1、Rec. ITU-R M.1039-2 1 RECOMMENDATION ITU-R M. 1039-2 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) (1 994- 1997-2000) 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 services (MSS) below 1 GHz, if shared with mobile services, must provide adequ
3、ate protection from harmfl interference; b) that Resolution 214 (Rev.WRC-97) invited the ITU-R to study and develop Recommendations on the performance requirements, sharing criteria and technical and operational issues relating to sharing between both the existing and planned services, and non-GSO M
4、SS below 1 GHz; cl that LEO MSS can provide beneficial radio-based services, including emergency alerting (see Note i); NOTE 1 However, these services will not be identified as safety services as defiied by the Radio Regulations. 4 e 1 GHz can lead to low Erlang loading on individual channels; f) sh
5、aring between mobile services and low power, low duty cycle MSS; g h) that the use of LEO enables practical use of frequencies below 1 GHz by space stations; that some coordination and channelization techniques used in fixed and mobile radio systems in bands below that dynamic channel assignment tec
6、hniques are technically feasible and may provide a means of spectrum that the non-GSO MSS users would operate throughout large geographic areas; that the transmission of the mobile earth station (MES) are short bursts; j that the signal characteristics in the MSS below 1 GHz may allow Co-channel sha
7、ring with mobile services; k) transmissions into MSS satellite receivers; that there is a need to determine MSS and MS sharing possibilities while considering the impact of MS 1) that statistical modelling techniques can estimate the probability of interference to the MS from the MSS, further consid
8、ering a periods of high traffic loading; b) that, in many countries, the allocations to the mobile services are extensively used, and in some cases with that a propagation model using scattering model for VHF band is provided by Recommendation ITU-R P.370, noting that additional studies are required
9、 to determine whether the statistical models are fully applicable to maritime a and aeronautical mobile services; 2 Rec. ITU-R M.1039-2 b) that the distribution of MES users may be concentrated into a specific area within the footprint of one satellite, taking into consideration geographical restric
10、tion; 4 that Recommendation ITU-R M. 1 184 provides technical characteristics of non-GSO MSS networks below 1 GHz that are considered appropriate for modelling and analysing sharing and potential interference between MES and stations in the mobile services, recommends 1 that the analytic methodology
11、 described in Annex 1 can be used to provide a first approximation to the interference probability fiom non-GSO MSS MES to land mobile stations (LMS) generally in the same fiequency band; 2 that a more precise calculation of the interference probability can be performed using the detailed statistica
12、l 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 fiequency band below 1 GHz; 3 that types of dynamic channel assignment techniques such as that described in Annex 4 could be u
13、sed 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 interference probability from non-GSO MSS earth station to LMS operating below 1 GHz 1 Introduction This An
14、nex describes an analytical methodology for calculating interference probability, considering potential interference fiom MES to base stations of the existing LMS station, and using a propagation model derived fiom Recom- mendation ITU-R P.370. The proposed method may be used to evaluate the interfe
15、rence probability easily, and applies to any non-GSO MSS systems using FDMA. The employment of this method could facilitate the fiequency sharing analysis between non-GSO MSS systems and the existing MS systems below 1 GHz. 2 Interference model between non-GSO MSS system and land mobile communicatio
16、ns system The fiequency band 148-149.9 MHz allocated for Earth-to-space direction in the non-GSO MSS system is used as forward and return links in the land mobile communications systems. The operation of non-GSO MSS system in the fiequency band 148-149.9 MHz could give rise to the following four int
17、erference cases between these two systems, as shown in Fig. 1: (1) interference fiom MES of non-GSO MSS system to base station of the existing MS system; (2) interference fiom MES to LMS of the existing MS system; (3) interference fiom gateway earth station of non-GSO MSS system to base station; (4)
