transport formats in umts radio network controller’s software implementation

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


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



• 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



• 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.



• UTRA radio interface protocol architecture (1/3)

3GPP TS 25.201 “Physical layer - general description” version 7.3.0 Release 7(2007-06)



• 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



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



• 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



• 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



• 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




TFI = Transport Format Indicator TFCI = Transport Format Combination Indicator


• 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 SRNC = Serving Radio Network Controller



• 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



• 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



• 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



• 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



• 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


Transport Formats in UMTS Radio Network Controller’s Software ImplementationThank you!

transport formats in umts radio network controller’s software implementation

Documents