1、ERC REPORT 20 7 European Radiocornunications Committee (ERC) within the European Conference of Postal and Telecommunications Administrations (CEFT) % . .- . c y-,-. COMPATIBILITY BETWEEN TFTS (1670-1675 MHZ/1800-1805 MHz) AND SERVICES IN THE SAME AND ADJACENT BANDS Montreux, October 1993 STD-CEPT ER
2、C REPORT 20-ENGL 3993 2326434 003535L 9bL I Copyright 1994 the European Conference of Postal and Telecommunications Administrations (CEFT) STD*CEPT ERC REPORT 20-ENGL 1993 W 2326434 0015152 8T i ERC REPORT 20 Page 1 COMPATIBILITY BETWEEN TFTS (1670-1675 MHZ/1800-1805 MHz) AND SERVICES IN THE SAME AN
3、D ADJACENT BANDS 1. 2. 3. 3.1 3.2 3.2.1 INTRODUCTION This report is a summary of the compatibility studies that have been done within the CER-Spectrum Engineering Working Group concerning Terrestrial Flight Telephone System (TFTS) and services in the same and adjacent bands. RADIO ASTRONOMY (1660 -
4、1670 MHz) See ERC Report 11. It should be noted that ETSI decided to increase the maximum EIRF for TPTS from 44 dBm to 49 dBm. METEOROLOGICAL SATELLITE, SPACE - TO - EARTH (1670 - 1710 MHz) Low-earth-orbit The upper portion of the band, from approximately 1695 to 1710 MHz is used for Low-Earth-Orbit
5、 Meteorological satellites. It is necessary to have tighter limits for the spurious emissions than those in the draft ETS. The value should be - 60 dBW / MHZ. Geostationary The geostationary satellites use the lower portion of the band, e.g. 1670 MHz to approximately 1695 MHz. METEOSAT Primary and s
6、econdary data user stations ( PDUS and SDUS) There are approximately 2000 user stations in Europe receiving the frequencies 1691 MHz and 1694,5 MHZ (Meteorological centres, airports, military installations, universities, etc.). The frequency 1695,7 MHz is or will be received by approximately 200 to
7、300 stations which are already in operation or planned to be installed in the future. The conclusion is the same as for the LEO-METSAT, i.e. the spurious level should be reduced to - 60 dBW / MHZ. Data acquisition telecommand and tracking station (DATTS) The DAITS are receiving on frequencies close
8、to 1675 MHz, see below: 1676.180 MHz 1675.281 MHz 1686.833 1675.929 1676.228 1676.328 1676.028 1676.128 Housekeeping, telemetry Data collecting platform Raw Image Telemetry (p) 11 II 11 II 11 II 11 II These frequencies are presently received only in: - Michelstadt (Germany) - Lannion (prance) ERC RE
9、PORT 20 Page 2 land Ah AH=50 AH= 100 O 25 O 200 10 200 150 20 140 110 30 85 65 Additional receiving equipment for these frequencies is planned in: SM 650 - Italy (Fujino) - Ireland (one location) - Germany (Usingen?) The coordination distance is 7 km for frequencies below 1673 MHz. Since it has not
10、been possible to achieve enough information about the filter characteristics, the coordination distance for frequencies above 1673 MHz is 250 km (land) but this distance can be reduced CONSIDERABLY by better information about the specific earth station (including the filter characteristics, antenna
11、pattern, C/N, etc.), by taking into account the terrain, and using the same measures as for Radio Astronomy (see ERC-report 11). The table below indicates how much the coordination distance can be reduced by taking into account the terrain. Coordination distance, (km) due to ducting, 0.1 % of time.
