1、Rec. ITU-R F.1402 1RECOMMENDATION ITU-R F.1402*,*FREQUENCY SHARING CRITERIA BETWEEN A LAND MOBILE WIRELESSACCESS SYSTEM AND A FIXED WIRELESS ACCESS SYSTEM USING THESAME EQUIPMENT TYPE AS THE MOBILE WIRELESS ACCESS SYSTEM(Questions ITU-R 215/8 and ITU-R 140/9)(1999)Rec. ITU-R F.14021 IntroductionNowa
2、days, technology of land-mobile systems is used for fixed wireless access (FWA) systems. Such FWA systems arebecoming popular and implemented at a remarkable speed, since large demands for mobile communications bring abouteconomical equipment production for this application. In this Recommendation,
3、a land mobile system is called mobilewireless access (MWA) system, and the FWA system that utilizes the same type of equipment as the MWA is calledMWA-based FWA system or simply FWA system. These terminologies are based on Recommendation ITU-R F.1399.In most cases, such FWA systems are designed in t
4、he same frequency band as the MWA systems to enhance themanufacturing efficiency. Therefore it is an urgent and critical subject to study the sharing criteria, particularly necessarygeographical separation, between both systems.Such criteria is needed when one administration wishes to utilize the fr
5、equency band with dual allocations (i.e. to thefixed and the mobile services) for both FWA and MWA applications in certain geographical separation.Recommendation ITU-R F.1334 presents a statistical technique for calculating interference conditions for the cases thatthe land-mobile system and fixed s
6、ystem use different types of equipment from each other. With the purview ofproviding complementary information, this Recommendation mainly describes interference between an MWA systemand an FWA system using the same type of equipment with the same design parameters.2 ScopeThis Recommendation describ
7、es the frequency sharing criteria between the FWA and MWA systems on the assumptionthat both systems use the same frequency and type of equipment. Necessary geographical separations between bothsystems are calculated for the cases that the systems employ time division duplex (TDD) or frequency divis
8、ionduplex (FDD).3 ReferencesRecommendation ITU-R F.1334: Protection criteria for systems in the fixed service sharing the same frequencybands in the 1 to 3 GHz range with the land mobile service;Recommendation ITU-R F.1399: Vocabulary of terms for wireless access;_*This Recommendation was developed
9、jointly by Radiocommunication Study Groups 8 (Working Party 8A) and 9 (WorkingParty 9B), and any further revision should also be undertaken jointly.*This draft new Recommendation should be brought to the attention of Radiocommunication Study Groups 3 (Working Party 3K)and 8 (Working Party 8A).2 Rec.
10、 ITU-R F.14024 Recommendation4.1 Interference modelThe prerequisites for setting an interference model are as follows: The MWA and FWA system use equipment with the same specifications. The MWA and FWA systems are point-to-multipoint systems. The MWA and FWA systems employ either TDD or FDD for dupl
11、exing.Figure 1 shows an interference model, where various interference can be classified into the following eight types:Case I : MWA system is interfered-with side I-a) FWA base station MWA user station I-b) FWA user station MWA user station (TDD system only) I-c) FWA user station MWA base station I
12、-d) FWA base station MWA base station (TDD system only)Case II : FWA system is interfered-with side II-a) MWA base station FWA user station II-b) MWA user station FWA user station (TDD system only) II-c) MWA user station FWA base station II-d) MWA base station FWA base station (TDD system only).1402
13、-01FIGURE 1Interference modelMWA system FWA systemInterference I-c)Interference II-a)Interference I-a)Interference II-c)Interference I-b)Interference II-b)Interference II-d)Interference I-d)MWA base station FWA base stationFWA user stationMWA user stationI-d) and II-d): dominant interference in TDD
14、environmentI-c) and II-c): dominant interference in FDD environmentFIGURE 1/F.1399.D01 = 3 CM4.2 Dominant interferenceIf the service areas of the FWA and MWA systems are fully separated from each other, the greatest factor determininginterference level is not an individual position of the stations,
15、i.e. the distance between the interference source and theinterfered-with equipment. Interference level depends on the transmit output power, antenna gain, antenna height and thedirection of the antenna main beam.Rec. ITU-R F.1402 3It is assumed that in the above eight types of interference the line-
16、of-sight path is maintained with no obstacles.Concerning the antenna type only FWA user stations employ directive antennas, while other three kinds of stations useomnidirectional or sectorized type.In Case I for FDD environment, interference I-c) is considered to be more critical than interference I
17、-a), because FWAuser station has directive antenna. Similar consideration is applied in Case II for FDD environment.In case I for TDD environment, interference I-d) is considered to be more critical than interference I-c), because theFWA base station is located at a higher point so that it covers th
