 3 degrees and procedures specified in Appendix 29 of the ITU Radio Regulations.[EN 20]

As stated earlier, the FDR term used in the interference calculation is the summation of two terms. The first term takes into account the rejection provided by specific detuning of the terrestrial receivers with respect to the SGLS earth station transmitters. As shown in TABLE D-3, the SGLS earth station uplink transmission bandwidth is 4 MHz with subcarriers.[EN 21] The subcarriers extend beyond 1845 MHz, and cannot be filtered without impacting vital satellite command and control functions. A value of 30 dB will be used in this analysis for the off-frequency rejection based on a 5 MHz guard band. The second term is the power attenuation provided by the terrestrial receiver to the SGLS earth station uplink transmission when the terrestrial receiver bandwidth is narrower than the SGLS uplink transmission bandwidth. Although the channel bandwidth is 4 MHz, the SGLS uplink transmission is not always spread over the entire channel. Air Force states that the worst-case for producing possible interference is a 1 kHz transmission modulating each of the subcarriers.[EN 22] Since a large portion of the signal energy is often concentrated within 1 to 2 kHz on one or more subcarriers, there is no attenuation resulting from the bandwidth mismatch.

Using the above equation and the parameters specified in TABLE D-3, the path loss required for terrestrial receiver protection is given in TABLE D-9.

=============================================================================== TABLE D-9: Required Path Loss to Preclude Interference to Terrestrial Stations =============================================================================== Indoor Station Outdoor Station SGLS Station Lreq(dB) Lreq(dB) ------------------------------------------------------------------------------- Fixed Mainbeam Gain 196 198 Sidelobe Gain 178 180 Transportable Mainbeam Gain 188 190 Sidelobe Gain 170 172 ===============================================================================The values shown in TABLE D-9 represent the path loss that is required to protect the indoor and outdoor personal stations from interference resulting from fixed and transportable SGLS earth station transmissions. In order to determine the required distance separation, the Egli propagation model for ground-to-ground propagation shown below will be used.[EN 23]

Lreq = 48 + 20 LogF + 40LogDsep + (10-10Logh1) + (10-10Logh2) where Dsep is the required distance separation (km); h1 is the height of the personal or mobile receiver antenna (m); h2 is the height of the SGLS earth station transmitter antenna (m); F is the frequency (MHz).Antenna heights of 1 meter (terrestrial) and 15 meters (SGLS earth station) will be used to determine the required distance separation. Using the above equation, the required distance separations necessary to preclude interference between SGLS earth stations and terrestrial receivers are given in TABLE D-10.

============================================================================= TABLE D-10: Required Distance Separations to Preclude Interference Between SGLS Earth Stations And Terrestrial Receivers ============================================================================= Indoor Station Outdoor Station SGLS Station Dsep (km) Dsep (km) ----------------------------------------------------------------------------- Fixed Mainbeam Gain 73 82 Sidelobe Gain 26 29 Transportable Mainbeam Gain 46 52 Sidelobe Gain 16 18 =============================================================================Provided that the calculated distance separations given in TABLE D-10 can be maintained, the impact on terrestrial stations from fixed SGLS earth station transmitters is expected to be manageable. However, the transportable SGLS earth stations present a more difficult problem, since their exact locations are not always known, hence making coordination difficult.

The ACTS airborne receivers are most susceptible to interference in the Frequency Shift Key (FSK) demodulation stage. This FSK detection, which is accomplished by mark and space filters, uses a selectable FSK data rate of 62 kHz or 198 kHz. It is assumed that the mark and space filter bandwidths are equal to the data rate.[EN 25]

========================================= TABLE D-11: Nominal ACTS Characteristics ========================================= ACTS Ground Station Transmitter ----------------------------------------- Frequency 1840 MHz Output Power 5 W Bandwidth 600 kHz Antenna Gain 0 dBi ----------------------------------------- ACTS Airborne Station Receiver ----------------------------------------- Selectivity -3 dB 1.2 MHz -60 dB 12 MHz Antenna Gain 0 dBi =========================================Aggregate Interference at ACTS Aircraft Receivers The net interference power at the ACTS receiver can be determined using the following equation:

