1、 Rec. ITU-R M.1641-1 1 RECOMMENDATION ITU-R M.1641-1*A methodology for co-channel interference evaluation to determine separation distance from a system using high-altitude platform stations to a cellular system to provide IMT-2000 service (2003-2006) Scope This Recommendation contains a methodology
2、 for evaluating co-channel interference and a separation distance between a high-altitude platform stations (HAPS) system as a base station for IMT-2000 and a terrestrial tower-based cellular system providing IMT-2000 service. Annex 1 describes a methodology for co-channel interference evaluation fr
3、om a HAPS base station and cellular base stations to a cellular mobile station to provide IMT-2000. The C/I ratio is used as a criterion to set separation distance between a HAPS system and a cellular system. For evaluating the interference within a cellular system, a simplified extended version of
4、Hatas model is applied. An example of calculation for the separation distance between a HAPS system and a cellular system is contained in Annex 2. Appendices 1 and 2 present the equations for interference calculations used in Annex 1 and the antenna radiation pattern, respectively. The ITU Radiocomm
5、unication Assembly, considering a) that new technology utilizing high-altitude platform stations (HAPS) in the stratosphere is being developed; b) that WRC-2000 made provision for use of HAPS providing IMT-2000 in the bands 1 885-1 980 MHz, 2 010-2 025 MHz and 2 110-2 170 MHz in Regions 1 and 3 and
6、1 885-1 980 MHz and 2 110-2 160 MHz in Region 2; c) that Resolution 221 (WRC-03) requested studies on sharing between HAPS and other stations within IMT-2000, and considered the compatibility of HAPS within IMT-2000 with some services having allocations in the adjacent bands; d) that, in accordance
7、with No. 5.388A of the Radio Regulations (RR), HAPS may be used as base stations within the terrestrial component of IMT-2000 in the bands 1 885-1 980 MHz, 2 010-2 025 MHz and 2 110-2 170 MHz in Regions 1 and 3 and 1 885-1 980 MHz and 2 110-2 160 MHz in Region 2; the use by IMT-2000 applications usi
8、ng HAPS as base stations does not preclude the use of these bands by any station in the services to which they are allocated and does not establish priority in the RR, recommends 1 that the methodology in Annex 1 should be used as guidance for determining separation distance between HAPS systems and
9、 cellular systems to provide IMT-2000 service in the frequency bands in considering b) above. *This Recommendation should be brought to the attention of Radiocommunication Study Group 9. 2 Rec. ITU-R M.1641-1 NOTE 1 Recommendation ITU-R M.1456 should be referred to for the typical parameters regardi
10、ng a HAPS system for sharing studies between a HAPS IMT-2000 and a cellular service in the frequency bands in considering b) above. Annex 1 A methodology for co-channel interference evaluation to determine separation distance from a system using HAPS to a cellular system to provide IMT-2000 service
11、1 Introduction Recommendation ITU-R M.1456 provided a co-channel spectral power flux-density (spfd) limit on HAPS emissions and out-of-band spfd limits on HAPS emissions on the Earths surface, as well as HAPS performance requirements to protect terrestrial mobile stations and fixed stations operatin
12、g in bands adjacent to transmissions from HAPS. However, for designing a cellular system, the multi-users interference in the system should be considered as well as other services interferences; the spectrum efficiency depends on the interference from the same and adjacent cells. In this Recommendat
13、ion, guidance is provided to estimate the co-channel interference effects into the terrestrial cellular IMT-2000 system, which is tower-based, from a HAPS IMT-2000 system considering two interferers: the same and adjacent cells interference in the cellular system itself, and the HAPS IMT-2000 interf
14、erence. Since HAPS IMT-2000 interference is based on the HAPS antenna pattern described in Recommendation ITU-R M.1456, this pattern is used to evaluate the appropriate interference power of cellular systems so that all interference power can be derived. The interference to a cellular mobile station
15、 from cellular base stations and a HAPS base station is estimated in terms of the C/I with the parameters of the HAPS system such as the number of users per cell, cell radius, and transmission power. For each estimated case, the optimum values are determined for the above parameters in the HAPS IMT-
16、2000 system in order to be compatible with the cellular system. This Recommendation will give guidance for evaluating the separation distance between a HAPS IMT-2000 system and a cellular IMT-2000 system to IMT-2000 service providers using those different systems. Rec. ITU-R M.1641-1 3 2 System mode
