wsgprspresentationprofwagen

8/6/2019 WSGPRSPresentationProfWagen

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Introduction to the challenges

of current GSM and GPRS planning

Technical PresentationTechnical Presentation


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Slide 2Prof. Dr. Volker Amelung / Dr. Karim Rizk Wavecall SA

Wavecall SA

Prof. Dr. Fred Wagen

Senior Consultant

Wavecall SA

Lausanne, Switzerland

[email protected]

Prof. in telecommunication at the Univ. of Applied Sciences(HES-SO)

in Fribourg, Switzerland (www.eif.ch/telecom)


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Outline

GSM-vs-GPRS = circuit-vs-packet:

so what ?

GSM & GPRS planning:

similarities and differences

The crucial role of radio propagation

prediction:

accurate model is a must

The challenges ahead:

prepare to react quickly


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The challenges of GSM and GPRS planning


so what ?




prediction:





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GSM and GPRS

BCCH

GSM-vs-GPRS : so what ?

but flexible multi-slots allocation for GPRS

GSM

Voice

GPRS

3 up

1 down

GPRS

1 up

2 down

then 3 down

GPRS

1 up

2 down

then 3 down

=> fewer empty slots


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GSM

Voice: a few errors can be tolerated but no delay

(< 200 ms)SMS: store & forward

WAP: connecting

data: 9.6 kbps CS or HSCSD on the move but notmoving


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GSM-vs-GPRS : Voice-vs-Data bearers

GSM voice GSM data13 kbps (Full Rate) 9.6 kbps

20 ms

12.2 kbps (EFR)

20 ms 20 ms

260 bits (FR) 260 bits (FR) 192 bits+padding

Interleaving on 8 bursts

R=1/2

456 bits

R=1/2 R=1/2

456 bits 456 bits


2x57 bits2x57 bits

Average 22.8 kbps per slot

270 kbps bursts on air interface




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GSM-vs-GPRS : GPRS Data

GPRS

9.05 kbps or 13.4 or 15.6 or 21.4 kbps

20 ms

181 bits or 268 or 312 or 428 bits

R=1/2 or 2/3 or 3/4 or no coding

CS1 or CS2 or CS3 or CS4456 bits

Similar to GSM data but

4 Coding Schemes

=> 4 data rates




2x57 bits


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GSM-vs-GPRS : coverage

GSM voice

Voice Quality

(e.g.,MOS)

Analog

voice Sufficient quality

Transmission quality

GSM

C/I

Good

enough

bad

9 to 12 dB


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GSM-vs-GPRS : quality coverage

Quality is a subjective opinion

Good

Threshold

Bad

Must be set by operator to quantify quality

and simplify the identification of problems.


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GSM-vs-GPRS : coverage

GPRS : even more difficult

Voice Quality

(e.g.,MOS)

Analog

voice

Sufficient quality

Transmission quality

GSM

C/I

Good

enough

bad

9 to 12 dB

Data Quality

(here bit rate)

CS1

CS2CS3

CS4GSM voice

C/I9 13 17 25 dB


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GSM-vs-GPRS : coverage - urban

GPRSGSM voice

No coverage or

other cell

coverage

CS4

CS3CS1

CS2

2

3

3.5

4

9 kbps

13 kbps

16 kbps

21 kbps

Urban environment


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GSM-vs-GPRS : coverage - LOS

GSM voice GPRS

CS4

CS3

CS1

CS2

Free space

4

8

12

16

13 kbps

16 kbps

21 kbps

9 kbps

No coverage or

other cell

coverage


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GSM-vs-GPRS

Requirements for planning


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GSM-vs-GPRS : Voice-vs-Data

GSM voice

13 kbps (Full Rate)

1 slot up /

1 slot down

(total of 2)

Support ~1% FER

Plan coverage for voice service

GSM data

CS: 9.6 kbps (or 14.4 kbps)

HSCSD

n*9.6 (or 14.4) kbps

1,2 or 3 slots up /3, 2 or 1 slots down

(total of 4)

Error must be handled with ARQ

For users on the moveaccepting best effort service

and/or non-moving


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GSM voice

13 kbps (Full Rate)

1 slot up /

1 slot down

(total of 2)

Support ~1% FER

Plan coverage for voice service

GPRS

Packet data

n*9 or *13 or *16 or *21 kbps

n = 1,2 or 3 slots up /3, 2 or 1 slots down

(total of 4)

Errors must be handled with ARQ

Plan multi-coverage

for new services


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GSM voiceTraffic characteristics are well

known

Quality is in fact

a best effort service

but

good planning

lead to acceptable quality

GPRSTraffic characteristics are unknown

Quality depends on service profile:Precedence class: indicates the importance

of the packet with regard to discarding it in

case of problems and degradation of QoS

when necessary.