I = PR + GR - FDR - L where I is the interference power at the ACTS receiver (dBm); PR is the aggregate interference power into the receiver antenna under free-space propagation (dBm); GR is the ACTS airborne receiver antenna gain (dBi); FDR is the frequency dependent rejection (dB); L is the building penetration, shadow loss, and urban/rural field-of-view loss (dB).The aggregate interference power PR can be derived from a computer program (PDOME), developed by NTIA for this purpose.[EN 28] PDOME computes the power-sum aggregate interference at an airborne receiver by modeling the emitter distribution and integrating their collective effect under free-space propagation. The user specifies the aircraft altitude, the emitter density, the emission level and the emission frequency. Using these values, PDOME determines the number of emitters in the field-of-view of the aircraft and computes the aggregate power-sum into the aircraft receiver.

Using PDOME and the parameters for the mobile and personal stations given in TABLE D-2, the aggregate received power levels into an aircraft receiver at 30,000 feet were determined to be

PR = -16.3 dBm (mobile stations) PR = -27.3 dBm (personal stations)The FDR value used in the calculation of the interference power is the attenuation of an undesired signal power by the ACTS receiver because of off-frequency rejection. The off-frequency rejection is the rejection provided by detuning of the ACTS receiver with respect to the terrestrial transmitters. A value of 62 dB corresponding to a 7 MHz frequency separation for the lower ACTS channel (1768 MHz) and 56 dB corresponding to a 5 MHz frequency separation on the upper ACTS channel (1840 MHz) will be used in this analysis. The other values used in the calculation of I were defined earlier.

Using the above results, the net interference power at the ACTS receiver from the terrestrial station emitters is given in TABLE D-12.

================================================================================== TABLE D-12: Net Interference Power at The ACTS Receiver From Terrestrial Stations ================================================================================== Mobile Station Personal Station ACTS Channel I (dB) I (dB) ---------------------------------------------------------------------------------- Lower -98 -109 Upper -92 -103 ==================================================================================The values of FDR used in the calculation of I represents a worst-case scenario insofar that it locates all of the mobile and personal stations in the first adjacent channel (minimum frequency separation) from the ACTS receiver. In a more realistic scenario, the terrestrial stations will be distributed across the entire band, which will result in further reduction of interference levels at the ACTS receiver.

The minimum desired signal level in the detection filter of the ACTS receiver is given by:

S = PT + GT + GR - LFS where S is the minimum desired signal in the detection filter of the ACTS receiver (dBm); PT is the ACTS ground station transmitter power (dBm); GT is the ACTS ground station transmitter antenna gain (dBi); GR is the ACTS airborne station receiver antenna gain (dBi); LFS is the free-space propagation loss between the ACTS ground and airborne stations at a maximum altitude of 30,000 feet (dB).Using the equation above, the minimum desired signal level in the detection filter of the ACTS receiver is given below:

S = -80 dBmThe S/I ratios can now be evaluated for the personal and mobile terrestrial stations as follows:

S/I = S - IThe calculated S/I ratios for the lower and upper channels of the ACTS receiver are given in TABLE D-13.

====================================================== TABLE D-13: Calculated S/I Ratios for ACTS Receivers ====================================================== Mobile Station Personal Station ACTS Channel S/I (dB) S/I (dB) ------------------------------------------------------ Lower 18 29 Upper 12 23 ------------------------------------------------------The calculated S/I ratios for the lower ACTS receiver channels exceed the protection threshold. However, the calculated S/I for the upper channel is below the protection threshold of 15 dB. Hence, reallocation of the 1845-1850 MHz band segment will degrade the ACT uplink transmission.

