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
06/09/2005
Master's Thesis Seminar - Jesse Kruus
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Agenda
Background, research questions and
methods
 Analysis of real 3G network traffic
 Base load development
 Conclusions and future considerations
 Questions
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06/09/2005
Master's Thesis Seminar - Jesse Kruus
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Background, research question and
methods
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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.
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3G Network architecture
UE – User Equipment
UTRAN – UMTS Terrestrial Radio
Access Network
RNC – Radio Network Controller
MSC – Mobile Switching Center
GMSC – Gateway MSC
VLR – Visitor Location Register
HLR – Home Location Register
SGSN – Serving GPRS Support
Node
GGSN – Gateway GPRS Support
Node
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Handovers
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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
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Handovers (2)
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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
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Handovers (3)
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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)
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Handovers (4)
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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)
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Master's Thesis Seminar - Jesse Kruus
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Radio Access Beares (RAB) services
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The RAB Service provides confidential transport of signalling and
user data between MT and CN Iu Edge Node.
TE - Terminal Equipment
MT – Mobile Termination
UTRAN – UMTS Terrestial Radio Access Network
CN – Core Network
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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)
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Analysis of real 3G traffic
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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.
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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.
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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.
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Results of the analysis (3)
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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.
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The base load development
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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.
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The base load development (2)
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The updated automated testing system:
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The base load development (3)
The designed base load for three cells e.g. 1+1+1 CEC, duration one hour.
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The base load development (4)
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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.
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Conclusions and future considerations
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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.
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Thank you!
Questions?
Comments?
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