1、 Rec. ITU-R S.1427-1 1 RECOMMENDATION ITU-R S.1427-1 Methodology and criterion to assess interference from terrestrial wireless access system/radio local area network*transmitters to non-geostationary-satellite orbit mobile-satellite service feeder links in the band 5 150-5 250 MHz*(Question ITU-R 2
2、48/4) (2000-2006) Scope This Recommendation provides a methodology and criterion that allow assessment of interference from terrestrial WAS/RLAN transmitters into non-GSO MSS feeder links (Earth-to-space) in the band 5 150-5 250 MHz, reflecting also results of WRC-03 as regards this issue. The ITU R
3、adiocommunication Assembly, considering a) that the potential large-scale deployment of wireless access system/radio local area network WAS/RLAN transmitters in the band 5 150-5 250 MHz could cause interference to non-geostationary-satellite orbit mobile-satellite service GSO MSS satellite systems o
4、perating their feeder uplinks in this band; b) that the potential large-scale deployment of WAS/RLAN transmitters in the band 5 150-5 250 MHz could cause significant reduction in MSS satellite transponder capacity; c) that WAS/RLAN transmitters in the band 5 150-5 250 MHz are operating on a license-
5、exempt or class-licensed basis in many countries; d) that the non-GSO MSS feeder-link beam coverage is of a regional and/or global nature; e) that WAS/RLAN interference can only be accounted for in terms of an aggregate and constant increase in the non-GSO MSS feeder-link noise floor and its consequ
6、ences to reduction in satellite capacity; f) that resolves 3 of Resolution 229 (WRC-03) states that administrations may monitor whether the aggregate pfd levels given in Recommendation ITU-R S.1426 have been, or will be, exceeded in the future, in order to enable a future competent conference to tak
7、e appropriate action; g) that a method of assessing the interference from WAS/RLAN emissions to non-GSO MSS satellite feeder-link receivers, as well as, a method of processing the measurements, is required; *In this Recommendation WAS/RLAN is to mean wireless access system/radio local area network,
8、or any other transportable or fixed devices offering local network connectivity (e.g. high performance RLANs (HIPERLANs), U-NII, wireless local area network (WLAN), or others; see also Recommendations ITU-R F.1244 and ITU-R M.1450). *This Recommendation should be brought to the attention of Radiocom
9、munication Study Groups 8 and 9 for information. 2 Rec. ITU-R S.1427-1 h) that the evolution of WAS/RLANs in the marketplace will occur independently on a national or regional basis; j) that there is a need to protect the non-GSO MSS feeder links from WAS/RLAN interference, noting a) that the 5 150-
10、5 250 MHz band is subject to other sources of interference (including unwanted emissions from transmitters in nearby bands) to non-GSO MSS feeder links, in addition to that from WAS/RLAN transmitters; b) that the methodologies given in Annexes 1, 2 and 3 are only applicable to non-GSO constellations
11、 with a large number of satellites which are sufficiently spaced, recognizing a) that the band 5 150-5 250 MHz is allocated worldwide to FSS (Earth-to-space) for use by non-GSO MSS feeder links on a co-primary basis without restriction in time as per No. 5.447A of the Radio Regulations (RR); b) that
12、 the band 5 150-5 250 MHz is also allocated on a worldwide primary basis to the aeronautical radionavigation service (ARNS); c) that the band 5 150-5 216 MHz is also allocated to feeder links of the radiodetermination-satellite service (space-to-Earth) subject to RR No. 5.446; d) that the band 5 150
13、-5 216 MHz, under RR No. 5.447B and the provisions of RR No. 9.11A, is also allocated to the fixed-satellite service (FSS) (space-to-Earth) for use by non-GSO MSS feeder links on a worldwide primary basis; e) that the band 5 150-5 250 MHz has been allocated to the mobile service in accordance with R
14、R No. 5.446A, RR No. 5.446B, and Resolution 229 (WRC-03); f) that the band 5 150-5 250 MHz is allocated via RR No. 5.447 to the mobile service in a number of countries subject to coordination under RR No. 9.21; g) that Resolution 229 (WRC-03) limits the WAS/RLAN transmission to indoor transmissions,
15、 recommends 1 that the assessment of interference from WAS/RLAN emissions to non-GSO MSS satellite feeder-link receivers, operating in the band 5 150-5 250 MHz, should be based on the increase (Tsatellite) in satellite noise temperature (Tsatellite); 2 that in order to ensure the adequate protection
16、 for the non-GSO MSS feeder links in the band 5 150-5 250 MHz the aggregate Tsatellite/Tsatellitefrom WAS/RLAN emissions should be no more than 3%; 3 that if the measurement of interference from WAS/RLAN emissions to a non-GSO MSS satellite feeder-link receiver is made, the methodology described in
17、either Annex 2 or 3 to this Recommendation could be used for that purpose by the interfered-with non-GSO feeder-link system. Background information regarding such methodologies can be found in Annex 1; 4 that the following Notes are considered as part of the Recommendation. NOTE 1 The impact of the