18、e area, and the propagation condition between MWAbase station and FWA base station is better than that between MWA base station and FWA user station. Similarconsideration is applied in Case II for FDD environment.Consequently, the sharing criteria should be determined by considering the following do
19、minant interference:a) Case I : TDD environment: I-d) FWA base station MWA base station FDD environment: I-c) FWA user station MWA base station.b) Case II : TDD environment: II-d) MWA base station FWA base station FDD environment: II-a) MWA base station FWA user station.It should be noted that the s
20、ame combination of interference with opposite direction, i.e. I-d) and II-d), or I-c) and II-a),will result in the same level since MWA and FWA use the same system parameters.Moreover, it should be noted that if the synchronization of TDD transmission within the system and with the interferingsystem
21、 is achieved in TDD environment, the combination for FDD environment can be applied.In the above interference a directive antenna at an FWA user station is oriented toward the MWA base station. Inaddition the worst case is assumed when an FWA user station is located near the FWA base station.4.3 Pro
22、tection criteria for MWA systems from FWA system interference4.3.1 Conditions under TDD environmentThe interference level I (dBm) (median value) at the MWA base station can be calculated as follows:I = PtC LfC LfB+ GC+ GB L (1)where:L : propagation loss (dB)PtC: transmit power of FWA base station (d
23、Bm)LfC: feeder loss of FWA base station (dB)LfB: feeder loss of MWA base station (dB)GC: antenna gain of FWA base station (dBi)GB: antenna gain of MWA base station (dBi).Then, the maximum allowable interference level for the MWA system can be calculated as follows:I NB+ X (2)where:NB: thermal noise
24、level at the MWA receiver (dBm)X : allowable relative (I/N) ratio at the long term criteria (dB).4 Rec. ITU-R F.1402X indicates the allowable interference compared with the thermal noise. For the MWA system operating at a thresholdrelated to the thermal noise, it is required that the mutual influenc
25、e of MWA and FWA is minimal (say, 1 dB); in thiscase the interference must be approximately 6 dB below thermal noise, and X will be around 6 dB.In some cases, the mutual influence of MWA and FWA can be the same level as thermal noise to improve thegeographically efficient sharing, and in this case X
26、 will be around 0 dB.Another possible approach for the frequency sharing is that some level of interference is accepted for both MWA andFWA, because this system has the interference avoidance functions. Although the traffic capacity may be reduced, thesystem can be operated even when there is some i
27、nterference. In this case, X can be greater than 0 dB and the separationdistance will become shorter.In the link design of FWA systems, L is usually calculated from the free-space propagation when sufficient Fresnelradius is obtained. On the other hand, in case of MWA systems a different approach ma
28、y be adopted. It is very likely thatthe propagation path with sufficient Fresnel radius is not obtained for each interference path in Fig. 1. In such casespropagation loss greater than the free-space propagation is anticipated. Suppose that the propagation loss at the distanced is expressed by L(d),
29、 the minimum distance dminbetween both stations is given by the following formula derived fromformulas (1) and (2):L(dmin) = PtC LfC LfB+ GC+ GB (NB+ X) (3)4.3.2 Conditions under FDD environmentUnder the FDD environment, the minimum distance dminbetween both stations can be calculated for different
30、dominantinterference but in the same way as follows;L(dmin) = PtS LfS LfB+ GS+ GB (NB+ X) (4)where:PtS: transmit power of FWA user station (dBm)LfS: feeder loss of FWA user station (dB)GS: antenna gain of FWA user station (dBi).4.4 Protection criteria for FWA systems from MWA system interferenceThe
31、protection criteria for FWA systems from MWA system interference can be derived from the results in the previoussection. As mentioned before, in Case II the interference levels of II-d) and II-a) are equivalent to those of I-d) and I-c)in Case I.4.5 Examples of the calculationExamples of the interfe
32、rence calculation based on the actual system are shown in Annexes 1 and 2.ANNEX 1Examples of calculation of interference conditions in the 1.9 GHz bandThe example below shows how to calculate the conditions between a personal handy-phone system (PHS) andPHS-FWA (or PHS-WLL (wireless local loop) in t
33、he 1.9 GHz band (TDD environment). Even under otherenvironments, similar results will be obtained by changing the parameters.PHS technology employs dynamic channel assignment (DCA). By using this technology, more than one system, possiblyoperated by different operators, share the same radio channels