18、 interference fiom gateway earth station to LMS. Among these four interference cases, (1) and (2) are the interference paths fiom MES to the existing MS systems. Rec. ITU-R M.1039-2 3 FIGURE 1 Interference model between non-GSO MSS and MS systems . I Gateway earth station Terrestrial user Non-GSO sa
19、tellite LMS MS system Non-GSO MSS system Wanted signal . Interfering signal 1039-01 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 sy
20、stems in both of the following 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 mod
21、e, the receiver, except for the receivers with use of tone squelch techniques, will have a squelch break during burst length +a (max. 450 ms +a, for example) emitted by MES with the interference probability mentioned hereunder. The following presents the methodology for evaluating the interference p
22、robability occurring in the interference paths (1) and (2) as shown in Fig. 1, where the existing systems are both in the communications and waiting modes. 3 Amongst the ITU-R texts, Recommendation ITU-R P.370 describes the propagation loss in the VHF band fiom the antennas at high altitude. This Re
23、commendation 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 interference coordination distance betw
24、een MES and the base station, is evaluated in this model on the basis of Recommendation ITU-R P.370. Figure 2 shows the VHF propagation loss to the propagation distance for the various antenna heights obtained fiom Recommendation ITU-R P.370. In the computation of propagation loss shown in Fig. 2, 1
25、0% of the time values are used. For other fiequency bands, Fig. 2 would need to be recalculated. Propagation loss between MES and base station of MS system 4 220 200 i 80 v rn m O d l a pi 3 .z 160 3 i? Y 140 12c 1 O0 Rec. ITU-R M.1039-2 FIGURE 2 Propagation loss in the VHF band (based on Recommenda
26、tion ITU-R P.370) i 7 200 m Percentage o ime = 1 Effective transmitting antenna height h, = 1.5 n 250 300 350 400 150 O 50 100 Distance (km) - Effective receiving antenna height, h, = 300 m - - Effective receiving antenna height, h, = 500 m -.-.-.-.-.- Effective receiving antenna height, h, = 1 O00
27、m Effective receiving antenna height, h, = 2 O00 m 1039-02 _ Recommendation ITU-R P.529 (h, x h,) = (1.5 m x 1.5 m) . Effective receiving antenna height h, = 1.5 m _.-.-.-. -.-.-.- Effective receiving antenna height, h,= 37.5 m 4 System parameters Figure 3 shows the interference model fiom the MES t
28、o the base station and to the LMS of the existing MS 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 bas
29、e station and LMS, respectively. 4.1 MES parameter (interfering station): - Transmission side - Transmission power: Pit (am) - Transmission antenna gain: Git (dB) - MES antenna height: hi (m) Rec. ITU-R M.1039-2 5 FIGURE 3 Interference model between MES and existing MS system Base station 4.2 - Tran
30、smission side Base station parameter (interfered station): - Transmission power: (dBm) - - Transmission feeder loss: (dB) - Transmission antenna gain: Gbwt (dB) Base station antenna height: hbw (m) - Receiver side - - - - Receiver sensitivity: cb (dBm) - Required C/k (c/ however, there might be a bl
31、ockage between LMS and the satellite that disables the DCAAS to detect the signals transmitted fiom LMS. Taking into account this fact, the probability that DCAAS fails to detect the active channel being used by the existing system is assumed to be qo. Parameter 3: Satellite visibility factor in the
32、 case of multiple gateway earth stations If more than one gateway earth station is installed in an area, the number of satellites increases so that MESS can access simultaneously, and the interference probability to the existing system also increases. q is assumed as the ratio of available number of
33、 channels with multiple gateway earth stations to a single gateway earth station. Parameter 4: Number of interfering signals within the occupied bandwidth of the MS carrier If the occupied bandwidth for the non-GSO MSS carrier is narrower than that for the MS carrier, a multiple interfering carrier
34、would be observed in the wanted MS carrier occupied bandwidth. Under the assumption described above, the additional interference power level given by equation (26) might be considered in the calculation of Clk Other parameters to be considered I = 1Olog - where B, and Bi are the occupied bandwidths
35、for the MS carrier and MES carrier, respectively. Under the condition that non-GSO systems shall not assign more than one channel in each fiequency grid allocated for the existing system, it is unnecessary to consider the additional interference power level given by equation (26). Rec. ITU-R M.1039-
