05 RN20025EN20GLA0 (E)GPRS Network Optimization

8/13/2019 05 RN20025EN20GLA0 (E)GPRS Network Optimization

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(E)GPRS Network Optimization

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1 © Nokia Siemens Networks RN20025EN20GLA0

EGPRS Explain

(E) GPRS Network optimization




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Module objectives

After c ompleting this lea rning ele ment, the partici pan t wi ll be able to:

Theory:

• Sketch the (E)GPRS Optimisation process and the main optimisation tasks• List the most important tools for (E) GPRS planning and optimisation• Know some important KPIs




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(E)GPRS BSS Network Optimization - Structure

GSM Network Optimization

• Coverage maximization

• Interference reduction• Capacity optimization (air interface and connectivity)


• Signaling capacity & resource allocation improvement

• Data Rate

– Connectivity Capacity (MS-SGSN)

– TSL data rate improvement and multislot usage maximization (BSS)

– End to End (E2E) data rate (applications)

• Mobility improvement

– NCCR /NACC

– Intersystem interworking




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GSM Network OptimizationThe optimal GSM network from PSW services point of view has:

As high signal level as possible

• It means that even the indoor signal level should be high enough to have MCS9 for getting the highestdata rate on RLC/MAC layer.

As low interference as possible

• The aim of having high C/I is to avoid throughput reduction based on interference.

Enough capacity

• Enough BSS hardware capacity (interface and connectivity) is needed to provide the required capacity forPSW services in time. Both CSW and PSW traffic management should be harmonized with the layerstructure and long term plans.

As few cell-reselection as possible

• The dominant cell coverage is important to avoid unnecessary cell-reselections for mobility. The PCUallocation can help to reduce the inter PCU cell reselections.

• Dominant cell structure can help to maximize the signal level and reduce the interference, too.

Features

• All the features should be used which can improve the PSW service coverage, capacity and quality ingeneral. Examples:

– Since S14 it is possible to use (E)GPRS on DFCA TRXs – The (E)GPRS coverage can be used in the extended area

Before any (E)GPRS optimization related activities the GSM network should be optimized!!!




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GSM Network Optimization - features

The following information should be collected related to the volume of network element and connectivity usageof network elements:

• # of BSCs• # of PCU/BSC ratio

• # of BCF/PCU ratio

• # of Cells/PCU

• # of Abis TSLs/PCU (only legacy Abis)

• # of DAP/PCU (only legacy Abis)

• Average DAP size/BCF (only legacy Abis)

• # of Gb links size/PCU or PSEThe connectivity limits can be estimated based on the list above.

The following information should be collected related to terminals used in the network:

• Ratio of AMR capable terminals (they are more tolerant to interference)

• Ratio of R97, R98, R99, R4, R5, R6, R7, R8 capable terminals (some functionalities are related with

Release• Ratio of the different tsl capability terminals (like 1+2, 4+2, dual carrier capable, etc)The capacity requirements and feature possibilities can be analyzed by the list above


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Mobility Planning

Outage measurements: Trace example:

Event name Time Channel Message

RLC/MAC Uplink 20:42.0 PACCH "EGPRS_PACKET_DOWNLINK_ACK/NACK"Layer 3 Downlink 20:42.0 BCCH "SYSTEM_INFORMATION_TYPE_1"

Layer 3 Downlink 20:42.0 BCCH "SYSTEM_INFORMATION_TYPE_2"



… … … …


Cell Reselection 20:42.8 from CI 5032 to CI 5033


… … … …


L ayer 3 Upl ink 2 0:43 .1 R ACH "CH ANNE L_REQU ES T"

Layer 3 Downlink 20:43.2 CCCH "IMMEDIATE_ASSIGNMENT"

Layer 3 Downlink 20:43.2 CCCH "PAGING_REQUEST_TYPE_1"




… … … …


RLC/MAC Uplink 20:43.8 PACCH "PACKET_RESOURCE_REQUEST"

RLC/MAC Downlink 20:44.0 PACCH "PACKET_UPLINK_ASSIGNMENT"RLC/MAC Downlink 20:44.0 PACCH "PACKET_DOWNLINK_DUMMY_CONTROL_BLOCK"

RLC/MAC Downlink 20:44.0 PACCH "PACKET_DOWNLINK_DUMMY_CONTROL_BLOCK"

… … … …

RLC/MAC Downlink 20:44.2 PACCH "PACKET_DOWNLINK_DUMMY_CONTROL_BLOCK"RLC/MAC Downlink 20:44.2 PACCH "PACKET_DOWNLINK_ASSIGNMENT"

RLC/MAC Uplink 20:44.3 PACCH "EGPRS_PACKET_DOWNLINK_ACK/NACK"

Cell Outage

Data Outage




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Diff. Between BSS andtill Packet Uplink Assign. (ms) till Packet Downlink Assign. (ms) full cell-outage (ms)

