1、 Recommendation ITU-R M.1474-1(01/2010)Methodology to evaluate the impact of interference from time division multiple access/frequency division multiple access (TDMA/FDMA) mobile-satellite service (MSS) systems on baseband performance in digital line-of-sight fixed service receivers based on statist
2、ics of radio-frequency interference in the frequency range 1-3 GHzM SeriesMobile, radiodetermination, amateurand related satellite servicesii Rec. ITU-R M.1474-1 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use of the radio-frequen
3、cy 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 Regional Radiocommun
4、ication 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 submission of patent
5、 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 ITU-R Recommendations (
6、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, amateur and related
7、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 news gathering TF Time
8、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, 2010 ITU 2010 All rights reserved. No part of this publication may be reproduced, by
9、any means whatsoever, without written permission of ITU. Rec. ITU-R M.1474-1 1 RECOMMENDATION ITU-R M.1474-1*Methodology to evaluate the impact of interference from time division multiple access/frequency division multiple access (TDMA/FDMA) mobile-satellite service (MSS) systems on baseband perform
10、ance in digital line-of-sight fixed service receivers based on statistics of radio-frequency interference in the frequency range 1-3 GHz (Questions ITU-R 201/4 and ITU-R 118/5) (2000-2010) Scope This Recommendation provides a methodology to assess the impact of interference from TDMA/FDMA mobile-sat
11、ellite service (MSS) space-to-Earth and Earth-to-space transmissions on the performance of digital line-of-sight (LoS) fixed service (FS) receivers in the frequency range 1-3 GHz. This methodology may also be used in detailed MSS/FS coordination. The ITU Radiocommunication Assembly, considering a) t
12、hat the frequency band 1 518-1 525 MHz is allocated to the MSS (space-to-Earth) and the fixed service (FS) on a co-primary basis in all Regions; b) that the frequency bands 1 525-1 559 MHz and 1 626.5-1 660.5 MHz are also allocated to the MSS (space-to-Earth and Earth-to-space, respectively) on a pr
13、imary basis in all Regions; c) that the frequency band 1 525-1 530 MHz is also allocated to the fixed service on a primary basis in Regions 1 and 3, and the frequency bands 1 550-1 559 MHz, 1 626.5-1 645.5 MHz and 1 646.5-1 660 MHz are also allocated to the fixed service on a primary basis in some c
14、ountries; d) that the frequency band 1 668.4-1 675 MHz is allocated to MSS (Earth-to-space) and fixed service on a co-primary basis in all Regions; e) that the frequency bands 1 980-2 010 MHz and 2 170-2 200 MHz in all Regions, 2 010-2 025 MHz and 2 160-2 170 MHz in Region 2 are allocated to the MSS
15、 (Earth-to-space and space-to-Earth) and the fixed service on a co-primary basis; f) that transmissions from mobile satellites could cause interference to line-of-sight (LoS) fixed service receivers operating in these bands; g) that transmissions from mobile satellites and associated mobile earth st
16、ations (MESs) could cause interference to LoS fixed service receivers operating in these bands; h) that such interference involves time-varying phenomena such as interference geometry, propagation conditions and MSS traffic; j) that simulation usually is the only way to accurately evaluate such inte
17、rference; k) that the output of such simulations is typically in the form of C/I, C/N and C/(N + I ) statistics; *This is a joint Radiocommunication Study Groups 4 and 5 Recommendation, and any revision shall be undertaken jointly. 2 Rec. ITU-R M.1474-1 l) that the impact of such interference often
18、can be assessed by studying RF statistics only; m) that, in critical cases, there is a need to evaluate the interference impact on fixed service baseband performance objectives, recommends 1 that the methodology in Annex 1 should be used as guidance in detailed bilateral coordination for initial ass
19、essment of the impact of interference from TDMA/FDMA MSS satellites and associated MESs, operating in the 1-3 GHz MSS allocations, on baseband performance in digital LoS fixed service receivers based on statistics of RF interference. NOTE 1 The methodologies in Annex 1 are considered as provisional.
