Transport Formats in UMTS Radio Network
Controller’s Software Implementation
Seminaariesitelmä / Jukka Valtanen / 08.01.2008
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© Nokia Siemens Networks
Seminaariesitelmä / Jukka Valtanen / 08.01.2008
Transport Formats in UMTS Radio Network
Controller’s Software Implementation
• Introduction
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– 3G network structure
UTRA radio interface protocol architecture
– logical channels / transport channels / physical channels
Transport formats
– data transmission between the physical (L1) and data link (L2) layer
– transport format set (TFS) / transport format combination set (TFCS)
Transport format implementation in the RNC
– RNC software architecture / program block under investigation
– current implementation / analysis / improvements / further changes
Testing of transport formats in RNC software
– testing process / testing methods / testing environment
– test cases / analysis / improvements / results
Discussion and conclusion
© Nokia Siemens Networks
Seminaariesitelmä / Jukka Valtanen / 08.01.2008
Transport Formats in UMTS Radio Network
Controller’s Software Implementation
• Introduction - 3G network structure (1/2)
Core
network
User Equipment
Node B
(Base Station)
Radio Network Controller
– 3G networks offer
 wide range of advanced services
 constantly growing network capacity, shorter delay times and higher bit rates
 seamless mobility and inter-working with the existing GSM/GPRS networks
– Need for resource optimisation from all underlying network components
GSM = Global System for Mobile Communications
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GPRS = General Packet Radio Service
Seminaariesitelmä / Jukka Valtanen / 08.01.2008
Transport Formats in UMTS Radio Network
Controller’s Software Implementation
• Introduction - 3G network structure (2/2)
Uu
Iu
Node B
MSC/VLR
GMSC
PLMN
PSTN
ISDN
RNC
USIM
Node B
Cu
Iub
ME
UE
HLR
Iur
Node B
Internet
RNC
Node B
SGSN
UTRAN
CN = Core Network
RNC = Radio Network Controller
UE = User Equipment
UMTS = Universal Mobile Telecommunications System
UTRAN = UMTS Terrestrial Radio Access Network
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GGSN
CN
External
networks
The RNC is a service access point for all
services that UTRAN provides the core
network.
It owns and controls radio resources in
its domain, i.e. Node Bs connected to it.
Seminaariesitelmä / Jukka Valtanen / 08.01.2008
Transport Formats in UMTS Radio Network
Controller’s Software Implementation
• UTRA radio interface protocol architecture (1/3)
3GPP TS 25.201 “Physical layer - general description” version 7.3.0 Release 7(2007-06)
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© Nokia Siemens Networks
Seminaariesitelmä / Jukka Valtanen / 08.01.2008
Transport Formats in UMTS Radio Network
Controller’s Software Implementation
• UTRA radio interface protocol architecture (2/3)
Physical channels:
• layer 1 communication streams (frequency, scrambling etc.)
• 5 dedicated UL channels and 1 common UL channel
• 4 dedicated DL channels and 10 common DL channels
Transport channels: • a service offered by the physical layer (L1) to the MAC
• how and with what characteristics data is transferred
• 2 dedicated channels (DCH, E-DCH)
• 5 common channels (BCH, FACH, PCH, RACH, HS-DSCH)
• the RNC deals with transport channels
Logical channels:
• a service provided by the MAC layer to higher layers
• for which purpose and what type of data is transferred
• 6 control channels
• 3 traffic channels
DCH = Dedicated Channel
E-DCH = Enhanced Dedicated Channel
BCH = Broadcast Channel
FACH = Forward Access ChannelPCH = Paging Channel
RACH = Random Access Channel
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HS-DSCH = High Speed Downlink Shared Channel
Seminaariesitelmä / Jukka Valtanen / 08.01.2008
Transport Formats in UMTS Radio Network
Controller’s Software Implementation
• UTRA radio interface protocol architecture (3/3)
– Mapping of transport channels onto physical channels
Transport channels Physical Channels
Dedicated Physical Data Channel (DPDCH)
DCH
Dedicated Physical Control Channel (DPCCH)
Fractional Dedicated Physical Channel (F-DPCH)
E-DCH Dedicated Physical Data Channel (E-DPDCH)
E-DCH
E-DCH Dedicated Physical Control Channel (E-DPCCH)
E-DCH Absolute Grant Channel (E-AGCH)
E-DCH Relative Grant Channel (E-RGCH)
E-DCH Hybrid ARQ Indicator Channel (E-HICH)
Physical Random Access Channel (PRACH)
RACH
Common Pilot Channel (CPICH)
Primary Common Control Physical Channel (P-CCPCH)
BCH
Secondary Common Control Physical Channel (S-CCPCH)
FACH
Synchronisation Channel (SCH)
PCH
Acquisition Indicator Channel (AICH)
Paging Indicator Channel (PICH)
MBMS Notification Indicator Channel (MICH)
High Speed Physical Downlink Shared Channel (HS-PDSCH)
HS-DSCH
HS-DSCH-related Shared Control Channel (HS-SCCH)
Dedicated Physical Control Channel (uplink) for HS-DSCH (HS-DPCCH)
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Seminaariesitelmä / Jukka Valtanen / 08.01.2008
Transport Formats in UMTS Radio Network
Controller’s Software Implementation
• Transport formats (1/3)
– Data transfer between MAC and PHY is organised by the transmission
of transport blocks.
