1、 Recommendation ITU-R S.2029(12/2012)Statistical methodology to assess time-varying interference produced by a geostationary fixed-satellite service network of earth stations operating with MF-TDMA schemes to geostationaryfixed-satellite service networksS SeriesFixed-satellite servicesii Rec. ITU-R
2、S.2029 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use 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
3、Recommendations are adopted. The regulatory and policy functions of the Radiocommunication Sector are performed by World and Regional Radiocommunication Conferences and Radiocommunication Assemblies supported by Study Groups. Policy on Intellectual Property Right (IPR) ITU-R policy on IPR is describ
4、ed 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 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 o
5、f the Common Patent Policy for ITU-T/ITU-R/ISO/IEC and the ITU-R patent information database can also be found. Series of ITU-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 t
6、elevision BS Broadcasting service (sound) BT Broadcasting service (television) F Fixed service M Mobile, radiodetermination, 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
7、Frequency sharing and coordination between fixed-satellite and fixed service systems SM Spectrum management SNG Satellite news 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 det
8、ailed in Resolution ITU-R 1. Electronic Publication Geneva, 2012 ITU 2012 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without written permission of ITU. Rec. ITU-R S.2029 1 RECOMMENDATION ITU-R S.2029 Statistical methodology to assess time-varying int
9、erference produced by a geostationary fixed-satellite service network of earth stations operating with MF-TDMA schemes to geostationary fixed-satellite service networks (Question ITU-R 208/4) (2012) Scope This Recommendation provides a statistical methodology to assess time-varying interference resu
10、lting from a geostationary network of earth stations, operating with MF-TDMA schemes, over a geostationary-satellite orbit fixed-satellite service network. The methodology considers the potential interference to another GSO FSS network. Furthermore, the methodology can be used to adjust the power le
11、vels of the interfering terminals such that the performance objectives of the interfered-with satellite network are not impacted. The ITU Radiocommunication Assembly, considering a) that FSS GSO satellites are well suited to provide broadband communication applications including Internet and data se
12、rvices; b) that satellite networks use a variety of network topologies and multiple access schemes, including the multi-frequency time division multiple access (MF-TDMA) scheme; c) that through the use of efficient modulation and coding, higher satellite e.i.r.p. levels, and other techniques, some n
13、etworks can support full mesh (point-to-point) connectivity with small aperture terminals; d) that it is necessary to protect networks of the FSS from any potential interference from these terminals; e) that it would be useful to have methodologies to assess the time-varying interference from a GSO
14、FSS network to another GSO FSS network; f) that it would be useful to have methodologies for assessing interference levels to satellite networks resulting from earth stations operating with MF-TDMA schemes; g) that many of the technical characteristics of these networks which affect performance and
15、orbit spectrum/utilization have time-varying characteristics which are best modelled by stochastic processes, noting a) that maximum permissible levels of inter-network interference from GSO networks to GSO/FSS networks operating in the same frequency band are provided in Recommendation ITU-R S.1323
16、; b) that maximum permissible levels of inter-network interference and the methodology for determining this interference, from non-GSO systems and to GSO/FSS networks operating in the same frequency band are provided in Recommendation ITU-R S.1323; c) that time invariant interference is typically es
17、timated using the T /T method, described in Recommendation ITU-R S.738; 2 Rec. ITU-R S.2029 d) that methodologies to estimate the off-axis e.i.r.p. density levels and to assess the time-varying interference towards adjacent satellites resulting from pointing errors of a vehicle mounted earth station
18、 are provided in Recommendation ITU-R S.1857, recommends 1 that the methodology given in the Annex should be used to assess the time-varying interference due to multiple earth stations operating in a MF-TDMA scheme; 2 that the methodology provided should be used to determine the off-axis emission le
19、vels of the interfering earth stations such that these satisfy the performance objectives of the interfered-with satellite network; 3 that the methodology provided should be used so that the type of MF-TDMA networks described in this Recommendation would not create interference to other FSS networks
20、 operating in the same frequency bands beyond the level accepted by administrations; 4 that the following Notes should be regarded as part of this Recommendation. NOTE 1 The methodology given in the Annex provides a statistical approach to assess the potential interference impacts of an MF-TDMA netw
21、ork to a neighbouring co-frequency GSO FSS network. NOTE 2 The parameters and the examples provided in the Annex represent a hypothetical system that operates in the 20/30 GHz frequency band. However, the methodology may also be used for other frequency bands after appropriate modifications of some
22、parameters. NOTE 3 The methodology of this Recommendation does not apply to networks operating with code division multiple access (CDMA) schemes. NOTE 4 To verify that the mathematical model described in the methodology truly represents the time-varying characteristics of an MF-TDMA network, it may
23、be useful to obtain the statistical characteristics of operational networks. NOTE 5 The apportionment of short-term interference for the MF-TDMA GSO/FSS networks considered in this Recommendation may be mutually agreed through the process of coordination. NOTE 6 The time allowance and the short-term
24、 interference criteria for GSO/FSS networks may be a subject for further study. Annex Statistical methodology to assess time-varying interference produced by a geostationary fixed-satellite service network of earth stations operating with MF-TDMA schemes to geostationary fixed-satellite service netw
25、orks 1 Introduction In recent years, the demand for satellite-based two-way Internet services has increased significantly. These services, especially for residential and small business users, are provided using small aperture satellite terminals. Typically, a single satellite network may consist of
26、a large number of small aperture terminals deployed over a wide geographical area. According to the location within the Rec. ITU-R S.2029 3 satellite footprint, the varying weather conditions, and the users data rates, these terminals may operate on a range of aperture sizes and may require differen
