1 / 24

Anatomy of Radio LAN

Anatomy of Radio LAN. Onno W. Purbo Onno@indo.net.id. Reference. http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Linux.Wireless.wlan.html. Functional Diagram. Spread Spectrum Techniques. Direct Sequence Frequency Hopping. Direct Sequence. Frequency Hopping. Comparisons.

gefen
Télécharger la présentation

Anatomy of Radio LAN

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Anatomy of Radio LAN Onno W. Purbo Onno@indo.net.id

  2. Reference • http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Linux.Wireless.wlan.html

  3. Functional Diagram

  4. Spread Spectrum Techniques • Direct Sequence • Frequency Hopping

  5. Direct Sequence

  6. Frequency Hopping

  7. Comparisons • DS modem more complicated, MAC in DS much simpler. • FH appears to be cheaper. • BW sharing, DS tends to have lower overhead on the air. • DS vs. FH = religion war  …

  8. Diversity • Diversity • Redudancy in the system to overcome noise and to increase the reliability of the system. • Antenna Diversity

  9. Antenna • Directional Antenna • Sectoral Antenna • Beam forming Antenna

  10. Range Issues • Propagation • Attenuation • Reflection • Fading

  11. Transmitter Power • Higher power: • Drain battery quickly • Frequency reuse drawback

  12. Sensitivity • Defined as • Point at 3% packet loss (400 byte packet in Gaussian channel). • 7 dB worse if we use Raleigh channel + antenna diversity. • Normally –80 dBm, better –90 dBm.

  13. Attenuation:Propagation & Range

  14. SNR • Signal-to-Noise Ratio • Difference of power in the receiver between a valid signal and noise.

  15. Modulation

  16. Multi-rate system • Better throughput more bandwidth. • The higher the signalling rate, the shorter the distance.

  17. 2FSK • B = base frequency • d = deviation • symbol • 0 B + d • 1 B – d

  18. Frequency Modulation 2FSK

  19. 4FSK • B = base frequency • d = deviation • Symbol • 00 B+ 1/2d • 01 B – 1/2d • 10 B + 3/2d • 11 B – 3/2d

  20. IEEE 802.11 (11Mbps) • CCK – Complementary Code Keying • 11 Mbps • 5.5Mbps

  21. IEEE 802.11a (OFDM) • Orthogonal Frequency Division Multiplex (OFDM). • Using equalization in post processing, overcome delay spread. • OFDM is pre-processing technique. • Use in 5Ghz UNII Band.

  22. Interference & Noise

  23. Interference & Noise • Fading • Variation in time. • Microwave oven & other interferer. • Forward Error Correction (FEC) • Not effective, better retransmit the packet. • Delay Spread

  24. Multipath & Delay Spread

More Related