The interference power at a victim receiver can be determined using the following equation:

I = PI + GI + GR - Lreq - FDR where I is the interference power at the terrestrial receiver (dBm); PI is the ACTS ground station transmitter power (dBm); GI is the ACTS ground station transmitter antenna gain in the direction of the terrestrial receiver (dBi); GR is the antenna gain of the terrestrial receiver (dBi); Lreq is the propagation loss required to preclude interference to the terrestrial receivers (dB); FDR is the frequency dependent rejection (dB).As stated earlier, the FDR term used in the interference calculation is the summation of two components. The first term takes into account the rejection provided by specific detuning of the terrestrial receivers with respect to the ACTS ground station transmitters. A conservative value of 50 dB will be used in this analysis, based on the assumption that the adjacent channel selectivity characteristics of the mobile and portable receivers will be similar to the current Federal land mobile receivers.[EN 29] The second term is the power attenuation provided by the terrestrial receiver to the ACTS ground station transmitter signal when the terrestrial receiver bandwidth is narrower than the ACTS emission bandwidth. As shown in TABLE D-11, the ACTS ground station transmitter bandwidth is 600 kHz. The bandwidth of terrestrial personal stations is 50 kHz as given in TABLE D-2. This bandwidth mismatch between the terrestrial receivers and the ACTS uplink transmitter will reduce the interfering signal by an additional 11 dB.

Using the above parameters, the required path loss to preclude interference can be determined and is given below:

Lreq= 93 dB (indoor personal stations) Lreq = 95 dB (outdoor personal stations)The values shown above represent the path loss required to protect the indoor and outdoor personal stations from the interference resulting from ACTS ground station transmitters. As stated earlier, the Egli propagation model was used to determine that the required distance separation to preclude interference is less than 1 km. Provided that the calculated distance separation can be maintained, the impact on terrestrial mobile and personal stations from ACTS ground station transmitters is expected to be manageable.

Reallocation of the 1845-1850 MHz band segment for terrestrial mobile and personal stations with a 5 MHz guard band will degrade uplink transmissions of transportable SGLS earth stations.

A maximum distance separation of 82 km between fixed SGLS earth stations and terrestrial mobile personal stations is needed to preclude interference. Provided the calculated distance separations can be maintained, the impact on terrestrial mobile and personal stations from fixed SGLS earth stations is expected to be manageable.

A maximum distance separation of 52 km between transportable SGLS earth stations and terrestrial mobile and personal stations is needed to preclude interference. However, because of the highly mobile nature of the proposed terrestrial service and the unknown location of the transportable SGLS earth stations, these distance separartions may be difficult to maintain.

Reallocation of the 1845-1850 MHz band segment for terrestrial mobile and personal stations with a 5 MHz guard band will degrade uplink ACTS transmissions.

To reduce the impact to and from Federal satellite command and control and combat training systems operating in the 1761-1842 MHz band segment, reallocation of the 1845-1850 MHz band segment for aeronautical or satellite links must be avoided.

