1、 Rec. ITU-R M.1039-3 1 RECOMMENDATION ITU-R M.1039-3 Co-frequency sharing between stations in the mobile service below 1 GHz and mobile earth stations of non-geostationary mobile-satellite systems (Earth-space) using frequency division multiple access (FDMA) (Questions ITU-R 83/8, ITU-R 84/8 and ITU
2、-R 201/8) (1994-1997-2000-2006) Scope This Recommendation presents calculation methodologies to deal with the co-frequency sharing between stations in the mobile services below 1 GHz and mobile earth stations of non-geostationary mobile-satellite systems. A quick methodology to give an approximation
3、 of the interference is given as well as more precise calculations using detailed statistical methods. The ITU Radiocommunication Assembly, considering a) that the spectrum allocated by the World Radiocommunication Conferences WARC-92, WRC-95 and WRC-97 for low-Earth orbit (LEO) mobile-satellite ser
4、vices (MSS) below 1 GHz, if shared with mobile services, must provide adequate protection from harmful interference; b) that LEO MSS can provide beneficial radio-based services, including emergency alerting (see Note 1); NOTE 1 However, these services will not be identified as safety services as def
5、ined by the Radio Regulations. c) that the use of LEO enables practical use of frequencies below 1 GHz by space stations; d) that some coordination and channelization techniques used in fixed and mobile radio systems in bands below 1 GHz can lead to low Erlang loading on individual channels; e) that
6、 dynamic channel assignment techniques are technically feasible and may provide a means of spectrum sharing between mobile services and low power, low duty cycle MSS; f) that the non-GSO MSS users would operate throughout large geographic areas; g) that the transmission of the mobile earth station (
7、MES) are short bursts; h) that the signal characteristics in the MSS below 1 GHz may allow co-channel sharing with mobile services; j) that there is a need to determine MSS and MS sharing possibilities while considering the impact of MS transmissions into MSS satellite receivers; k) that statistical
8、 modelling techniques can estimate the probability of interference to the MS from the MSS, further considering a) that, in many countries, the allocations to the mobile services are extensively used, and in some cases with periods of high traffic loading; 2 Rec. ITU-R M.1039-3 b) that a propagation
9、model using scattering model for VHF band is provided by Recommendation ITU-R P.1546, noting a) that additional studies are required to determine whether the statistical models are fully applicable to maritime and aeronautical mobile services; b) that the distribution of MES users may be concentrate
10、d into a specific area within the footprint of one satellite, taking into consideration geographical restriction; c) that Recommendation ITU-R M.1184 provides technical characteristics of non-GSO MSS networks below 1 GHz that are considered appropriate for modelling and analysing sharing and potenti
11、al interference between MES and stations in the mobile services, recommends 1 that the analytic methodology described in Annex 1 can be used to provide a first approximation to the interference probability from non-GSO MSS MES to land mobile stations (LMS) generally in the same frequency band; 2 tha
12、t a more precise calculation of the interference probability can be performed using the detailed statistical methods of either Annex 2 or Annex 3 to evaluate sharing between stations in the mobile services and FDMA non-GSO MES with primary allocations (Earth-to-space) in the same frequency band belo
13、w 1 GHz; 3 that types of dynamic channel assignment techniques such as that described in Annex 4 could be used by non-GSO MSS systems (narrow-band) operating in MSS allocations below 1 GHz in bands to promote compatibility with terrestrial services. Annex 1 An analytical methodology for calculating
14、interference probability from non-GSO MSS earth station to LMS operating below 1 GHz 1 Introduction This Annex describes an analytical methodology for calculating interference probability, considering potential interference from MES to base stations of the existing LMS station, and using a propagati
15、on model derived from the latest version of Recommendation ITU-R P.1546 (previously ITU-R P.370). The proposed method may be used to evaluate the interference probability easily, and applies to any non-GSO MSS systems using FDMA. The employment of this method could facilitate the frequency sharing a
16、nalysis between non-GSO MSS systems and the existing MS systems below 1 GHz. Rec. ITU-R M.1039-3 3 2 Interference model between non-GSO MSS system and land mobile communications system The frequency band 148-149.9 MHz allocated for Earth-to-space direction in the non-GSO MSS system is used as forwar
17、d and return links in the land mobile communications systems. The operation of non-GSO MSS system in the frequency band 148-149.9 MHz could give rise to the following four interference cases between these two systems, as shown in Fig. 1: (1) interference from MES of non-GSO MSS system to base statio