2.07 2.341 0.273.07 3.349 0.282.09 2.354 0.262.10 2.358 0.262.09 2.375 0.282.11 2.393 0.282.10 2.658 0.562.09 2.355 0.262.11 2.395 0.282.10 2.38 0.286.00 6.254 0.262.12 2.379 0.26

2.094 2.629 0.542.09 2.631 0.542.14 2.7 0.562.07 4.011 1.942.10 2.379 0.282.10 2.385 0.282.37 2.80 0.43

From EGPRS PACKET DOWNLINK ACK/NACK

Cell Outage Time witin one PCUOutage measurements:

-Cell Outage (MS - PCU) is measured between the first BCCH observation and PacketUplink Assignment

-Data Outage (MS - SGSN) is measured between the first BCCH observation andPacket Downlink Assignment

Measurement examples:

Big variations can beseen, values are onlyexamples and can not

be seen by counter

data




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Cell Outage Time with LAU/RAU change

Outage measurements as seen byMS:

Cell Outage (MS - PCU) is measuredbetween the first BCCH observationand Packet Uplink Assignment with LAand RA Update procedure

Data Outage (MS - SGSN) ismeasured between the first BCCHobservation and Packet Downlink

ACK/NACK after Routing Area UpdateComplete

… … … …

Layer 3 Downlink 8:44:05.801 BCCH "SYSTEM_INFORMATION_TYPE_1"… … … …

Layer 3 Downlink 8:44:10.797 BCCH "SYSTEM_INFORMATION_TYPE_13"Cell Reselection 8:44:10.906 from 5691 to 5753

Layer 3 Downlink 8:44:11.018 BCCH "SYSTEM_INFORMATION_TYPE_2"… … … …

L aye r 3 Up lin k 8:4 4:11.9 97 RACH " CHANNEL _REQUEST "Layer 3 Downlink 8:44:12.101 CCCH "IMMEDIATE_ASSIGNMENT"Layer 3 Upl ink 8:44:12 .313 SDCCH "LOCATION_UPDATING_REQUEST"Layer 3 Downlink 8:44:12.353 SACCH "SYSTEM_INFORMATION_TYPE_6"Layer 3 Upl ink 8:44:12 .388 SACCH "MEASUREMENT_REPORT"Layer 3 Upl ink 8:44:12 .548 SDCCH "CLASSMARK_CHANGE"Layer 3 Downlink 8:44:12.764 SDCCH "CIPHERING_MODE_COMMAND"Layer 3 Upl ink 8:44:12 .784 SDCCH "GPRS_SUSPENSION_REQUEST"Layer 3 Upl ink 8:44:13 .020 SDCCH "CIPHERING_MODE_COMPLETE"Layer 3 Downlink 8:44:13.224 SDCCH "IDENTITY_REQUEST"Layer 3 Upl ink 8:44:13 .350 SACCH "MEASUREMENT_REPORT"Layer 3 Upl ink 8:44:13 .490 SDCCH "IDENTITY_RESPONSE"Layer 3 Downlink 8:44:13.697 SDCCH "LOCATION_UPDATING_ACCEPT"Layer 3 Upl ink 8:44:13 .799 SACCH "MEASUREMENT_REPORT"Layer 3 Downlink 8:44:14.168 SDCCH "MM_INFORMATION"Layer 3 Upl ink 8:44:14 .284 SACCH "MEASUREMENT_REPORT"Layer 3 Downlink 8:44:14.399 SDCCH "CHANNEL_RELEASE"

… … … …

… … … …

… … … …

Layer 3 Uplink 8:44:16.258 PDTCH "ROUTING_AREA_UPDATE_REQUEST"RLC/MAC Uplink 8:44:17.401 PACCH "PACKET_RESOURCE_REQUEST"RLC/MAC Downlink 8:44:17.607 PACCH "PACKET_UPLINK_ASSIGNMENT"

… … … …

RLC/MAC Downlink 8:44:17.886 PACCH "PACKET_DOWNLINK_ASSIGNMENT"… … … …

Layer 3 Downlink 8:44:18.950 PDTCH "ROUTING_AREA_UPDATE_ACCEPT"Layer 3 Uplink 8:44:18.964 PDTCH "ROUTING_AREA_UPDATE_COMPLETE"RLC/MAC Uplink 8:44:19.119 PACCH "EGPRS_PACKET_DOWNLINK_ACK/NACK"

… … … …

Event name Time Channel Message




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PCU Allocation Plan

The proper allocation of the cells among PCUs can help to maximize the number of intra PCUcell re-selections, which is the most stable cell re-selection event.

• RLC/MAC layer: The intra PCU cell re-selection takes less time compared with inter PCU cellreselection• LLC layer: In case of intra PCU cell re-selection the un-transferred data is moved to new cell

(BVCI) and the transfer can be continued on new cell without packet loss on higher layer,while in case of inter PCU cell re-selection the un-transferred data is not moved to new cell(BVCI).