 One transport block belongs to one transport channel
 Several transport blocks can be sent simultaneously  transport block set
 Transmission Time Interval (TTI) defines the time interval between two
subsequent transport block set transfers between MAC and PHY
Transport Block Size
Transport Block
Transport Block
Transport Block Set Size
Transport Block
Transport Block
Transport Block Set
Transport Block Set
MAC
Transmission Time Interval
Transport Block Set
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© Nokia Siemens Networks
Seminaariesitelmä / Jukka Valtanen / 08.01.2008
PHY
Transport Formats in UMTS Radio Network
Controller’s Software Implementation
• Transport formats (2/3)
– Transport Format (TF)
 Defines the characteristics of a transport channel
 Specifies the physical layer processing to be applied to the channel
 Controls how much data is transferred during one TTI and how the data is
coded etc. by the physical layer
 Semi-static part and dynamic part
– Transport Format Set (TFS)
 The set of transport formats
associated to a transport channel
 Enables variable data rates
(multiple parameter sets)
Semi-Static
Part
Dynamic
Part
TF Indicator
TTI = Transmission Time Interval
CRC = Cyclic Redundancy Check
TB = Transport Block
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Seminaariesitelmä / Jukka Valtanen / 08.01.2008
Transport Format Set
TTI
Channel Coding
CRC Size
Rate Matching
TB Size
TB Set Size
…
…
TB Size
TB Set Size
TFI 1
…
TFI n
Transport Formats in UMTS Radio Network
Controller’s Software Implementation
• Transport formats (3/3)
– Transport Format Combination Set (TFCS)
 Several transport channels can be multiplexed together
 The set of transport format combinations of currently valid transport formats
Transport channel 1
Transport channel 2
Transport block
TFI
Transport block
Transport channel 1
Transport block and
error indication
Transport block
TFI
Transport channel 2
Transport block
TFI
Transport block and
error indication
Transport block and
error indication
TFI
Transport block and
error indication
Higher layers
Physical layer
TFCI
Coding and multiplexing
TFCI
decoding
Physical
control channel
Physical
data channel
Physical
control channel
TRANSMITTER
TFI = Transport Format Indicator
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Decoding and demultiplexing
Physical
data channel
RECEIVER
TFCI = Transport Format Combination Indicator
Seminaariesitelmä / Jukka Valtanen / 08.01.2008
Transport Formats in UMTS Radio Network
Controller’s Software Implementation
• Transport format implementation in the RNC (1/3)
– The RNC consists of several different hardware and software layers
 System blocks, service blocks and program blocks
– One particular program block was investigated in Radio Resource
Management (RRM) area
 Completely new program block, a result of a major architectural change
 Responsible for RRM related tasks and Layer 3 signalling inside the RNC
 Interfaces to a couple of other program blocks and RNC’s internal database
 Performs TFS and TFCS calculation for one Radio Resource Control (RRC)
connection
• RRC connection setup
• State transition from Cell_FACH to Cell_DCH
• RAB establishment / modification / release
• SRNC relocation
• Compressed mode activation / deactivation
RAB = Radio Access Bearer
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SRNC = Serving Radio Network Controller
Seminaariesitelmä / Jukka Valtanen / 08.01.2008
Transport Formats in UMTS Radio Network
Controller’s Software Implementation
• Transport format implementation in the RNC (2/3)
– TFS calculation is performed in one code module (Module 6)
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For each DCH separately, both uplink and downlink direction
Based on DCH type and maximum bit rates
HSDPA and HSUPA not considered here (TF calculation in the Node B)
Maximum of 8 simultaneous DCHs
Own internal procedures for calculating the different parts of the TFS
– TFCS calculation is performed in another code module (Module 7)
 Calculation is based on current DCH list and their TFS parameters
 Calculated Transport Format Combination (CTFC) is a tool for efficient
signalling of transport format combinations (3GPP TS 25.331)
 UE-capability is taken into account and it may also set limitations to TFCS