12、3.2.2 4. 4.1 The interference distance due to troposscatter is shorter than the distance above. Goes The frequencies 1687,l MHz and 1694,5 MHz are received in UK and in Ireland the Meteorological Service has the capacity to receive on 1691 MHz. Since the assigned frequency bands are 8.2 MHz, 400 kHz
13、 resp. 30 kHz, it is only spurious emission that can cause interference to these frequencies. In Spain the frequency 1687,l MHz has been received but is at present interrupted, however another GOES satellite will this year operate the service, probably at the same frequency. Since it is only spuriou
14、s that has to be taken into account, the same conclusion as for the METSAT (PDUS and SDUS) stations are valid. FIXED SERVICE In the frequency bands concerned, there exist different kinds of fixed services, both analogue and digital, wide and narrow band. Some administrations use fixed services accor
15、ding to CCIR Rec. 283 or CCIR Rec. 382 and some administrations use fixed services according to other channel arrangements. Analogue, 1 + 1 channels (1672 - 1676 MHz) In UK, the frequency band 1672 - 1676 MHz is used for analogue fixed links with a channel spacing of 0,05 MHz. It is recognised that
16、under some circumstances there could be considerable co-channel interference and some adjacent channel interference into fixed links from TFS and vice versa. Annex 1 identifies some elementary measures that may be taken, whereby any harmful mutual interference can be eliminated. 120 kHz from the car
17、rier, it is necessary to reduce the out-of-band emission to - 68 dBc. STD-CEPT ERC REPORT 20-ENGL 1993 I 23264lit 0015154 b70 I TFTS Spurious Emission Level As ETSI specification With 15 dB ERC REPORT 20 Page 3 Off-axis coordination Max % interference Max. aircraft height distance time for AS traver
18、sing likely to cause interfe- fixed beam rence (in main beam) 0.7 - 8.9 km 3.1% 2100 m 0.1 - 1.5 km 0.55% 400 m 4.2 1807.5 MHz to 1815.5 MHz, requirements for the spurious emissions The fixed links used in the UK, are analogue frequency division multiplex, with channel capacities of 1 + 1, 8, 12, 24
19、, 36 channels. Annex 2 gives the methodology used for determining interference from TFS aircraft station (AS) to a fixed link. The table below summarises the result of the analyses for a busy airport where aircraft arrive every 3 minutes. The results of this study show that with a 15 dB improvement
20、(at a frequency offset of 2.5 MHz) in the TFS AS spurious emission level, a significant increase of protection is afforded to the adjacent band fixed links. The coordination distance is not unrealistic and when combined with information on the location and direction of peak antenna gain of the fixed
21、 links, incompatibility problems will be minimised. 4.3 CCIR recommendation 283,2 x 8 Mbis The “S aircraft station can cause interference to fixed service on a height of 500 meter, i.e. when the aircraft is approximately 8 km from the airport. If there is a TFS ground station close to the airport th
22、e transmitter power may be reduced and the interference distance will then be reduced. In the worst case, Le. the mainlobe is pointing in the direction of the airport, the coordination distance is approximately 25 km 5. MOBILE SERVICE 5.1 DCS1800 In the band 1710 - 1785 MHz, DCS 1800 base stations S
23、) may receive interference from TFTS aircraft stations (AS) since it is likely that both systems could be operated physically close to each other. The most common scenario would be where a DCS 1800 BS is sited near or at an airport i.e. close to TFS AS. In the analysis it was assumed that the minimu
24、m separation distance between the TFTS AS and DCS 1800 BS would be 100 m. The existing radio parameter specifications were used. It is necessary to reduce the spurious emissions for the TFTS AS to - 62 dBW / 30 kHi. However, part of the additional attenuation will be achieved by the diplexor. In the
25、 band 1805 - 1880 MHZ, DCS 1800 may operate mobile receivers which are handportable and could operate very close to a TFTS AS at airport terminals. It was assumed in the analysis that the minimum separation between a DCS 1800 mobile receiver and a TFTS AS transmitter could be as little as 30 m, part
26、icularly when DCS 1800 mobiles are used at departures gates. The carrier can then cause interference if the frequency separation is less than 1.6 MHz. However, the main problem is the spurious emissions since they can cause interference at much greater frequency separations. It is necessary to reduc
27、e the spurious emissions to - 40 dBm / 30 WZ. It can be noted that the problem may be reduced if: i) an aircraft approaches an airport where a TFTS GS is situated, the TFTS AS will dynamically reduce transmit power in order not saturate the TPTS GS receiver; STDmCEPT ERC REPORT 20-ENGL 1773 II 23264
28、14 0015155 507 I ERC REPORT 20 Page 4 ii) a TFTS AS communicates to a TFTS airport station (low power TFTS GS for coverage around the airport; iii) Coordination, to ensure that near airports a DCS 1800 system should not use the frequencies adjacent to TFS AS frequency band; iv) Planning the DCS 1800
29、 base stations so that the wanted signal, at the departure gates, is kept on a level which gives the required protection ratio. In the scenarios (i) and (ii), the TFTS AS is unlikely to be transmitting at full power. The spurious emissions can be expected to be reduced when the output power is reduc
30、ed. This reduction may however not be linear. 5.2 Other mobile systems There is a potential for interference to the TFS ground stations from a Swedish aeronautical mobile system operating in the adjacent band. Theoretical calculations give interference distances from the aeronautical mobile aircraft
