1、232b414 0015338 29T M ERC REPORT 27 European Radiocommunications Committee (ERC) within the European Conference of Postal and Telecommunications Administrations (CEW -.-., -.* v ,. -._* A A,. %, COMPATIBILITY STUDY BETWEEN AND GLONASS MOBILE SATELLITE SERVICE IN THE 1610-1626.5 MHz Brussels, June 19
2、94 STD.CEPT ERC REPORT 27-ENGL 3994 II 2326414 0035339 126 E CONTENTS 1. Introduction 2. Interference fromMES to GLONASS 3. Interference from GLONASS satellites to MSS satellites 4. Interference from downlink MSS 5. Operational sharing techniques 5.1 GLONASS reconfiguration 5.2 Non-overlapping cover
3、age 6. Conclusion Annex 1 : GLONASS/GLONASS-M frequency data Annex 2 : Single entry Co-channel MSS MES interference into GLONASS Annex 3 : Interference from GLONASS satellites to MSS satellites P.2 P.3 P.3 P.3 P.3 P-4 Copyright 1994 the European Conference of Postal and Telecommunications Administra
4、tions (CEPT) _ _ ERC REPORT 27 Page 1 COMPATIBILITY STUDY BETWEEN AND GLONASS MOBILE SATELLITE SERVICE IN THE 1610-1626.5 MHz 1. INTRODUCTION WARC-92 (RR 731 E) allocated the band 1610-1626.5 MHz on a primary basis to the Mobile Satellite Service (MSS) in the earth-bspace direction (uplink) and the
5、band 1613.8-1626.5 MHz on a secondary basis to the MSS in the space-te earth direction (downlink). This report presents the results of the study concerning the sharing between GLONASS and MSS. The GLObal NAvigation Satellite System (GLONASS) provides global, 24 hour-a-day, all weather access, precis
6、e position, velocity and time position, similarly to the GPS and is operated by the Russian Administration. The channel centre frequencies are in increments of 0.5625 MHz from 1602.5625 MHz to 1615.5 MHz . A CoarsdAcquisition signal (UA carrier) is phase modulated with a chip rate of 0.5 11 Mbit/s (
7、1 MHz bandwidth) and a precise signal (P carrier) is phase modulated with a chip rate of 5.1 1 Mbit/s (10 MHz bandwidth). For the P signal, the maximum power density 1 MHZ outside, centred on the carrier, is 10 dB lower than the maximum power density for the C/A signal. It should be noted that two s
8、atellite networks have been submitted to the Radiocommunications Bureau : GLONASS (only C/A carrier) in June 82 and GLONASS M (C/A carrier and P carrier) in January 92. Though there are still some comments and objections to GLONASS M, 12 satellites are operating at this time GLONASS M, and 24 satell
9、ites will be operational in 1995. Below 1610 MHz, GLONASS/GLONASS M is considered as a part of the RadioNavigation Satellite service. Above 1610 MHz, this world-wide system can only operate as an element of the Global Navigation Satellite System (GNSS) and, thus, airborne GLONASS receivers will oper
10、ate under RR732 (use of airborne electronic aids to air navigation). Since it is coordinated under article 14, GLONASS is protected by RR731E, stating that MSS stations shall not cause interference or claim protection from stations operating under RR732. On the other hand, GLONASS M has not been coo
11、rdinated with article 14 and can not claim protection. Moreover, according to ICA0 (International Civil Aviation Organisation), GLONASS P carrier is not assumed to be part of GNSS and, therefore, has no clear status. In September 93, the Russian Administration concluded an agreement with radioastron
12、omers and gave a new allotment to existing GLONASS/GLONASS M satellites in order to protect Radioastronomy; but some channels in the MSS band are still used (see annex 1). This new allotment does not fully protect radioastronomy against 10 MHz P carrier and article 7 of this agreement states that “a
13、 solution of the interference problem caused by the main emission of class 10M2G7X and out of band emissions of GLONASS transmitters in the frequency band 1610.6-1613.8 MHz will be achieved only if the frequency plans of the GLONASS and GLONASS M systems are modified. The use of 12 channels with cen
14、tre frequencies from 1599.1875 MHz to 1605.375 MHz is envisaged. If implemented, this would solve the question of sharing between GLONASS and MSS in the band 1610-1626.5 MHz. Characteristics for MSS are not fully determined at the moment. Both TDMA and CDMA access techniques and both GSO and non GSO
15、 satellites are considered in calculations, with technical data already available. MSS systems are referred to by name for ease of identification. According to RR731E, the MES maximum EIRP should be -15dBW/4kHz when sharing with systems operating under RR732 and -3dBW/4 kHz elsewhere. For the time b
16、eing, only the Iridium project intends to use a secondary status downlink allocation in the band 16 16 MHz to 1626.5 MHz. STDaCEPT ERC REPORT 27-EMGL L994 II 2326434 0015343 884 ERC REPORT 27 Page 2 2. INTERFERENCE FROM MES TO GLONASS According to the aeronautical community, the minimum separation d
17、istance between an airborne GLONASS receiver and a MES is 100 m. Usually, aircraft at this altitude would only be found very close to airports. However, in an emergency, it is difficult to assess the lowest en-route altitude. Hence, it is estimated that 100 m should be the minimum required protectio