18、n of the existing MS system; (2) interference from MES to LMS of the existing MS system; (3) interference from gateway earth station of non-GSO MSS system to base station; (4) interference from gateway earth station to LMS. Among these four interference cases, (1) and (2) are the interference paths
19、from MES to the existing MS systems. 4 Rec. ITU-R M.1039-3 This Annex describes the methodology for evaluating the interference probability in the interference paths (1) and (2). For the interference paths (1) and (2), it is necessary to make an assessment of the existing systems in both of the foll
20、owing operation modes: the communications mode, the waiting mode. The waiting mode is the case that no information is being exchanged between two stations, but the MS receivers are turned on to accommodate any call or information. When the MS system is in the waiting mode, the receiver, except for t
21、he receivers with use of tone squelch techniques, will have a squelch break during burst length + (max. 450 ms +, for example) emitted by MES with the interference probability mentioned hereunder. The following presents the methodology for evaluating the interference probability occurring in the int
22、erference paths (1) and (2) as shown in Fig. 1, where the existing systems are both in the communications and waiting modes. 3 Propagation loss between MES and base station of MS system Amongst the ITU-R texts, Recommendation ITU-R P.1546 describes the propagation loss in the VHF band from the anten
23、nas at high altitude. This Recommendation shows the experiments results of the field strength of TV signals in the VHF band at the receiving station at d km away. The results are shown for various heights of antennas. For the above reasons, the propagation loss, required for obtaining the interferen
24、ce coordination distance between MES and the base station, is evaluated in this model on the basis of Recommendation ITU-R P.1546. Figure 2 shows the VHF propagation loss to the propagation distance for the various antenna heights obtained from the latest version of Recommendation ITU-R P.1546 (prev
25、iously ITU-R P.370). In the computation of propagation loss shown in Fig. 2, 10% of the time values are used. For other frequency bands, Fig. 2 would need to be recalculated. 4 System parameters Figure 3 shows the interference model from the MES to the base station and to the LMS of the existing MS
26、system. The system parameters of the base station, LMS and MES used in the following consideration are summarized below. Suffix i indicates interfering system, w is interfered system, t is transmitter, and r is receiver. Also, b and m indicate base station and LMS, respectively. 4.1 MES parameter (i
27、nterfering station): Transmission side Transmission power: Pit(dBm) Transmission antenna gain: Git(dB) MES antenna height: hi(m) 4.2 Base station parameter (interfered station) Transmission side Transmission power: Pbwt(dBm) Transmission antenna gain: Gbwt(dB) Transmission feeder loss: Lbwt(dB) Base
28、 station antenna height: hbw(m) Rec. ITU-R M.1039-3 5 Receiver side Receiving antenna gain: Gbwr(dB) Receiving feeder loss: Lbwr(dB) Base station antenna height: hbw(m) Receiver sensitivity: Cb(dBm) Required C/I: (C/I )br(dB) Permissible interference level: Ib(dBm) Squelch sensitivity: Pbsd(dBm). 6
29、Rec. ITU-R M.1039-3 4.3 LMS parameter (interfered station) Transmission side Transmission power: Pmwt(dBm) Transmission antenna gain: Gmwt(dB) LMS antenna height: hmw(m) Receiver side Receiving antenna gain: Gmwr(dB) LMS antenna height: hmw(m) Receiver sensitivity: Cm(dBm) Required C/I: (C/I )mr(dB)
30、 Permissible interference level: Im(dBm) Squelch sensitivity: Pmsd(dBm). 5 Computation of the interference coordination distance when the existing MS system is in the communications mode 5.1 Interference from MES to base station (path (1) in Fig. 3) It is assumed that d1is the maximum distance betwe
31、en the base station and LMS that the transmitted signal from LMS can be received with the necessary S/N at the base station. This d1is equivalent to the radius of the service area of the existing MS system, namely, the circle with a radius of d1surrounding the base station represents the service are
32、a for the MS system. Under the assumptions above, and the sensitivity of the base station receiver being assumed as Cb, equation (1) is obtained: Cb= Pmwt+ Gmwt L(d1) + Gbwr Lbwr(1) Rec. ITU-R M.1039-3 7 where: Pmwt: LMS transmission power Gmwt: LMS transmission antenna gain L(d1) : propagation loss
33、 along the distance of d1between the base station and LMS Gbwr: base station receiving antenna gain Lbwr: base station receiving feeder loss. From equation (1), propagation loss between the base station and LMS is expressed by equation (2) and the propagation distance, d1, can be obtained by using F
