ACP WGF11/WP3
AERONAUTICAL COMMUNICATIONS PANEL (ACP)
20-27 February 2004
Nairobi, Kenya
Agenda Item3: Results of ITU-R study Working Parties 8/B, 8/D and Study group 1
OUTPUTS FROM THE 15TH MEETING OF ITU-R WORKING PARTY 8D
FOR ACTION BY ACP WGF
(Presented by the Secretary)
The present paper reviews outputs of interest to civil aviation from the 15th meeting of ITU-R Working Party 8D (Geneva, 25 November – 3 December 2003. Proposals for action by WGF are provided. Excerpts of the WP8D meeting report are provided in attachment. The full report is available at:
1.Response to Liaison Statement from working party 1B (Criteria for the evaluation of interference between radiocommunication networks operating in a shared frequency band)
(WP8D15 Report, Annex 10, Sect.8)(see Attachment 1 to this WP)
WP1B had sent a proposal on the use of a single criterion "relative energy margin loss" (REML) to characterize the impact of interference on a radiocommunication network. WP8D agreed to investigate the applicability of the criterion to MSS and RNSS systems at the next meeting (September 2004). The WP1B PDNR containing the proposed definition of REML is also attached.
******WGF ACTION: to comment and assess need for ICAO input/action
2. Preliminary draft revision to Recommendation ITU-R M.1642
(WP8D15 Report, Annex 3) (not attached)
Recommendation ITU-R M.1642 provides a methodology for assessing the maximum aggregate epfd at an ARNS station from all RNSS systems operating in the1164-1215MHz band. However, the methodology provided in the original version only includes a means of assessing the epfd fromRNSS systems using GSO and circular non-GSO orbits. This deficiency of M.1642 is indicated by footnote 1 to recommends 1 and is resolved by a PDRR of ITU-R M.1642 that extends the applicability of the epfd simulation methodology in Annex 1 to elliptical orbits. It was noted that definition of highly-elliptical orbits is currently being discussed in ITU-R and the results of these discussions might have some consequences on the use of the term elliptical in this PDRR. The notation used to define non-GSO RNSS orbits was also improved by this PDRR which is Annex 3 to this meeting report. The update is not expected to have any impact on aeronautical systems. It addresses the calculations required for elliptical and highly-elliptical orbit constellations.
******WGF ACTION: to note
3.Draft new question on RNSS
(SG8 Document 8/19) (see Attachment 2 to this WP)
New ITU-R question addressingthe technical and operational characteristics of RNSS systems to be used in possible sharing and compatibility studies with other services or systems. Proposed by France/CEPT, with the stated intent to bring Galileo data into ITU-R Recommendations. This draft new Question was adopted by Study Group 8, category S1. Approval by consultation is applicable to this new Question.
******WGF ACTION: to comment and assess need for ICAO input/action
4.Liaison statement to the chairman of ITU-R Study Group 4 and ITU-R WORKING PARTIES 4A AND 4B on Resolution 415
(WP8D15 Report, Annex 10, Sect.11)(see Attachment 3 to this WP)
This liaison statement brings the topics of Res.415 (Satellite frequency allocations that could support the modernization of civil aviation - see WRC-2007 AI 1.6) to WP4A and 4B, on the grounds that Res. 415 addresses satellite communications in general (not just mobile-satellite) and therefore should be considered also by the fixed-satellite groups in SG4. This decision appears legitimate but increases considerably the burden on aviation to support ITU-R work on this item. The next meetings of WP4A and 4B will be in April 2004. The liaison statement recognizes that: "To date, Working Party 8D has received no contributions under Resolution 415 pertaining to the MSS, so the direction of studies within Working Party 8D, remains to be determined". Nevertheless, itattempts to provide guidelines to WP4A and 4B on subjects that could be explored pursuant to this Resolution, as follows:
"1)Identification of the fundamental technical characteristics and operational requirements of civil aviation telecommunication systems.
2)The extent to which the requirements of these systems can be accommodated on existing or planned FSS and MSS communication systems.
3)Whether any existing MSS and FSS allocations could be used to meet aeronautical requirements to support the modernization of civil aviation telecommunication systems in conjunction with existing telecommunication systems."
