Point-to-multipoint connection 5ghz or 2,4ghz?

Unanswered Question
Jul 8th, 2008

Hi guys,

I have 8 remote sites and i want to connect them to a central site. My question is: In this type of installation, i mean point to multipoint, all the remotes sites must be in the same channel? If no then i will use the 3 non-overlapped channel?

With this 3 channel i don't have enough to execute this configuration, so i must change the aironet that i have to 1242AG with 8 non-overlapped channel?.

Thank U

I have this problem too.
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Scott Fella Tue, 07/08/2008 - 03:42

With that setup, if you only have one root bridge on the central site with an omni, you will only be able to setup a single channel. So all your remote sites will have to be configured as non-root bridge with the same channel and encryption. The more non-root bridges you have to one root bridge, the lower the throughput since it is a shared media.

mohamed.farchado Tue, 07/08/2008 - 05:36

Thank you very much. My project consists in connect 8 security cameras via WIFI to the central site. Each camera will be connected directly to the Bridge 1310. I hope that the multicast can flow good in each of the links.

Have a nice day.

Richard Atkin Tue, 07/08/2008 - 12:12

Be very careful...

Even if all sites run at "54Mbps" your real throughput will be more like 20Mbps. Add in some inefficiencies for hidden nodes, real-world issues (etc), and each camera will only have about 2Mbps BW presuming they're all running none-stop, same BW req's, etc..

Multicast over wireless can also do strange things, but that depends on your design...

mohamed.farchado Wed, 07/09/2008 - 07:31


What do you mean about strange things, do you think if a choose the 5ghz is better for this configuration?

Scott Fella Wed, 07/09/2008 - 07:39

I think he is talking about multicast in general. I have seen in a lab with mesh with one WLC with one RAP and one MAP and around 8 WLC's. Each MAP had one D-LINK IP Camera and the 3750G switch locked up. You should test it out first just to make sure it will work.

Richard Atkin Wed, 07/09/2008 - 07:42

If your end-points are other bridges, then i think multicast should work fine.

If the end-points are the actual cameras, then WiFi treats multicast in the same way it treats broadcasts, ie - they're transmitted at lowest supported data rate, which is usually 1Mbps, even if all clients are running "54Mbps".

mohamed.farchado Wed, 07/09/2008 - 23:53

To resume my design:

8 remotes cameras connected directly to the aironet 1310, i mean directly without switch between them.

Finally this 8 cameras with his respecive bridges will be connected to the central site equiped with the same bridge and an omni antenna. This brige is connected to a cisco switch that can provide IGMP solution. At this point whe have a server who manage multicast to cameras and a DVR to record the cameras view.

Scott Fella Thu, 07/10/2008 - 03:27

Is this the only traffic that will pass through the link? Also, on the remote site, why don't you want to use directional antennas instead of an omni. The omni is needed on your main site where the root-bridge is located.


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