17、l 2.1 HAPS IMT-2000 HAPS is being developed in accordance with Recommendation ITU-R M.1457 to possibly provide IMT-2000 service in the 1 885-1 980 MHz, 2 010-2 025 MHz and 2 110-2 170 MHz in Regions 1 and 3, and 1 885-1 980 MHz and 2 110-2 160 MHz in Region 2. In addition, HAPS as a base station to
18、provide IMT-2000 will have its antenna pattern complied with the following: +=90forfororf0orfBiddBidBidBi)log(60)/(3)(3322112FNmbmLXLGGG (1) where: G(): gain at the angle from the main beam direction (dBi) Gm: maximum gain in the main lobe (dBi) b:one-half the 3 dB beamwidth in the plane of interest
19、 (3 dB below Gm) (degrees) LN: near-inside-lobe level (dB) relative to the peak gain required by the system design, and has a maximum value of 25 dB LF= Gm 73 dBi far side-lobe level (dBi) 1= 3/NbL degrees 2= b745.3 degrees X = )log(602+NmLG dB 3= 6010FLX degrees. The 3 dB beamwidth (2b) is again es
20、timated by: mGb1.0104427= degrees where Gmis the peak aperture gain (dBi). 2.2 Propagation model For the cellular system, a simplified extended version of Hatas model is considered and for the HAPS system, the free space loss model is used. This free space loss model is adequate for a high elevation
21、 angle and it should be used with precaution for low elevation angles, until a better model is developed for HAPS systems; at that time this methodology should be reviewed. 2.2.1 Simplified model of an extended version of Hatas model An extended version of the Hatas model in equation (2) is widely u
22、sed for the radio channel modelling of cellular systems in urban areas with a base station antenna height of 30 m and a mobile antenna height of 1.5 m. 4 Rec. ITU-R M.1641-1 )(log2.35)(log9.3387.251010RFL += (2) where: L: path loss (dB) F: frequency (MHz) R: range (km). The general use of the fourth
23、 power path loss law in terrestrial cellular networks as a simplified extended version of Hatas model is applied as shown in equation (3) to simplify the derivation of the formula. )(log40)(log9.3387.251010RFL += (3) 2.2.2 Free space loss model )(log20)(log204.321010RFL += (4) where: L: path loss (d
24、B) F: frequency (MHz) R: range (km). 3 C/I analysis at a cellular mobile station and the required C/I to determine the separation distance between HAPS system and cellular system 3.1 C/I analysis at a cellular mobile station Figure 1 shows the interference model to a cellular mobile station from cel
25、lular base stations and the HAPS base station. An interfered cellular mobile station is assumed to be located at the nearest point of the HAPS service area as shown in Fig. 1. The interference power received by a cellular mobile station can be obtained by equation (5), taking into account the interf
26、erence from the cellular base stations and the HAPS base station (see Appendix 1). Since the cellular mobile station is located at the border of the coverage of the cellular system, it is assumed that the intra-cell interference is negligible. +=+=10)(12411011010hnmhnhniniGcmhhnhinmcmGicNnHAPSCellul
27、ardSKdSKIII (5) where: i: voice activity factor in cellular system Si: cellular forward link power from cellular base station to the user at the edge of each cell (mW) Mi: number of cellular users per cell li: cellular system path loss per kilometre cin: number of interfering cells of n-th tier in c
28、ellular system (= 2n + 1, n: integer) N: number of tier Rec. ITU-R M.1641-1 5 chn: number of HAPS interfering beams in n-th tier within a distance of (2N-1) (HAPS cell radius) around the edge of the victim cell under consideration dinm: distance between a cellular mobile station and cellular base st
29、ations (km) dh: distance between a cellular mobile station and HAPS base station (km) hnm: angle between a cellular mobile station and the beam direction of cell served by the HAPS base station (degrees) Shn: HAPS forward link power from HAPS base station to the user at the edge of HAPS cell located
30、 in n-th tier (mW) Gi: antenna gain of the base station in cellular system Ghn: gain of the antenna as expressed in equation (1) according to tier 3iiiclMK= hhhhlMK = h: voice activity factor in the HAPS system Mh: number of HAPS users per cell lh: HAPS path loss per kilometre. The C/I ratio of a ce
31、llular mobile station can be obtained by equation (6). IRlrPICiijFiG41010)(/= (6) 6 Rec. ITU-R M.1641-1 where: PF(rj): transmitted power dedicated for one user link at distance rjrj: distance between the cellular base station for carrier and the j-th cellular user Ri: cellular cell radius (km). 3.2
32、The required C/I to determine the separation distance In this Recommendation, the separation distance is defined as a distance from the HAPS coverage contour to the coverage contour of the nearest cell serving the interfered cellular mobile station. In order to share the spectrum between the HAPS sy
33、stem and the cellular system to provide IMT-2000 service in adjacent area, it is necessary to set an appropriate separation distance. The required C/I in a cellular CDMA is expressed by equation (7): =cbbreqBRIEIC0)/( (7) where: Eb: the energy/bit I0: interference power/Hz Rb: bit/s Bc: radio channe
