1、 Recommendation ITU-R SA.1155-1(12/2013)Protection criteria related to the operation of data relay satellite systemsSA SeriesSpace applications and meteorologyii Rec. ITU-R SA.1155-1 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use
2、 of the radio-frequency spectrum by all radiocommunication services, including satellite services, and carry out studies without limit of frequency range on the basis of which Recommendations are adopted. The regulatory and policy functions of the Radiocommunication Sector are performed by World and
3、 Regional Radiocommunication Conferences and Radiocommunication Assemblies supported by Study Groups. Policy on Intellectual Property Right (IPR) ITU-R policy on IPR is described in the Common Patent Policy for ITU-T/ITU-R/ISO/IEC referenced in Annex 1 of Resolution ITU-R 1. Forms to be used for the
4、 submission of patent statements and licensing declarations by patent holders are available from http:/www.itu.int/ITU-R/go/patents/en where the Guidelines for Implementation of the Common Patent Policy for ITU-T/ITU-R/ISO/IEC and the ITU-R patent information database can also be found. Series of IT
5、U-R Recommendations (Also available online at http:/www.itu.int/publ/R-REC/en) Series Title BO Satellite delivery BR Recording for production, archival and play-out; film for television BS Broadcasting service (sound) BT Broadcasting service (television) F Fixed service M Mobile, radiodetermination,
6、 amateur and related satellite services P Radiowave propagation RA Radio astronomy RS Remote sensing systems S Fixed-satellite service SA Space applications and meteorology SF Frequency sharing and coordination between fixed-satellite and fixed service systems SM Spectrum management SNG Satellite ne
7、ws gathering TF Time signals and frequency standards emissions V Vocabulary and related subjects Note: This ITU-R Recommendation was approved in English under the procedure detailed in Resolution ITU-R 1. Electronic Publication Geneva, 2014 ITU 2014 All rights reserved. No part of this publication m
8、ay be reproduced, by any means whatsoever, without written permission of ITU. Rec. ITU-R SA.1155-1 1 RECOMMENDATION ITU-R SA.1155-1*Protection criteria related to the operation of data relay satellite systems (1995-2013) Scope This Recommendation specifies the protection criteria for data relay sate
9、llite systems and presents them in the form of I/N values and provides a supporting analysis and text consistent with and relevant to the protection criteria. The ITU Radiocommunication Assembly, considering a) that data relay satellite systems are in operation or are planned corresponding to the hy
10、pothetical reference system as described in Recommendation ITU-R SA.1018; b) that these data relay satellite systems support links with widely different characteristics as described in Annex 1; c) that preferred frequency bands for data relay satellite systems have been identified in Recommendation
11、ITU-R SA.1019; d) that sharing between data relay satellite systems and other space and terrestrial radio systems is required in all of the preferred frequency bands, identified in Recommendation ITU-R SA.1019; e) that the numbers of space and terrestrial radio systems using the shared bands with da
12、ta relay satellite systems will increase in the future, thus increasing the potential of interference situations; f) that the link margins for data relay satellite forward and return links are typically 2 to 4 dB, but in some cases may be on the order of 1 dB; g) that the link design margin for the
13、space-to-space link is often the limiting factor; h) that the data relay satellite system will transmit and receive signals in the space operation, space research, Earth exploration-satellite (EES) and the fixed-satellite (FS) services; j) that detailed technical information regarding protection cri
14、teria is contained in Annex 1, recommends 1 that protection criteria, specified in maximum aggregate interference power spectral density to system noise power density ratio, from all sources to be exceeded for no more than 0.1% of the time for the various links of data relay satellite systems are as
15、 indicated in Table 1; 2 that the protection criteria in Table 1 should be used as the basis for developing sharing criteria in studies with other terrestrial and space systems. *This Recommendation should be brought to the attention of Radiocommunication Study Groups 4, 8 and 9. 2 Rec. ITU-R SA.115