Reliability class: specifies the mode of

operation for various error detection andrecovery protocols & how securely the data

should be delivered.

Delay class: specifies the transfer delay

including the uplink radio channel access or

downlink radio channel scheduling delay, theradio channel transit delay, and GPRS

network transit delay.

Peak throughput class: defines the

maximum transfer rate.

Mean throughput class: defines the long

term average transfer rate.


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so what ?




prediction:





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GSM & GPRS planning: similarities & diff.

GPRSNumber of subscribers ???

Traffic statistics ???

+??? simulation

+

Reserve channels for GPRS

if needed

combined planning

With GSM

Very difficult to plan

Offer best effort servicethen plan to be flexible

and follow the demand

GSM voiceNumber of subscribers

Traffic statistics

+Erlang B

+

Add control channel if SMS traffic

increases

Conventional planning

Still not easy to plan when

exponential growth


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GSM voice GPRS

no drop regions

(e.g., indoor)Blue = with indoor coverage

Red = enhanced capacity

Green = GPRS capacity

Brown = GPRS high throughput

handy coveragemust work


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GSM voice GPRS

Coverage Traffic data

Interference

Matrix

Tools Experience

FP (Frequency Plan)

C/I

OK

Yes, load FP in network

No

C/I

= propagation

prediction

CoverageTraffic data

Interference

Matrix

Tools Experience

FP (Frequency Plan)

C/I

OK

Yes, loadFP in network

No

C/I

Combine

GSM planning and

GPRS-CS1 to 4 analysis

Many more and faster

iterations are required


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GSM voice and GPRS

Cannot be planned separately ( or consider full load).

Introduce GPRS slowly but be prepared for rapid take-off( i-mode scenario):1. If easy user interfaces are developed (e.g., a mobile

internet button on every terminals),

2. If appropriate charging is used (e.g., set-up time is eithershort or not billed, flat rate combination),3. If the market can decide (open to innovative services).

New Key Performance Indicators (KPI) must be developedand used.

Tools must be as accurate and as easy to use as possible toconcentrate on difficult tasks.


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so what ?


similarities and differences The crucial role of radio propagation

prediction:


The challenges ahead:prepare to react quickly


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Radio propagation prediction

CoverageTraffic data

Interference

Matrix

Tools Experience

FP

C/I

OK

Yes,

load FP in network

No

C/I

Since GPRS traffic is unknown, only

various scenarios can be investigated.

Starting with a best-effort GPRS add-on to

an existing GSM network, various growth

scenarios must be taken into account or

ways to deploy rapidly the required level of

GPRS quality must be found.

In both cases, tools allowing to quickly and

accurately assess the quality of a possibledeployment are then critical.

Proper coverage is key:

=> accurate and fast radio propagation

prediction model is a must in an integratedplanning tool.


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Radio propagation prediction

Conventional models.

The smaller the cell the worse

the inaccuracy.

Need tuning => measurements

=> time.

Need experience to mitigate the

drawbacks.

OK with GSM: took 10 years to

be fully deployed.

Fast and accurate

WaveSight.

Accuracy independent of cellsize.

No need for tuning.

Need measurements to

convince first time users.

Allows to test various GSM-

GPRS scenarios before fieldtests and deployment.


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so what ?


similarities and differences The crucial role of radio propagation

prediction:


The challenges ahead:prepare to react quickly


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The challenges ahead: react quickly

!! !

!

? Plan all possibilities ?

Or prepare to react quickly ?


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The challenges ahead: react quickly

Everything may not work as expected :

Suppress the guess work wherever you can

accurate propagation predictions will help

C l i


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Conclusion

GSM and GPRS have the same FDMA-TDMA air-

interface.

But different coverage characteristics depending ondata rate (Coding Scheme), on unused voice slots,

and on expected or required user services.

Challenges are coming from the many unknowns.

Number of unknowns can be reduced by using more

accurate planning tools wherever possible. Gather

the proper tools, databases and methodology now !

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