34、l bandwidth (Hz). Annex 2 Example of calculation of separation distance between a HAPS system and a cellular system to provide IMT-2000 service 1 Parameters for C/I calculation Table 1 shows parameters and values used to calculate the C/I at a cellular mobile station from a HAPS base station and cel
35、lular base stations. TABLE 1 Parameters for C/I calculation Parameter Value Frequency (MHz) 1 950 Number of users per cellular cell 50 Number of interfering tiers 5 Cellular cell radius (km) 1 Cellular transmission power per user (mW) 100 HAPS altitude (km) 20 Radius of HAPS cell coverage (km) 55 Ce
36、llular voice activity factor (i) 0.375 HAPS voice activity factor (h) 0.375 Rec. ITU-R M.1641-1 7 If Eb/I0,Rband Bcis 4.5 dB, 8 kbit/s, and 1.25 MHz, respectively, required C/I, (C/I)reqis obtained 17.438 dB by equation (7). The C/I obtained by equation (7) is used as a criterion to determine the se
37、paration distance between a HAPS system and a cellular system for IMT-2000 service. 2 Calculation of separation distance For the interference analysis of a cellular system, in this example 17.4 dB of C/I is used as a criterion for the internal design C/I of the terrestrial cellular system and is use
38、d to determine the separation distance between a HAPS system and a cellular system. This criterion should be considered as a limit for an operation of a mobile station; normally the criteria used is more stringent. The number of interfered tiers is assumed to be up to 5, because the additional inter
39、ference is negligible for a number of tiers greater than 5. The maximum antenna gain of the HAPS base station is considered to be adequate according to the HAPS cell radius. From equation (5) and the above considerations, the calculated C/I as a function of the separation distance are shown in Figs.
40、 2, 3 and 4 for the simplified extended Hatas model, taking into account the number of users per cell, transmission power and cell radius for HAPS, respectively. FIGURE 2 C /Ivs. separation distance with different numbers of HAPS users per cell 8 Rec. ITU-R M.1641-1 FIGURE 3 C /I vs. separation dist
41、ance with different transmission power Rec. ITU-R M.1641-1 9 FIGURE 4 C /I vs. separation distance with different HAPS cell radii Figure 2 shows C/I as a function of the separation distance, taking into account the number of HAPS users per cell. The C/I values at a cellular mobile station are below
42、the threshold value of 17.4 dB at the contact point of the two systems. When the HAPS transmission power per user is 10 mW and the HAPS cell radius is 2 km, the separation distances needed between the two systems are: 7.2, 8.8, 10.8 and 14.1 km for the numbers of HAPS users per cell of 50, 100, 200
43、and 500 respectively, as shown in Table 2. Figure 3 shows C/I as a function of the separation distance, taking into account HAPS transmission power per user. The C/I values at a cellular mobile station are below the threshold value at the contact point of the two systems. When the number of HAPS use
44、rs per cell is 50 and the HAPS cell radius is 2 km, the separation distances needed between the two systems are: 7.2, 11.5, 14.1 and 17.4 km for the transmission powers per user of 10, 50, 100 and 200 mW respectively, as shown in Table 3. Figure 4 shows C/I as a function of the separation distance,
45、taking into account HAPS cell radius. The C/I values at a cellular mobile station depend on the HAPS cell radius. When the number of HAPS users per cell is 50 and the transmission power per cell is 10 mW, the separation distances needed between two systems are: 8.3, 7.2 and 5 km for HAPS cell radii
46、of 4, 2 and 1 km respectively, as shown in Table 4. 10 Rec. ITU-R M.1641-1 In the example of calculation with C/I = 17.4 dB, the C/I which would have been obtained assuming cellular deployment only (i.e. without HAPS) is about 8 dB, which means that a significant margin is allowed for external inter
47、ference. In the second example of calculation, it is assumed that C/I would be limited to 12 dB. TABLE 2 Separation distance with number of HAPS users per cell Separation distance (km) HAPS users per cell C/I = 17.4 dB C/I = 12 dB 50 7.2 10.6 100 8.8 12.9 200 10.8 15.9 500 14.1 20.9 TABLE 3 Separati
48、on distance with transmission power Separation distance (km) HAPS power (mW) C/I = 17.4 dB C/I = 12 dB 10 7.2 10.6 50 11.5 17 100 14.1 20.9 200 17.4 25.7 TABLE 4 Separation distance with HAPS cell radius Separation distance (km) HAPS cell radius (km) C/I = 17.4 dB C/I = 12 dB 1 5 7.1 2 7.2 10.6 4 8.
49、3 16.1 Rec. ITU-R M.1641-1 11 Appendix 1 to Annex 1 Derivations of the interference between a HAPS system and a cellular system 1 Interference to a cellular mobile station 1.1 Interference from a cellular base station The transmission power of a cellular base station considering simplified power control laws is given by: )(jFrP = ijiiijijiiiRrrSRrrrSRr04040for0for(8) where: Ri: cellular cell radius rj: distance to j-th mobi
