GO_NA23_E1_1 GSM Power Control Algorithm-34

7/15/2019 GO_NA23_E1_1 GSM Power Control Algorithm-34

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GSM Power Control Algorithm

Zte university



Brief Introduction

Rudiments of Power Control

ZTE Power Control Algorithms

Setting of Power Control Parameters

Application of Power Control



1. What is power control? Why we carry out

power control?

2. Classification of power control

3. Difference among various kinds of power

control

4. What’s the main object of power control?

5. How to conduct power control?

I. Rudiments of Power Control



1. What is power control? Why we carry out power

control?

What is power control?

Why should we carry out

power control?

Definition: Power control is to adjust the transmitting power of BTS

and MS according to real needs. Base: result of UL/DL measurement

Goal: to lower transmitting power, reduce interference in the whole

network and power consumption, on condition that speech quality is

ensured.



2. Classification of power control

Ordinary power control

Rapid power control



3. Difference among various kinds of power control

Static power

control

Under the non-idle mode, the network flexibly decides the

transmitting power of MS or BTS in a dynamic manner according to

radio environment.

Adopt fixed step to adjust power.

Adopt non-fixed step to adjust power, i.e. to settle power adjustment

at one go.

Power control in CS service.

Power control in PS service.

Impose restrictions on the max transmitting power of MS or BTS at

OMCR

Dynamic

power control

Ordinary power

control

Rapid power

control

CS power

control

PS power

control



4.What’s the main body of power control?

The main object of power control: TS and MS

Power control is directed at single subscribers, so the main

object of UL power control is single MS; for DL, it’s some timeslot

(ST) in the BTS used by the MS, Note it’s not the whole carrier.

It’s stipulated in the protocol that the transmission must be performed at

full power on the carrier of BCCH, so only UL dynamic power control

(not DL dynamic power control) can be carried out on the carrier of

BCCH.



5.How to conduct power control?

Collection of MS/BTS

measurement reports

Weighted average of MRs

If the average satisfies

conditions of power controldecision?

Condition for power

increase is satisfied

Condition for power

maintenance is satisfied

Condition for power

decrease is satisfied

Increase MS/BTS

transmitting power

Maintain MS/BTS

transmitting power

Decrease MS/BTS

transmitting power

Save the average

No

Yes



1. What power control algorithms are supported in ZTE systems?

2. What features do ZTE power control algorithms have?

3. What is sliding-window averaging?

4. What is Rapid averaging?

5. How is the initial state of ZTE power control algorithms defined?

6. How is the stable state of ZTE power control algorithms defined ?

7. What’s the relation between the initial state and stable state of ZTE power control

algorithms? 8. In which network element is ZTE power control realized?

9. How is measurement reports processed in ZTE power control algorithms?

10. How to judge conditions for power increase/decrease in ZTE power control

algorithms?

11. How to decide power increase/decrease value in ZTE power control algorithms (I)?

12. How to decide power increase/decrease value in ZTE power control algorithms (II)?

13. How to decide power increase/decrease value in ZTE power control algorithms (III)?

14. How to decide power increase/decrease value in ZTE power control algorithms (IV)?

15. Why bySub is introduced for the initial state of ZTE power control algorithms?

16. How is power control result measured in ZTE systems?

II. ZTE Power Control Algorithms



1. What power control algorithms are supported in

ZTE systems?

UL and DLRapid power control are notdiscriminated inversion 6.20and previousones.



2. What features do ZTE power control algorithms

have?



3. What is sliding-window averaging?

Definition: during averaging of measurement reports, when number of MR

reaches the window size (suppose it’s 4), calculate the first 4 MRs and get the

first average value; then calculate MR no.2 -5 and get the second average

value; and so on. Advantage: it can effectively disperse the influence of signal

fluctuation.

Disadvantage: it takes quite a bit of time to get the first average.



