1、STDOCEPT ERC REPORT 49-ENGL 3997 232b4LY 0033273 b29 = ERC REPORT 49 * European Radiocommunications Committee (ERC) within the European Conference of Postal and Telecommunications Administrations (CEPT) ERC REPORT ON SHARING BETWEEN MOBILE EARTH STATIONS AND RADIOASTRONOMY OBSERVATORIES Moscow, Sept
2、ember 1997 _ - STDmCEPT ERC REPORT 49-ENGL 3997 232b434 003327Y 565 D ERC REPORT 49 Copyright i 998 the European Conference of Postal and Telecommunications Administrations (CEPT) STD-CEPT ERC REPORT 49-ENGL 3997 H 2326434 0033275 4Tl 9 ERC REPORT 49 ERC REPORT ON SHARING BETWEEN MOBILE EARTH STATIO
3、NS AND RADIOASTRONOMY OBSERVATORIES 1 INTRODUCTION . 1 2 PROTECTION OF THE RADIO ASTRONOMY OBSERVATIONS 1 3 GENERAL PRINCIPLE USED IN THE METHODOLOGY STEP 1 . INTERFERENCE CRITERIA . 2 4 CONCLUSION . 2 ANNEX 1 . 3 1 introduction . . 3 2.a Monte Carlo method 3 2 . b 3 3 4 4.a 4.6 4.c 4.6 4.e Calculat
4、ion of the number of effective number of new calls newiter, it and of the number of calls ncalliter, it 7 4 . f 4.g Calculation of the date of end of the (new) calls . 8 4 . h 4 .i Calculation of recgoweriter, . 10 5 Determination of meangowerite4 11 1 Introduction 17 2 ANNEX 3 . 19 ANNEX 4 . 21 2 G
5、eneral principles used in the methodology . 3 Protection of radio astronomy observations Presentation of the methodology of calculation Calculation of the interjering power experienced during a sub-time step - Monte Carlo random trials Calculation of the initial number of calls: Miter . Calculation
6、of the number of dropped calls: drppediter, it . 6 Calculation of the potential number of attempted calls: borniter, it 7 Assignment of the new) calls to the available trafic channels 7 Calculation of the other parameters linked to the (new) calls 8 ANNEX 2 . 17 Proposed enhancements to step 1 metho
7、dology . 17 STD-CEPT ERC REPORT 49-ENGL 1997 232b414 00L327b 338 9 ERC REPORT 49 Page I ERC REPORT ON THE SHARING BETWEEN MOBILE EARTH STATIONS AND RADIOASTRONOMY OBSERVATORIES 1 INTRODUCTION WARC 92 allocated the band 1610-1626.5 MHz on a primary basis worldwide to the Mobile Satellite Service (MSS
8、) in the earth-to-space direction (uplink) and the band 1613.8-1626.5 MHz on a secondary basis worldwide to the MSS in the space-to-earth direction (downlink). The band 1660-1660.5 MHz is allocated on a primary basis worldwide to the land mobile satellite service (LMSS) in the earth-to-space directi
9、on (uplink). The bands 1610.6-1613.8 MHz and 1660-1670 MHz are used, as primary allocations, by radio astronomers to observe the spectral line of the Hydroxyl molecule, which is considered to be among the most important lines below 275 GHz. The band 1660- 1670 MHz is also used by radioastronomers fo
10、r measurements of continuum observations and for VLBI. The radioastronomy service in these bands is protected by footnote S5.149 stating that “in making assignments to stations of other services to which the bands 1610.6-1613.8 MHz and 1660-1670 MHz are allocated .I, administrations are urged to tak
11、e all practicable steps to protect the radio astronomy service from harmful interference. Emissions fi-om spaceborne or airborne stations can be a particularly serious source of interference to the radio astronomy service (see Nos. S4.5 and S4.6 and Article S29)“. Footnote S5.372 stating that “harmf
12、ul interference shall not be caused to stations of the radio astronomy service using the band 1610.6-1613.8 MHz by stations of the radiodetermination-satellite and mobile-satellite services (No S29.13 applies)“ also applies. 2 The protection of radio astronomy observations can be provided through th
13、ree different steps: PROTECTION OF THE RADIO ASTRONOMY OBSERVATIONS Step 1: step 2: Step 3: by setting a separation distance by default between a radio astronomy site and Mobile Earth Station (MES), which defines an area around a radio astronomy site outside of which no restriction applies to the op
14、eration of mobile earth stations. by setting a restriction zone around a radio astronomy site, which defines an area within which there may be some restriction to the operation of mobile earth stations. These restrictions should be defined by the regulator and agreed by the radio astronomy community
15、 and MSS operator. by setting an exclusion zone around a radio astronomy site, defined by means of detailed assessment of the characteristics of the systems involved and measurements if necessary, within which no operation of mobile earth stations should be allowed. Annex 1 and Annex 2 describe meth
16、odology which can be used for the calculations respectively for Step 1 and Step 2. Until precise details are included in Annex 4 in order to evaluate the conditions for the operation of the mobiles in the restriction zone, the restriction zone has to be considered as an exclusion zone, following the
17、 definition above in Step 3. Annex 3 provides the list of the set of characteristics, which are necessary for running the simulation. Annex 4 gives examples of results which can be obtained using Step 1 methodology. STDmCEPT ERC REPORT 49-ENGL 3997 D 232b414 0033277 274 D ERC REPORT 49 Page 2 3 GENE
