On Wed, Jan 21, 2015 at 11:28:32AM +0000, Steger, Marco via Devel wrote: > Are there any parameters which will change while I'm increasing the > distance between the two nodes? Bit rate? Anything else? Any parameter > which can probably change? (I really want to have a clear and proper > result)
You can expect rate to decrease as distance increases. In practice, it's difficult to control for the channel conditions in such an experiment, because small movements may cause large changes in the channel properties. > To get the packet error rate I want to periodically/permanently send > message from one node to the other one. Can I use normal UDP packets > for that? Is there a possibility to send packets on a lower layer in > Linux? (I think raw Ethernet sockets will be helpful but I will have > to investigate some more here) You may wish to distinguish (layer 3) packet loss and (layer 2) frame loss. The frame loss is probably the more interesting number... for that I believe there are some counters you can use that are exported in debugfs. Note that for unicast traffic over wifi, there is a retry mechanism at the MAC layer, so some levels of frame loss may not show up as UDP packet loss but as latency instead. For multicast traffic, there's no retry, but there's also no rate scaling. Relevant to mesh: besides channel conditions, latency and bandwidth are also determined by the number of nodes that are communicating, because only one station in a given listening area can transmit at a time. So consider that in a 3-node, multihop scenario (A<->B<->C), you'll probably see a factor of 2 reduction in achievable throughput compared to just two nodes. -- Bob Copeland %% http://bobcopeland.com/ _______________________________________________ Devel mailing list [email protected] http://lists.open80211s.org/cgi-bin/mailman/listinfo/devel