18、n distance. Co-channel interference distance calculations between airborne GLONASS and both CDMA and TDMA MES have been carried out. The AU-lines Electronic Engineering Committee (AEEC) indicates in ARINC characteristic 743A that “the GLONASS sensor unit shall acquire and maintain code and carrier l
19、ock of a GLONASS signal at -137 dBm in the presence of an in-band wide band (r600 Hz) interfering signal of -116 dBm (-21 dB protection ratio). According to the results of measurements given in an FCC document, the sensitivity of a GLONASS receiver is -145 dBm and the wanted signal ranges from -135
20、dBm to -132 dBm when a GLONASS satellite is visible. According to a Russian contribution to WARC 92 (Addendum 1 to doc. 184E), the wanted signal value is between -126 and -131 dBm and the protection ratio is -16 dB. AEEC figures are used throughout. Then, the protection level for GLONASS is assumed
21、to be -1 16 dBm. Considering the -15 dBW/4kHz limit of RR731E for MES power flux density, separation distances vary from 118 km for TDMA MES to 695 km for CDMA MES. TDMA systems tend to use higher powers, which means, according to RR731E, no sharing with GLONASS. CDMA system power could be, at maxim
22、um, -25 dBW/4 WZ, leading to a 220 km interference distance. This is obviously not tolerable compared to the 100 m criteria ! Annex 2 provides detailed calculations. In the reverse order, 100 m protection distance leads to a maximum EIRP of -92 dBW/4kHz for MES having a bandwidth wider than the GLON
23、ASS bandwidth (CDMA systems). Considering a narrowband TDMA system (20 WZ), the maximum MES EIRP should be -76 dBWI4 kHz. These two figures are not realistic. It is interesting to notice that the values of -92 dBW/4 kHz is also the maximum MES out-of-band emission (due to modulation or wideband nois
24、e) power in GLONASS band and will therefore establish the frequency separation between MSS and GLONASS, depending on the MES out-of-band specification. Less stringent assumptions (antenna discrimination, shielding etc.) will yield a higher value. 3. INTERFERENCE FROM GLONASS SATELLITES TO MSS SATELL
25、ITES Satellite to satellite interference is a complex matter when taking into account every parameter: satellites location and speed, earth rotation, antenna pattern, wanted signal level etc. Hence, only some very rough calculations have been carried out to assess the order of magnitude of the inter
26、ference and identify the main problems. Two interference cases have been studied for LEO and IC0 space segment configurations : GLONASS satellite into MSS satellite backiobe and the two satellites over the earth horizon. As a conclusion, the first interference case might be solved by appropriate ant
27、enna design, when the second interference case cannot be avoided. For GSO space segment configuration, interference is likely to occur when the MSS satellite is visible to the GLONASS backlobe, but also when the two satellites are over the earth horizon. Detailed calculations are presented in annex
28、3. An initial dynamic simulation has been undertaken by Inmarsat to assess the time varying nature of the GLONASS satellite to Inmarsat IC0 satellite interference. This initial study assumed the use of CDMA parameters for the Inmarsat MSS system. The provisional results indicate that MSS uplink carr
29、iers could be subjected to interference for about 0.5 to 3% of the time with a typical excess interference duration of up to 250 seconds. Further study is required in this respect. STD-CEPT ERC REPORT 27-ENGL L994 I 2326414 0015342 710 RE ERC REPORT 27 Page 3 4. INTERFERENCE FROM DOWNLINK MSS TO GLO
30、NASS RECEIVERS The specified GLONASS protection level is -1 16 dBm for a wanted signal of -137 dBm. Considering a 3 dBi GLONASS maximum antenna gain and a 700 kHz receiver noise bandwidth, this gives a maximurn power flux density of -146 dBW/m2/4 HIz. More optimistic assumptions on wanted signal or
31、antenna gain will yield higher values. However, unless there is confirmation by ICAO or the Russian Administration it is more appropriate to use this value, which is below TDMA MES sensitivity. Thus Co-frequency sharing between downlink MSS and GLONASS is not possible unless an operational sharing t
32、echnique is used. It should be noted that the value of -146 dBW/m2/4 kHz is also the maximum downlink MSS out-of-band emission (due to modulation or wideband noise) power in GLONASS band and will therefore lay down the frequency separation between celocated, simultaneous operations of downlink MSS c
33、hannels and GLONASS, depending on the MSS out-of-band specification. 5. OPERATIONAL SHARING TECHNIQUES Overlapping coverage and Co-channel sharing of MSS uplink carriers with GLONASS carriers will be difficult. As indicated in the introduction of this report, there is currently an attempt to reconfi
