transport formats in umts

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

o 3G network structure• UTRA radio interface protocol architecture

o logical channels / transport channels / physical channels• Transport formats

o data transmission between the physical (L1) and data link (L2) layero transport format set (TFS) / transport format combination set (TFCS)

• Transport format implementation in the RNCo RNC software architecture / program block under investigationo current implementation / analysis / improvements / further changes

• Testing of transport formats in RNC softwareo testing process / testing methods / testing environmento test cases / analysis / improvements / results

• Discussion and conclusion


Transport Formats in UMTS Radio Network Controller’s Software Implementation

• Introduction - 3G network structure (1/2)

o 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

o 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)

CN = Core NetworkRNC = Radio Network Controller UE = User EquipmentUMTS = Universal Mobile Telecommunications SystemUTRAN = 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 channelsDCH = 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



• UTRA radio interface protocol architecture (3/3)o Mapping of transport channels onto physical channels



• Transport formats (1/3)o 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 formats (2/3)o 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

o 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



• Transport formats (3/3)o Transport Format Combination Set (TFCS)

Several transport channels can be multiplexed together The set of transport format combinations of currently valid transport

formats

TFI = Transport Format Indicator TFCI = Transport Format Combination Indicator


• Transport format implementation in the RNC (1/3)o The RNC consists of several different hardware and software layers

System blocks, service blocks and program blockso 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)o 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

o 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)o The implementation has been ported from the old architectural solution,

dates back to year 2002 and 2003o Originally 3500 code lines in Module 6 and 4000 code lines in Module 7o Deploys global data structures, problems with information hidingo Now the code was fully inspected and improvedo Lots of commentary lines were added, code optimisation was done and

obsolete code was removed – also minor bugs were correctedo The implementation still deploys global data structures and clumsy data

conversions that could (and should) be improvedo More profound changes and a complete re-design are still possibleo The software is under constant state of change – code maintainability

and proper testing is important



• Testing of transport formats in RNC software (1/2)o 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

o 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)o Windows workstation + RNC software emulator + definition databaseo 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

o Test cases were inspected and analysed for code coverage propertieso 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

o Designed test case set will remain as an essential part of normal regression testing of the program block



• Discussion and conclusion (1/1)o Transport formats are applied in the data exchange between the

physical layer and the data link layero Transport formats enable variable bit rates and multiplexing of serviceso The theory is largely based on 3GPP specifications, but manufacturer

specific implementations enable efficient usage of radio resourceso The program code of a program block in RRM area was inspected and

analysed o Code maintainability was improved and minor bugs were correctedo Testing of TFS and TFCS functionalities was carried out, a test case

set was designed and the related code was found to be fully functionalo Used testing methods were considered to be applicable o The observed features are now fully tested in module level testingo 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

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