1 Session 2, Presentation: Modelling of physical layer behaviour in a HS-DSCH network simulator Modelling of physical layer behaviour in a HS-DSCH network simulator Frank Brouwer Twente Institute for Wireless and Mobile Communications

2 Session 2, Presentation: Modelling of physical layer behaviour in a HS-DSCH network simulator Overview  Network simulator Link adaptation Physical layer model requirements Hybrid ARQ  Modeling for network simulator Narrow band modeling Wide band modeling  Physical layer behaviour  Conclusions

3 Session 2, Presentation: Modelling of physical layer behaviour in a HS-DSCH network simulator Overview  Network simulator Link adaptation Physical layer model requirements Hybrid ARQ  Modeling for network simulator Narrow band modeling Wide band modeling  Physical layer behaviour  Conclusions

4 Session 2, Presentation: Modelling of physical layer behaviour in a HS-DSCH network simulator Network simulator  End-to-end performance analysis HSDPA  Streaming video, web browsing, file transfer  Mutual influence PHY, MAC, RLC <> IP, TCP/UDP Detailed implementation of MAC, RLC, IP, TCP/UDP Abstract and realistic model PHY  Abstract PHY model Channel conditions  Distance loss  Shadowing (correlation distance)  Channel model (Vehicular A, Pedestrian A, Indoor A, …) Physical layer characteristics  BLER per TTI  Link adaptation, Hybrid ARQ

5 Session 2, Presentation: Modelling of physical layer behaviour in a HS-DSCH network simulator Link adaptation  Keep BLER constant by changing Transport Block Size  More data under good channel conditions  UE transmits CQI: max TBS with BLER = 0.1  Node-B decides TBS: CQI + own algorithm

6 Session 2, Presentation: Modelling of physical layer behaviour in a HS-DSCH network simulator Physical layer model requirements  Condition in network simulator includes: 30 Transport Block Sizes Any SNR value (-20 to 15 dB continuous)  Required output Monotonous relation SNR – BLER for given TBS More focus on relative than on absolute accuracy One BLER value per TTI  Calculation should not require more that some (tens of) floating point operations

7 Session 2, Presentation: Modelling of physical layer behaviour in a HS-DSCH network simulator PDU Hybrid ARQ  Reception in error => combine received signal with a second reception  Possible H-ARQ schemes Incremental redundancy (Send additional information) Chase combining (Repeat the same information)  Chase combining assumed  Maximum Ratio Combining (= add powers) Power of first reception aids second reception Higher probability of successful reception PDU + = PDU Erroneous Success Node B UE NACK ACK

8 Session 2, Presentation: Modelling of physical layer behaviour in a HS-DSCH network simulator Overview  Network simulator Link adaptation Physical layer model requirements Hybrid ARQ  Modeling for network simulator Narrow band modeling Wide band modeling  Physical layer behaviour  Conclusions

9 Session 2, Presentation: Modelling of physical layer behaviour in a HS-DSCH network simulator Narrow band modeling  Generate a varying SNR in network simulator All received power of wanted signal is captured PHY layer behavior equal to AWGN  WP2 PHY AWGN simulations as input  Modeled through analytical approximation Shape of curve equal for all CQI Steepness function of CQI Offset function of CQI Can generate for each CQI, SNR and BLER CQI = Channel Quality Indicator 10

10 Session 2, Presentation: Modelling of physical layer behaviour in a HS-DSCH network simulator Wide band modeling (1)  Channel produces delayed copies  RAKE receiver: Estimate tap delay line One finger per tap Maximum Ratio Combine  ISI model: All power over symbol border turns into noise Transmitted signal Channel Received signal RAKE fingers SignalInterference 10

11 Session 2, Presentation: Modelling of physical layer behaviour in a HS-DSCH network simulator Wide band modeling (2)  Symbol time options:  Raw symbols (240 ksymbols/s for all CQI)  Bitrate including overhead  Bitrate excluding overhead  Corrections needed for ISI performance of receiver  Example: Vehicular A  is 0.3 times bitrate excluding overhead

12 Session 2, Presentation: Modelling of physical layer behaviour in a HS-DSCH network simulator Overview  Network simulator Link adaptation Physical layer model requirements Hybrid ARQ  Modeling for network simulator Narrow band modeling Wide band modeling  Physical layer behaviour  Conclusions

13 Session 2, Presentation: Modelling of physical layer behaviour in a HS-DSCH network simulator Physical layer behaviour  SNR generated from channel model  BLER generated from PHY model  Observations: CQI lags to SNR (delay in reporting Actual BLER strongly varying  Rounding of CQI  Lagging of CQI (“wrong” selection of TBS)

14 Session 2, Presentation: Modelling of physical layer behaviour in a HS-DSCH network simulator Overview  Network simulator Link adaptation Physical layer model requirements Hybrid ARQ  Modeling for network simulator Narrow band modeling Wide band modeling  Physical layer behaviour  Conclusions

15 Session 2, Presentation: Modelling of physical layer behaviour in a HS-DSCH network simulator Conclusions  Network level simulations need “simple” model covering all CQIs and all SNRs No physical layer simulations No difficult look-up structures  Physical layer model provides subset  Analytical model matches perfectly in narrow band channel conditions  Model adaptation for wide band channel conditions has sufficient match