Hey Guido, the problem using one radio is explained further here (from another company, but this applies to any WiFi mesh technology)
http://revolutionwifi.blogspot.com/2012/02/mesh-network-performance-impact.html Also, if you use two-radio nodes, make sure that you use one module on 2.4 GHz and one 5 GHz - if you use two modules in the same frequency band with omni antennas, even if you use separate channels (like 1 and 11), they may interfere with each other if the antennas are near to each other. There are quite a few ppl who can confirm this, e.g. check this: https://hackerspace.be/Wbm2009v2/TestInterferenceResults Possible Solutions: * use different bands * use directional or sector antennas * have a reasonable distance between your omni antennas Cheers, Simon On Wed, Mar 28, 2012 at 07:41:05PM -0300, Guido Iribarren wrote: > (this time i'll keep the mail short, insane details are attached as text :) ) > > Well, luckily for batman-adv devs, but unfortunately for me, the > problem is in fact related to relaying between wlan interfaces in > mr3x20 hardware (at least) > > I understand this is not anymore batman related, but maybe someone has > experience on this, or can point me into the right direction / > maillist ? > Given you have a good deal of equipments at the BattleMesh, maybe > someone has already tried adding a wifi dongle and can confirm seeing > this behaviour? > (in a line of 2-radio nodes with static routing, packet throughput is > halved on each hop) > > ======== > > I've repeated the iperf tests in a controlled environment, this time > using different subnets on each interface and static routes built with > "route add". iptables flushed with -F and policy -P FORWARD ACCEPT > no batman at all. > > Packets coming in through wlan1 and out through wlan0 (or viceversa) > experience (unexpected) "bandwidth degradation". Throughput drops from > 30mbps to 15mbps (rough avg) > The speed is closely comparable to using only 1 radio (packet comes in > through wlan0, goes out through wlan0), so adding the dongle makes no > net difference. (besides alternating the channel for transmission, > throughput is halved over one hop anyway) > 2 consecutive hops, alternating wifi radios, yield 1/3 throughput. > (like it happens in a 1-radio mesh) > > this does not happen if the packet comes in through eth0 and goes out > through wlanX (or viceversa) . Throughput is maintained high at > 30mbps. > > ========= > > So the hardware (or kernel??) is uncapable of keeping up with the > transfer speed *when two radios are involved*. > > Has anyone bumped into a similar case, or has experience with these > equipments? Maybe (again!) i am doing something wrong? > > If this is confirmed, my only alternative to maintain good throughput > along the mesh will be to install 2 x mr3220 on each node, connected > back-to-back with ethernet cable. This will definitely work but the > cost for each node owner evidently rises ;( > > Thanks a lot! > > Guido
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