2011/2/28 Andrew Lunn andrew@lunn.ch:
In attachment you will also find a draft/proposals of a new routing approach. It is based on the collection of more link parameters (the current TQ, bit-rate and node-load) to write in OGM at each hop. This permit to develop a more thorough metric and can open new room of improvement such multi-path routing.
Hi Daniele
Do you have any suggestions how to collect this bit-rate information? Do you suggest measuring it, or asking the wireless LAN driver? Is there an API in the kernel to allow access to this information?
I'm not a kernel guru but i find out that the new core mac80211 and cfg80211 (http://linuxwireless.org/) offers the possibility to obtain a per-station bit-rate information that should be driver independent. The measurement is an alternative but I think it is more complex to implement. The load measurement instead is more difficult and at this moment have not idea of how to do it!!
Also, how do you see this interacting with the hidden node problem? In order to reduce the hidden node problem, you ideally want to use the lowest coding rate and transmit power possible to get your packets through. Currently this is not being done. Current wireless systems optimize for maximum bandwidth between two nodes, which may not be the optimum for the complete mesh bandwidth, due to inter node interference.
I have not mentioned the hidden node problem. But I think this problem is very difficult to remove, the only best practice to reduce the problem is to force the RTS/CTS mechanism to be active. Other phenomena such as capture effect instead are intrinsic in the wireless networking and are very difficult to eliminate. The optimization of bandwidth in my opinion does not influence the protocol because if the link is bad, rate adaption mechanism will reduce the bit-rate and I can read this information from the driver.
Anyhow collecting more information about link can help much in evaluating the best route I think, and offer a big opportunity to experiment new metrics.
Will you be at the WBMv4 next Month?
I'm afraid but I cannot be at WMBv4, I hope I can come to the next WBM, maybe with a working implementation :)
Andrew