16、5-1 TABLE 1 Protection criteria Data relay satellite link Receiver location I0/N0(dB) Forward inter-orbit link User spacecraft 2 025-2 110 MHz 13.4-14.3 GHz 22.55-23.55 GHz 10 Return inter-orbit link Data relay satellite 2 200-2 290 MHz 14.5-15.35 GHz 25.25-27.5 GHz 10 Forward feeder link Data relay
17、 satellite 14.5-15.35 GHz 27.5-31.0 GHz 6 Return feeder link Earth station 13.4-14.05 GHz 10.7-10.95 GHz 17.7-21.2 GHz 6 Annex 1 Analysis of interference susceptibility of data relay satellite links 1 Introduction Much of the spectrum suitable for space research is also allocated to one or more othe
18、r services and consequently frequency sharing between the services is required. This Recommendation discusses factors which affect the susceptibility to interference of links towards geostationary space stations operating as data relay satellites from low-orbiting spacecraft in the space research, s
19、pace operations and EES services and from earth stations operating both in these same services or in the FSS. It specifies appropriate protection criteria for these services in the frequency bands from 2 up to 30 GHz. The protection criteria are for use in coordination and interference analyses when
20、 actual system data are unavailable. 2 General considerations Space research, space operations and Earth exploration systems in the near-Earth region have always been reliant on regular, interference-free two-way communications between spacecraft and control centres and other installations on the Ea
21、rth. The evolution and expansion of these activities has become dependent on data relay satellites, described in Recommendation ITU-R SA.1414. These operations are dependent on space-to-space links, which are more difficult to design and implement than the space-to-Earth links because both the trans
22、mitting system and the receiving Rec. ITU-R SA.1155-1 3 system are subject to the mass and power limitations, and in most cases also to remote-control and non-maintainability constraints, of space-borne systems. The trend is for systems of these types to use bandwidth-efficient modulation schemes, s
23、uch as 2-PSK and 4-PSK, supplemented by forward-error-correction coding techniques, such as convolutional coding and block coding, both to increase the signal quality and to reduce the necessary signal power. In some systems, spread-spectrum modulation techniques are used to reduce the power density
24、 of the signal and pseudo-random sequence modulation techniques (similar or identical to the spread-spectrum modulation techniques) are used for range measurements to determine the location of spacecraft. Phase-locked loop circuitry is also used during search, acquisition and tracking sequences. 3 P
25、rotection criteria In space-to-Earth and Earth-to-space links there is an incentive to minimize link margins in order to save mass and power, to reduce interference and in the interests of economy. In space-to-space links this incentive is re-doubled as both ends of the link are space-borne. Typical
26、 overall link design margins, which consider in the case of data relay satellites the space-to-space link in tandem with the space-to-Earth or Earth-to-space link (sometimes referred to as the feeder link), are generally around 2-4 dB, but in some cases may be on the order of 1 dB after making allow
27、ance for any necessary margins to offset the effect of weather on the feeder link. The link design margin for the space-to-space link is often the limiting factor, due to the extreme constraints of launching both transmitting and receiving systems into space in contrast to the possibility of enlargi
28、ng the antenna of a ground receiving station. Considering these low design margins, levels of interference causing reduction of link margin by as little as 0.2 dB could be harmful to space-to-space links. However, in most cases, particularly at higher frequencies, these links will not be permanently
29、 affected by a single source of interference from the ground, as the link geometry is constantly changing due to the movement of the low-orbiting spacecraft. On the other hand, interference patterns which recur whenever a specific link geometry occurs will cause systematic problems to real-time obse
30、rvations of the Earths surface below a low-orbit spacecraft. The levels causing harmful interference to the Earth-to-space links will depend on the apportionment of margins to the tandem Earth-to-space and space-to-space links. The geometry of the Earth-to-space links towards the data relay satellit
