23C3 - 1.5

23rd Chaos Communication Congress
Who can you trust?

Speakers
Achim Friedland
Schedule
Day 3
Room Saal 2
Start time 11:30
Duration 01:00
Info
ID 1634
Event type Lecture
Track Science
Language English
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How to squeeze more performance out of your wifi

Cross-layer optimization strategies for long-range IEEE 802.11e based radio (mesh) networks

Most of today's long-range wireless mesh or point-to-point links suffer from a high overhead during channel access, frequent link failtures and the lack of taking a real advantage of the mesh network structure. This leads to a really bad performance for TCP-like traffic compared to UDP traffic over this links. We want to present your two different ideas for optimizing throughput and delay without breaking any wifi-standard (or at least not too much ;).

Most of today's wireless mesh networks can be characterised by the use of cheap half-duplex transmission technologies like IEEE 802.11. It suffers from a high overhead during channel access, frequent link failures and the lack of taking a real advantage of the mesh network structure. All this may result in low throughput and high end-to-end delay. To improve both properties, one may use diversity achieved through multiple channels directional high gain antennas, polarization multiplex and frame aggregation techniques. Additionally -- in order to take an advantage of the mesh network structure -- it is possible to divide the up- and downstream of a wifi point-to-point link into two seperate links. This eliminates the concurrency between both directions. Results of calculations, simulations and measurements show an improved distribution of delay and a significant higher throughput especially for TCP-like applications. Both values can furthermore be improved by an optimization of the IEEE 802.11e quality-of-service parameters.