18、RAL PRINCIPLE USED IN THE METHODOLOGY STEP 1 - INTERFERENCE CRITERIA Step 1 calculation is intended to provide separation distances by default. Annex 1 describes a general methodology of calculation, which can be used for that purpose, using the Monte Carlo method. The basis of this model is to calc
19、ulate the statistics of the interfering power produced at a radio astronomy site by MES in operation. In order to protect radio astronomy observations, it is stated that: “a 2000 seconds integration taken at any time of the day should have at least (100 - x)% probability of being interference free,
20、.e. the mean interference power is below the levels specified in Recommendation IT-R RA.769. The figure of 90% (x = 10) has its origin in propagation calculations (ITU-R Handbook on Radio Astronomy, chapter 4.2.4.). The wider interpretation of this figure is under consideration within ITU-R WP 7D.“
21、Thus, the Annex 1 methodology should be used with the following assumptions: - 2000 seconds integration time (constant for all trials) - peak traffic assumption - x% of time maximum interference criteria may be exceeded (10 % is the current value subject to revision by ITU-R WP 7D). In the case wher
22、e different sources of interference are identified for the radio astronomy observations, further studies are required on the possible splitting of the maximum interference power level. Some operators and Administrations have the opinion that the ITU-R RA.769 threshold is a single entry threshold to
23、trigger coordination, compatible with the concept of default separation distance, and therefore interference splitting is not appropriate. In addition, CEPT should ensure a level playing field for the entry into operations of individual satellite personal communication systems. Any interference spli
24、tting should be considered with extreme caution. Some operators and Administrations also have technical arguments against splitting. For example, existing services cannot be constrained to a portion of the interference threshold if they already use up all of the interference allowance. Further, inte
25、rference from different sources may not overlap in time or frequency. Also, the statistical effect of summing interference according to the centrai limit theorem mitigates the interference effect. Hence, interference splitting may be unnecessarily restrictive. It is considered by some, including the
26、 radio astronomy community, that the levels of harmful interference, as given in ITU-R RA769, refer to the mean power produced by the population of users belonging to all services operating in the band during the radio astronomy integration time. 4 CONCLUSION The methodology described in this report
27、 is to be used for the determination of the protection distances and zones around radio astronomy observatories in the band 1610.6-1613.8 MHz and 1660-1670 MHz. It has been determined with the cooperation of radioastronomers and operators of MSS systems and, hence, has taken into account all relevan
28、t aspects of the interfering phenomenon. The use of such methodology for other frequency bands is obviously highly recommended. STD-CEPT ERC REPORT 47-ENGL 1777 = 232b414 0013278 100 m ERC REPORT 49 Page 3 ANNEX 1 Step 1 methodology: Calculation of separation distances by default between radio astro
29、nomy sites and mobile earth stations 1 Introduction This annex describes a general methodology, which can be used for the calculation of separation distances by default between radio astronomy sites and the areas where MES are allowed to transmit. These separation distances, based on calculations us
30、ing a Monte Carlo methodology, should ensure the protection of radio astronomy observations. 2 General principles used in the methodology 2.a Monte Carlo method In order to calculate the separation distances by default between radio astronomy sites and MES, it is necessary to evaluate the probabilit
31、y function of the interfering power produced by the mobiles and experienced by the RAS receivers. This can be done by using statistical modelling of interference, such as a Monte Carlo methodology. The Monte Carlo method is based on the principle of sampling random variables from their defined proba
32、bility distributions. The variables to be sampled are often various and numerous, as the accuracy of the model usually increases with their number. In the particular case of the determination of separation distances by default, these variables may be the number of mobiles, the location of the mobile
33、s, the propagation condition, etc. The statistics of the interfering power produced at a radio astronomy site by MES in operation is then derived from the calculation of interfering powers experienced for each sample. 2.b Protection of radio astronomy observations Radio astronomy observations are pe