34、gure GLONASS. Another possibility which may be considered to facilitate MSS operation in the 1610-1620.5 MHz band is a dynamic frequency assignment scheme based on non-overlapping coverage. 5.1 Glonass Reconfimration The current GLONASS/GLONASS-M system can use 24 distinct carrier frequencies - one
35、for each satellite. It may be possible for the GLONASS/GLONASS-M system to operate with 12 frequencies - each frequency being used by anti-poda1 GLONASS satellites. This implies that the last centre frequency used by GLONASS would be 1608.75 MHz. If such a reconfiguration of the GLONASS system could
36、 be achieved, GLONASS C/A receivers would be protected against MSS interferers (providing that level of out of band emissions are lower than those calculated in section 2 and 4) and MSS satellites may suffer interference only from the attenuated P signal. The reconfiguration achieved in September by
37、 the Russian authorities in order to protect Radio astronomy does not fully comply with these requirements since the three last channels, above the Radio astronomy band, are still used. However, for the first time two anti-podal satellites are using the same channel which proves the feasibility of t
38、he required reconfiguration. As indicated in the introduction of this report, a shift to lower frequencies, which would totally avoid interference to radioastronomy, is likely to be achieved in the near future. This would provide more than 4 MHZ frequency separation between GLONASS and MSS which is
39、likely to solve any compatibility issues. 5.2 Non-overlappine Coverape Co-Channel Case The MES would normally be expected to report its position to the MSS Land Earth Station (LES) via a signalling channel. Generally the MSS operator may come to an agreement with the GLONASS system operator or ICAO
40、or relevant national Civil Aviation Authorities, whereby a minimum coordination distance would typically be assured between the MSS terminal and any GLONASS airborne earth station (AES) receiver. The MSS LES could be equipped to receive and process the orbital ephemeris data of the entire GLONASS sa
41、tellite constellation. The LES in the call Set-up process (Le. prior to assigning a carrier frequency to a MES) could, knowing the location of the MES terminai and the associated minimum coordination distance, determine for any AES located inside the coordination zone centred on the MES location, wh
42、ich GLONASS satellites would be visible and accordingly which GLONASS frequencies could be used by any AES located inside the MES coordination zone. The frequency selection algorithm would have to determine which GLONASS frequencies would remain “non-visible“ to the AES for the expected duration of
43、the MSS call. STD-CEPT ERC REPORT 27-ENGL 1994 111 232b414 0015343 657 1111 ERC REPORT 27 Page 4 Assuming a fully deployed constellation of 24 GLONASS satellites, typically between 4 and 8 GLONASS satellites would be visible to an AES at any given moment. Of these 4 to 8 GLONASS frequencies, only th
44、ose which are within the MSS band 1610-1626.5 MHz may need to be avoided by the LES in assigning a frequency to the MES. For example all the frequencies used within the 1610-1620.6 MHz band by GLONASS satellites located anti-pcdally could be potentially used by the MSS system. The above intelligent
45、dynamic frequency allocation by location (D-FABL) scheme, based on determining which GLONASS frequencies are non-visible to the AES and visible to the MES, may be feasible to implement by MSS operators. Further study is required in particular to assess the impact of such operational schemes on both
46、the MSS and GLONASS system in terms of technical feasibility and aggregate interference levels. While solving the interferences from MES to GLONASS receivers, simulation results provided in annex 3 show that, with this operational sharing technique, satellite to satellite interference over the Earth
47、 horizon could still be a problem for a high percentage of time. Therefore, sharing based on non-overlapping coverage seems not technically realistic. Then, unless GLONASS reconfigures, introduction of MSS in the 1610-1616 MHz band would cause interference to GLONASS C/A receivers and introduction o
48、f MSS in the 1610-1620.5 MHZ band would cause interference to GLONASS P receivers. 6. CONCLUSION Only a full reconfiguration of GLONASS (use of the same frequencies by anti-podal satellites and frequency shifting) would give a satisfactory solution for sharing between GLONASS and MSS. This reconfigu
49、ration is likely to be implemented due to the obligation for GLONASS to protect Radio Astronomy in the 1610.6-1613.8 MHz band. If GLONASS is reconfigured without frequency shifting (and because of the very short protection distance), special care should be given to out of band emissions from MES into GLONASS receivers. STD-CEPT ERC REPORT 27-ENGL 1994 I 2326434 0015344 593 E channelnumber 1 2 3 4 centre frequency (MHZ) satellite number 24 8 19 4 16025625 1603125 16036875 160425 ERC REPORT Z Page 5 5 6 7 8 9 10 11 12 16648125 1605375 I6059375 16065 1607MZ.5 1607625 1
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