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An Analysis of the Throughput of Packet Radio Networks

An Analysis of the Throughput of Packet Radio Networks. André Stranne Licentiate thesis presentation Lund, 16/5 – 2003. Outline. Introduction and background System model Packet collision analysis Interfering energy analysis Approximations Summary. Introduction and background.

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An Analysis of the Throughput of Packet Radio Networks

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  1. An Analysis of the Throughput of Packet Radio Networks André Stranne Licentiate thesis presentation Lund, 16/5 – 2003

  2. Outline • Introduction and background • System model • Packet collision analysis • Interfering energy analysis • Approximations • Summary

  3. Introduction and background An Analysis of the Throughput of Packet Radio Networks

  4. Wireline Wireless Internet IR Radio Sound An Analysis of the Throughput ofPacket Radio Networks Data communications 1011010010110 Fixed phone ADSL Ethernet GSM Bluetooth 3G

  5. Circuit switched Packet switched 1110 101 011 An Analysis of the Throughput of Packet Radio Networks Radio networks 1011010010110 Phone calls Internet data GSM (3G) Bluetooth GPRS (3G)

  6. Throughput 011 01 An Analysis of the Throughput ofPacket Radio Networks ? OK OK OK 0 101 1110

  7. An Analysis of the Throughput of Packet Radio Networks - What data rates can be expected in packet radio networks?

  8. Analysis: How to do it? • Analyze real packet radio networks • Realistic but not very convenient • Create mathematical models of packet radio networks

  9. Outline • Introduction and background • System model • Packet collision analysis • Interfering energy analysis • Approximations • Summary

  10. Main features • Networks, units • Packet transmissions • Packet-based slow frequency hopping • Different packet lengths

  11. Interference System model • System • Networks • Units

  12. Packet transmissions • Frequency channels • Packet-based frequency hopping

  13. Transmitted data Network Throughput Lost data Performance measure • Throughput = achieved data rate

  14. Packet reception models • What is the cause of packet losses in the networks? • Packet collision analysis: • Interfering energy analysis: Collisions Interfering energy

  15. Outline • Introduction and background • System model • Packet collision analysis • Interfering energy analysis • Approximations • Summary

  16. Collision analysis • Packet reception model • Packet losses from packet collisions ?

  17. Collision analysis • Packet reception model • Packet losses from packet collisions

  18. Collision analysis • Probability of collision? • Probability of successful packet reception? • Throughput?

  19. Calculation outline • Calculate how probable n collisions are with packets transmitted from a single interferer j, • Hard to find that expression • Details in the thesis

  20. Convolutions of PDFs (probability distribution functions) Calculation outline • Calculate how probable n collisions are with packets transmitted by all interferers Assumption: independent packet transmissions

  21. Calculation outline • Sum the probabilities for the number of collisions that can be tolerated for successful packet reception • If no collisions can be tolerated:

  22. 625 μs Bluetooth example • System of Bluetooth ”piconets” • 79 frequency channels

  23. No collisions Single interferer! 79 channels 1 collision 2 collisions Bluetooth example Prob. of number of collisions from single interferer Low collision probability!

  24. 20 interferers 40 interferers 60 interferers 80 interferers 100 interferers Bluetooth example Prob. of total number of collisions Medium size packet type All interferers!

  25. No interferers More interferers 50 % 26 Bluetooth example Network throughput More collisions More lost packets Reduced data rate

  26. Decreasing system throughput Maximum system throughput Increasing system throughput Bluetooth example System throughput Total throughput for all piconets in the system

  27. Outline • Introduction and background • System model • Packet collision analysis • Interfering energy analysis • Approximations • Summary

  28. no collision collision collision Energy analysis • Collision-based packet reception model

  29. Energy analysis • New packet reception model • More detailed • The collision analysis does not account for • the duration of the packet overlaps in the collisions • the strength of the received interfering signals • Interfering energy

  30. 1 2 3 3 Single frequency channel 1 2 Energy analysis • Interfering energy Time

  31. 1 Length of overlap Signal strength Energy analysis • Interfering energy Time

  32. 2 Energy analysis • Interfering energy 1 Time

  33. 3 Energy analysis • Interfering energy 1 2 Time

  34. Energy analysis • Interfering energy

  35. Calculation outline • Basically the same as for the collision analysis Variables for number of collisions Variables for amount of interfering energy

  36. Bluetooth example • Link budget

  37. Distance between interferers and reference nodes Increasing interference Bluetooth example Network throughput

  38. Bluetooth example System throughput

  39. Outline • Introduction and background • System model • Packet collision analysis • Interfering energy analysis • Approximations • Summary

  40. Complexity issues • Exact expressions complicated • Simple approximations needed • For the collision-based analysis, we have such an approximation • Approximation of energy-based analysis is beyond the scope of this thesis

  41. Approximation Full expression / approximation Accurate enough?

  42. 10 channels Bluetooth 79 channels 30 channels Approximation error (Bluetooth example)

  43. Outline • Introduction and background • System model • Packet collision analysis • Interfering energy analysis • Approximations • Summary

  44. Contributions • Probabilistic framework for analysis of PRNs that transmit packets of different lengths • Exact expressions for the throughput • Approximate expression which can be used for strongly interfering networks

  45. Publications • F. Florén, A. Stranne and O. Edfors, Analysis of Slow Frequency Hopping Networks, NRS 01, Sweden, 2001 • F. Florén, A. Stranne, O. Edfors and B.-A. Molin, Throughput Analysis of Strongly Interfering Slow Frequency-Hopping Wireless Networks, VTC Spring 2001, Greece, 2001 • A. Stranne, F. Florén and O. Edfors, Evaluating a Performance Analysis of Slow FH Systems by Simulations, RVK 02, Sweden, 2002 • A. Stranne, F. Florén, O. Edfors and B.-A. Molin, Throughput of IEEE 802.11 FHSS Networks in the Presence of Strongly Interfering Bluetooth Networks, PIMRC 2002, Portugal, 2002

  46. Publications • A. Stranne, F. Florén, O. Edfors and B.-A. Molin, Throughput of Strongly Interfering Slow Frequency-Hopping Networks, submitted to IEEE Transactions on Communications, 2003 • A. Stranne, F. Florén, O. Edfors and B.-A. Molin, Analysis of Strongly Interfering Slow Frequency-Hopping Systems, Technical Report, Department of Electroscience, Lund University, 2003

  47. Future work • Approximations • Development of system model • Applications of the results

  48. Special thanks to

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