27、t transmit power levels. To utilize network resources efficiently, these networks may employ time- and frequency-division multiple access methods. A particular characteristic of small aperture terminals is that they have large antenna beamwidths and hence may produce uplink interference towards adja
28、cent satellites if the transmit power levels are not adjusted properly. Additionally, some small terminals mounted on air/sea vessels, trains, or ground vehicles as well as stationary terminals may produce antenna pointing errors which may result in potential interference that must be mitigated. The
29、se combined effects contribute to a time-varying interference pattern from the network of terminals to a victim receiver in another satellite network. This Annex presents a statistical approach to determine the interference to a GSO network from another GSO network consisting of multiple terminals o
30、perating using a time-division multiple access scheme and antenna pointing errors. The Annex discusses a long-term interference criterion and criteria to satisfy the short-term performance objectives, it provides some examples to illustrate the impacts on the neighbouring satellite network, and it p
31、resents a step-by-step approach on how to compute the resulting interference. The methodology presented may be useful to determine the off-axis emission levels of the interfering terminals such that these satisfy the short-term and long-term performance objectives of the victim satellite system. 2 L
32、ong- and short-term components of interference The interference signal at the victim receiver consists of signals that belong to a large number of transmit terminals from a single interfering network that operate using a time-division multiple access protocol. The terminals may employ antenna apertu
33、res of different sizes and may transmit at different power levels depending on their location within the footprint of the satellite beam. Additionally, these terminals may have small antenna pointing errors. Therefore, when the observation interval is sufficiently large to contain transmissions from
34、 several interfering terminals, the interference level at the victim receiver is time-varying. In such cases, for illustrative purposes, the interference signal at the victim receiver, nullnullnullnull, may be expressed as the sum of a long-term interference component, nullnullnullnullnull, and a sh
35、ort-term interference component, nullnullnullnullnullnull, so that nullnullnullnull=nullnullnullnullnull+nullnullnullnullnullnull.The long-term interference component is constant over short time intervals but it may exhibit small variations when observed over long time intervals (of the order of sev
36、eral minutes). These variations are statistical in nature resulting from the slow changing characteristics of the transmit signals. On the other hand, the short-term interference component is due to the transmissions from different terminal types and may vary over very short time intervals, for exam
37、ple over fractions of a second. Note that this short-term and long-term interference components are used only for illustrative purposes; interference analysis is carried out for the total interference. Figure 1 shows the interference levels at the victim receiver due to transmissions from Terminals
38、T1, T2, T3, T4and T5. In general, as shown in this figure, the interference levels and the transmission durations depend on the particular terminal. The long-term component shown here represents the average level of the interference and the short-term interference component is given by the differenc
39、e between the total interference and this long-term interference component. To quantify and limit the effects of interference, this Annex gives methods for assessing and limiting the long-term interference, short-term interference, and total interference. Specifically, long-term interference and the
40、 criteria to satisfy the short-term performance objectives are given to limit the effects of interference at the victim receiver. 4 Rec. ITU-R S.2029 FIGURE 1 Interference observed at the victim receiver due to time-division multiple access transmissions from Terminals T1, T2, T3, T4and T5S.2029-01I
41、nterference signal at victim receiverI totalinterferencetotT1T2T3T2T4 T5T1I long-termcomponentlongTime3 Long-term interference criterion Assessment of time invariant interference is typically carried out using the T/T method, for example as described in Recommendation ITU-R S.738. In order to make u
42、se of a similar approach consider the hypothetical situation when the interference level at the victim receiver is not time-varying: that is the e.i.r.p. density levels at the terminals are adjusted so that the interference level seen at the victim receiver is given by long-term interference level,
43、nullnullnullnullnull. Also, in this case the terminals do not produce antenna pointing errors. The long-term interference criterion in this case is expressed in terms of the T/T ratio as: svvvlonglongkITT+= /(1) where nullnullnullnullnullnullis defined as the ensemble-averaged interference power spe
44、ctral density computed in a bandwidth of nullnullnullnullnull, k is the Boltzmann constant, nullis the victim receiver noise temperature referred to the output of its antenna, nullnullis the noise temperature at the receiver of the victim satellite referred to the output of its antenna, and nullis t
45、he transmission gain from the output of the victim satellites input antenna to the output of the victim receivers antenna. Clearly, when the ensemble-averaged power of the interference is a constant, the interference power-to-noise ratio considered in this hypothetical case is time invariant. Howeve
46、r, in practice, rather than the ensemble-average value the time-averaged value of the long-term interference component is generally available. This time average value may exhibit small variations when computed over different time intervals. This time-averaged value, nullnullnullnullnullnull, when co
47、mputed over the long-term time interval of duration nullnullnullnullnullmay exhibit variations because the underlying interference is a statistical process. Additionally, statistical characteristics of the terminals may change during this interval resulting in small variations about this average val
48、ue. These variations can be limited by imposing constraints on the cumulative distribution function (CDF) of the variable ()longTT / as follows: PrTTlong X%0 dB for 0.005% of any month; Rec. ITU-R S.2029 5 (I / N) 2.4 dB for 0.03% of any month; (I / N) 10 dB for 20% of any month; and (I / N) 12 dB f
49、or 100% of any month. 4 Criteria to satisfy short-term performance objectives In the preceding section, limits were imposed on the long-term interference. In this section, a criterion is presented to limit the total interference so that it meets the short-term performance objectives of the victim receiver. The total interference may exhibit variations over a few milliseconds. According to Recommendation ITU-R S.1323-2, victim links should contain sufficient link margins to overcome degradations due to the combined effects of propagat
