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Investigation of Voice Traffic in Wi-Fi Environment

Investigation of Voice Traffic in Wi-Fi Environment. Jukka Kantanen, 21.10.2019. IEEE 802.11b WLAN Some Basics of Voice Traffic What is VoIP? Parameters Affecting VoIP Quality Measurement Setup Results. Topics. IEEE 802.11b WLAN. Operating in the ISM band at 2.4 GHz

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Investigation of Voice Traffic in Wi-Fi Environment

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  1. Investigation of Voice Traffic in Wi-Fi Environment Jukka Kantanen, 21.10.2019

  2. IEEE 802.11b WLAN Some Basics of Voice Traffic What is VoIP? Parameters Affecting VoIP Quality Measurement Setup Results Topics Investigation of Voice Traffic in Wi-Fi Environment

  3. IEEE 802.11b WLAN • Operating in the ISM band at 2.4 GHz • Uses CSMA/CA for channel sharing • Also RTS/CTS can be used for that • Manufacturers have Wi-Fi compatibility if the products are tested • Max. data rate 11 Mbit/s Investigation of Voice Traffic in Wi-Fi Environment

  4. IEEE 802.11b AP IEEE 802.11b WLAN • PHY layer headers transmitted at 1 Mbit/s • Hidden node problem Investigation of Voice Traffic in Wi-Fi Environment

  5. Some Basics of Voice Traffic • Voice (speech) is processed in frames using voice codecs => small bit rate • G.711 64 kbit/s, G.723.1 6.3 or 5.3 kbit/s, G.729 8 kbit/s. G.711 provides toll quality • Speech tolerates more packet errors than data traffic • Delay bounds exist for conversational speech Investigation of Voice Traffic in Wi-Fi Environment

  6. Some Basics of Voice Traffic • The effect of overheads is significant Investigation of Voice Traffic in Wi-Fi Environment

  7. What is VoIP? • Transmission of voice traffic using an IP network => more overheads • VoIP connections are established using signaling protocols, e.g. SIP an H.323 Investigation of Voice Traffic in Wi-Fi Environment

  8. Parameters Affecting VoIP Quality • Delay due to buffers and channel access methods • Packet losses due to collisions, bad radio channel and buffer overflow • Delay variation - even 1 ms counts Investigation of Voice Traffic in Wi-Fi Environment

  9. Parameters Affecting VoIP Quality • Delays greater than 150 ms begin to decrease the quality • Packet loss rate 1 % mostly acceptable. Depends on the codec used • Delay variations must me compensated using buffers (static or adaptive) buffer frames Investigation of Voice Traffic in Wi-Fi Environment

  10. Measurement Setup • The goal was to measure the delay, packet losses and delay variation of IEEE 802.11b network of a G.711 VoIP call • The end user devices were not considered Investigation of Voice Traffic in Wi-Fi Environment

  11. Measurement Setup • Indoor office environment • Hidden node situation and max. interference • RTS/CTS on/off • One/two interfering STAs Investigation of Voice Traffic in Wi-Fi Environment

  12. Results • G.711 is a good choice for voice codec, because it is robust against packet losses • One STA can’t model several interfering STAs Investigation of Voice Traffic in Wi-Fi Environment

  13. Results – one interfering STA • One STA can’t interfere the VoIP call much Investigation of Voice Traffic in Wi-Fi Environment

  14. Results – two interfering STAS • RTS/CTS could be more useful in VoIP if more contending STAs were used Investigation of Voice Traffic in Wi-Fi Environment

  15. Results – two interfering STAs • Interference of 1 Mbit/s was enough Investigation of Voice Traffic in Wi-Fi Environment

  16. Conclusions • ITU-T E-model was used for VoIP quality evaluation. VoIP call quality was fair when interference < 1 Mbit/s. • These measurements describe only a specific situation (worst-case). • The measurements should be done again in the actual environment Investigation of Voice Traffic in Wi-Fi Environment

  17. The End Thank You!

  18. Results – one interfering STA Investigation of Voice Traffic in Wi-Fi Environment

  19. Results – one interfering STA with RTS/CTS Investigation of Voice Traffic in Wi-Fi Environment

  20. Results – one interfering STA Investigation of Voice Traffic in Wi-Fi Environment

  21. Results – two interfering STAs with RTS/CTS Investigation of Voice Traffic in Wi-Fi Environment

  22. Measurements with one interferer Measurements with two interferers Bit rates of STA B [Mbit/s] Bit rates of STA B1 [Mbit/s] Bit rates of STA B2 [Mbit/s] 0.1 0.05 0.05 0.3 0.15 0.15 0.5 0.25 0.25 0.7 0.35 0.35 0.9 0.45 0.45 1 0.5 0.5 3 1.5 1.5 5 2.5 2.5 Additional information Investigation of Voice Traffic in Wi-Fi Environment

  23. Protocol Overhead in bytes RTP 12 UDP 8 IP 20 LLC 4 802.11b MAC MAC 34 802.11b PHY with short preamble 15 with long preamble 24 Additional information Investigation of Voice Traffic in Wi-Fi Environment

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