1、. m 2326434 0006865 3 m TR25-03 Page E 1 Recommendation TIR 25-03 (Stockholm 1976) CO-ORDINATION OF FREQUENCIES FOR THE LAND MOBILE SERVICE IN THE 80,160 AND 460 MHZ BANDS AND THE METHODS TO BE USED FOR ASSESSING INTERFERENCE Recommendation proposed by “Radiocommunications” Working Group T/WG 3 (R)
2、Text of the Recommendcition adopted by the “Telecommurtications” Commission : “The European Conference of Posts and Telecommunications Administrations, considering (a) that it is necessary to harmonize procedures for the Co-ordination of frequencies for the land mobile service in frontier regions, (
3、b) that it is important that a simple method of Co-ordination be established which Administrations will be able to implement as widely as possible, (c) that it is a matter of utmost necessity that the available spectrum be used with maximum efficiency, in particular avoiding according land mobile se
4、rvice radio stations greater protection than justified by operating requirements, (d) that exceptionally some stations require increased protection, for example stations of the public land mobile radio telephone service, (e) that in practice it is advantageous both for determining the field strength
5、 of the wanted signal and for determining that of the interfering signal to use the same propagation curves, (f) that it may be very useful to determine a maximum permissible value for the field strength of the interfering signal, (g) that account needs to be taken of the variable nature of propagat
6、ion phenomena, which depend on location and (h) that the use of certain selective calling devices can to a certain extent improve the quality of the service by O time, eliminating a large amount of interference, recommends that in Co-ordinating frequencies in frontier regions for the land mobile ser
7、vice Administrations should be guided by the foilowing provisions: 1. for determining field strength, the CCIR propagation curves valid for 50% of locations and 50% of the time shall be used in every case, 2. calculations shall be made following the procedure set out in part A of the Annex to this R
8、ecommendation, 3. the parameters contained in part B of the Annex shall be used to determine the need for Co-ordination and for dealing with practical cases of Co-ordination, 4. .Administrations sha divide stations into 3 groups: Group 1 : stations requiring an exceptional quality of service and con
9、sequently a high level of protection; Group 2: stations requiring a normal quality of service; Group 3: stations requiring no protection, 5. Administrations shall classify under group 2 the largest possible number of stations not classified under group 3. For this purpose users may, for example, be
10、invited to use, as appropriate, selective calling devices and effective methods of coding so as to reduce the effects of interference in the absence of the wanted signal.” Edition of September 15, 1988 - = 2326434 0006866 3 - TIR 25-03 E Page 3 Annex A. CALCULATION OF FIELD STRENGTH 1. PRINCIPLE The
11、 sensitivity of a receiver is determined by the electromotive force which enables a given value for the output signal to noise ratio to be obtained; if the gain of the antenna and the feed line losses are known, the minimum value Co of the electrical field can be deduced from this. The electrical fi
12、eld produced at a distance by a radio-electrical transmitter of known characteristics is subject to propagation variations and its strength varies with time and according to the location. It is accepted that, according to the laws of probability, its value will follow a normal distribution in dB. In
13、 that case, if the value of the standard deviation is known, it is possible to determine the median value of the field so as to obtain the value Co with a given probability P. The median value must be where o is the value of the standard deviation and x a coefficient. The relationship between P and
14、x is given by tables or curves. Given the random nature of the distribution of the field, a service quality may be characterised by the percentage of locations where, in a given zone, the field exceeds the value Co. However, this is inadequate if unwanted transmissions reach the receiver, thus causi
15、ng interference. If reception of the wanted signal is not to be disturbed by the interfering signal, the ratio between their values at any given time must be sufficiently high. The minimum value of this ratio is the protection ratio (Ro). Given that the variations in the interfering field obey the s
16、ame statistical laws as those affecting the wanted field, the ratio between them also varies according to a statistical law of the same kind, in accordance with the following rules: - the median value of the ratio between the wanted field and the interfering signal, expressed in dB, is equal - the v
17、alue of the standard deviation for the statistical-distribution of this ratio is: where o, = standard deviation for the wanted field ob = standard deviation for the interfering field Since the nature of the two fields is the saine, o, = ob = o and o? = fi In order to arrive at a complete definition
