comparison of 40w & 20w pa

8/4/2019 Comparison of 40W & 20W PA

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2 QUALCOMM CONFIDENTIAL

Introduction

Service providers frequently come across with suggestions of using

higher power amplifier (40W instead of 20W PA) for Node B to avail of

capacity advantages.

This document discusses comparative advantages & disadvantages of

using higher Node B power (40W vis-a-vis 20W PA) based on both

theoretical (link budget) analysis and case study done with Merida for

following scenarios.

a) Interference Limited Scenario (Multi-BTS environment; 28 sites)

b) Noise Limited (Coverage Limited) Scenario (Outskirts area)

Impact of 40Watt PA on HSDPA throughput for uneven traffic

distribution has also been discussed separately.

The details of all the above are provided in the following slides.


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Interference LimitedScenario

Analysis Based on Link Budget(Uniform Traffic Distribution)


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Interference Limited

Scenario

Analysis Based on Link Budget (Uniform Traffic Distribution)

Analyses were carried out to ascertain max. number of CS64 users (at cell

edge) with uniform forward link loading of 70% for i) 20 Watt & ii) 40 Watt PA.

It is calculated from link budget that in order to meet same pilot and CS64service coverage targets, all channel powers need to be increased by 3 dB.

As a result, total number of users that can be served does not increase with

40 Watt PA.

Based on link budget, it can therefore be concluded that if traffic is uniformlydistributed, usage of 40 Watt PA will not provide any capacity advantage.

Summary of results along with link budgets are provided in following slide.


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Interference Limited

Scenario

Analysis Based on Link Budget (Uniform Traffic Distribution)

DownlinkBudget- W- W22 22

PA TypeRequired Pilot

Power (dBm)

Required Traffic

(CS ) Channel22

Power (dBm)

Max. No. of CS Users22

at Cell Edge (with %22

PA Loading)

Watt22 22 22 .444

Watt22 22 22 .222


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Analysis Based On StaticSimulation in Asset

(Uniform Traffic Distribution)


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Interference Limited Scenario

Analysis Based on Static Simulation in Asset (Uniform FL Loading)

Static coverage analyses were carried out for a cluster of 28 sites of Merida for

following scenarios to determine forward link pilot coverage improvement.

a) Static pilot coverage with 70% FL load for 20 Watt PA

b) Static pilot coverage with 70% FL load for 40 Watt PA (all common channel

powers increased by 3 dB as per link budget)

c) Static pilot coverage with 70% FL load for 40 Watt PA (common channel

power remain same as 20 Watt case)

From the statistical report, it is established that no improvement in Ec/Io isobserved in (b) with respect to (a). Also, (c) is found to be very poor in terms

of Ec/Io.

Summary of results along with detailed simulation statistics are provided in

following slide.





Pilot RSCP >

- dBm222

Pilot Ec/Io >

- dB44

Watt22 Static Simulation with % FL Load22 . %2222 . %4444

Static Simulation with % FL Load22

(Control Channel power increased by d2

as per link budget)

. %2222 . %2222

Static Simulation with % FL Load22

(without increasing Control Channel

power by dB)2

. %2222 . %2222

Percentage of Area with

PA Type Scenario

Watt22

Static Comparison

W W22 22





Conclusion

Considering the fact that forward link pilot coverage is determined by both

RSCP and Ec/Io, maximum coverage area percentage (98.95%) does notincrease by using 40W PA.

Usage of 40W PA shall necessarily have to be associated with increase of

pilot and other control channel powers by 3dB. Otherwise, significant

deterioration in Ec/Io coverage will be experienced. Usage of 40W PA however, increases pilot RSCP strength. In case of forward

link pilot RSCP limited scenario, this might help in improving coverage.




Analysis Based On MCSimulation in Asset

(Uniform Subs Distribution)




Analysis Based on MC Simulation in Asset (Uniform Subs Distribution)

MC simulations were carried out for the same cluster of Merida under

following scenarios to determine improvement in forward link blocking.

a) MC simulation with 5,000 voice users for 20 Watt PA

b) MC simulation with 5,000 voice users for 40 Watt PA (all common channelpowers increased by 3 dB as per link budget)

c) MC simulation with 5,000 voice users for 40 Watt PA (common channel

power remain same as 20 Watt case)

d) MC simulation with 5,000 voice users with 40Watt PA at FL limited sectors

only (other sectors with 20Watt PA)

The voice users have been allowed to be distributed uniformly as per

simulation process. No clutter weight has been used for this study.

Summary of results along with detailed simulation statistics are provided in

following slide.





MC Simulation

Comparison

Low Pilot Low Eb/No

Watt22MC Simulation with ,22 2 2

voice users. %444 . %222 . %222 . %222

MC Simulation with ,22 2 2

voice users (Control Channel

power increased by dB as2

per link budget)

. %222 . %444 . %222 . %444


voice users (without

increasing Control Channel

power by dB)2

. %222 . %222 . %222 . %222

Watt &22

Watt22


voice users ( Watt PA used2 2

for FL limited sectors)

. %222 . %222 . %222 . %222

Percentage

of Failures

(due to RL)

Total

Percentage

of Failure

ScenarioPA Type

Watt22

Percentage of Failures

(due to FL)





Conclusion

From the previous analyses, it is evident that increasing PA power to 40W

does not result in any improvement of total failure percentage.

