ITU-R REPORT M 2119-2007 Sharing between aeronautical mobile telemetry systems for flight testing and other systems operating in the 4 400-4 940 and 5 925-6 700 MHz bands《在4400-494.pdf
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1、 Rep. ITU-R M.2119 1 REPORT ITU-R M.2119 Sharing between aeronautical mobile telemetry systems for flight testing*and other systems operating in the 4 400-4 940 and 5 925-6 700 MHz bands (Question ITU-R 231/8) (2007) 1 Introduction This Report assesses frequency sharing between wideband aeronautical
2、 mobile telemetry (AMT) systems and other systems operating under primary allocations in the 5 925-6 700 MHz and 4 400-4 940 MHz bands. The Report is intended to address the technical and operational aspects of these sharing scenarios. These AMT systems are used to transmit supplementary data from a
3、ircraft to ground (aeronautical) stations in support of testing of aircraft at test ranges. Section 2 presents technical and operating parameters of AMT systems that are used in the analyses, which are presented in annexes and summarized in the sections below. Annex 1 addresses compatibility with FS
4、S space station receivers in the 5 925-6 700 MHz band; Annex 2 addresses compatibility with FSS earth station transmitters in the 5 925-6 700 MHz band and earth station receivers operating in the 4 500-4 800 MHz band under RR Appendix 30B; Annex 3 addresses sharing between AMT ground station receive
5、rs and FSS satellite transmitters in the 4 500-4 800 MHz band; Annex 4 addresses sharing between AMT and the radio astronomy service in the 4 825-4 835 MHz band; and Annex 5 addresses sharing between AMT and FS/MS systems in the 5 925-6 700 MHz and 4 400-4 940 MHz bands. 2 Parameters of AMT systems
6、2.1 General characteristics Table 1 provides representative values for parameters of AMT systems, which consist of aircraft transmitters and receiving ground stations that use high-gain antennas which track the aircraft. Link budgets encompassing these parameters show fade margins exceeding 13 dB, w
7、hich is necessary to maintain a reliable telemetry link and minimize signal dropouts due to nulls in the aircraft antenna pattern, obstruction by the aircraft fuselage, and multipath fading at the tracking receive station. The specified permissible levels of interference are based on interference-to
8、-noise power ratios (I/N) of 3 dB (long-term) and 0 dB (short-term. 2.2 AMT deployment scenario The assumed AMT deployment scenario consists of 17 representative test areas or flight zones shown in the map of Fig. 1. These zones indicate approximate airspace volumes within which test aircraft operat
9、e. Among all worldwide deployments, this deployment would yield the maximum potential AMT aggregate interference at the geostationary satellite orbit (GSO). For purposes of aeronautical safety, administrations authorize flight testing only in designated areas. *This Report addresses only flight appl
10、ications, and not other applications in these bands. 2 Rep. ITU-R M.2119 2.3 AMT frequency reuse For worst case analyses, no more than two co-frequency aircraft could operate in each of the four largest or most active test zones (DFRC, Utah, WSTF, and PAX in Fig. 1) where sufficient separation betwe
11、en co-channel aircraft is possible in order to avoid interference between aircraft. Self-interference among AMT systems is avoided by rigorous scheduling of AMT frequency usage by frequency managers. Only one aircraft would use a given frequency in the other test zones, for a worst-case total of 21
12、co-frequency aircraft transmitters. Although aircraft testing using AMT is conducted only several hours per day, all 21 co-frequency aircraft are assumed to be operating simultaneously in order to avoid underestimating aggregate interference. TABLE 1 Representative AMT system parameters Parameter Sy
13、mbol Value Aircraft antenna pattern Omni-directional Peak aircraft antenna gain (dBi) Gtmax3 Average aircraft antenna gain (dBi) Gtave4.8 Maximum aircraft e.i.r.p. density (dB(W/MHz) 2.2 Average aircraft e.i.r.p. density (dB(W/MHz) 10.0 Peak aircraft antenna input power density (dB(W/MHz) Pt5.2 Grou
14、nd receiver antenna aperture (m) 2 to 5 Ground receiver antenna pattern Rec. ITU-R F.1245 Ground receiver antenna height (m) 30 Ground antenna elevation angles (degrees) 0-20 Nominal permissible long-term interference at receiver antenna output (dBW/MHz to be exceeded for no more than 20% of the tim
15、e) 145.5 Nominal permissible short-term interference at receiver antenna output (dBW/MHz to be exceeded for no more than 0.4% of the time) 142.5 FIGURE 1 Map of assumed AMT test zones Rep. ITU-R M.2119 3 2.4 AMT aircraft antenna characteristics The AMT aircraft transmitter antenna gain (and e.i.r.p.
16、) in the direction of the receiving ground station fluctuates as a result of multipath and blockage effects of the aircraft fuselage. The aircraft antenna gain statistics were based on the Rayleigh model specified in Recommendation ITU-R M.1459, which yields 3 dBi peak gain, 1.5 dBi gain exceeded fo
17、r 1% of the time, and 6 dBi gain for 50% of the time (average). It should be noted that the average aircraft antenna gain of 4.8 dBi in Table 1 was found by calculating the expected value of gain using the Rayleigh-like probability density function in Recommendation ITU-R M.1459 (thus the average ga
18、in and e.i.r.p. density is 3 (4.8) = 7.8 dB below the peak value rather than 9 dB using the 6 dBi/50% statistic). The antennas typically are of slot or blade (dipole) type. Installation locations of these temporary AMT antennas typically are on the underside of the aircraft so as to direct the radia
19、tion toward the ground during level flight. These temporary installations for testing are constrained by load-bearing aircraft structural features, such as stringers that cannot be cut; thus, the antenna locations cannot be freely optimized to achieve the best possible AMT transmission performance.
20、2.5 AMT e.i.r.p. and modulation The total average power out of the telemetry transmitter, Pt, typically is 10W. It is common in test installations for a single transmitter to simultaneously feed two or more antennas on the aircraft fuselage. For example, a power split of 90%/10% is typical in which
21、90% of the total transmitter power is fed to an antenna on the bottom of the aircraft (since most of the time it is the one in view of the ground station) and 10% to an antenna on the top of the aircraft. Although the peak e.i.r.p. density in any direction (2.2 dB(W/MHz) is based on use of a single
22、antenna with 3 dBi peak gain, the power splitting and two-antenna arrangement could theoretically produce the same peak e.i.r.p. in directions emanating from underside of the aircraft fuselage. Wideband AMT systems are expected to operate at data rates upwards of 20 Mbit/s. The assumed peak e.i.r.p.
23、 is based on the highest power density associated with the modulation and coding techniques used in narrowband aircraft telemetry systems at frequencies below 3 GHz. Other modulation and coding choices tend to have more uniform spectral power density distributions such that the assumed 10 W AMT tran
24、smitter would produce a lower peak e.i.r.p. density. 3 Sharing between AMT and space station receivers in the 5 925-6 700 MHz band AMT transmitters operate well below the power limits specified in Article 21 of the Radio Regulations (RR) for terrestrial stations in frequency bands shared with space
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