recommendation of ce expansion

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Recommendation of CE Expansion For Internal Use only

Product Name Confidentiality Level

WCDMA RNP For Internal Use Only

Product Version

Total 17 Pages1.0

Recommendation of CE Expansion

(For Internal Use only)

Prepared by

Luo Dan Date 2010-08-10

Reviewed by

Date

Approved by

Date

Huawei Technologies Co., Ltd

All Rights Reserved

5/30/2013 Huawei Confidential of 17




Contents

1.1 Overview..................................................................................................................................................................4

1.2 Basic of CE............................................................................................................................................................ ...4

1.3 Overview..................................................................................................................................................................6

1.4 Preparation................................................................................................................................................................6

1.4.1 Triggered Items...................................................................................................................................................6

1.4.2 Metric..................................................................................................................................................................7

1.5 Working Flow................................................................................................................................................. ......... .8

1.6 Overview.................................................................................................................................................................11

1.7 Load Control...........................................................................................................................................................11

1.8 Dynamic CE...........................................................................................................................................................12

1.9 CE Consumption.....................................................................................................................................................14

1.9.1 SRB Consumption............................................................................................................................................14





List of Figures

Counters may used..........................................................................8

Work Flow.......................................................................................9

Resources used by different load control algorithms........................12

LDR actions for CE..........................................................................12

HSUPA CEs consumption.................................................................13

Overview of dynamic CE resource management...............................13

SRB CE Consumed in HSDPA...........................................................15





1Overview

1.1 Overview

The present document gives a general way of Channel Element expansion

planning steps. Some basic ideas of CE are included too.

Procedures of hardware expansion are introduced in section 2and parameter optimization is covered in section 3. If part of below sections is used in the

report to operator, please select proper content accordingly.

1.2 Basic of CE

CE is the logical quantitative concept of DSP capability in baseband board

representing the capability of modulation/demodulation and coding/decoding.

This word is normally used in NodeB side while credit is more common in RNC

side (e.g. in counters of RNC) although these two words have the same

concept. The relation is 1 CE=2 credit in UL and 1CE=1credit in DL.

The CE resource in one NodeB is shared by cells/cell groups. It is one of the

kinds of resource that directly limit the cell load. Especially in live network,

customer may need suggestion from vendor, or even plan to guide the

expansion of CE as it’s a fast and efficient way to add more boards andeliminate the congestions caused by CE limitation.

The total CE capacity is restricted by two aspects. One is the physical capacity

which is limited by the baseband board configuration. Another one is license.

The overall capacity will be Min｛Physical capacity, License｛

Detailed of CE usage is not depicted in the protocol. The protocals describe the

coding and modulation principle but not the realization. The way of baseband





process and the metric of describing the capability are designed by vendor

itself.





2 Expansion Strategy

1.3 OverviewThe expansion strategy in this section introduces the steps of hardware

expansion of baseband board (WBBP etc.). The targets for CE expansion are

decreasing CE congestions and to meet the future traffic needs.

In planning period of network constructions, the planning of CE per site is

usually based on traffic model given by operaters. But in live network expansion

period, it is not always easy to use planning tools due to:

Usually the customer cannot or will not provide a detailed and precise

traffic model for planning.

Many planning tools (E.g. RND) put emphasis on the whole instead of

sites. And in live network it’s very common to have huge difference in

traffic or CE utility distribution among sites (or sites with the same

scenario).

So the strategy on a site basis is explained here to provide the estimation which

is more close to the network traffic.

1.4 Preparation

1.4.1 Triggered Items

The possible reasons for any resource expansion may come from:





Alarms. The alarms such as Number Of Users Almost Up To 90% Of

System Capacity can be monitored from OMC side to indicate the

resource threshold is near and attention should be paid.

KPI monitoring. The congestions due to resource limitation in terms of

KPIs (Cell basis).

New service introduced. When HSPA is introduced in hot spots or

more sites, it’s a common way of adding separate carrier for improving

HSPA performance effectively and efficiently.