4. What is Rapid averaging? Definition: during averaging of measurement reports, which is not restricted by

average window, the first average value is obtained when the first MR is submitted;

and the second average value is obtained by calculating the first and second MRs;when number of MRs reaches the window size, rapid averaging is converted tosliding-window averaging.

Advantage: it reduces the time for triggering the first power control.

Disadvantage: its reliability is a bit low, as there are fewer samples of MRsparticipating in the decision.



5. How is the initial state of ZTE power control algorithms

defined?

When MS initially accesses into channel (SDCCH or TCH),the power control status it enters is referred as initial state.

Features of this state:

There is a big difference between the max transmitting power MS initially uses

and that actually needed.

It produces heavy influence on MS using other channels.

There is dramatic adjustment on MS and BTS power ranks, so there will be big

changes on MS and BTS power.

Usually it needs several consecutive times of rapid power adjustment.

Features of power control algorithm at this state:

Perform power control decision to each MR, adjust MS and BTS power

rank and make it reach the demanded level and quality in the shortest

time.



6. How is the stable state of ZTE power control

algorithms defined?

After experiencing the dramatic adjustment of power, MS reaches the requested UL

level and quality and enters a relatively stable situation, which is called stable state.

Conditions for MS entering stable state from initial state (either 1 or 2 is acceptable):

Condition 1: in most cases, MS power takes downward modulation in initial state; if

it stops downward modulation for N1 times, it’s supposed to have entered stable state.

Condition 2: when the number of measurement reports received reaches N2, MS

directly enters stable state.

Explanations on N1/N2 value:

Principle:N1<N2

Recommended value: N1-4, N2-11

N1 and N2 not only can be set some fixed value according to test result, but also can

be configured at OMCR; in order to maintain the compatibility of OMCR, currently

N1 and N2 are set the default value, and they can be adjusted through hyper-terminal.



7. What’s the relation between the initial state and

stable state of ZTE power control algorithms?

When MS enters initial state

of power control, it quickly

adjusts its power up to

demand;

When MS power stops

downward modulation for

N1 times, or when number

of received MRs reaches

N2, MS enters stable state;

Initial state and stable state

adopt different power

control strategies.

Initial state

MS power stops downward modulation for N1 times

Stable stateChannel release

Number of MRs received reaches N2

Channel power control enters

initial state



8. In which network element is ZTE power control

realized?

In ZTE system, power control is realized in BTS, which masters UL/DL dynamic

power control and reports the results to BSC at certain intervals, so that BSCcan collect related performance statistics. Refer to the following figure for the

logical location of power control elements.



9. How is measurement reports processed in ZTE

power control algorithms?



10. How to judge conditions for power

increase/decrease in ZTE power control algorithms?

LEVEL

CAUSE

QUAL

CAUSE

RESULT

0 0 POWER_STAY

0 1 DECREASE_BYQUALIT

Y0 2 INCREASE_BYQUALIT

Y

1 0 INCREASE_BYLEVEL

1 1 INCREASE_BYLEVEL

1 2 INCREASE_

BYQUALITY

2 0 DECREASE_BYLEVEL

2 1 DECREASE_BYLEVEL

2 2 INCREASE_BYQUALIT

Y

High level

threshold

Low level

threshold

Upper limit

of RxQual

Lower limit

of RxQual

Level HO

threshold

Quality HO

threshold

Increase

power

Decrease

power

Power stays

unchanged

RQ=0--7

R x l e v e l = 0 - - 6 3

LEVELCAUSE = 1

LEVELCAUSE = 0

LEVELCAUSE = 2

QUALCAUSE = 2

QUALCAUSE = 0

QUALCAUSE = 1



11. How to decide power increase/decrease value in

ZTE power control algorithms (I)?



12. How to decide power increase/decrease value of

in ZTE power control algorithms (II)?

Power control in initial state:

With the aim to carry out power control effectively, whether power is to increase or decrease, the step shall be the one set for power decrease, which shall be fixed.

