Learn, hack!

URL

http://dewy.fem.tu-ilmenau.de/CCC/23C3/video/23C3-1634-en-how_to_squeeze_more_performance_out_of_your_wifi.m4v

File name

23C3-1634-en-how_to_squeeze_more_performance_out_of_your_wifi.m4v

File size

172.6 MB

MD5

841818d6f05b6c165cabca36bc5b759e

SHA1

9c24559b92c69ca971ce0069e5b66ac729a595c9

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.