The following rules can be followed:• The cells of one BCF should be connected to the same PCU• The neighbor relations with high re-selection traffic should be connected to the same PCU• The neighbor relations in very bad signal and quality environment should be connected to the

same PCU

NACC* and NCCR can be used to enhance the performance of cell reselections, becauseoffsets can be defined avoiding too many inter PCU cell reselections for example(* NACC basically is working inside BSCs only, can be enhanced to work between BSCs)




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LA/RA Design – Radio Aspects

Radio Aspect of LA/RA Design• too big LA/RA will increase the paging, while too small LA/RA will increase the amount of

LA/RA Updates. So the balance should be found between too big and too small LA/RAs.• a bad LA/RA border design can significantly increase the amount of signaling what can lead

to an increase of the cell-reselection outage on the LA/RA border.• The LA/RA border should be moved from those areas where the normal CSW and PSW

traffic is very high.• The combined RAU (NMO I with Gs) is shorter compared to NMO II

• A class B MS (and class A MS without DTM support) has to suspend GPRS services while indedicated mode. Once the dedicated connection is finished, GPRS services have to beresumed. This can be done by an RA update. Since S11.5 the Resumption is provided by theBSC without need for RA update.




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(E)GPRS Network Optimization - Netact

BSCNetAct

Measurement data

Measurement administration

NetAct Reporter is a family of applications for processing, analysing, andvisualising performance data that is coming from different sources. Raw data

becomes meaningful information that is visualised in graphical and textualreports. NetAct Reporter gives a view of the network and serviceperformance and makes it possible to analyse network data, create reportsbased on the data and distribute the information.




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(E)GPRS Network Optimization - KPI

NetAct reporter counter and KPI analysis gives exact picture about network performance.

The analysis of KPIs can be based on the following list:

Signaling related KPIsCCCH usage and congestion

TRXSIG congestion

BCSU load

Data rate and Territory related KPIs

Network usage (RLC Payload, Packet Erlangs, etc)

Data rate (CS - MCS selection, retransmission, UL BLER, throughput, etc.)

Blocking (timeslot sharing, soft blocking, hard blocking, EDAP congestion, PCU congestion,Gb congestion, etc)

Mobility related KPIs

TBF release due to flush

Features like NCCR and NACC will not only increase the performance of thenetwork in general, additionally better statistics will get available, helping again toincrease the performance of the system!




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Tools for (E)GPRS Planning

The field measurements and drive tests are usually used for analyzing accessibility, data ratemeasurements in stationary and mobility environment to see the end-users perception.

PSW (Packet Switched) accessibility analysis

The PSW accessibility measurements measure the success rate and time period of access tothe PSW core (GPRS attach and PDP context activation), as well as the access to BSS(TBF establishment).

- Accessibility measurements contain GPRS attach/detach, PDP contextactivation and TBF establishment/release measurements.

- The attach/detach, PDP context activation/deactivation and Routing AreaUpdate are LLC related measurements (MS-SGSN) and can be measured andtrouble shooted.




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TCP/IP measurementsUseful commands in IP networks to estimate end to end performance:

1. Ping: The command Ping can be used to check the network Round Trip Time to one orseveral remote hosts. The command runs an application which generates an ICMP (Internet

Control Message Protocol) Echo Request data packet (this is an IP packet with Protocol = 1,Type field = 8) which is sent to the host. An Echo Reply is expected from the host (this is anIP packet with Protocol = 1, Type field = 0

Example: Ping 0.0.0.0 – 1000 where 0.0.0.0 is an IP address and 1000 the size ofthe ping package in Bytes

2. Tracert: The Tracert (trace route) tool checks the route to a destination by sending ICMP(Internet Control Message Protocol) Echo Request data packets with different TTL (time tolive) values starting with TTL=1 for the first packet, then TTL=2 for the next packet,…

Example: tracert 0.0.0.0 where 0.0.0.0 is an IP address

3. PathPing: The tool PathPing extends the features of the Ping and Tracert commands andoffers more information than those commands do.

During a certain time, data packets are sent to each node contained in the path to a certaindestination. Statistics are calculated based on the data packets which are sent back from

these nodes. Since the PathPing command shows losses of packets for each of the nodesand each connection, this command can be used to localize those nodes and/or connectionsmaking problems.

Example: pathping 0.0.0.0 where 0.0.0.0 is IP address




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Throughput analysis – Stationary

- Average throughput (RLC/MAC and Application)

- MCS distribution- RX Level

- BLER

- C/I ratio

Throughput analysis – Mobility (intra/inter PCU and RAU cell-reselection)

- Cell reselection latency

- RLC/MAC

- LLC

- Application level

- Retransmission based on cell reselection

The throughput analysis is always the analysis of signal level and C/I, becauselow data rate can be caused by signal, capacity and interference issues

Tools for (E)GPRS Planning


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Tools for (E)GPRS Planning As supplement to drive tests from network side protocol analyzer provide real-timemonitoring and analysis on different interfaces. Several vendors supported by NSN

- Nethawk- Tektronix- AgilentOther post-processing toolscan help to analyzethe measurementscaptured by thedrive test tools,protocol analyzersand applicationtesters.

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05 RN20025EN20GLA0 (E)GPRS Network Optimization