So does CE expansion. Considering the difference between busy hour and

normal hour as well as the users’ experience, the triggering indicators for CE

expansion can be:

− Resource Occupied Ratio of Busy Hour

− Congested times in Busy Hour

− Resource limited alarms in a Week (just for reference)

The most important items and thresholds can be decided according to network

condition and top concerns.

During data preparation period, the data to be analyzed should be of certain

length to be representative (two weeks for example). Furthermore the peak

value can be averaged to exclude abnormal burst in sites with special event

during observing period.

1.4.2 Metric

The average CE utility ratio during the measurement period would be:

− UL: VS.LC.ULCreditUsed.CELL/Overall Capacity

− DL: VS.LC.DLCreditUsed.CELL/Overall Capacity

The result above is on a cell basis and by summing up we can have the NodeB

CE utility. Note that sometimes the sum of peak value will exceed the CE

capacity. This is because the maximum CE utility of every cell may happen at

different point in the measurement period.

Congestion times can be the sum of RRC and RAB failures caused by CE





rejection in UL and DL.

− UL: VS.RAB.FailEstCs.ULCE.Cong +VS.RAB.FailEstPs.ULCE.Cong + VS.RRC.Rej.UL.CE.Cong

− DL: VS.RAB.FailEstCs.DLCE.Cong +VS.RAB.FailEstPs.DLCE.Cong + VS.RRC.Rej.DL.CE.Cong

UL DL

VS.RAB.FailEstCs.ULCE.Cong VS.RAB.FailEstCs.DLCE.Cong

VS.RAB.FailEstPs.ULCE.Cong VS.RAB.FailEstPs.DLCE.Cong

VS.RRC.Rej.UL.CE.Cong VS.RRC.Rej.DL.CE.Cong

VS.LC.ULCreditUsed.CELL VS.LC.DLCreditUsed.CELL

VS.LC.ULCreditUsed.CELL.Max VS.LC.DLCreditUsed.CELL.Max

Figure 1.1 Counters may used

The congestion counters used are number of RRC/RAB failures and occupied

CE in the measurement period. Although the direct shortage of CE is hard to

obtain, we still consider the number of rejection can reflect part of the fact that

more CE should be added to sites with higher congestions.

————————————————————————————————————————

To get the counters, the Network Element takes the samples periodically. At the end of the measurement period, the accumulated data will be divided by the number of samples

and the result will be the counter value. So it is common for most of the counters having

average results. For some items there're dedicated counters for recording the peak value

in the measurement period.

1.5 Working Flow

With different limitation, input and threshold, there’re two calculation methods

we can use to decide what the number of boards adding to each site is.

1) Direct Threshold

This algorithm is to make thresholds for sites adding CE and repeat expansion

when monitoring congestions afterwards. The threshold (e.g. THD1) can be

loose or aggressive, restricted to the planned CE resource for expansion.





Figure 1.1 Work Flow

R avg is the average utility ratio reflecting the daily/hourly average utility ratio. It

equals to Used CE/ CE Capacity using counters above in 1.4.2. THD1 is the

threshold of CE congestion times for adding resource. N rep is the threshold of

number of days/BHs with threshold over THD1. The thresholds can be adjusted

based on different sets of parameters above.

2) Proportional Distribution

With defined number of baseband boards to be added (the number of CE is

also defined with typical type of baseband board), we can also get the allocation

in a proportional way.

THD2= Cong TOT/ Nbd

Where THD2 is the threshold for expansion, Cong TOT is the total congestion

times of all sites in selected time and N bd is the number of boards to be added.

For each site, the number of boards to add in site i will be:

Ni = [Congi / THD2] + 1

Where Cong i indicates the congested times of site i and [ ] is the integer of





numbers inside.

————————————————————————————————————————

If there’s traffic model forecast for future growth, the expected CE can be calculated by

adding that for PS, CS and other services. The part of CE eliminating current congestionsshould also be included in the traffic margins. Normally the model is not for typical site

so the result is not detailed to a site basis. It’s not covered here in present document.





3 Optimization Methods

1.6 OverviewBefore hardware expansion deployed, the parameter optimization also helps to

decrease the congestions due to CE limitation. Basic CE consumption is also

included in this part.

