1- planeación gsm

8/6/2019 1- Planeacin GSM

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Siemens AG, 08/09/00Manfred Petzendorfer N MN VN 11

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Purpose:

Definition of technical parameters

Check for balanced up- and downlink

Fast overview of required BTS

Input for Coarse Planning with TORNADO

Method:

Max. possible pathloss calculation with input datas

Cell radius calculation using Okumura-Hata propagation model

Link Budget


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Downlink (BTS ---> MS):

Balanced Up- and Downlink

BTS

MS

TX-Power

RX-Sensitivity

Uplink (MS ---> BTS):

BTS

MS

TX-Power

RX-Sensitivity

Balance Condition: Luplink = Ldownlink


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1. Definition:

Maximum allowed attenuation between transmitter (TX) and receiver (RX) to obtainthe specified grade of quality

2. Calculation

Lmax = TX_Power - RX_SensitivityExample: Lmax = 40dBm - (-100dBm)

Lmax = 140dB

TX_Power = EiRP (effective isotropic radiated power)

2.1.Downlink

TRX

Back off

Combiner CableTX-Antenna

Example: EiRP = 46dBm - 1dB - 3dB - 3dB + 15dBi = 54dBm = 251,2W

Maximum Pathloss

EiRP= BS_Power_Output - PA_Back Off - Total_Combiner_and_Duplex_Loss - TX_Antenna_Cable_Loss + TX_Antenna_Gain

P[dBm]= 10*log(P[mW])


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RX_Sensitivity = Min_RX_Level_50%_loc._prob.

Maximum Pathloss

Min_RX_Level_50%_loc._prob. = Sensitivity_Level + RX_Antenna_Cable_Loss - Frequency_Hopping_Gain -

RX_Antenna_Gain + Interference_degradation_margin + Body_Loss

MS Cable

RX-Antenna

Interferer

Carrier

Example: Min_RX_Level_50%_loc._prob. = -102dBm + 0dB - 0dB - 0dBi + 3dB + 3dB = -96dBm


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Maximum Pathloss

2.1.Uplink

MS CableTX-Antenna

EiRP= MS_Power_Output - TX_Antenna_Cable_Loss + TX_Antenna_Gain

Min_RX_Level_50%_loc._prob. = Sensitivity_Level - Frequency_Hopping_Gain + RX_Antenna_Cable_Loss -

Tower_Mounted_Pre-Ampliufier_Gain - RX_Antenna_Gain - Antenna_Diversity_Gain +

Interference_degradation_margin + Body_Loss

BTS

Cable

RX1-Antenna

Interferer

Carrier

Cable

RX2-Antenna

TMPA

TMPA

Example: EiRP = 33dBm - 0dB + 0dBi = 33dBm = 2W

Example: Min_RX_Level_50%_loc._prob. = -107dBm - 0dB + 3dB - 0dB - 15dBi - 4dB + 3dB + 3dB = -117dBm


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Example:

Lmaxdownlink = 54dBm - 96dBm = 150dB

Lmaxuplink = 33dBm - 117dBm = 150dB

Balanced System

Untill now we always have calculated with a 50% location probability for coverage. But a

customer will not be satisfied with only 50% probability for a successfull call. Typical values for

an acceptable grade of service are location probabilities above 90%. How to calculate the

necessary receiving level for a given location probability will be shown on the next sheets. To

understand this calculation we have to look at the two main fading mechanisms.

Maximum Pathloss

Lmax = EiRP - Min_RX_Level_50%_loc._prob.


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Fading:

Long term fading due to shadowing

Short term fading (Rayleigh fading) due to reflexions

Location Probability

Receiving Level

distanceVariations dueto shadowing

Global mean

Variations due

to Rayleigh fading

Long and short term fading


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Rayleigh Distribution

A) Short-term fading

Receiving Level P

Pmedian

Pm in

P

Fading margin

area r

pr

ti

the probability P(P < Pmin)


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B) Long-term fading

ormal Distribution

area rpr

ti

the probability P(Pr < Prmin)

Re c eiv i g Le ve l r

r mi

( )r

r

Fa i g margi

r mea


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Min_Rx_Level_x%_loc._prob. = Min_Rx_Level_50%_loc._prob. + z * standard deviation

Max_Pathloss_x%_loc.prob. = Max_Pathloss_50%_loc._prob. - z * standard deviation


z is taken from tables for the normal distribution function

The percentage value in the normal distribution table is the probability at the cell border.

To obtain the cell coverage probability the value must be converted with the curves given by

Jakes: "Microwave Mobile Communication",1974.

75% at cell border ~ 90% cell coverage

90% at cell border ~ 98% cell coverage


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Example: Min_Rx_Level_75%_loc._prob. = -96dBm + 0,675 * 6dB = -92dBm

Max_Pathloss_75%_loc._prob. = 150dB - 0,675 * 6dB = 146dBm


(urban)

Dense urban : 10dB

Urban : 8dB

Suburban : 6dB

Rural / open : 5dB

Forest : 5dB

Standard deviation


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To obtain indoor coverage the Min_Rx_Level_x%_loc._prob. must be available

inside the building. For estimation of an appropriate outdoor level the average

indoor loss has to be determined. The average indoor loss depends on

morphologie of course. Typical values are:

Indoor coverage

Average Indoor Loss

Dense urban : 20dB (10-25dB)

Urban : 15dB (10-15dB)

Suburban : 10dB (5-10dB)

Rural / open : 8dB (5-10dB)

Incar : 7dB (5-8dB)

Min_Rx_Levelindoor= Min_Rx_Leveloutdoor+ Average_Indoor_Loss


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Free Space Path Loss

Propagation Prediction

L0 = 32,4 + 20 * log (f[MHz]) + 20 * log (d[km])

L0 = 91,72 + 20 * log (d[km]) fr f = 925MHz

Hata for urban area

L = 69,55 + 26,16 * log (f[MHz]) - 13,82 * log (HBS) - a(HMS) + (44,9 - 6,55 * log (HBS)) * log(d[km])

L = 147,14 -13,82 * log (HBS) - a(HMS) + (44,9 - 6,55 * log (HBS)) * log (d[km]) for f = 925MHz

a(HMS) = 0 for HMS = 1,5m

General L = A + B * log (d [km])

L: Loss in dB B: propagation index (loss per decade)

A: unit loss (at 1km) d: distance MS - BS [km]

For other morphologic classes correction factors for this formula are used.

(see the macro of the link budget calculation program)


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With L=Lmax it is possible to calculate the cell radius d

Cell Radius Calculation

d[km] = 10(Lmax - 147,14 +13,82 * log (HBS) + a(HMS) ) / (44,9 - 6,55 * log (HBS))

Example:

d[km] = 10(146dB - 147,14 +13,82 * log (30) + 0) / (44,9 - 6,55 * log (30))

d = 3,52km

The formula is valid in the following area: HBS = 30 ... 200m, HMS = 1 ... 10m, d >1km

The cell coverage area is calculated by:

Cell_Coverage = Pi * r2

for omni cell

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