1. How to avoid killing the wireless internet with your phone
Patrick Verkaik, Yuvraj Agarwal, Alex C. Snoeren
contact:
Voice-over-IP in wireless
Voice-over-IP =telephony over Internet
Voice-over-IP in WiFi
WiFi VoIP phone
Phone call
VoIP over WiFi
Access point
Internet
Internet café offering WiFi
But now add more callers..
How not to kill wireless
1. Prioritise (no backoff) and schedule outgoing VoIP
Time
Note: no collisions
VoIP traffic
2. Access point aggregates incoming VoIP, saving overhead
Web traffic
packet
Time
No changes to non-VoIP computers at all
Less airtime for e.g. web users
More airtime wasted on collisions and backoff
Current impact on TCP
Reduced impact on TCP
WiFi contention procedure
packet
Expected (from
To transmit data:
Wait for everyone to be quiet
Wait a bit more (back off)
Transmit
In case of a collision, back off more, then retry
Our solution
size of VoIP packets)
(emulated)
Measured (802.11b)
Our solution
(calculated)
Inefficiency of VoIP
Current
(measured)
TCP capacity destroyed!