1、Rec. ITU-R F.1095 1RECOMMENDATION ITU-R F.1095A PROCEDURE FOR DETERMINING COORDINATION AREA BETWEENRADIO-RELAY STATIONS OF THE FIXED SERVICE(Question ITU-R 129/9)(1994)Rec. ITU-R F.1095The ITU Radiocommunication Assembly,consideringa) that in some neighbouring countries the same frequency band may b
2、e shared by fixed radio-relay stations;b) that the accuracy of interference considerations should be as high as necessary;c) that not all of the data needed to be exchanged between concerned countries may be available;d) that the concept of coordination area would be useful in avoiding undue interfe
3、rence between fixed terrestrialstations;e) that some guidelines to determine such a coordination area would be useful;f) that some existing procedures to determine the coordination area for fixed terrestrial services may identifystations for which detailed interference studies may not be required,re
4、commends1. that with the agreement of administrations concerned: the procedure described in Annex 1 may be used as a guide to determine the frequency coordination areafor interference studies between stations of the fixed service; the maximum level of interference and the achievable accuracy of coor
5、dination distances referred to inAnnex 1 have to be assessed.ANNEX 1A procedure for determining coordination area betweenradio-relay stations of the fixed service1. IntroductionThis Annex describes a procedure for using the concept of coordination area for fixed radio-relay systems. Itpresents a met
6、hodology for determining the number of stations that need to be coordinated and the probability ofinterference that may exist between those stations.Because of the directivity of microwave antennas, a keyhole concept may be used for the development of acoordination distance analysis procedure. The k
7、eyhole concept takes into account the larger distance along the mainbeam (keyhole zone) of a microwave station, and the probability of interference over this region. It then follows that theregion outside the keyhole zone (the area off the main beam) requires shorter coordination distances as shown
8、in Fig. 1.The specific numerical figures for coordination distances for the keyhole zones and off-main-beam regions depend onthe types of antennas and the frequencies used.2 Rec. ITU-R F.1095Interfered-with station Keyhole distanceCoordination distance foroff-keyhole regionKeyhole regionFIGURE 1Basi
9、c concept for keyhole coordination distanceD01FIGURE 1/F.1095.D01 = 7 CM2. Calculating coordination distanceThe coordination distance can be obtained by solving the relation between the power of the interfering signalreceived by the victim station and the distance from the interfering station,I = PT
10、+ GR DR() L(d) + GT DT () (1)where:I : power at distance d originating from the interfering station (dBm)PT: the maximum transmitting power level (dBm) in the reference bandwidth at the input to the antenna ofthe interfering stationGT: gain (dBi) of the transmitting antenna of the interfering statio
11、nGR: gain (dBi) of the receiving antenna of the interfered-with stationDT: antenna discrimination (dB) of the transmitting antenna (at different angles )DR: antenna discrimination (dB) of the receiving antenna (at different angles )L(d) : total path loss (dB) for the Earths curvature, with K = 1.33.
12、As an example for intersystem radio-relay interference analysis, a C/I ratio of greater than or equal to 65 dBcan be assumed and expressed as follows:C I 65mmmmmmdB (2)where:C : nominal received desired signal power (dBm)I : maximum tolerable interfering power (dBm)C PT+ GR DR() L(d) + GT DT () + 65
13、 (3)The coordination distance d, at different angles can be calculated for different values of discriminationpattern DT () of the interfering station. For DT () = 0, equation (3) represents a situation where the interfering stationsare directed toward the proposed station. Coordination distance calc
14、ulated under this condition will specify a regionwithin which all interfering stations will be located. However, on some occasion, the conservative coordination distancemay include a large number of stations resulting in the coordination process being quite burdensome. Under thiscondition, the coord
15、ination region may be reduced with a certain probability of interference.Rec. ITU-R F.1095 33. Coordination distance versus reliabilityHere, the coordination distance can be obtained for = 1, which will include all interfering stations whosedirections toward the proposed station will make angle 1wit
16、h their main axes. However, the area specified bythese coordination distances for = 1does not include those stations whose directions toward the victim station makeangles less than 1. Thus there is a finite probability that the victim station will receive interference from a stationlocated outside t
17、he region specified by the coordination distances as shown in Fig. 2. = 0Coordination distanceExisting stations outside the regionand not considered for interferenceanalysisExisting stations inside the regionand considered for interferenceanalysisFIGURE 2Coordination of existing and proposed station
18、sD02 1 1FIGURE 2/F.1095.D02 = 14 CMUnder this condition, the probability of alignment of the existing station with the proposed station locatedoutside the region specified by the coordination distance will be as follows:P() = N1/ Nt(4)where N1is the number of existing stations located outside the re
19、gion whose antenna axes make angles less than 1withbeam direction towards the proposed station, and Nt is the total number of existing stations in the concerned area.The above probabilities for different angles can be calculated from a known database where station azimuthsare known. Here, N1can be o
20、btained by calculating the number of stations whose antenna axes lie within an angularwindow of width 2 1. If the window is rotated in small increments, for example 0.1, the number N1maxfor thatwindow size will give the maximum number of stations that can create interference caused by their alignmen
21、t with the4 Rec. ITU-R F.1095proposed station. Under the worst-case, all of these stations will be outside the region specified by the coordinationdistance obtained at = 1. Thus the probability of interference associated with the coordination distance can beexpressed as:Pi(i) = Nimax/ Nt(5)where i c
22、orresponds to the window of size i. For the worst possible case of antenna alignment, a homogeneousdistribution of the microwave stations, randomly oriented, is assumed. The probability of interference under thiscondition can be expressed as:Pi(i) = 1/ 180 (6)The reliability of the coordination dist
23、ance that represents the accuracy of the coordination procedure can bedefined as follows:Ri() = 1 Pi() (7)The distance along the main axis of the antenna can be considered to be the keyhole coordination distance.There may be several approaches to find the off-axis coordination distances. An example
24、indicating the use of theprocedure is given in Appendix 1.APPENDIX 1OF ANNEX 1The following example illustrates the relation between reliability and coordination distance. These calculationsare done for the 4 GHz band with a 150 m antenna height, using a database of about 2 000 stations. The off-axi
25、scoordination distances correspond to the first sidelobe peak of the antenna. Results are shown in Fig. 3.2001751501251001 0.927 0.839 0.750 0.661 0.572 0.483Key-hole distanceOff-axis distanceCoordination distance(km)Reliability of the coordination distanceFIGURE 3Coordination distances, 4 GHzD03FIGURE 3/F.1095.D03 = 11 CM_