18、of a quality of service it is therefore necessary not only to define the percentage of locations in which the zone to be served must be covered, but also at what percentage of locations protection against interference must be provided, in other words, for what percentage of locations the ratio betwe
19、en the wanted field and the interfering field must be greater than Ro in dB. If this probability is fixed at P, the median value for this ratio must be Since C, the median value of the wanted field, has been determined by the quality of service, the level of protection enables R, to be determined, t
20、hus giving the median value for the interfering field: c, = Co + xo to the difference between the median values of these fields; o? = 4- R, = Ro + x o? B, = C, - R, 2. SENSITIVITY OF RECEIVERS The sensitivity to be taken into account for co-ordination at frontiers shall be 6 dB in relation to one mi
21、crovolt (e.m.f.). Previous page is blank Edition of September 15, 1988 ?- W 232b414 000bBb7 5 TIR 25-03 E Page 4 3. CORRESPONDING VALUE OF THE FIELD Power received p, = - gi c2 A2 120n 4n which gives P, = C + Gd - 20 log f - 105 If the antenna and the receiver have the same impedance of 75 ohms the
22、power received is therefore e e2 p=-=- 4 Z 300 (3) which gives It follows that P, = E - 145 C = E + 20 hg f - Gd - 40 (5) Account is taken of mismatching loss caused by using antennas and receivers with different input impedances by making a correction D, and of antenna inefficiency by making a corr
23、ection A, depending on the type of installation. We then obtain For example, in the case of an antenna h/4 and receiver input impedance of 50 ohms, we can admit from which it follows that This gives the following values for the field C in the different frequency bands: C = E + 20logf - Gd - 40 + D +
24、A (6) Gd= 3dB D=2dB A= 3dB C = E + 20 log f - 38 80 MHz 160 MHz 460 MHz 6 dB 12 dB 21 dB pr = power received in watts P, = power received in dB in relation to the watt c = field in volts per metre C = field in dB in relation to pV/m gi = isotropic gain Gd = gain in relation to h/2 dipole in dB h = w
25、avelength in metres f = frequency in MHz e E Z = receiver input impedance D = antenna mismatch correction A = antenna efficiency correction = electromotive force in volts = electromotive force in dB in relation to pV 4. EFFECT OF EXTERNAL NOISE SOURCES The effect of external noise sources is negligi
26、ble in the 460 MHz band. However, it is very considerable in the 80 MHz and 160 MHz bands in high-density urban area. Measurements have shown that to obtain the same quality of reception as is obtained in the absence of external noise, the e.m.f. of the signal must be 10 pV at 80 MHz and 5 pV at 160
27、 MHz. Since these figures apply only to particular areas, no account will be taken of them below, in view of the statistical nature of the problem. Edition of September 15, 1988 TIR 25-03 E Page 5 Wanted field Protection ratio Interfering field 5. QUALITY OF SERVICE AND NECESSARY FIELD In the case o
28、f group No. 1, if at 75% of locations the field must be greater than the minimum value for Co, the corresponding value for x is 0.675. In the view of the CCIR, the standard deviation assumes the foliowing values: 8 dB 460 MHz band (A h = 50 m): 10 dB This gives the following median values for the wa
29、nted field: 80 and 160 MHz bands: 80 MHz 160 MHz 460 MHz (A h = 50 m) In the case of group No. 2, where the percentage of locations is 50%, x is equal to O and the median values for the field are respectively : 80 MHz 160 MHz 460 MHz 6 dB 12 dB 21 dB 6 + 0.675 x 8 = 11.4dB 12 + 0.675 x 8 = 17.4dB 21
30、 + 0.675 x 10 = 27.7 dB 6 dB 12 dB 21 dB 8 dB 8 dB 8 dB -2 dB 4 dB 13 dB 6. PROTECTION RATIO Where the wanted transmission and the interference are both in class F3, which is the most usual case, an instantaneous value of 8 dB is admitted for the protection ratio. If reception has to be protected fo
31、r 75% ) of locations in the case of group 1, the median value must therefore be R, = Ro + 0.675 G. It follows that for 80 MHz 160 MHz G = GA = 11.3 R, = 8 + 0.675 x 11 = 15.6 dB G = O& = 11.3 R, = 8 + 0.675 x 11 = 15.6 dB 460 MHz O = O& = 14.1 R, = 8 + 0.675 x 14 = 17.5 dB In the case of group 2, th
32、e median value of the protection ratio is 8 dB since x = O. 7. THEORETICALLY TOLERABLE INTERFERING FIELDS (median values) Group 1 I I 80MHz 1 160 MHz 1 460 MHz Wanted field Protection ratio 17.5 dB Interfering field -4.2 dB 10.2 dB Group 2 I I 80MHz I 160MHz I 460MHz I The values for the to 1 )A pro
33、tection probability of P% means that for a link operating alternately on two frequencies, the probability of interference is (100-P)% for a call to a mobile unit at the edge of the service zone, assuming that the interfering base station is permanently on the air (1 trafic unit). If the stations tra