WP8D was informed that ICAO did not have any inputs to offer at this time on the appropriate direction that should be followed, but would consider the issue again at the next WGF meeting (Nairobi). The ICAO representative also pointed some potential difficulties with the proposed guidelines and expressed general concerns with regard to attempts to bring safety communications into existing MSS and FSS allocations without due regard to the suitability of the allocation for safety use. The summary of the discussion that led to the development of this statement stresses that "the Resolution, by its language, directed study of the extent, if any, to which current satellite frequency allocations could be used to meet aeronautical requirements to support the modernization of civil aviation telecommunication systems, and that the Resolution specifically did not contemplate the making of any new allocations in satellite frequency bands or of any changes to current satellite frequency allocations." (emphasis added).
******WGF ACTION: to develop inputs for WP4A/B and WP8D to provide guidance to ITU-R based on the draft ICAO position on Res. 415 as developed in Nairobi
5.Establishment of correspondence group on UWB issues within WP8D
(WP8D15 Report Sect. 2.3 (1) and Annex 10, Sect. 15) (see Attachment 4 to this WP)
WP8D agreed to create a new correspondence group concerning the protection criteria for MSS and RNSS from UWB devices. The objective of this correspondence group is to support the liaison activities with TG1/8 that is studying the issues of UWB devices mainly for sharing and compatibility analysis. The mandate of this correspondence group consists of collection of relevant information, in particular on protection criteria of MSS so that WP 8D is well prepared to provide timely response to TG 1/8 as follows.Chaired by Dr Putcha, Inmarsat. Work to be completed by the next meeting of WP8D (September 2004). In the meantime, WP8D sent a provisional reply to TG 1/8. An I/N criterion of -20 dB is offered as appropriate for GSO MSS systems in L-band. However, L-band AMS(R)S systems and other MSS are excluded, together with RNSS,because WP8D is not ina position to give an I/N critierion for those systems (to be addressed by the correspondence group). The issue of aggregate interference vs single entry is mentioned.
******WGF ACTION: to develop inputs on protection of ICAO AMS(R)S and RNSS systems to be submitted to the correspondence group (or directly to WP8D)
7.Consideration on possible revision of recommendation ITU-R M.1480
(WP8D15 Report, Annexes 1 and 2 to Annex 9)
The revision addresses interference from GSO MSS (eg Inmarsat) out-of-band emissions into the Iridium band. Very controversial (work ongoing since 2000 without reaching a conclusion).
******WGF ACTION: to note.
8.Preliminary Draft Report on determination of feasibility and practicability of prioritization and real-time pre-emptive access between different networks of MSS in the bands1 525-1 559 MHz and 1 626.5-1 660.5 MHz.
(WP8D15 Report, Annex 5) (see Attachments 5 and 6 to this WP)
Developed by Mr Suzuki's drafting group “but not fully discussed nor agreed”.
******WGF ACTION: to review and propose inputs for next meeting of WP8D
Attachment 1 (WP8D15 Report, Annex 10, Sect.8)
Response to the liaison statement from Working Party 1B – Criteria for the evaluation of interference between radiocommunication networks operating in ashared frequency band
Source:Document 8D/TEMP/11
Contact: / Mr. A. KlyucharevE-mail:
Status: / For information
Working Party 8D took note of the liaison statement from WP1B (Doc. 8D/20) at the 15th meeting concerning the use of a single index “relative energy margin loss” (REML) to characterize the harmful effect on a radiocommunication network caused by interference from other links, networks or radiocommunication systems working in a shared frequency band.
WP 8D recognized that the subject is relevant to Questions ITU-R 83-4/8, ITU-R 1101/8,
ITU-R 2011/8, ITU-R 2112/8 and ITU-R 217/8, and agreed to investigate the applicability of the PDNR to mobile-satellite services and radionavigation satellite service at the next WP 8D meeting to be scheduled in September 2004.
A response from WP 8D will be provided before the next meeting of WP 1B in October 2004.
(ICAO Secretary note: The definition of REML is given in the WP1B PDNR below)
Working Party 1B
(WG1B-2)
Preliminary draft new recommendation itur sm.[...]
