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Transport Formats in UMTS Radio Network Controller’s Software Implementation

Transport Formats in UMTS Radio Network Controller’s Software Implementation. Seminaariesitelmä / Jukka Valtanen / 08.01.2008. Transport Formats in UMTS Radio Network Controller’s Software Implementation. Introduction 3G network structure UTRA radio interface protocol architecture

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Transport Formats in UMTS Radio Network Controller’s Software Implementation

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  1. Transport Formats in UMTS Radio Network Controller’s Software Implementation Seminaariesitelmä / Jukka Valtanen / 08.01.2008 Seminaariesitelmä / Jukka Valtanen / 08.01.2008

  2. 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. Transport Formats in UMTS Radio Network Controller’s Software Implementation • Introduction - 3G network structure (1/2) • 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. Transport Formats in UMTS Radio Network Controller’s Software Implementation • Introduction - 3G network structure (2/2) 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. CN = Core Network RNC = Radio Network Controller UE = User Equipment UMTS = Universal Mobile Telecommunications System UTRAN = UMTS Terrestrial Radio Access Network Seminaariesitelmä / Jukka Valtanen / 08.01.2008

  5. 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. 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. Transport Formats in UMTS Radio Network Controller’s Software Implementation • UTRA radio interface protocol architecture (3/3) • Mapping of transport channels onto physical channels Seminaariesitelmä / Jukka Valtanen / 08.01.2008

  8. 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 Seminaariesitelmä / Jukka Valtanen / 08.01.2008

  9. 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 Seminaariesitelmä / Jukka Valtanen / 08.01.2008

  10. 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 = Transport Format Indicator TFCI = Transport Format Combination Indicator Seminaariesitelmä / Jukka Valtanen / 08.01.2008

  11. 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 SRNC = Serving Radio Network Controller Seminaariesitelmä / Jukka Valtanen / 08.01.2008

  12. 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. 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. 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. 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. 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. Transport Formats in UMTS Radio Network Controller’s Software Implementation Thank you! Seminaariesitelmä / Jukka Valtanen / 08.01.2008

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