34、ig. 2: L(d1) = Pmwt+ Gmwt+ Gbwr Lbwr Cb(2) The required (C/I )brat the base station can be given by equation (3): (C/I )br= Cb Ib(3) where: (C/I )br: ratio of the required desired signal power to the interference signal power at base station Cb: sensitivity of the base station receiver Ib: permissib
35、le interference power from MES. From equation (3), the permissible interference power level is expressed by equation (4): Ib= Cb (C/I )br(4) Assuming that more than one non-GSO MSS system is operated in the same band, the permissible interference power level given in equation (4) will be shared by t
36、hese non-GSO MSS systems. In the case of multiple non-GSO MSS systems operating in the same frequency band, equation (5) should substitute for equation (4): Ib= Cb (C/I )br (5) where is the correction factor for the case of multiple operations of non-GSO MSS systems with use of the same frequency ba
37、nd. If each non-GSO MSS system could use the dedicated frequency band by using the band segmentation method, the permissible interference power level for each system can be given by equation (4). When the base station and MES are apart by the interference coordination distance, dbcor, the interferen
38、ce signal power from MES would be received by the base station as the permissible interference power level, Ib. Therefore, equation (6) can be obtained. This relationship is shown in Fig. 4. Ib= Pit+ Git L(dbcor) + Gbwr Lbwr Iso(6) where Isorepresent the isolation in the case that the non-GSO MSS sy
39、stem adopts those channels interstitial between the existing system channels. Annex 2 shows the computer simulation results on the improvement of the adjacent channel isolation level in the interstitial channelling. 8 Rec. ITU-R M.1039-3 FIGURE 4 Interference coordination distance for base station i
40、n the communications mode From equations (4) and (6), when the base station and MES are apart by the interference coordination distance, dbcor, the propagation loss, L(dbcor) is expressed by equation (7): ()brbsobwrbwrititbsobwrbwrititbcorICCILGGPIILGGPdL)/(+=+=(7) From equation (7) and Fig. 2, dbco
41、rcan be obtained which represents the interference coordination distance between the base station and MES when LMS of the existing system is communicating at the edge of the service area. In other words, it is assumed that all LMSs are operating at the edge of the service area. It is obviously under
42、stood from Fig. 4 that those LMSs nearer to the base station can secure higher S/N. 5.2 Interference from MES to LMS (path (2) in Fig. 3) It is assumed that d2is the maximum distance between the base station and LMS and that the transmitted signal from the base station can be received with the neces
43、sary S/N at LMS. This d2is equivalent to the maximum distance for LMS to receive the signals from the base station with the necessary S/N. Under the assumption above and the sensitivity of the LMS receiver being assumed as Cm, equation (8) can be obtained: Cm= Pbwt+ Gbwt Lbwt L(d2) + Gmwr(8) where:
44、Pbwt: base station transmission power Gbwt: base station transmission antenna gain Rec. ITU-R M.1039-3 9 Lbwt: base station transmission feeder loss (d2) : propagation loss in the distance d2between the base station and LMS Gmwr: LMS receiving antenna gain. From equation (8), the propagation loss be
45、tween the base station and LMS can be expressed by equation (9): L(d2) = Pbwt+ Gbwt Lbwt+ Gmwr Cm(9) where: (C/I )mr: ratio of the required desired signal power to the interference signal power at LMS Cm: LMS receiver sensitivity Im: permissible interference power. This is expressed by equation (10)
46、: (C/I )mr= Cm Im(10) From equation (10), the permissible interference level, Im, can be expressed by equation (11): Im= Cm (C/I )mr(11) In the case that more than one non-GSO MSS system is operated in the same band, the same correction factor defined in equation (5) is required to obtain the permis
47、sible interference power level for each non-GSO MSS system. If LMS and MES are apart by the interference coordination distance, dmcor, the interference power from MES would be received by LMS as permissible interference power, Im, as shown in Fig. 5. This can be expressed by equation (12): Im= Pit+
48、Git L(dmcor) + Gmwr Iso(12) From equations (11) and (12), L(dmcor), the propagation loss of the interference coordination distance, dmcor, can be expressed by equation (13): mrmsomwrititmsowrmititmcorICCIGGPIIGGPdL)/()(+=+=(13) From equation (13) and Fig. 2, dmcorcan be obtained which represents the
49、 interference coordination distance between LMS and MES. This coordination distance corresponds that LMS is communicating at the edge of the service area of the existing system. This assumption allows those LMS nearer to the base station to enjoy higher S/N, as illustrated in Fig. 5. 6 Computation of the interference coordination distance when the existing MS system is in the waiting mode 6.1 Interference from MES to base station (path (1) in Fig. 3) As illustrated in Fig. 6, it is assumed t