20、 Administrations are invited to contribute to this annex with a view to further developing these methodologies. Annex 1 1 Introduction Sharing between MSS and fixed service involves time-varying phenomena such as interference geometry, propagation conditions, etc. Simulation is usually the only way
21、to accurately evaluate interference between MSS and fixed service systems. The output of such simulations is typically in the form of RF C/I, C/N and C/(N + I ) statistics presented usually as a cumulative distribution function. Recommendation ITU-R M.1319 provides a methodology whereby inter alia B
22、ER objectives for digital FS systems can be translated into equivalent RF C/(N + I ) requirements for an associated percentage of time. These equivalent RF performance objectives are plotted on the cumulative distribution plots of C/(N + I ) in order to determine if the interference from MSS satelli
23、tes is acceptable. The method described in Recommendation ITU-R M.1319 although it requires extensive computer simulation is relatively straightforward to implement in software, since all calculations and comparisons are undertaken in the RF domain. The methodology of Recommendation ITU-R M.1319 sho
24、uld be used in the detailed coordination phase between administrations, when coordination is formally required and triggered in application of Article 9 of the Radio Regulations (RR) and RR Appendix 5, in order to determine if interference is acceptable or not considered in the context of actual fix
25、ed service system information and the relevant ITU-R performance and availability objectives. In some cases during the bilateral coordination phase, it may be necessary for the parties concerned to further examine the impact of MSS interference on the performance objectives of digital fixed service
26、systems. This could be the case where the results of the simulation method described in Recommendation ITU-R M.1319 above are not sufficiently definitive to enable conclusion of frequency coordination. The objective of this annex is to present methodologies to convert RF C/(N + I ) statistics into b
27、aseband performance measures for digital fixed service carriers. Rec. ITU-R M.1474-1 3 2 Conversion of C/(N + I ) into BER A C/(N + I ) value can be converted into an equivalent symbol error ratio (SER) using the equations or curves given in Recommendation ITU-R SF.766. For example, for a M-PSK modu
28、lated carrier: =MMSERbsin)(logerfc2(1) where: b= Eb/(N0+ I0) = C/(N + I )(B/R ) (numerical ratio) B: noise bandwidth of the fixed service receiver R: bit rate M: number of states. The SER can then be converted to BER assuming that BER = SER/log2(M ). 3 Other performance objectives Other common digit
29、al fixed service performance objectives (besides BER) are: unavailability; errored second ratio (ESR); severely errored second ratio (SESR); background block error ratio (BBER). Accurate assessment of these measures requires continuous monitoring of the fixed service system performance. In a simulat
30、ion this would mean that ideally the time interval should be very small, say of the order of milliseconds. This may not be practicable in a computer program simulating interference from a non-GSO MSS system into fixed service receivers, due to the necessity of also modelling the longer term variatio
31、ns, since the run time could be prohibitive. For these reasons it is proposed that the above performance measures be evaluated based on an averaging approach, i.e. BER is assumed to be constant between time samples. Furthermore it is assumed that the bit errors are uniformly spread over time. Such a
32、n approach will generally give conservative estimates, since the bit errors will be spread across a maximum number of blocks (for definition of a block see 3.2); a greater variation in the clustering of bit errors would result in fewer blocks being affected (assuming that the total number of bit err
33、ors is given). The following sections describe methods that can be used for this evaluation. 3.1 Unavailability Recommendation ITU-R F.557 defines unavailability for digital fixed service links: “The period of unavailable time begins at the onset of ten consecutive severely errored second (SES) even
34、ts, in at least one direction of transmission. These ten seconds are considered to be unavailable time. For the definition of SES refer to related ITU-T Recommendations G.821 and G.826. A new period of available time begins at the onset of ten consecutive non-SES events for both directions of transm
35、ission. These ten seconds are considered to be available time. For the definition of SES refer to related ITU-T Recommendations G.821 and G.826”. 4 Rec. ITU-R M.1474-1 Since it is assumed that the only available information is the probability density function of C/(N + I ), a simplified approach has
36、 to be used here. The unavailability will therefore be estimated as the percentage of time that the BER exceeds, 1 103. The unavailable time TU(s) is then: =xaiisUpdfNT (2) where: Ns: total simulation time in (s) pdfi: calculated probability density function of C/(N + I ) a: smallest C/(N + I ) valu
37、e represented in the distribution x: C/(N + I ) value corresponding to BER = 1 103. The unavailability in per cent is thus 100 TU/Ns. 3.2 Errored seconds ITU-T Recommendation G.826 defines an errored second (ES) as “a one-second period with one or more errored blocks or at least one defect”. An erro
38、red block is defined as a block with one or more bits in error. Only available time should be considered in the calculation of ESR: UsTNESESR= (3) where ES is the number of errored seconds during available time. The number of errored seconds during available time can be calculated as: =bxisisiBlockE
39、pdfNES )(,1min (4) where: b: highest C/(N + I ) value represented in the distribution BlockEs(i ): average number of block errors per second for C/(N + I ) = i Note that if the average number of block errors per second is greater than 1, all seconds with C/(N + I ) = i are considered to be errored )
40、(,1min)(/iBENiBlockEBlocksBlockss= (5) where: NBlocks/s: number of blocks per second BEBlock(i ): average number of bit errors per block for C/(N + I ) = i. Similarly to above, if the average number of bit errors in a block is greater than 1, all blocks for C/(N + I ) = i are considered to be errore
41、d blockBiBlockNBERiBE/)( = (6) where: BERi: BER corresponding to C/(N + I ) = i NB/block: number of bits per block. Rec. ITU-R M.1474-1 5 3.3 SESs ITU-T Recommendation G.826 defines an SES as “a one-second period which contains 30% errored blocks or at least one defect”. In the following, the concep
42、t of defect has been ignored. Only available time should be considered in the calculation of SESR. UsTNSESSESR= (7) where: SES: number of SESs during available time: =bxiiisCHECKpdfNSES 1 (8) where: CHECK1i= 1 if BlockEs(i ) 0.3 NBlocks/s, else CHECK1i= 0. 3.4 Background block error (BBE) ITU-T Reco
43、mmendation G.826 defines a BBE as “an errored block not occurring as part of an SES”. UsTNBBEBBER= (9) where: BBE : number of block errors occurring during available time: iBlockbxiisBlocksCHECKiBEpdfNNBBE 2)(,1min/ = (10) where: CHECK2i= 1 if BlockEs(i ) 0.3 NBlocks/s, else CHECK2i= 0. 4 Conclusion
44、 This annex has presented equations that can be used to derive estimates of the impact of interference on baseband performance for digital fixed service systems based on RF C/(N + I ) statistics. The methods are based on an averaging approach, which will give conservative estimates, since the bit er
45、rors will be spread across a maximum number of blocks; a greater variation in the clustering of bit errors would result in fewer blocks being affected (assuming that the total number of bit errors is given). The methods given in this annex should be used only in critical cases, when examination of the RF interference statistics does not provide sufficiently definite results to enable conclusion of the frequency coordination.