For 20W scenario, 1.8% failure happened due to forward link limitations (low

pilot and low Eb/No).

Although above were almost resolved by using 40W PA, this however could

not result in any overall improvement as additional failures happened due to

reverse link limitation.

It can therefore be concluded that improvement of only forward link does not

guarantee any betterment of performance.



Coverage Limited Scenario

Analysis Based On StaticSimulation in Asset

(Unloaded Scenario)


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Analysis Based on Static Simulation in Asset (Unloaded Scenario)

Unloaded static coverage analyses were carried out in following scenarios for

an outskirts site of Merida to ascertain coverage improvement (if any) by

using 40Watt PA.

a) 20Watt PA with control channel powers as per link budget

b) 20Watt PA with control channel powers increased by 3dB from (a) above

c) 40Watt PA with control channel powers increased by 3 dB from (a) above

d) 40Watt PA with control channel powers increased by 6 dB from (a) above

Summary of results along with link budgets are provided in following slide.


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Pilot RSCP >

- dBm222

Pilot Ec/Io >

- dB2

Unloaded Static Simulation(CPICH= dBm)22

.444 .222

Unloaded Static Simulation

(CPICH= dBm)44.444 .2222


(CPICH= dBm)22.222 .2222


(CPICH= dBm)22.444 .2222

PA Type Scenario

Forward Link Coverage

Area (Sq. Km.) for

Watt22

Watt22

Isolated Coverage

Comparison


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Conclusion

From the previous analyses, it is evident that for same CPICH (and other

control channel) powers, pilot coverage boundary remains unchanged for

both 20W and 40W PA.

Forward link coverage continues to increase with the increase in control

channel powers.

Accordingly, for 37dBm of pilot power setting, maximum coverage is obtained

for 40Watt PA.

It may however be noted that above does not guarantee any actual coverage

improvement. Actual coverage improvement will be obtained if reverse link is

found to be strong enough to meet larger pilot coverage footprint.


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Impact OnHSDPA

Qualcomm Simulation(Uneven Traffic Distribution)


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Impact On HSDPA

Qualcomm Simulation (Uneven Traffic Distribution)

In order to investigate whether 40Watt PA would result in significant gain in

terms of single user application layer throughput, simulations were carried out

by Qualcomm for Cat. 8 and Cat. 12 UE.

The CS load (voice users) of neighboring cells were varied between 0% to

100% while the HSDPA serving cell was always loaded to 100% with HSDPA

traffic (20% of the power was allocated to common channels of the cell).

The following slide shows the derived average results for the single-user

application (eg. FTP) layer throughput.


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Impact On HSDPA


UE TypeNeighbor Cell

Load

Average Application

Throughput Gain from

W to W22 22

%2 . %22

%22 . %22

%222 . %22

%2 . %444

%22 . %222

%222 . %22

Cat. 22

Cat. 2


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Impact On HSDPA


Conclusion

Gain of low capability UE (Cat.12) is quite limited (max. 7.4%) as more power

does not help a limited number of codes.

On the other hand, significant gain (33%) is experienced with Cat. 8 UE due to

better utilization of 16QAM modulation (in case of no neighbor cell load).

This gain gradually diminishes with increasing neighbor cell load and virtually

no gain (0.3%) is experienced with 100% neighbor cell load.

Based on above, it can be concluded that 40Watt PA does not provide

capacity gain in an evenly loaded scenario but does provide gains in isolated

or typically indoor cell scenario.

The detailed document on above [80-W0976-1] will be released for AMX.


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Conclusi

on


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Conclusion

For interference-limited scenario (likely to exist in high & medium traffic areas)

usage of 40Watt PA is unlikely to provide any capacity advantage over 20Watt

PA under near-uniform radio network loading condition.

For isolated coverage scenario, usage of 40Watt PA will enable the user to

increase forward link coverage footprint while reserving adequate power for

traffic channels (compared to 20Watt PA). This however will ensure actual

coverage gain if reverse link is strong enough to match larger forward link

coverage boundary.

For uneven traffic scenario, as observed in HSDPA simulation study, capacity

gain is expected by using 40Watt PA. The gain will however largely depend onUE capability and loading of surrounding cells. As the surrounding cell loading

increases, the gain will diminish.

In view of all the above, it is recommended to opt for case-by-case decision to

select power amplifier type (20Watt or 40Watt).


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Conclusion

Considering the vendor-specific cases for AMX, it is understood that for

Ericsson, NodeBs will be equipped with 40Watt PA which can be used as

either 40Watt single carrier PA or two carriers each of 20Watts. Therefore, for

Ericsson regions, it is recommended to start service with 20Watt PA and

reconfigure the site for 40Watt as per requirement.

For Nokia on the other hand, NodeBs are fitted with 40Watt PA but will require

an additional software key to activate the same. Therefore, for Nokia regions,

it is recommended to use 20Watt PA (40Watt PA without software activation)

at the launch of service and activate the software key based on site specific

requirement.


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You

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