34、fic is t traffic units, the probability of interference will bet x (100-P)%. Edition of September 15, 1988 -=a TIR 25-03 E Page 6 8. EFFECT OF RELIEF AND OF STATISTICAL DISTRIBUTION OVER TIME Generally speaking, if the field has a normal distribution in relation to location and to time, with standar
35、d deviations of o, and o, respectively, the resulting standard deviation for distribution is o= Jm It is dependent on frequency and distance. The effect of the effective antenna height is negligible for the heights involved in the land mobile service. For group 2 stations, the maximum tolerable inte
36、rference field is indepen- dent of ot and of A h. For group 1 stations, the median value of the tolerable interference field for A h x 50 m and q = O is B,Io = Bmz - 0.675 oc,o (JZ - 1. where Bm, = the median value of the tolerable interference field for group 2 stations and The reference median val
37、ues for the tolerable interference field are given in paragraph 7. The effect of different types of relief (A h) and of the standard deviation in relation to time of the interfering signal (ot) are accounted for by a correction factor. whereB, = median value of the tolerable interference field for g
38、roup 1 stations where o,o = standard deviation for the distribution in relation to location for A h = 50 m e, = mi - mio 1 = x ,o (JZ - 1) - JO,: + ob,: + ob,? + ou,e = standard deviation of the distribution of the wanted field in relation to the locations ob,e = standard deviation of the distributi
39、on of the interfering field in relation to the locations ob, = standard deviation of the distribution of the interfering field in relation to time For P = 75% (x = 0.675), the correction factors are given in the following table: = ob,e (i.e. where the wanted field and the interfering field cross the
40、 same type of relief) and, for I VHF (80 MHz, 160 MHz) I UHF (460 MHz) -0.3 100 - 1.4 150 -2.2 -2.5 - 3.8 - 5.2 land - 1.1 -2.2 O, = o 1.4 - 0.6 -1.9 I sea + Oe = 18 -2.3 9 -3.3 -2.6 14 -6.7 -2.9 20 -10.7 Edition of September 15, 1988 TIR 25-03 E Page 7 Minimum wanted field to be protected B. B.l. 8
41、0MHz 160MHz 460MHz 6 dB 12 dB 21 dB If the path of the wanted field is characterised by the value oe, and the path of the interfering field by different values of q, the correction factors are those given in the following table: Protection ratio Maximum tolerable interfering field (80 MHz, 160 MHz)
42、I UHF (460 MHz) 8dB 8dB 8 dB -2 dB 4 dB 13 dB sea land 1 I land 1 sea I 3 -0.3 1.9 2 -0.1 -2.7 -4.4 9 -0.5 7 -1.4 0.5 5 -0.6 -3.1 -4.8 14 -2.1 9 -2.2 -0.5 7 -1.1 -3.5 -5.1 20 -5.6 11 -3.0 -1.6 LIST OF VALUES TO BE TAKEN INTO ACCOUNT IN CO-ORDINATION AGREEMENTS Administrations responsible for Co-ordi
43、nation will adapt the values set out below to the various cases they encounter and, in particular, to the type of station concerned (base or mobile stations operating on one or two frequencies) and to the characteristics of their antennae (gain, height above ground level, polarisation and, where app
44、ropriate, directivity diagram). A height above ground level other than 3 metres may be used in particular Co-ordination agreements where the consulting Administration is aware that the stations across the frontier likely to cause interference are base stations. Such agreements must enable the countr
45、ies concerned to be aware of the distribution of base stations and mobile stations in the different frequency sub-bands. Interference to group 2 stations Co-ordination between the Administrations concerned is necessary where the following field strength values are exceeded at the frontier at a heigh
46、t of 3 metres above ground level. 80 MHz 160 MHz 460 MHz -2 dB 4 dB 13 dB (Values expressed in relation to 1 pV/m.) The values taken into account for Co-ordination and which apply to cases using the antennae most frequently found are: Edition of September 15, 1988 W 2326434 0006873 7 W TIR 25-03 E P
47、age 8 B.2. Interference caused to group 1 stations In this case, the percentage of locations and the protection probability to be taken into account are set at 90% (x = 1.3) for a type of relief corresponding to A h = 50 m. (See paragraph 6. of part A.) For other types of relief see paragraph 8. par
48、t A. The field strength which must not be exceeded at the frontier at a height of 3 metres above ground level is: 80 MHz 160 MHz 460 MHz -6.2 dB -0.2 dB 7.7 dB (Values expressed in relation to 1 pV/m.) The values taken into account for Co-ordination and under the same conditions as for group 2 are:
49、I I 80 MHz I 160 MHz I 460 MHz I I Wanted field to be protected I 16.3 dB I 22.3 dB I 33.8 dB I I Protection ratio I 22.5 dB I 22.5 dB I 26.1 dB I I Maximum tolerable interfering field I -6.2 dB I -0.2 dB I 7.7 dB I (The values of the wanted field and the interfering field are expressed in relation to 1 pV/m.) In order to avoid group 2 stations being too penalised by the increase in the repetition distance, it is very much to be desired that in frontier regions group networks should be operated in the same frequency sub-bands. B.3. Interference caused t