36、2 13 Among the above-mentioned parameters, parameters 1 to 4 are required for the evaluation of interference probability when the existing system is in the communication mode, and parameters 3 and 4 are required for the evaluation of interference probability when the existing system is in the waitin
37、g mode. 7.3 Overall of interference probability On the basis of what is presented in the above sections, the interference probability, Pt, for two potential interference paths fiom MES to the base station, and MES to LMS, both in the communications mode and in the waiting mode, are given by the foll
38、owing equations: - Existing MS system is in the communications mode pt (basestation) = Pbc x qo x q It should be noted that the percentage of time of interference can be calculated by multiplying Pt by the factor qm. Existing MS system is in the waiting mode - PI (basestation) = Pbw x qG (29) ANNEX
39、2 Methods and statistics for determining sharing between MSS earth station transmitters below 1 GHz and mobile stations 1 Introduction The methods presented in this Annex describe a method to be used to determine if MSS earth station (MES) transmitters can share spectrum with mobile services. The me
40、thods described provide a basis for evaluating the effectiveness of power level limits for MES e.i.r.p. that may be established to allow sharing with mobile services (see Note 1). NOTE 1 - In addition, the uplink transmissions fiom the MES have an optimum length for sharing with certain terrestrial
41、voice services. It has been indicated this might be up to 500 ms. The duration of time over which such transmissions would take place is under study (1% in 1-15 min has been suggested). 2 Potential interference from MSS to mobile services Mobile services in the VHF band are typically characterized b
42、y fiequency modulated voice and data carriers assigned on a periodic channel grid. Channel spacings used include 12.5 kHz, 15 kHz, 25 kHz and 30 kHz. MSS systems below 1 GHz may use a dynamic channel assignment algorithm which allows the space station to identifl those channels not occupied by the m
43、obile stations which are sharing the spectrum. Thus it is expected that there will typically be significant fiequency separation (1 5 kHz or less) between the MSS transmission and the mobile station receiver centre fiequency. However, for the purposes of this methodology, the efficiency of the dynam
44、ic channel assignment process cannot yet be predicted; MSS uplink channel selection is therefore assumed to be randomly distributed in 2.5 kHz (see Note 1) steps within the mobile allocation. NOTE 1 - This step size represents practical restrictions on synthesizer implementation with little loss in
45、generality of the analysis. 14 Rec. ITU-R M.1039-2 3 Summary of the methodology Several steps must be undertaken in order to determine the potential for harmful interference to mobile stations fiom MES transmitters. The methodology for so doing is outlined in this section. Detailed descriptions of e
46、ach step are contained in the following sections. 3.1 Coordination contour The first step is to determine a typical coordination contour around a mobile receiver to be protected. This is described by the range at which an MES transmitter or group of transmitters will produce a pfd in excess of a lev
47、el determined to be a protection criteria. To perform this calculation one must know the following values: e.i.r.p.mes: maximume.i.r.p. oftheMES (W) B W, : Pfdt : signal bandwidth of the MES transmitter (Hz) pfd considered to be harmful (W/m2) Nt : L(d) : expected maximum simultaneous MES transmitte
48、rs propagation loss as a function of distance. If it can be determined that the coordination contour is small enough as compared to the expected movements of mobile stations and MESS, then no further calculations are required. If the coordination contour is too large for this determination to be mad
49、e, the following steps must be executed. 3.2 Probabilistic techniques are used to determine the percentage of time that the protection pfd will be exceeded at a particular mobile station receiver. If this “exceedance probability“ is low enough, exceeding the protection level is not considered to be harmful interference. Calculation of threshold exceedance probability 3.2.1 The first step is to determine an area over which transmissions fiom MESs will contribute significantly to the statistics of received pfd at the mobile receiver. If too large an area is used,