Interference cCriteria for the evaluation of harmful effect of interference between radiocommunication networks operating in a shared frequency band
(Question ITU-R 209/1)
The ITU Radiocommunication Assembly,
considering
a)that development of radiocommunication facilities could causes increase in mutual interference between radiocommunication networks working in the same frequency band;
b)that setting maximum acceptable emission parameters determining the value of interference caused to other radiocommunication networks is one of the most important ITU-R tasks;
c)that the interests of the parties causing interference and affected by interference are opposite and therefore acceptable emission limits are a result of compromise;
d)that the ITU goal is to provide a harmonious access to spectrum distribution among all networks and radio by communication services on an equitable basis;
e)that, to evaluate the harmful effect of interference, in ITU practice various indices have been used which are related to the signal quality at the communication channel output, channel availability, increase in the receiving link noise, etc., which makes such evaluations incomparable;
f)that, for these reasons, it would be suitable to use, in all cases, the same unified criteria for of evaluation harmful effect of interference on affected link or network performance,
recommends
1that, when evaluating and comparing the harmful effect of interference caused by another network or radiocommunication system operating in a shared band, such an interference criteria as the relative energy margin loss (REML) in the affected communication link be used:.It characterizes relative value of a transmitter power which should be added to the power of the transmitter to restore protection of receiving signal against noise which existed before appearance of the harmful interference under consideration, as it is given by formulas:
REML(dB) = 10 log [(С/N)/(С/(N+I))] = 10 log (1+I/N) = 10 log (1+ Т/T),
where:
Cis the carrier power at the input of the affected link terminal
Nis the power of the thermal noise referred to the terminal input
Iis the power of the interference referred to the same point
Tis the equivalent noise temperature of the affected link
Тis the change in this temperature.
The criteria characterizes relative value of a transmitter power which should be added to the power of the transmitter to preserve protection of receiving signal against noise which existed before appearance of the harmful interference under consideration;
2that in the event when the value of interference is time-variant and different for various implementations of mutually affecting networks (for example, when it depends on the location of networks on the Earth’s surface or in the space), it is necessary to determine not only the maximum value of decrease in capacity, but also the probability of its occurrence, and the value of REML averaged over time and the set of realizations;
3that the REML value should be calculated for the approved reference interacting circuits with the parameters (a set of parameters)typical for these networks.
***
Temporary eExplanatory notes[*]
The development of radiocommunication facilities results in an increase in mutual interference between networks operating in a shared frequency band. Setting the limits of acceptable emission causing interference to other networks or radiocommunication links (in the same or different radiocommunication service) is one of the crucial and most difficult tasks of the International Telecommunication Union. Its difficulty is conditioned by the fact that the interests of the mutually affecting networks are contradictory since an increase in the acceptable interference limit lowers the affected network capacity but makes it possible to increase either the capacity of networks causing the interference or the number of such networks. Therefore acceptable emission limits are always a result of a compromise.
When working out such a compromise, various indices are used which characterize the harmful effect of interference on the network operation and are related to the signal quality at the channel output, the channel’s or network’s availability, an increase in the receiving link noise, etc. As a rule, the value of the interference and its harmful effect are estimated for the worst combination of conditions, disregarding the probability of such a situation. The values of such parameters are often incomparable since they depend on the used signals, methods of transmission and reception, and link or network configuration.
In view of the above, it seems expedient to recommend using a single interference criteria characterizing the harmful effect caused by interference from other links, networks, and radiocommunication systems working in a shared frequency band. It is suggested that the relative energy margin loss (REML) in the communication link affected by the interference be used as this interference criteria. It characterizes relative value of transmitter power which should be added to the power of the transmitter to restore preserve protection of receiving signal against noise which existed before appearance of the harmful interference under consideration, as it is given by formulas:
REML(dB) = 10 log [(С/N)/(С/(N+I))] = 10 log (1 + I/N), (1)
where:
Cis the carrier power at the input of the affected link terminal
Nis the power of the thermal noise referred to the terminal input
Iis the power of the interference referred to the same point.