34、 avoiding the use of the same frequency at each time slot.Rec. ITU-R F.1402 5Therefore, it is technically feasible for an FWA and an MWA with DCA to share the same frequency band in the samearea. However, in this calculation, the existence of the DCA function is not considered, as in real systems. I
35、nstead, onlythe ordinary sharing conditions, in which two systems use the same frequency, accepting a certain level of degradationby mutual interference, are examined.In this example, the interference from PHS-FWA to PHS conditions are calculated on the assumption that the conditionsfrom PHS-FWA to
36、PHS and the conditions from PHS to PHS-FWA are symmetrical in radio path design.1 Calculating the necessary propagation lossSystem parameters for assumed FWA base station and MWA base station are given in Table 1.TABLE 1Assumed system (FWA base station and MWA base station)The necessary propagation
37、loss for the system assumed in Table 1 will be as follows, based on equation (3):L(dmin) = PtC LfC LfB+ GC+ GB (NB+ X)= 22 1 1 + 10 + 10 (109 + X)= 149 X dB (5)2 Calculating the separation distanceAssuming the coexistence of the MWA system mainly in an urban area and the FWA system mainly in a rural
38、 area, theseparation distance is calculated using the propagation loss characteristics in a rural area.The Appendix 1 to Annex 1 shows the concept of estimating the propagation characteristics in rural area.In Fig. 2, the separation distance is calculated using the estimated curve of the received po
39、wer distance characteristicsshown in Fig. 4. The separation distance will be about 30 km at X = 0 dB.Parameter ContentsInterface R2System PHS to PHS-FWAAccess/duplex method TDMA/TDDNumber of slots 4Transmit power PtC13 dBm (average)/22 dBm (peak)Bandwidth 300 kHzNoise figure 10 dBNoise floor 109 dBm
40、Antenna gain, GC, GB10 dBiFeeder loss, LfC, LfB1 dBHeight of feeder point, hC, hB10 mAllowable I/N ratio X dB6 Rec. ITU-R F.14021402-022040608010012014010252101011021525252X = 10 dBX = 0 dBX = 10 dBReceivedpower(dBm)Distance (km)Okumura-HatacurveEstimatedcurveFree space lossAbout 30 kmNote 1 hCis ou
41、t of its application range (30-200 m) in Okumura-Hata curve.Adjustment based on the topographical and building conditions is not considered.FIGURE 2Calculation of separation distanceFIGURE 2/F.1399.D02 = 3 CMAPPENDIX 1TO ANNEX 1Propagation characteristics in the 1.9 GHz band in rural areas*1 Short-d
42、istance propagation characteristics in rural areaThe propagation loss increased from the free-space loss in 1.9 GHz band was calculated from the measured propagationloss in a comparatively flat and open land where only houses and small-scale groves exist on the propagation route. Withthe transmittin
43、g antenna height, receiving antenna height, and transmission distance as parameters, the additionalpropagation loss was calculated using the following experimental formula:La= 52.53 36.45 log (ht+ hr) log d + 61.93 log (ht+ hr) 89.24 (6)where:La: additional propagation loss (not including a free-spa
44、ce loss) (dB)ht: transmitting antenna height (m) (about 10 m to 20 m)hr: receiving antenna height (m) (about 2 m to 10 m)d : transmission distance (m)maximum value for (ht+ hr) is 25 m.The experimental formula of (6) is applicable to short-distance propagation from about 100 m up to about 5 km._*Pro
45、pagation characteristics proposed in this Appendix and the applicability of formulae (6) and (7) applicable to frequency bandsother than 1.9 GHz should be further reviewed in the work of Radiocommunication Study Group 3 (Working Party 3K).Rec. ITU-R F.1402 72 Long-distance propagation characteristic
46、s in rural areasAccording to the long-distance propagation characteristics in an extremely open area where there are no obstacles on thepropagation route, the propagation loss is proportional to the square of the distance up to the break point, Bp, and almostthe fourth power of the distance over Bp.
47、For calculating Bp, formula (7) is assumed:Btrfphhk=42l(7)where:kf: fresnel radius factorl : wavelength.Fig. 3 shows Bpcalculated from hrand ht.1402-030246810121 0002 0003 0004 0005 0006 0007 0008 0000ht= 15 mht= 10 mhr(m)Bp(m)(kf= 0.7)FIGURE 3Calculation of BpFIGURE 3/F.1399.D03 = 3 CM8 Rec. ITU-R
48、F.14023 Estimation of propagation loss in rural areas3.1 Propagation loss estimation methodConsidering the above results, the propagation loss in a comparatively flat and open land where only houses and small-scale groves exist on the propagation route can be estimated as follows:Step 1 : calculate
49、Bpusing formula (7) (kf= 0.7).Step 2 : when the propagation distance is up to Bp(d Bp):LL La=+0Where:L : total propagation loss (dB)La: additional propagation loss (dB) calculated using formula (6)Lo: free-space propagation loss (dB).Step 3 : When the propagation distance is beyond Bp(Bp d):L (dB) = L (dB), at Bp+ 40 log (d/Bp).3.2 Example of estimating received power versus distance characteristicsWhen the transmitted power is 22 dBm (peak), the transmitting antenna gain is 10 dBi, t
