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WirelessWireless
The Good The BadThe Good The Bad
and the UGLYand the UGLY
Мариян HackMan Маринов
<mm@1h.com>
Who am I?Who am I?
➢ Chief system architect of
➢ Sysadmin since the stone age
➢ Linux Sysadmin & Network security
courses ...
What you will hear :)What you will hear :)
➢Radio frequency
➢Radio antennas
➢WiFi protocols
➢WiFi protocol options
➢OpenWR...
No Brands HereNo Brands Here
➢Everything I will be showing should be considered
brand neutral
➢I have strong affinity towa...
FrequencyFrequency
➢It does not exist... :)
Radio waveRadio wave
FrequencyFrequency
FrequenciesFrequencies
➢Human hearing: 20Hz to 20KHz
➢Radio: 3 kHz to 300 GHz
➢More info here:
http://ironbark.xtelco.com....
ModulationsModulations
802.11g802.11g
➢Припокриващи се канали
➢Други технологии на същите честоти
2.412Ghz – 2.472Ghz
5.170Ghz – 5.320Ghz
5.500Gh...
Radio antennasRadio antennas
➢Different types based on direction
➢ Omni-directional
➢ Directional
➢Based on design
➢ A LOT...
Radio antennasRadio antennas
Dipol antenna radiation
Blade antenna
Slot antennaSlot antenna
Slot antennaSlot antenna
WiFi signal impactWiFi signal impact
➢Reflection
➢Refraction - different speed
➢Diffraction - go around objects
➢Scatterin...
WiFi signal absorptionWiFi signal absorption
➢Plasterboard/drywall 3-5 dB
➢Glass wall and metal frame 6 dB
➢Metal door 6-1...
Signal dispersionSignal dispersion
WiFi protocolsWiFi protocols
➢IEEE
➢ Standards
➢ http://standards.ieee.org/getieee802/802.11.html
➢Wi-Fi Alliance
➢ Certif...
WiFi protocolsWiFi protocols
➢ 802.11-2007, 802.11-2011, 802.11-2012
➢ 802.11 a,b,g,n,ac
➢ 802.11i – WPA2
➢ 802.11w – Prot...
Assemble frame
Is the
channel
free
Wait for Random
backoff time
Transmit RTS
CTS
Received
Transmit application
Data
RTS - ...
Въпроси?Въпроси?
Мариян HackMan MarinovМариян HackMan Marinov
E-Mail:E-Mail: mm@1h.commm@1h.com
IRC: irc.freenode.net Hack...
WiFi protocol optionsWiFi protocol options
➢Bitrate
➢TX Power
➢beacon
➢mcast_rate
➢Channel bonding (HT20, HT40, HT80, HT16...
OpenWRTOpenWRT
Wifi the good bad and ugly
Wifi the good bad and ugly
Wifi the good bad and ugly
Wifi the good bad and ugly
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Wifi the good bad and ugly

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WiFi basics and practical considerations

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Wifi the good bad and ugly

  1. 1. WirelessWireless The Good The BadThe Good The Bad and the UGLYand the UGLY Мариян HackMan Маринов <mm@1h.com>
  2. 2. Who am I?Who am I? ➢ Chief system architect of ➢ Sysadmin since the stone age ➢ Linux Sysadmin & Network security courses in FMI Sofia and SoftUni
  3. 3. What you will hear :)What you will hear :) ➢Radio frequency ➢Radio antennas ➢WiFi protocols ➢WiFi protocol options ➢OpenWRT configuration options
  4. 4. No Brands HereNo Brands Here ➢Everything I will be showing should be considered brand neutral ➢I have strong affinity toward atheros WiFi chips, but that is all
  5. 5. FrequencyFrequency ➢It does not exist... :)
  6. 6. Radio waveRadio wave
  7. 7. FrequencyFrequency
  8. 8. FrequenciesFrequencies ➢Human hearing: 20Hz to 20KHz ➢Radio: 3 kHz to 300 GHz ➢More info here: http://ironbark.xtelco.com.au/subjects/DC/lectures/7/
  9. 9. ModulationsModulations
  10. 10. 802.11g802.11g ➢Припокриващи се канали ➢Други технологии на същите честоти 2.412Ghz – 2.472Ghz 5.170Ghz – 5.320Ghz 5.500Ghz – 5.700Ghz
  11. 11. Radio antennasRadio antennas ➢Different types based on direction ➢ Omni-directional ➢ Directional ➢Based on design ➢ A LOT :) ➢ Dipol ➢ Loop ➢ Blade ➢ Slot ➢ YAGI
  12. 12. Radio antennasRadio antennas
  13. 13. Dipol antenna radiation
  14. 14. Blade antenna
  15. 15. Slot antennaSlot antenna
  16. 16. Slot antennaSlot antenna
  17. 17. WiFi signal impactWiFi signal impact ➢Reflection ➢Refraction - different speed ➢Diffraction - go around objects ➢Scattering - dust, humidity ➢Absorption
  18. 18. WiFi signal absorptionWiFi signal absorption ➢Plasterboard/drywall 3-5 dB ➢Glass wall and metal frame 6 dB ➢Metal door 6-10 dB ➢Window 3 dB ➢Concrete wall 6-15 dB ➢Block wall 4-6 dB
  19. 19. Signal dispersionSignal dispersion
  20. 20. WiFi protocolsWiFi protocols ➢IEEE ➢ Standards ➢ http://standards.ieee.org/getieee802/802.11.html ➢Wi-Fi Alliance ➢ Certification, Interop and Early Standards ➢ http://www.wi-fi.org/
  21. 21. WiFi protocolsWiFi protocols ➢ 802.11-2007, 802.11-2011, 802.11-2012 ➢ 802.11 a,b,g,n,ac ➢ 802.11i – WPA2 ➢ 802.11w – Protected management frames ➢Drafts ➢ Draft 802.11s – Mesh networking ➢ Draft 802.11u – Interworking with external networks WPA – replaced by WPA2 WPS HALF DUPLEX COMMUNICATIONHALF DUPLEX COMMUNICATION
  22. 22. Assemble frame Is the channel free Wait for Random backoff time Transmit RTS CTS Received Transmit application Data RTS - Ready to Send CTS – Clear to Send CSMA/CA
  23. 23. Въпроси?Въпроси? Мариян HackMan MarinovМариян HackMan Marinov E-Mail:E-Mail: mm@1h.commm@1h.com IRC: irc.freenode.net HackManIRC: irc.freenode.net HackMan ICQ: 7556201ICQ: 7556201 Jabber/Gtalk:Jabber/Gtalk: hackman@jabber.orghackman@jabber.org http://github.com/hackman/http://github.com/hackman/
  24. 24. WiFi protocol optionsWiFi protocol options ➢Bitrate ➢TX Power ➢beacon ➢mcast_rate ➢Channel bonding (HT20, HT40, HT80, HT160) ➢Channel bandwidth 5, 10, 20 ➢antenna - horizontal/vertical ➢country http://wiki.openwrt.org/doc/uci/wireless
  25. 25. OpenWRTOpenWRT

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