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LTE Mac Layer

LTE Harq simulation based on Link Abstraction Author : Tomasi Giovanni Advisors : Marco Miozzo (CTTC), Marco Mezzavilla (DEI). LTE Mac Layer. Link Abstraction. Compression. Effective SINR. Tuning. Metrics Performances. MIESM mutual information effectiveSINR.

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LTE Mac Layer

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  1. LTE Harqsimulationbased on Link AbstractionAuthor: Tomasi GiovanniAdvisors: Marco Miozzo (CTTC), Marco Mezzavilla (DEI)

  2. LTE MacLayer

  3. Link Abstraction

  4. Compression

  5. Effective SINR

  6. Tuning

  7. MetricsPerformances

  8. MIESMmutual information effectiveSINR The computation of the mutual information per coded bit can be derived from the received symbol-level mutual information; this approach is termed received bit mutual information rate (RBIR). An alternative is a method that directly arrives at the bit-level mutual information; this method called mean mutual information per bit (MMIB).

  9. RBIR

  10. MMIB

  11. MMIB

  12. MMIB Forothersmodulations

  13. MMIB

  14. MI-Blermapping

  15. MI-Blermapping approximation BCR blockdimension and code rate

  16. MI-Blermapping

  17. MultipathChannel (alreadyimplemented in ns3) • Based on randomselectionof a 250 ms window on 3 s Jakessequences dB [ms] dB [ms] dB [ms] dB [ms]

  18. MultipathChannel

  19. MultipahChannel

  20. Shadowing • Modelwith a log-normalrandomvariable

  21. Simulation: error vs multipath dB [ms]

  22. LTE Simulator • Simulationsparameter

  23. Allocation • Symb per Frame = nSubCarr*nSubCh*nSymbOfdm = 42000 • Data Symb per Frame = (Symb per Frame) – ( ContolSymb) = 28248 • Mean Data Symb per SubFrame≈ 2825 • Packets per SubFrame = 5 • Mean Data Symb per Packet≈ 565

  24. Harq in LTE Only 4 processes are used in a idealack/nakchannel

  25. Harqin LTE

  26. HarqCombining • CC • Sistematicsymbols: 565 • New symbols per rtx: 0 • Retransimittedsymbols: 565 • IR v1 • Sistematicsymbols: 565 • New symbols per rtx: 377 • Retransimittedsymbols: 280 • IR v2 • Sistematicsymbols: 565 • New symbols per rtx: 377 • Retransimittedsymbols: 0

  27. HarqCombining • CC - case combining • IR - incrementalredundancy

  28. Throughput • throughput = (n_pak_to_tx - n_drop_pak) * simb_per_pak * modulation_order * code_rate / simulation_time Capacity (Shannon formula) • Capacity = F * B * log2 (1 + SNR) • System bandwidth • B = NsubCh * NsubCarr * NofdmSymb / TsubFrame • Correctionfactor • F = (Tframe – TcyclicPref)/Tframe * (NsubCarr*NofdmSymb/2-4) • NsubCarr*NofdmSymb/2 CP loss ReferenceSymbol loss

  29. Conclusions • Understand and implement the link abstraction • Create Harq system and the part of the Schedulerthatmanages the harqprocesses • Performance in octave • Import the system in ns3

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