18、aggregate long-term interference due to WAS/RLANs into non-GSO MSS feeder links, in terms of the reduction in non-GSO MSS satellite capacity, should also be considered in conjunction with the methodology proposed in the above recommends. This is to ensure that the interference power captured by the
19、non-GSO MSS satellites should account for a Rec. ITU-R S.1427-1 3 reduction in available satellite capacity less than or equal to 1%. This value may require further study. NOTE 2 By the term “aggregate” it is meant that the interference to the satellite receiving beam is to be calculated from all of
20、 the WAS/RLAN devices within the field of view of the non-GSO satellite feeder-link receiving beam. NOTE 3 Annexes 2 and 3 to this Recommendation describe two alternative implementations of a measurement payload on board a satellite to determine the aggregate noise and interference that would be rec
21、eived at an operational satellite of the same type as the rest of the satellites in the constellation. Furthermore, the Annexes also describe the respective methods to process, on the ground, the measurements made at the satellite. NOTE 4 The methodologies described in Annexes 2 and 3 may be used to
22、 measure the aggregate interference into the space station receiver of the feeder link of any non-GSO MSS satellite system. To provide explicit results, the technical parameters of the LEO-D constellation as described in Recommendation ITU-R M.1184 are used. Further study may be required to determin
23、e what portion of that aggregate interference comes from WAS/RLAN transmitters. That study can best be carried out when the results of the measurements obtained using one of the methodologies described in Annexes 2 and 3 are available. Annex 1 The measurement of the aggregate noise and interference
24、into the space-station receiver of the 5 GHz Earth-to-space feeder link of a LEO-D MSS satellite system 1 Introduction This Annex describes how the aggregate interference into the receiving antenna of the space-station receiver of a 5 GHz Earth-to-space feeder link of a non-GSO MSS satellite system
25、is measured. Given that the overall objective of Annex 2 or 3 is to be able to estimate the magnitude of the aggregate RLAN interference with high accuracy, this Annex describes in general terms how the measurement of the total power received at the satellite antenna may be made with an r.m.s. error
26、 of about 0.03% of the thermal and background noise in the uplink. 2 The Dicke radiometer receiver The Dicke radiometer receiver has been used for decades by the radio astronomy community and others to measure very low levels of Gaussian noise in an environment of much higher levels of Gaussian nois
27、e in the receiver itself. The application considered here is almost identical, in that the aggregate interference signal from a very large number of transmitting RLAN devices would have Gaussian stochastic characteristics, independent of the detailed characteristics of an individual transmission. Si
28、milarly, the stochastic characteristics of the background receiver noise would be Gaussian in Earth exploration-satellite (passive) applications, space research (passive) applications, radio astronomy applications, and the interference measurement of WAS/RLAN interference application described in th
29、is Recommendation. 4 Rec. ITU-R S.1427-1 A block diagram of a generic Dicke radiometer is shown in Fig. 1. In general, the Dicke radiometer is built around the “receiver system” block, which is the actual 5 GHz MSS feeder-link receiver before the addition of Dicke radiometer blocks. The additional b
30、locks are added to enable the receiver to: integrate the detected envelope of the wideband Gaussian signal in the RF and IF stages of the satellite receiver itself for a measurement time ; calibrate its measurements so that gain variations of the receiver over time do not affect the accuracy of the
31、measurement, and so that the estimates of the noise level being measured do not include the receiver internal noise. To do these tasks two reference noise sources are used, and compared with the incoming Gaussian signal to be measured. One of these reference signals is comparable with the noise in t
32、he receiver; the other is comparable with the external signal being measured. FIGURE 1 A generic Dicke radiometer 3 Performance of the Dicke radiometer A Dicke radiometer is designed to switch rapidly between the antenna and a reference load or noise source, at a rate faster than the most rapid gain
33、 variations. Typically, gain fluctuations have a spectrum extending out to at least 5 Hz, so the RF switch should switch between the antenna and reference at a rate of at least 30 Hz or so. The gain variations then only act upon the difference between the inputs. Ideally, therefore, the reference te