================================================================================================= ENDNOTES FOR APPENDIX D Requests for copies of references from Federal departments and agencies should be referred to the originating organization. Parts of the reference material may be exempt from public release. 1. REPORT FROM THE FEDERAL COMMUNICATIONS COMM'N, to Ronald H. Brown, Secretary, U.S. Dep't of Commerce, Regarding the NTIA PRELIMINARY REPORT, FCC 94-213, at 27 (Aug. 9, 1994) [hereinafter FCC REPORT]. 2. NAT'L TELECOMMUNICATIONS AND INFO. ADMIN. (NTIA), U.S. DEP'T OF COMMERCE, SPECIAL PUBLICATION 94-27, PRELIMINARY REPORT, at 4-30, (Feb. 1994) [hereinafter NTIA PRELIMINARY REPORT and all comments cited refer to this report, unless otherwise stated]. 3. NTIA, U.S. Dep't of Commerce, NTIA Report 92-285, "Federal Spectrum Usage of the 1710-1850 and 2200-2290 MHz Bands", at 5-10 (March 1992). 4. NTIA PRELIMINARY REPORT, supra note 2, at 2-27. 5. Id. at 4-30. 6. Int'l Telecommunication Union Radiocommunication Sector (ITU-R) Document, U.S. Working Party (USWP) 7B/4, at 1 (Aug. 12, 1994). 7. Memorandum from the U.S. Dep't of the Air Force, to Chairman of IRAC, Subject: Comments on Draft Final Reallocation Report Executive Summary and App. D, at 2 (Jan. 6, 1995). 8. The 1992 World Administrative Radio Conference: Technology and Policy Implications, at 77 (May 1993). 9. Int'l Radio Consultative Comm. (CCIR) Recommendation 687-1, "Future Public Land Mobile Telecommunication System (FPLMTS), Annex 1, at 16 (Sept. 22, 1992). 10. Id. 11. NTIA, U.S. Dep't of Commerce, NTIA Report 80-47, "Spectrum Resource Assessment in the 1710-1850 MHz Band", at 55 (Sept. 1980); Spectrum Planning Subcommittee (SPS) Submission SPS-9082, Loral Model CXS-800 SGLS Transponder; Int'l Telecommunications Union Radio Regulations, Appendix 29, Annex III, at AP29-14 (1990 Edition). 12. Document U.S. Study Group (USSG) 8A/39 (Rev. 1), "Criteria for Sharing Between the Mobile Services and Space Research, Space Operations and Earth Exploriation-Satellite Service Space Stations in the 2025-2110 and 2200-2290 MHz Bands", at 6 (Nov. 12, 1991) [hereinafter USSG Sharing Study]. 13. Id. at 7. 14. Id. at 9. 15. Id. at 11. 16. Id. at 12-13. 17. Id. at 16. 18. B.B. Pottorff and N.A. Wilett, Allied Signal Bendix Field Engineering Corp., "Analysis of the Air Force Satellite Control Network Spectrum Usage in the 1760-1850 MHz and 2200-2300 MHz Bands", at 31 (June 11, 1991). 19. CCIR, supra note 9, at 17. 20. Id. at 8. 21. Air Force Memorandum, supra note 7, at 2. 22. Id. at 5. 23. W.G. Duff, Don White Consultants, Inc., MOBILE COMMUNICATIONS, at 24 (1976). 24. Memorandum from the Dep't of the Air Force, to Chairman of IRAC, Subject: Air Force Comments on Title VI of the Omnibus Budget Reconciliation Act (OBRA) of 1993, at 2-3 (Jan. 5, 1995). 25. Electromagnetic Compatibility Analysis Center, "Electromagnetic Compatibility (EMC) of the Proposed Fallon NAS TACTS Expansion", ECAC-CR-87-098, at 3-10 (Oct. 1987); Electromagnetic Compatibility Analysis Center, "EMC Analyis of the Proposed Cherry Point MCAS TACTS and the Dare County Expansion", ECAC-CR-86-066, at 3-8 (June 1986); Electromagnetic Compatibility Center, "EMC of Air Combat Maneuvering Instrumentation (ACMI) System at Nellis Range", ESD-TR-75-020, at 48 (Oct. 1975). 26. EMC Analysis of the Proposed Fallon NAS TACTS Expansion, supra note 25, at 3-8. 27. Id.; Spectrum Planning Subcommittee (SPS) Submission SPS-10045, Technical Data Information of the TACTS ACMI Aircraft Instrumentation Subsystem (AIS) Pods, at 2 (Aug. 31, 1994). 28. NTIA, U.S. Dep't of Commerce, NTIA-TM-89-139, "Single and Aggregate Emission Level Models for Interference Analysis", at 4-1 (March 1989). 29. NTIA Manual of Regulations and Procedures for Federal Radio Frequency Management, at Sec. 5.6, 5-27-5-28 (June 6, 1994).

Return to Report Table of Contents.

Proceed to Appendix E, Federal Government Fixed Microwave Stations in the 1710 - 1755 MHz Band Exempted from Reallocation.