1）MS power increase:

a) UL signal is bad, and no MS MR is received. If the difference between the MS power value

(computed through the current power control) and the last valid MS power value exceeds8dbm, then the current power control decision is valid, and MS power increase shall be

continued;

b) UL signal is good, MS MR is received by BTS; DL signal is bad, the power control value

hasn’t effectively controlled MS power, and the difference (bySub) exceeds 8dbm, then

power control shall not be imposed on MS any more;

2）MS power decrease:Regardless whether BTS has received MS UL MR or not, once the difference is less than

8dbm, power control shall not be imposed on MS;

3） As in BTS power measurement, the power adjustment benchmark value shall be the power

rank value of current BTS transmitting signal, and the calculation method is the same as that

of power control in stable state.




ZTE power control algorithms (III)?

Rapid power control: power increase/decrease in rapid power control shall be

carried out according to the following criteria. For level-related power increase/decrease control, specific conditions are needed in decision; if the

conditions are not satisfied, use the ordinary power control method.




ZTE power control algorithms (IV)?

Graph of ULordinary

power control:

Graph of UL

ordinary power

control with

rapid averaging

adopted:

Graph of ULrapid power

control:



15. Why bySub is introduced for the initial state of

ZTE power control algorithms?

After sending new power rank to MS, it takes an interval of at least three

MRs for BTS to receive MS power rank report, which makes it unable to

meet the requirement for each MR to adjust the last sent power control

value( byMSpowerSet) by 2dB in the initial state of power control.

A variable bySub is introduced, which represents the difference between

the power control value to be sent and the currently received power

value, whose limit is 8dbm.



16. How is power control result measured in ZTE

systems?

BTS reports power control results to BSC for performance statistics. Reporting period is

controlled by PwrCtrlReportPrd (SACCH multi-

frame) .

ZTE power control statistics are in collected inBTS measurement tasks, including cause and

times of power control. For details, please refer to

the fascicule of performance counters in attached

manuals.



1. What are the general cares of setting powercontrol parameters?

2. Recommended values of power control

parameters

3. What factors influence the speed of dynamic

power control?

III Setting of Power Control Parameters



1. What are the general cares of setting power

control parameters?



2. Recommended values of power control parameters

The recommended values are for reference, please make

appropriate adjustment according to actual network situations.

Parameter Recommended value 6.20.101e &subsequent

versions 6.20.101e&subsequent

versions Average window size 4 4

UL/DL RQ increase threshold 3 2 UL/DL RQ increase P/N value 2/3 2/3 UL/DL RQ decrease threshold 1 0 UL/DL RQ decrease P/N value 2/3 2/3

UL/DL level increase /

decrease thresholddefault default

UL/DL level increase /

decrease P/Nvalue2/3 2/3

Increase step 4db 4db Decrease step 2db 2db

Rapid averaging Enabled Disabled

Rapid power control Enabled Disabled

Power decrease limit 10，8，6，4，2，2，2，2 default Power control min interval 1 0

MS min power rank 18（900M）、14（1800M) 18（900M）、14（1800M) BS min power rank 15(900M)、14（1800M） 15(900M)、14（1800M）



3. What factors influence the speed of dynamic

power control?



1. In which circumstances can power control beapplied?

2. Which KPIs will be influenced by power

control?

3. In which aspects will power control influence

subscriber’s satisfaction?

IV Application of Power Control



1. In which circumstances can power control be

applied?

Normally UL ordinary power control is enabled, other power control types are

mainly applied in areas with dense sites, which can help reduce interference.The following table is for reference.



2. Which KPIs will be influenced by power control?

Power control influences transmitting power, which may impose some negative

effects on the level of coverage, and result in dramatic decrease in the

proportion of level above -75dbm.



3. In which aspects will power control influence

subscriber’s satisfaction?

GO_NA23_E1_1 GSM Power Control Algorithm-34

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