splitting 802.11b channels Edit


>I am getting to many customers and a lot of CSMA contention and busy 
>holdoffs on a mesh network.  There are 40 - 50 dhcp leases on each 
>of 10 APs.  A lot of duplication.  I was thinking of putting some 
>APs on channel 11 and some on channel 1.  I would have two gateway 
>APs at the data line backhaul, one on each channel.  My concern is 
>having two gateway APs and their antennas mounted on one mast at the 
>headend of my network.  Even though the channels are separated by 
>40Mhz, will it cause contention and busy conditions between the two 
>gateway APs?  The two antennas on the mast would only be separated 
>by a few feet.  Has anyone tried two gateway APs in very close 
>proximity running on two b channels?


I can go one better! Using a splitter, I am running two gateways through the same antenna - one is on channel 1, and the other is on channel 11. Although they can see each other using MaxiSpy , SigSpy they are not meshing with each other, and there is no appreciable performance hit.

I set up a test network at my shop with the two boxes/antennas 3 ft. apart - one channell 11, one channel 1. The boxes were each put on a switch to a 4MB cable feed. Set the owner download/upload to 4Mbit for two clients in the next room and got them to associate one with each box, and did concurrent downloads at over 1.6MB. By themselves they did 2.4MB. I turned off one access point and used one laptop and got the same 2.4MB. It might be contention at the switch, or the cable providers 4MB service. But I feel confident enough to take it out to the field and try, especially with the feed back from the user group. An interesting footnote is that one of the APs saw the other in sigspy, but the other one did not. I thought this to be a little strange.

More - I do RV parks in the Naples, FL area.

I'm using the VIA-MII motherboards with built on pci-pcmcia adapter, 2100 DDR RAM, CF to IDE, and Engenius/Senao 200mw cards. The installation of Locustworld's distro is really simple. I've had the older VIA boards in the field for three years now with no failures - zero. I am giving up on the PCEngine boards. Way to many problems especially in a dense environment. Those little pigtails and miniPCI cards are to intolerant. A little bit off on the pigtail to card adapter, or a little bit off on the other end and I get signal quality all over the place. And they simply don't have the capacity to handle many users and mesh. I think they might work fine for a single AP hotspot.

I've also dropped the SMC 2532w-b cards for cpe. I use Zcom's XI-325HP cards. They are the same as the old SMCs. Zcom private brands for SMC. The new 2532w-b cards are not the same. Terrible signal quality and strength. I buy the Zcoms through O2 Secure Wireless in Atlanta. They have an Ebay store, but contact them directly for volume pricing. I use EUB-362(EXT) USB radios from Netgate. They are 200mw with an external antenna adapter.

I love both of these radios, one for laptops the other for desktops, because if they cannot associate well with one of my APs I simply put an external 6dbi flat patch antenna with lmr195 wire and pigtails. Most of the time I can mount the antenna inside for GREAT improvement in signal strength and quality. Plus they're directional antennas that cut down on the rf. At last resort, I go outside with the anetenna. I've used over 60 Ft. of cable with insignificant RF loss. The most important thing is to not pinch or crimp the cable. The cpe costs me between $50 and $125 using this stuff. I've found nothing cheaper or better. And, I almost forgot, for the 6 Apple Macs I have that cannot hit the antennas with built in Airport, I use 2611CB3 bridges. They are great. Set them up on a laptop and plug them into the Apple Mac. A little expensive, but I'm dealing with Apple ...

I have a Linux computer with three Ethernet adapters running Fedora 4 at the headend. I bridge two Ethernet adapters between the Wireless Gateways and the T1(2 of them) router. I use the third for access to the box to monitor the bridge. I run iptraf on the bridge to monitor the network and IpTables for firewall management. I block known p2p ports and other bad traffic as I see it. This has been invaluable. I tried Squid on this box, and it helped so little I took it off. It only cashes the obvious, and client web browsers all ready do a pretty good job of that.

I'm still a little worried about dense cpe environments and the mesh. If I can get my complaints down to zero for a week or so I will be a happy camper. I hope my comments help those getting started with the mesh. And I really do appreciate the list. It's helped me many times.

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