06/09/2005Master's Thesis Seminar - Jesse Kruus 1 Analyzing and Developing Base Load for WCDMA Base...

06/09/2005 Master's Thesis Seminar - Jesse Kruus 1

Analyzing and Developing Base Load for WCDMA Base Station

Automated Testing System

Thesis written at Nokia Networks in Espoo

Author: Jesse Kruus

Supervisor: Prof. Sven-Gustaf Häggman

Instructor: M.Sc Markku Pellava

Master's Thesis Seminar - Jesse Kruus 206/09/2005

Agenda

Background, research questions and methods

Analysis of real 3G network traffic Base load development Conclusions and future considerations Questions


Background, research question and methods The Thesis was done as a part of an automation project at Nokia

Networks. The purpose of the Thesis was to improve the quality in the R&D work of WCDMA Base Station Verification.

The idea was to develop base load for the automated testing system, which simulates real 3G network traffic as well as possible.

Base load related theory was studied and an analysis of real 3G network traffic was done to prepare the base load development.

Handovers and RAB services were examined in the theory part. Statistics about RAB services and handovers that occured in the

analyzed 3G network were examined. The current testing environment had to be updated also for the

needs of base load development.


3G Network architecture

UE – User EquipmentUTRAN – UMTS Terrestrial Radio Access NetworkRNC – Radio Network ControllerMSC – Mobile Switching CenterGMSC – Gateway MSCVLR – Visitor Location RegisterHLR – Home Location RegisterSGSN – Serving GPRS Support NodeGGSN – Gateway GPRS Support Node


Handovers

The handover types can be divided in softer, soft and hard handovers.

In softer handover the radio links are made under the same Base Station within the different cells (sectors).

The UE can have multiple simultaneous active radio link connections from different sectors.

Softer handover


Handovers (2)

Soft handover is performed between two cells belonging to different Base Stations.

In a soft handover event the source and target cells have the same frequency.

The UE can have multiple simultaneous active radio link connections from different Base Stations.

Soft handover


Handovers (3)

The inter-frequency handovers (IFHOs) are categorized to hard handovers.

The source and target cells have different frequencies when performing IFHOs.

Several carriers can be used in the WCDMA network e.g. with high capacity sites or between micro and macro cells.

Inter-frequency handovers(IFHOs)


Handovers (4)

Inter-system handovers (ISHOs) are categorized also to hard handovers.

ISHOs are made between WCDMA and GSM systems. These handovers can be used e.g. for coverage or load balancing

reasons.

Inter-system handovers(ISHOs)


Radio Access Beares (RAB) services

The RAB Service provides confidential transport of signalling and user data between MT and CN Iu Edge Node.

TE - Terminal EquipmentMT – Mobile TerminationUTRAN – UMTS Terrestial Radio Access NetworkCN – Core Network


Different RAB services

Circuit Switched RAB services: CS Voice services (e.g. AMR calls) CS Conversational services (e.g. video calls) CS Streaming services

Packet Switched RAB services: Non Real Time (NRT) PS Data services (UMTS QoS

profiles: Background and Interactive) Real Time (RT) PS Data Services (UMTS QoS profiles:

Streaming and Conversational)


Analysis of real 3G traffic

Two foreign 3G operator were contacted and asked desired data for the analysis. But only from one operator were possible to get the desired statistics in time.

The analysis was based on the Key Performance Indicator (KPI) statistics.

The analyzed Radio Access Network (RAN) topology: 18 RNCs and ~4000 Base Stations.

The statistics were collected from all 18 RNCs during Spring 2005. The RAB services statistics based on the call attempts made in the

analyzed network. The statistics were lacking some needed soft handover information,

but some older statistics were used to cover that part.


Results of the analysis

The distribution of RAB services: Almost as much PS Data call

attemtps (46,6%) as normal CS voice call attempts (50,9%).

Also a noticeable amount of CS Conversational (2,4%) call attemtps (video calls).

The amount of call attempts per day: In average 40000 CS voice call

attempts through one RNC.


Results of the analysis (2)

The hourly statistics: During ”busy hour” over 6000 call

attempts were made. During nights there were more PS

Data call attempts than CS voice call attempts.

The distribution of delivered bits by different PS Data bit rates:

Downlink bit rates: 64, 128 and 384 kbps.

Uplink bit rate: 64 kbps. Proportionally the most used bit

rates were 64 and 128 kbps.


Results of the analysis (3)

Soft handovers were definately the dominating type of handovers.

More ISHOs were made than IFHOs.

The amount of IFHOs should increase after the operators start to use more carrier frequencies.


The base load development

The base load was developed according to the results of the analysis part.

The base load was designed to operate with 32 UEs. There was already developed a tool (Program X) to configure and control these UEs.

A programmable attenuator (JFW box) was added to the existing automated testing system to initiate handovers.

An automation tool was developed with Labview to control both Program X and JFW box. This tool will be actually a good platform for base load tool development.

Three fixed call durations was decided to use in the base load. These are: 30 s, 5 min and 20 min.


The base load development (2)

The updated automated testing system:



The designed base load for three cells e.g. 1+1+1 CEC, duration one hour.



The call setups were designed to be done stepwise to avoid simultaneous signalling.

432 calls are done during one hour in the base load. This simulates a high traffic Base Station.


Conclusions and future considerations

The developed base load simulates the analyzed 3G traffic quite well. Only the call durations were decided to have three fixed durations.

The base load is designed for the system testing phase in the product development. The base load can be used as a background traffic when testing different Base Station features. It can be used also when testing other network elements (e.g. RNC).

New analysis will be done every now and then. New base loads can be implemented according to the new analysis.

A base load tool development work will also continue in the future. For example, succes rates for RAB setups and handovers would be nice features to implement.


Thank you!

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06/09/2005Master's Thesis Seminar - Jesse Kruus 1 Analyzing and Developing Base Load for WCDMA Base...

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