 Generally more complex than TFS calculation
DCH = Dedicated Channel
HSDPA = High Speed Downlink Packet Access
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HSUPA = High Speed Uplink Packet Access
Seminaariesitelmä / Jukka Valtanen / 08.01.2008
Transport Formats in UMTS Radio Network
Controller’s Software Implementation
• Transport format implementation in the RNC (3/3)
– The implementation has been ported from the old architectural solution,
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dates back to year 2002 and 2003
Originally 3500 code lines in Module 6 and 4000 code lines in Module 7
Deploys global data structures, problems with information hiding
Now the code was fully inspected and improved
Lots of commentary lines were added, code optimisation was done and
obsolete code was removed – also minor bugs were corrected
The implementation still deploys global data structures and clumsy data
conversions that could (and should) be improved
More profound changes and a complete re-design are still possible
The software is under constant state of change – code maintainability
and proper testing is important
© Nokia Siemens Networks
Seminaariesitelmä / Jukka Valtanen / 08.01.2008
Transport Formats in UMTS Radio Network
Controller’s Software Implementation
• Testing of transport formats in RNC software (1/2)
– The product and all program blocks are tested in separate phases
 Module testing (the focus in the thesis)
• integrated part of design and implementation
• new functionalities should be verified as soon as possible
• regression testing after major corrections or other changes in later phases
• should be thorough (code coverage), repeatable, well maintainable and automatic
 Integration and load testing
 Functional testing
 System testing
– Testing methods
 Black box testing: no insight into the code itself, based on inputs and outputs
 White box testing: system state can be observed, more complicated
 Hybrid test strategies
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© Nokia Siemens Networks
Seminaariesitelmä / Jukka Valtanen / 08.01.2008
Transport Formats in UMTS Radio Network
Controller’s Software Implementation
• Testing of transport formats in RNC software (2/2)
– Windows workstation + RNC software emulator + definition database
– 47 initial test cases were prepared for TFS and TFCS features
 mainly different kind of RAB setup scenarios
 other TFS/TFCS calculation scenarios use the same procedures
 inputs sent to the program block  calculation  output data verified
– Test cases were inspected and analysed for code coverage properties
– During the thesis work, a need for some changes was discovered
 10 test cases updated
 6 totally new test cases designed
 all 53 test cases finally passed, no bugs found in later testing phases
– Designed test case set will remain as an essential part of normal
regression testing of the program block
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© Nokia Siemens Networks
Seminaariesitelmä / Jukka Valtanen / 08.01.2008
Transport Formats in UMTS Radio Network
Controller’s Software Implementation
• Discussion and conclusion (1/1)
– Transport formats are applied in the data exchange between the
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physical layer and the data link layer
Transport formats enable variable bit rates and multiplexing of services
The theory is largely based on 3GPP specifications, but manufacturer
specific implementations enable efficient usage of radio resources
The program code of a program block in RRM area was inspected and
analysed
Code maintainability was improved and minor bugs were corrected
Testing of TFS and TFCS functionalities was carried out, a test case set
was designed and the related code was found to be fully functional
Used testing methods were considered to be applicable
The observed features are now fully tested in module level testing
The obtained results will act as a reference for any future improvements
© Nokia Siemens Networks
Seminaariesitelmä / Jukka Valtanen / 08.01.2008
Transport Formats in UMTS Radio Network
Controller’s Software Implementation
Thank you!
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© Nokia Siemens Networks
Seminaariesitelmä / Jukka Valtanen / 08.01.2008