34、mperature should be as close to the antenna temperature as possible. An antenna looking at the ground will always have an antenna temperature of at least 150 K or so (if the antenna beam is not filled by the ground if it is something like 250 K is more likely). A matched load or noise source would t
35、herefore be a practical reference. Indeed, a PIN diode attenuator could be driven to match the inputs to the receiver so that the receiver is always balanced. A calibration noise source adds a known amount of noise to the receiver, increasing the input by a known amount. Switching to a matched load
36、is a useful adjunct to the calibration process, so that the basic noise level can be calibrated. However, when the matched load is connected, the antenna is not, so the baseline noise level will change. Rec. ITU-R S.1427-1 5 The Dicke radiometer output is an unbiased measurement of the power level o
37、f the signal received by the 5 GHz satellite antenna over the bandwidth B of the receiver. The r.m.s. error of that measurement is: Terror= Tsys/(B)0.5 (1) where: Terror: r.m.s. error in the measurement of the noise temperature of the random signal at the antenna output Tsys:noise temperature of the
38、 total noise in the receiver, the sum of the satellite receiver noise temperature and the noise temperature of the received signal, as described in Recommendation ITU-R RS.515 B: bandwidth (Hz) of the receiver : integration time of the receiver (s). If the noise level being measured is 3% of the tot
39、al noise in the receiver, and the r.m.s. error in the measurement of that quantity is required to be in the order of 1% of the measurement, the quantity (B)0.5must be in the order of 3 104. 4 Radiometers appropriate for use in the LEO-D system The design of the radiometers used in the LEO-D system c
40、an be simplified if the measurement can use as reference-channel measurement of the noise in nearby reference-band spectrum immediately below 5 150 MHz, and use of those measurements in estimating the interference above 5 150 MHz. Application of this possibility allows a simplification of the in-orb
41、it radiometer required to accurately measure the aggregate interference into the satellite receiver in the 5 150-5 250 MHz band, compared to the general-purpose Dicke radiometer in Fig. 1. Further, this modification in the measurements made by the radiometer modifies what on-ground data-processing o
42、f in-orbit measurements are necessary to make those aggregate-interference measurements. This simplification of the radiometer used in the LEO-D satellite is based on the following five observations: Recommendation ITU-R S.1427 does not place a limit on the aggregate interference I from WAS/RLAN dev
43、ices as such. Rather, it rather limits the ratio of that interference to the baseline noise level N, or the ratio I/N, equivalent to the ratio T/T at the satellite receiver, which should not exceed 3%. In the LEO-D system that operates from 5 091 MHz to 5 250 MHz there are eight RF channels, each 16
44、.5 MHz wide. Channels 1 and 2 operate completely below 5 150 MHz, the lowest frequency at which WAS/RLAN devices operate. Channel 3 operates at the 5 150 MHz boundary, and Channels 4 to 8 inclusive operate above 5 150 MHz in an environment in which there may be WAS/RLAN interference. The background
45、noise N does not change appreciably over the frequency range from 5 091 MHz to 5 250 MHz, although there may be a slight variation. All of the slowly time-varying variations in N are common between the background noise N in the lower two RF channels and the upper five channels. The reasons for this
46、time-variation of N may not be known, but the variations are embedded in variations in the noise in the lower two RF channels. There may be more rapid variations in the gains of satellite components at rates up to about 10 Hz, which must be taken into account in making observations that would lead t
47、o estimates of the interference I. 6 Rec. ITU-R S.1427-1 In determining how to effectively use the reference signals in Channels 1 and 2 to estimate the I/N ratio in Channels 4, 5, 6, 7, and 8, it is observed that the “calibration” of the radiometer could be done through making measurements in Chann
48、els 1 and 2. An additional advantage of this approach is that all of the time variations in the background noise levels in different 16.5 MHz wide channels due to the varying location of the satellite, and time that the measurements are taken, are embedded in the simultaneous measurements of the noi
49、se level in Channels 1 and 2, subject to the minor variations in the background noise level over the frequency band 5 091 MHz to 5 250 MHz. The two radiometers described in Annexes 2 and 3 respectively take into consideration the above mentioned observations. In both of those radiometers the “calibration” signals can be the noise levels in Channels 1 and 2, because the variations in the noise levels in Channels 4 to 8 inclusive is fully embedded in the noise levels in Channels 1 and 2. Because of this, the 550 K calibration noise source and the 16.5 K pre