DCCC which is not covered below can also change consumed CE when

changing the BE data rate.

1.7 Load Control

As WCDMA is a self-interfering system, there must be load control algorithms to

control the system load in order to maintain a stable and effective system. They

also work on CE as that’s one of the major resources.

The resources triggered Load control actions are listed below. In fact, any

procedure which adjusts the system load would have impact on CE as well. For example, if PUC increases the possibility of UEs camping on F2 cell instead of

F1 cell (F1, F2 are two-carrier cells of same sector, planned to have the same

coverage), then the CE congested possibility in the near future is decreased in

F1 cell. Initial rate negotiation in IAC when different data rate selected, CE

consumed varies.





Figure 1.1 Resources used by different load control algorithms

In LDR action, the relative procedure triggered by any kinds of resource can

have a direct influence on CE consumed:

Figure 1.2 LDR actions for CE

When load control algorithms work, congestions of CE may be decreased.

1.8 Dynamic CE

In the uplink the CE is shared by HSUPA and R99 channels. When the data rate

of HSUPA is high, the UL CE consumed is really considerable. That's quite

possible of the UE having a very small throughput while CE corresponding to

maximum rate is allocated, which is a significant waste of resource.





Figure 1.1 HSUPA CEs consumption

Since RAN10, the dynamic CE resource management is introduced to provide a

more flexble solution.

Figure 1.2 Overview of dynamic CE resource management

The algorithm periodically adjusts the available CE resource for the users or

when a new user is permitted. NodeB calls back the unused CE when detecting

it's not fully used in a certain time, and also try to balance CE equitably among

serving RLS. In that case the CE utility ratio is improved. Note that when

Dynamic CE is activated, the HSUPA DCCC function should be deactivated

from RNC side.

In RAN11, 2ms fast CE scheduling is introduced with boards EBBI/EBBC/

WBBPb. Boards older than that adopt 500ms CE scheduling.





————————————————————————————————————————

The relation between HSUPA dynamic CE resource management and HSUPA DCCC is:

If all cells in AS support HSUPA dynamic CE, BE data rate is adjusted to MBR if it's not.HSUPA DCCC doesn't work.

If any cell in AS doesn't support HSUPA dynamic CE or the RNC cannot get any

capability information on this, HSUPA DCCC works.

1.9 CE Consumption

The CE consumption can be found in RNP Reference Guide, with conditions

and restrictions inside. The CE for R99 Bearers is regular and easy to see.

For HSDPA, seperate dedicated module is used to process HSDPA traffic. Thus

the HSDPA channel (HS-DSCH, HS-SCCH) itself don't cost any CE. But it's not

the same story for HSUPA (with original name E-DCH) and the CE consumed

for a high speed HSUPA service is quite remarkable. (However, NodeB of 3900

series have improvement and Dynamic CE would help as well)

1.9.1 SRB Consumption

Before SRBoverHSPA introduced in RAN10, SRBs are mapping to DPCH and

whenever there's SRB in DL/UL, there're CE occupied by these DPCH. Take

HSDPA UL SRB as example, the number of CE is more with a higher data rate.





Figure 1.1 SRB CE Consumed in HSDPA

When SRBoverHSPA is activated, DPCH for HSDPA DL SRB will be replaced

by F-DPCH and the former one CE for SRB channel can be saved. The UL SRB

is now mapped to HSUPA channels without additional CE consumed.

————————————————————————————————————————

Till second quarter of 2010, most UE still cannot support SRBoverHSDPA. So far most

SRB in DL is still on DPCH and cost one CE.

For most HSUPA UE, the SRBoverHSUPA is supportive.





4 Conclusion

The implementation and result of CE expansion is relatively easy and obvious.

But how to choose the site and the number of boards adding should be clear to

be accepted by operators.





5 References

3GPP 25.213 Spreading and modulation3GPP 25.331 Radio Resource Control

RAN Performance Counter Reference

RAN Feature Description

RNP Reference Guide


recommendation of ce expansion

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