Seminaariesitelmä / Jukka Valtanen / 08.01.2008 1 © Nokia Siemens Networks
Transport Formats in UMTS Radio Network Controller’s Software ImplementationSeminaariesitelmä / Jukka Valtanen / 08.01.2008
Seminaariesitelmä / Jukka Valtanen / 08.01.2008 2 © Nokia Siemens Networks
Transport Formats in UMTS Radio Network Controller’s Software Implementation
• Introduction– 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
Seminaariesitelmä / Jukka Valtanen / 08.01.2008 3 © Nokia Siemens Networks
Transport Formats in UMTS Radio Network Controller’s Software Implementation
• Introduction - 3G network structure (1/2)
User Equipment Node B(Base Station)
Radio Network Controller
Core network
– 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 GPRS = General Packet Radio Service
Seminaariesitelmä / Jukka Valtanen / 08.01.2008 4 © Nokia Siemens Networks
Transport Formats in UMTS Radio Network Controller’s Software Implementation
• Introduction - 3G network structure (2/2)Uu Iu
Node B
Node B
Node B
USIM
ME
Cu
RNC
RNC
Node B
HLRIub Iur
MSC/VLR
SGSN
GMSC
GGSNUEExternal
networks
PLMNPSTNISDN
Internet
UTRAN CN
CN = Core Network
RNC = Radio Network Controller
UE = User Equipment
UMTS = Universal Mobile Telecommunications System
UTRAN = UMTS Terrestrial Radio Access Network
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 5 © Nokia Siemens Networks
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)
Seminaariesitelmä / Jukka Valtanen / 08.01.2008 6 © Nokia Siemens Networks
Transport Formats in UMTS Radio Network Controller’s Software Implementation
• UTRA radio interface protocol architecture (2/3)Physical channels:
Transport channels:
Logical 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
• 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
• 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 Channel PCH = Paging Channel
RACH = Random Access Channel HS-DSCH = High Speed Downlink Shared Channel
Seminaariesitelmä / Jukka Valtanen / 08.01.2008 7 © Nokia Siemens Networks
Transport Formats in UMTS Radio Network Controller’s Software Implementation
Transport channels Physical ChannelsDCH Dedicated Physical Data Channel (DPDCH)
Dedicated Physical Control Channel (DPCCH)Fractional Dedicated Physical Channel (F-DPCH)
E-DCH E-DCH Dedicated Physical Data Channel (E-DPDCH)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)
RACH Physical Random Access Channel (PRACH)Common Pilot Channel (CPICH)
BCH Primary Common Control Physical Channel (P-CCPCH)FACH Secondary Common Control Physical Channel (S-CCPCH)
PCH Synchronisation Channel (SCH)Acquisition Indicator Channel (AICH)Paging Indicator Channel (PICH)MBMS Notification Indicator Channel (MICH)
HS-DSCH High Speed Physical Downlink Shared Channel (HS-PDSCH)HS-DSCH-related Shared Control Channel (HS-SCCH)Dedicated Physical Control Channel (uplink) for HS-DSCH (HS-DPCCH)
• UTRA radio interface protocol architecture (3/3)– Mapping of transport channels onto physical channels
Seminaariesitelmä / Jukka Valtanen / 08.01.2008 8 © Nokia Siemens Networks
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
Transmission Time IntervalMAC PHY
Transport Block Set
Transport Block Set
Seminaariesitelmä / Jukka Valtanen / 08.01.2008 9 © Nokia Siemens Networks
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)
TTI = Transmission Time Interval
CRC = Cyclic Redundancy Check
TB = Transport Block
Semi-StaticPart
Dynamic TB Size … TB SizePart TB Set Size … TB Set Size
TF Indicator TFI 1 … TFI n
Rate Matching
Transport Format Set
TTIChannel Coding
CRC Size
Seminaariesitelmä / Jukka Valtanen / 08.01.2008 10 © Nokia Siemens Networks
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
TFI TFI TFI TFI
Higher layers
Physical layer
TFCITFCI
decoding
Physical Physical Physical Physicalcontrol channel data channel control channel data channel
Transport channel 1
Transport block
Transport block
Transport block
Transport block
Transport channel 2
Coding and multiplexing
TRANSMITTER RECEIVER
Decoding and demultiplexing
Transport channel 1 Transport channel 2
Transport block anderror indication
Transport block anderror indication
Transport block anderror indication
Transport block anderror indication
TFI = Transport Format Indicator TFCI = Transport Format Combination Indicator
Seminaariesitelmä / Jukka Valtanen / 08.01.2008 11 © Nokia Siemens Networks
• 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
Transport Formats in UMTS Radio Network Controller’s Software Implementation
RAB = Radio Access Bearer SRNC = Serving Radio Network Controller
Seminaariesitelmä / Jukka Valtanen / 08.01.2008 12 © Nokia Siemens Networks
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)
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 HSUPA = High Speed Uplink Packet Access
Seminaariesitelmä / Jukka Valtanen / 08.01.2008 13 © Nokia Siemens Networks
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,
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
Seminaariesitelmä / Jukka Valtanen / 08.01.2008 14 © Nokia Siemens Networks
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
Seminaariesitelmä / Jukka Valtanen / 08.01.2008 15 © Nokia Siemens Networks
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
Seminaariesitelmä / Jukka Valtanen / 08.01.2008 16 © Nokia Siemens Networks
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
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
Seminaariesitelmä / Jukka Valtanen / 08.01.2008 17 © Nokia Siemens Networks
Transport Formats in UMTS Radio Network Controller’s Software ImplementationThank you!