To compensate for the effect of interference of a constant value, it would be necessary to increase the carrier power by С determined from an evident condition:
(С + С)/(N + I) = С/N,(2)
from which it follows that С/С=I/N, and
REML = 10 log (1 +С/С).(3)
It should be noted that the suggested interference criteria coincides with one of the indices offered for the fixed service in Recommendation ITU-R F.1108 [1] – fade margin loss (FML).
This proposal is based on the idea that the value of interference is acceptable for an affected communication link or network as long as this link is within the power budget. If the interference worsens the link power budget to such an extent that the quality standards established for links of this type are violated (for a digital link such standards are based on error rate and/or unavailability period), it becomes necessary to increase the ratio of signal to aggregate noise in the link. In all cases, the acceptability of an interference of a certain value or costs of its compensation depend on the change in the link power budget caused by the interference.
An important advantage of the suggested interference criteria (unlike error rate, unavailability time or fractional degradation of performance) is that it does not depend on the method of transmission and reception used in the link.
The parameter Т/Т, which is often used for interference estimate, is directly related to the ML value:
REML = 10 log (1+Т/Т).(4)
The calculation of ML should be performed for approved reference circuits of both interacting networks with their typical parameters (or a set of parameters with a subsequent evaluation of the maximum and averaged results). Hypothetical reference circuits have already been defined by ITUR recommendations for many systems (see, for example, Recommendations ITU-R F.391, F.392, F.396, F.556, S.352, S.521), however, typical parameter values of such networks required for calculating mutual interference, should be additionally approved.
In case when the value of interference varies with time or differs for various implementations of mutually affecting networks (for example, depending on the location of stations on the Earth’s surface or in the space), it is necessary to determine not only the maximum value of the capacity reduction but also the probability of its occurrence and to calculate the REML value averaged over time and the set of realizations.
Let us consider an example of using this interference criteria. Document4A/501 [2] shows that nine high elliptical orbit (HEO) satellites of the MOLINIYA type in the fixed-satellite service (FSS) (18active satellites each of them causing the maximum power flux-density at the Earth’s surface allowed for geostationary satellites) cause an interference to a typical fixed service (FS) station whose maximum value Im exceeds the station’s thermal noises tenfold, i.e. Im/N = 10 dB (with the satellite directly in the FS station antenna beam and the worst station’s location).
In connection with the WRC-03 decision to lower by 10 dB the pfd limit permissible for FSS-HEO, Im/N will be 0 dB. In this case the FDP factor is used for the evaluation of interference caused to the FS links will be equal to FDP = Im/N = 100%, and for the FS link with a diversity reception and maximum signal power combining [1].
DFDP=2 Im/N + 1.5 (Im/N)2 = 350%,(5)
which seems highly significant.
A corresponding energy margin loss at this section of the FS link is:
ML = 10 log (1 + Im/N) = 3 dB.
Then, in accordance with the methodology suggested herein, the probability of this event should be taken into account; this probability is defined in [2] and equals 0.00186. It should be also taken into consideration that the interference caused by a moving HEO satellite is time variant and its average value [2] IAV = 0.133 Im .
In this case:
FDP = 13.3%,DFDP=(1/T) [(2 I(t)/N + 1.5(I(t)/N)2]dt = 55%,(6)
which still seems significant but the corresponding energy margin loss is:
REML = 10 log (1 + IAV/N) = 0.54 dB.
Such an energy loss can be easily compensated or allowed at one of the hops of the FS link, or can be easily compensated by a uniform increase in the power budget at all hops of a 50-hop FS link by the value of 13.3%/50 = 0.27% or 0.01 dB (since only one station of the link can be affected by the maximum interference).
Noteworthy is that if not the maximum value but the time and station location average value of the interference is determined, the indices for one station and for the FS link as a whole will not differ significantly [3].
Another example of using the suggested interference criteria can be given:
When evaluating acceptable interference caused by FSS-HEO satellites to FS links, the documents drawn up by Working Party 4-9S, which was responsible for the preparation of this agenda item for WRC03, the interference acceptability limit was considered to be the value of DFDP = 10%, i.e.0.1. According to formulas (5, 6), this value of DFDP corresponds to IAV/N = 0.05, and, therefore: