Claro Network Dimension Ing Ppt

8/6/2019 Claro Network Dimension Ing Ppt

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(E)GPRS NetworkDimensioning


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CONTENTS

Introduction

Inputs & Outputs Procedure

Summary

Example


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INTRODUCTION

Current GSM networks were design only for speech services:

Simple design (utilizing the ErlangB formula) Do not include dimensioning for PS services

The procedure here presented allows to dimension an (E)GPRS network:

With few and simple input parameters For an average PS load (kbps/cell) Optionally, with guaranteed capacity and/or quality


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INPUTS & OUTPUTS

(E)GPRS NETWORKDIMENSIONING

Without guarantees

With guarantees(optional)

CS load (Erlangs CS)CS blocking allowedPS load (kbps/cell)

Active features (DTX, PC, ...)TSL capability

Average user throughputMinimum user throughputMinimum PS load supported

Number of TRXs

Number of TRXsNumber of dedicated timeslots


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PROCEDURE

Using ErlangB formula

Calculate Erlangs PS and Timeslot capacity in an iterative way. Obtain the minimum number of TRXs needed to support this load.

Calculate the reduction factor (how resources are shared). Evaluate quality indicators (maximum, average andminimum PS load supported, average user throughput, etc).

Guarantee an average and a minimum user throughputs increase the number of TRXs if not achieved. Guarantee a minimum PS load in the cell depends on the number of channels dedicated for PS.

1. CSdimensioning

2. PSdimensioning

3. Calculateperformance

4. Guaranteeingperformance

OPTIONAL(only if operator wants

to guarantee somecapacity or quality)


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SUMMARY

DIMENSIONING CS dimensioninng (Erlang B formula) Calculate PS load (Erlang PS) Timeslot capacity [kbps] Calculate number of TRXs for those loads

PERFORMANCE Calculate Reduction Factor (how PS resources are shared) Evaluate performance:

E.g. Average user throughput = Average timeslot capability x RF x Timeslot capacity

GUARANTEING PERFORMANCE Incrementing the number of TRXs (more traffic can be supported or

the same with better quality) Dedicating timeslots for PS (a minimum capacity is guaranteed)


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EXAMPLE OF DIMENSIONING (1/10)

First phase: without guaranteeing capacity nor quality

EGPRS deployed on hopping layer (number of frequencies 12) CS traffic in busy hour is 5 Erlangs/cell PS traffic in busy hour is 200 kbps/cell CS blocking allowed is 2% Average MS timeslot capability is 3 timeslots DTX and PC for CS features are active


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Timeslot capacity

0

10

20

30

40

50

60

0 2 4 6 8 10 12 14

EFL [%]

TimeslotC

apacity[kbit/s]

Reuse 1/1 (9; 3) Reuse 1/1 (18; 3)



Step 2: Calculate Erlangs PS (1st iteration)

Initial TSL capacity = 40 kbps (EGPRS, BCCH)

Timeslot capacity = 37 kbps

Step 1: CS traffic dimensioning

ErlangB (5 Erlangs, T timeslots) < 2% T= 10 timeslots

==kbps

kbps

40

200Erlangs PS 5

Step 3: Calculate the timeslot capacity

Error 8.1 % Another iteration would be provide more accurate values=

= 10037

3740

Step 4: Compute accurate values

Backoff gain = 0.2 (assumed that transmission uses always 8-PSK)Equivalent Erlangs PS 7.2 EFL = = 7.5%=

+=

2

)2.05()2.05(

CSErlangsPSErlangs

)(12)(8

2.7

freqTSL

Timeslot capacity

= 37 kbps


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Step 5: Timeslots needed to support average PS load

Ns= int 5.4 = 6 timeslots

Step 6: Minimum number of TRXs for the average CS and PS loads

Assuming 2 or 3 TRXs, dedicated timeslots = 2 and guard timeslots = 2:

Total no. TSL = Max {10, (int 5 +2) + (int 5.4 - 2) }+ 2 = 13 timeslots

The number of TRXs is the minimum that fulfills: 12 timeslots < timeslots available for traffic

Number of TRXs Number of timeslots

1 7

2 14

3 22

4 30

5 37

Table 1. Timeslots available for traffic

2 TRXs are needed to support the average CS and PS loads

Shared timeslots = 10 Dedicated timeslots = 2 Guard timeslots = 2


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Step 7: Calculate the reduction factor

Using the RF table for EGPRS and 2 TRXs, and the interpolation procedure:

PS usage (%)

Erlangs PSP1

P0

P2

P3

P

( )%1.77

0185.0152212

4.5100(%) =

+=usagePS

RF = 0.175

Repeating this procedure withthe 10th percentiles,10th percentile of RF = 0.02126

where:P (5 ErlangsCS, 59.2% PS usage, RF)P0 (4, 70%, 0.208)P1 (4, 80%, 0.333)P2 (5.333, 80%, 0.198)P3 (5.333, 70%, 0.121)


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Step 8: Evaluate the performance of the EGPRS network

Maximum possible PS load = 12 timeslots available for PS traffic x 37 kbps/TSL = 444 kbps/cell

Average PS load supported = [12 TSL available for PS 5 ErlangsCS ] x 37 kbps/TSL = 259 kbps/cell

Minimum PS load supported = 2 dedicated TSLs x 37 kbps = 74 kbps

Average user throughput = 3 (timeslot capability) x 0.175 (RF) x 37 kbps/TSL = 19.4 kbpsMinimum user throughput = 3 (timeslot capability) x 0.02126 (10th perc. RF) x 25 kbps (TSL capacity at

the border of the cell for EGPRS) = 1.6 kbps

It should be noticed that the supported load (259 kbps/cell) is greater than the requirement (200 kbps/cell), so thedesign is correct.


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Second phase: guaranteeing capacity and quality(optional, only if operator wants to guarantee

some capacity and/or quality) Average throughput per MS is 64 kbps Minimum throughput (90% of the time at the cell

border) per MS is 32 kbps Minimum PS traffic supported is 100 kbps/cell


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Second phase: guaranteeing capacity and quality

Step 9: Guarantee a certain capacity and quality

a) Guarantee an average user throughputAverage user throughput = 3 (TSL capability) x 0.175 (RF) x 37 (TSL capacity)

= 19.4 kbps < 64 kbps another TRX is needed repeat from step 7

Step 7: Calculate the reduction factor: 3 TRXs RF = 0.986, 10th

percentile of RF = 0.980Step 9a) Guarantee an average user throughput

Av. user throughput = 3 x 0.986 x 37 = 109.4 kbps > 64 kbps 3 TRXs are enough

b) Guarantee a minimum user throughput (90% of connection time in bad radio link conditions)Minimum user throughput = 3 (TSL capability) x 0.980 (10th perc. RF) x 25 (min TSL capacity) =

= 73.5 kbps > 32 kbps 3 TRXs are enough


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Step 9: Guarantee a certain capacity and quality

c) Guarantee a minimum PS loadminimum load [Erlangs PS] = 100 (kbps/cell) / 37 (kbps) = 2.7 Erlangs PS

dedicated TSLs = 2.7 = 3

The following condition should be fulfilled:10 TSLs (CS) + 3 TSLs (dedicated) = 13 < 22 TSLs available for traffic OK


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Step (810): Evaluate the performance of the EGPRS network

Maximum possible PS load = 20 timeslots available for PS traffic x 37 kbps/TSL = 740 kbps/cell

Average PS load supported = [20 TSL available for PS 5 ErlangsCS ] x 37 kbps/TSL = 555 kbps/cell

Minimum PS load supported = 3 dedicated TSLs x 37 kbps = 111 kbps

Average user throughput = 3 (timeslot capability) x 0.986 (RF) x 37 kbps/TSL = 109.4 kbpsMinimum user throughput = 3 (timeslot capability) x 0.980 (10th perc. RF) x 25 kbps (TSL capacity at

the border of the cell for EGPRS) = 73.5 kbps

With 3 TRXs all the requirements are fulfilled.

Claro Network Dimension Ing Ppt

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