Collection of GSM RNP Technical Problems and Replies(No.15)-20050308-A-1.0

Collection of GSM RNP technical problems and replies(No. 15)

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Problem 308 General propagation models adopted for 1800M network by Huawei Overview

General propagation models for 1800M network by Huawei.

Details

What kind of propagation models is adopted for 1800M network by Huawei

 Answer

1. COST231-HaTa model expression is adopted in theoretic calculation:

) = 46.3+33.9log F −13.82log Hb+ (44.9 −6.55log Hb)logd − a( Hm) +C   L(Urban L(Urban) is the medium value loss (dB) in flat city area F is frequency, range:1500MHz-2000MHz Hb is the height of base station antenna (30-200m) Hm is the height of mobile station antenna (1-10m) d is propagation distance (1-20km) a(Hm) is the revision factor of mobile station antenna Cm = 0dB in medium-size cities or small cities, suburbs. Cm = 3dB in big cities 2. The model provided in ASSET software by AIRCOM is adopted in systematic emulation: Ploss=K1+K2lgd+K3(Hms)+K4lg(Hms)+K5lg(Heff)+K6lg(Heff)lg(d)+K7+Kclutter In the above expression: Pathloss: Path loss(dB) K1:

The constant related to frequency

K2:

The constant related to distance

K3, K4: The revision coefficient of mobile station antenna height K5, K6: The revision coefficient of base station antenna height K7:

The revision coefficient of diffraction

Kclutter: The revision coefficient of clutter attenuation d:

Distance between the base station and mobile station (km)

Hms, Heff: Available height of the mobile station antenna and base 2005-03-08

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Collection of GSM RNP technical problems and replies(No. 15)

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station antenna (m) K value parameters for typical cities are as follows: 900M City Name

1800M Cangzhou Renqiu

Chongqing Xian

Shenzhen

 

Jinan

K1

130

132

159

164

164.2

156

K2

38

38

44.9

28.5

45

44.8

K3

1

1

-2.88

-2.88

-2.88

-2.88

K4

0

0

0

0

0

0

K5

-13.55

-13.55

-13.82

-13.82

-13.82

-13.82

K6

-6.3

-6.3

-6.55

-6.55

-6.55

-6.55

K7

1

1

-0.7

0.8

0.21

-0.7

Problem 309 Why is there no description about the influence of downtilts on coverage in the propagation models? Overview

Why is there no description about the influence of downtilts on coverage in the propagation models?

Details

When we calculate the coverage distance of BTS, we need to know the coverage receiving level request in preplanning; the maximum path loss is worked out according to EIRP; and the coverage radius of the base station is worked out according to the propagation model. But the real coverage is worked out according to the relative height of the base station antenna, the vertical half-power angle and the downtilt. Both Hata model and Cost-231 model seem to neglect the influence of the antenna downtilt on path loss though the influence is actually remarkable. Is there contradiction?

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Collection of GSM RNP technical problems and replies(No. 15)

 Answer

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The coverage distance is related with the antenna downtilt. In Hata model and Cost-231 model we calculate the coverage distance by assuming that there is no antenna downtilt or the downtilt is very small (The antenna height, azimuth angle, gains, power and ground object is to be considered). But the ASSET network planning tools involves prediction of the coverage distance with the fixed downtilt. If the downtilt is very large, the coverage distance cannot be figured out because the usual propagation model does not involve the downtilt. The following equation can be applied in this case: a=arctg(H/D)+b/2. In this equation: a is the downtilt; b is the vertical half-power angle; H is the antenna height; D is the coverage distance. Restriction to the equation: the downtilt must be larger than half of the vertical half-power angle; D must be shorter than the distance surveyed when there is no downtilt.

Problem 310 The vertical half-power angle for the small base station antenna Overview

The vertical half-power angle for small base station antenna

Details

The index for small antenna used in BTS3001C is as follows: Frequency: 890--960MHZ, Gains: 8dBi, Half-power Angle: 65, Preset Downtilt: 0, How about the vertical half-power angle?

 Answer

We can use a approximation equation (taken from Huawei GSM Wireless Network Planning and Optimization) to calculate: Ga=10log (32400/(α*β))

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Collection of GSM RNP technical problems and replies(No. 15)

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In the equation, Ga is antenna gain (dBi); α is horizontal half-power angle (degree); β is the vertical half-power angle (degree). Introduce Ga and α into the equation and β is worked out as 79 degree, and the actual β given by the manufacturer is about 75 degree.

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