34、rformed by using time averaging, to significantly reduce noise fluctuations. In order to reflect such practice, statistics of received interfering power are based on integration time samples used during the observations. The interference power coming from the MSS population is acceptable provided th
35、at no more than x% of the 2000 seconds integration periods have mean interference power above the RAS harmful level. The following is based on this definition. 3 Presentation of the methodology of calculation As stated in Section 2 above, statistics of interfering powers are based on integration tim
36、e samples. niter is then the number of integration time samples needed for the statistic. integr is the duration ofthe integration time sample. In the following, integr is supposed to be constant. During each integration time sample integr, the mean interference power produced by MESS is calculated
37、by averaging ( instantaneous ) interfering powers produced within sub-time steps of dt seconds duration. ERC REPORT 49 Page 4 integr integr integr integr integration - - - . . 2 time samples iter : 1 ,/ I .a .* / d t .,. t:1 . - sub-time t: dt steps integr it : 1 Figure 1: Division of integration ti
38、me samples During each sub-time steps, interfering powers are determined by making random trials on the traffic load of the MSS system under consideration and on the location of each mobile in operation. The outline flow chart of the calculation is given below: entry of the Daqters 1 w I i ter=l : n
39、i te a integration time sample loop u sub-time step loop meangoweriter if) (averaging of reCgOweriter,it f) over integr) meangowerite= if I (mean-poweri ter f) for ilOO-x)% of Calculation of the interference power produced by MESS in operation at the frequency f for integration time sample iter and
40、sub- time step it Calculation of the mean interference power produced by HESS in operation for integration time sample i ter (averaging of each interfering power of sub-time steps over the integration time Comparison of the mean interfering power experienced for (100- x)% of the number of the integr
41、ation time samples and the radio astronomy harmful interference level Figure 2: General flow chart of the calculation ERC REPORT 49 Page 5 W 4 Calculation of the interfering power experienced during a sub-time step - modelling of traffic (see 4.h) The interfering power experienced during each sub-ti
42、me step at the frequency fis calculated by summing power produced by each mobile in operation during this time step. calculation of the other parameters linked to the calls : distance to the RAS site percentage of time (path loss) azimuth elevation path loss gain of the RAS antenna For each time ste
43、p it, it is thus necessary to determine: - - the location of the mobiles around the radio astronomy site distance, azimuth . . the number of mobiles in operation during it (derived from a given traffic law); the channels the active MES are using; calculation of the other parameters linked to the new
44、 calls : distance to the RAS site (see 4. h) percentage of time (path loss) azimuth elevation 1 path loss gain of the RAS antenna In order to keep the correlation between each sub-time steps, the number of mobiles in operation for sub-time step it is derived from the number of mobiles in operation f
45、or it-1, by taking into account the number of calls dropped and initiated in-between. For the first sub-time step, the initial number of call is calculated by making a random trial. The following figure gives the outline flow chart for calculation of reCgweriter.il(f) (integration time sample iter,
46、sub- time step it). Calculation of recqoweriter, i u3 I I I calculation of the initial number of I (see 4.b) I calls : iniiter Calculation of recJowerter,iru3 dropped calls : dropped;ter, it calculation of the potential number of initiated calls : bornite, il I calculation of the number of effective
47、 new calls tiewiter,it and of assignment of the new calls to the virtual available channels (see 4.J new calls (see 4.g) Figure 3: Calculation of recqoweriter,it() ERC REPORT 49 Page 6 4.a Monte Carlo random trials As stated in section 2.a, the Monte Carlo methodology is based on the principle of sa
48、mpling random variables from their defined cumulative distribution functions. Consider for example a variable x, with the cumulative distribution function on the figure. P(X) is then the probability p(x 5 X). P(X) is uniformly distributed between O and 1. Xi X So, a random uniform trial of P=P(xi) b
49、etween O and 1 leads to one single value of xi, and enables to plot x=f p). 4.b Calculation of the initial number of calls: hiam At the beginning of each integration time sample, the initial number of calls is calculated using the formula giving the cumulative distribution function of having iniiter simultaneous calls at any instant t: “% E c, where: P is the cumulated probability of having iniiter simultaneous calls at the instant t (iniiter I Ncail) E is the peak demanded load on the system measured in Erlangs Ncall is the maximum number of simultaneous call