31、e does not vary with time. In the analyses which follow, the bench-mark of link margin reduction by 0.4 dB due to single-entry interference has been assumed, which has been used in other similar cases. This corresponds to a required ratio of interference power to system noise power (I/N) within the
32、referenced bandwidth of at most 10 dB. 3.1 Reference bandwidth The systems use direct-modulation schemes, so that the reference bandwidth in which a protection ratio must be specified depends upon the lowest data rate and receiver bandwidth likely to be employed. For space-to-space links operating a
33、t frequencies in the 2 GHz band, the minimum data rate is likely to be around 1 kbit/s whereas for the higher frequency bands, it is likely to be at least 1 Mbit/s. Thus, the recommended value for the reference bandwidth in the 2 GHz band is 1 kHz and in the higher bands is 1 MHz. 4 Rec. ITU-R SA.11
34、55-1 3.2 Reference percentage of time For manned missions, a loss of communications for more than 5 min during critical phases, such as rendez-vous and docking or extra-vehicular activities, could seriously affect the mission. For manned and unmanned missions, the reference is 0.1% of the time. For
35、the space-to-space link, the percentage of time should be referenced to the period when the user satellite is in view of the corresponding data relay satellite (DRS), as this latter corresponds to the time when communications takes place, and receiving interference when communications does not take
36、place is not relevant. 3.3 Required protection levels Communications through a data relay satellite comprise two links in series, either “forward”, being an Earth-to-space “feeder” link in tandem with a space-to-space “inter-orbit” link, or “return”, being a space-to-Earth “feeder” link. The determi
37、nation of protection levels requires the consideration of both the feeder link and the inter-orbit link. 3.3.1 Space-to-space links The total noise temperature of a typical space-station receiver is generally 600 K at 2 GHz increasing to 1 200 K at 20 GHz when the spacecraft antenna points at the Ea
38、rth (290 K). These noise values should be used when the actual values are not available in determining if the requirement for I/N of 10 dB is met. The noise contribution of the forward feeder link is small due to the negative transmission gain of the data relay satellites and has consequently not be
39、en considered. 3.3.2 DRS-to-Earth and Earth-to-DRS links Table 2 shows the interaction between the two parts of the overall end-to-end link, both for return links and forward links, and for several different frequency bands. The link margins are typical values of USA system links. Since the links ar
40、e typically “bent-pipe”: i.e. there is no onboard processing at the DRS, noise is additive, so the overall link margin is determined by a cascaded combination of the individual link margins. In some cases, the two links have similar margins (e.g. Return 15 GHz/13 GHz) and so both links are about equ
41、ally sensitive to noise. In other cases, the space-to-space link has a much lower margin than the feeder link (e.g. Return 2 GHz /13 GHz, Forward 15 GHz/13 GHz), so the former is much more sensitive to noise. This means that more interference can be allowed in the feeder links, so the I/N criterion
42、is relaxed to 6 dB for those links. Rec. ITU-R SA.1155-1 5 TABLE 2 Interference into a data relay satellite Return link Band 2/13 15/13 User-to-DRS link Margin at TDRS (dB) 4.01 4.01 3.31 3.31Degradation (dB) 0.40 0.00 0.40 0.00Margin at TDRS degraded (dB) 3.61 4.01 2.91 3.31DRS-to-Earth link Margin
43、 at Earth (dB) 50.30 50.30 4.45 4.45Degradation (dB) 0.00 1.00 0.00 1.00Margin at Earth degraded (dB) 50.30 49.30 4.45 3.45End-to-end link Margin Total (dB) 4.01 4.01 0.83 0.83Degradation (dB) 0.40 0.00 0.23 0.46Margin Total degraded (dB) 3.61 4.01 0.60 0.37Forward link Band 15/2 15/13Earth-to-DRS l
44、ink Margin at TDRS (dB) 35.04 35.04 23.63 23.63Degradation (dB) 0.00 1.00 0.00 1.00Margin at TDRS degraded (dB) 35.04 34.04 23.63 22.63DRS-to-user link Margin at user (dB) 3.90 3.90 3.50 3.50Degradation (dB) 0.40 0.00 0.40 0.00Margin at user degraded (dB) 3.50 3.90 3.10 3.50End-to-end link Margin Total (dB) 3.90 3.90 3.46 3.46Degradation (dB) 0.40 0.00 0.40 0.01Margin Total degraded (dB) 3.50 3.90 3.06 3.45
