On Sat, 27 Sep 2014, Nishant Sharma wrote:
Hi David,
Thanks for your quick reply.
On Saturday 27 September 2014 06:20 PM, David Lang wrote:
This actually sounds very typical for the way that a wireless network
collapses under load. This behavior is why the OLPC dream of using mesh
networks for everything ended up failing.
If you can, deploy more nodes with lower power per node to reduce the
interference. I'm not familiar with batman, but more nodes also gives
you more channels to play with (assuming you can use multiple channels)
BATMAN does a layer2 meshing without any complicated routing required
between nodes. It was all working fine as long as we had 5 nodes and 3
of which were connected to the cabled LAN.
Do you suggest we use multiple channels and multiple backhauls on 5GHz
for different set of nodes, instead of creating a single mesh? We can do
that if it helps.
I notice that you use 40MHz channels for 5GHz, unless you have wired
connections between the nodes, this seems like it's probably a waste as
you only have 20MHz channels on 2.4GHz. In theory it takes less time to
transmit the data on the 40MHz channels, but in practice I'm not sure it
really gains you a lot (it definantly doesn't gain you as much as if you
had two 20MHz channels operating independently in that area)
The gateways are connected to 100Mbit/s switch directly that is why I
thought of using HT40- in order to provide full LAN bandwidth to the
stations in case it is available. I can also try to change it to HT20
and see if it makes any difference.
In reading your config, it looked like you were using 5GHz for the mesh.
The more channels you can use, the better off you will be. In an ideal world you
would have one set of channels used by the clients, and another set used by the
APs to relay to a gateway unit (with directional antennas on the AP-AP links).
you may be able to use 5GHz for both if you deploy a pair of APs to a point that
doesn't have a cable. Configure one of them as if it had a wired link, and use
the other to take that wire and connect it to a nearby location that does.
a 20MHz channel that's only used by two APs to talk directly to each other will
wildly outperform a 40MHz channel with even a handful of clients on it as well
as the two APs
The key to your problem is to solve the radio side of things. See what you can
do to configure the radio side to have as little overlap as possible between
different users and different locations. Then you will see things work MUCH
better.
David Lang
I cover a lot of this in the talk I gave at LISA in 2012
https://www.usenix.org/conference/lisa12/building-wireless-network-high-density-users.
Thanks for the link. I am going to study and decide on the strategy.
Regards,
Nishant
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