31、 to TPTS GS, ranging from 15 km for the TFS frequency 1800 MHz to 50 km for 1805 MHz. Field measurements will be carried out, as soon as the first TPTS test station is taken into operation, to verify these values. 6. CONCLUSIONS It can be concluded that there are potential incompatibility problems b
32、etween TFTS transmitter and adjacent services. The incompatibility stems from the transmitter mask for the TFTS ground station (GS) as well as for the TFTS aircraft station (AS) defined in the draft ETS, permitting high levels of spurious emissions. Some improvement of 15 dB is required at the TFS A
33、S for 2.5 MHz frequency offset in order to minimise the coordination distance with fixed links. Reduction in spurious emissions will also aid the coordination between TFTS GS and fixed links. A reduction of the spurious emissions for the TFS GS to -30 dBm / MHz is necessary to prevent interference t
34、o MET-SAT. A reduction to -40 dBm / 30k.H for the TFTS AS is necessary to prevent interference from TFS AS to DCS 1800 mobile stations operating at airports. ERC REPORT 20 Page 5 1670 - 1671.88 1671.88 - 1672 1672 - 1672.45 1672.45 - 1673.88 1673.88 - 1674 1674 - 1675 1. TITS Coordination Band* Fixe
35、d Links Fixed Links Coordination Band* TFTS 2. 1675 - 1675.12 1675.12 - 1676 ANNEX 3 Coordination Band* Fixed Links Measures to eliminate interference between TFTS GS and fiied service Partition of fixed link and TFTS bands It would seem that there is a scope for the TFTS and Fixed Link operators to
36、 agree to a mutuaily beneficial partitioning of the band 1670 - 1675 MHz. An EXAMPLE is given here: a b d e f S h C Fill from bottom up Currently in use Fill from bottom up Fill according to usage of sub bands (d) &i (h) Fill from toD down *) Band where careful coordination between services is requi
37、red Analysis in the UK assumes that the existing fixed links would be protected by not using cschannel TFTS assignments (including 120 kHz coordination band). It has been shown that coordination is required close to a TPTS GS if adjacent channels are to be used by fixed links. The exact separation d
38、istance required depends on the terrain profile and ground clutter between the services as well as the exact gain of the fixed antenna towards the TITS GS. Careful coordination of some specific links may be required. Further analysis has shown that it may be possible to coordinate some fixed links c
39、o-channel to TFS if the services are sufficiently separated. POSSIBLE 3 DB REDUCTION OF TFTS AMPLIFIER PRODUCTS The draft ETSI standard specifies that TFS out-of-band (OOB) products should be at a level less than -65 dBc at more than 120 IrHz from the centre of a TFS carrier. Manufacturer of the TFS
40、 airborne equipment, has stated that measurements on bench development equipment shows that the out-of-band is expected to be 10 dB better than the -65 dBc specified (except for isolated spikes where the out-of-band level degrades back to - 65 dBc). Unlike the airborne equipment, the TFTS GS equipme
41、nt is not constrained in weight, size and heat dissipation and discussions with one manufacturer suggested that an extra 3 dl3 may be possible (i.e. improving the OOB spec to - 68 dBc). The example in chapter 2.2 provides a minimum of 120 Wz guard band, i.e. a minimum of -65 dBc for the rf spectrum
42、mask. It can be safely assumed that separations much greater than 120 IrHz will be initially obtained as the bands fill in the most judicious manner. STDOCEPT ERC REPORT 20-ENGL L993 I 2326414 00115157 38T E ERC REPORT 20 Page 6 3. ANTENNA GAIN The fixed link antennas are directional and have gain a
43、s follows: main beam 17 dBi 20“ 12 dBi ( 5 dB rejection of sidelobe) 50“ 4 dBi (12 dB rejection of sidelobe) 100“ -5 dBi (23 dB rejection of sidelobe) By careful selection of TPTS and Fixed links sittings, it should be possible for the fixed link operators to obtain 23 dB rejection of interference f
44、rom TFTS. The TFTS uses omni-azimuthal antennas so no gain discrimination is possible by the TPTS antennas. 4. POLARISATION The TFTS GS uses only vertical polarisation. The fixed links uses both vertical and horizontal polarisation and has cross-polarisation discrimination as follows: main beam 20 d
45、B rejection of X-polar 20“ 14 dB rejection of X-polar 40“ 9 dB rejection of X-polar 60“ 5 dB rejection of X-polar 100“ O dB rejection of X-polar If it is possible to arrange the fixed link networks so that stations near a TFTS GS (and particularly those links that look towards a TFTS GS) use horizon
46、tal polarisation, then considerable rejection of unwanted signals may be obtained. 5. PATH LOSS Ideally, fixed links and TPTS stations should be widely separated in order to increase the path loss between them. It will not be possible to achieve large separation distance between the different statio
47、ns in some areas, since the station sites are already fixed. Fixed link antennas could possibly be shielded in the direction of a TFTS GS by the erection of a metal blinker. No such shielding can be fixed to the TFTS GS because TFTS GSs are required to be omni-azimuthal. 6. POSSIBLE RELAXTION OF FIX
48、ED LINK U1 MARGIN A figure of 40 dB has been given as the minimum required C/I margin for fixed link system. This figure is under review. So far, there has been no indication that these fixed link parameters may be either improved or relaxed. STD.CEPT ERC REPORT 20-ENGL L993 111 2326414 0035358 2Lb
49、I ERC REPORT 20 Page 7 ANNEX 2 Methodology for determining interference from TFTS (aircraft) to Tied service 1. THE NECESSARY ATTENUATION To prevent interference from the aircraft, the necessary attenuation is given by : A = E - Sr(0 - Si(0 + linterp (Gr ,0) - I + lOlog(n) Where: E = EIRP of the TFTS Sr(f) = Rf - filter attenuation (receiver) Si(f) = IF - filter attenuation (receiver) linterp (Gr, 0 = Receiving antenna gain, depending on the off-axis angle (degrees) I = Max tolerable interference level at the fixed Rx, including feeder losses n = number of transmitte
