AnteNnas

Antenna deployment
* AntennaDeployment * PcmciaDiversity

Interference channels
I have been playing around with Mesh boxes for a few years in testing, and I have a few questions which I thought some of the experts on this  list might be able to place some opinion on.

1. There is a lot of controversy about antenna's. I am currently testing    the mesh concept in a rural area and have one main gateway which has a   omni antenna about 13 metres up in the air. The other repeater nodes are quite far apart with distances of around 1.5 to 2.5 km apart. The repeater nodes are using flat panel antennas directed at the gateway. The question I have on this setup is this, is it the best option to have  the omni as a gateway antenna, or should I use something different? I know that noise from the omni can be a problem, but remember that I am in a rural area where not that many people have wireless stuff operating so that is not a big problem.

> /If you are getting good signal to noise ratio, then I would leave > well alone - Antenna and propagation theory is only a guide, but you > never know until you try it. If SNR falls off due to noise, then you > may consider putting three sector antenna up in the same location, as > described by Kenny in a previous post (2 Mesh and one access point) Be

>    2. Given the info above, on the repeater nodes, which are using >    the flat >    panel to connect to the gateway, would it be best to then use a >     second >    radio card in the node to provide local access to the repeater and >    connect this up to an omni, or would it be better to use something >    like >    a linksys 54 to provide local access and bridge that to the repeater >    using a wired link or place it in the path of the link to the gateway?

> /This sounds like a candidate for the new 2100 series software on > www.locustworld.com  using a combination > of A and B, but assuming you are using the Open mesh software, a > second radio card - if you can prevent it interfering with the first, > or an access point on the wired side of the mesh box would work - my > preference would be for a good access point. /

3. Given the above info, in order to provide the redundancy links to the gateway, should I use a second radio card to provide a flat panel link to another repeater node if possible?

> /You can use quite a lot of money inducing redundancy - your call, > based on how reliable its been so far./

>    4. I have a mixture of Wrap boards and white box pc's acting as nodes. >    On all of the nodes I use Senano wireless cards either pcmcia or mini >    pci on the wrap. These cards have two antenna connections, one for the >    main antenna and one for diversity. At the moment I only use the main >    one to connect to either a flat panel or omni as described above. >    Should

>    I be using this second diversity antenna, and how does one us it. >    Do you >    connect a second similar antenna, or use a lower gain antenna? >    Where do >     you mount the second antenna in relation to the first one? I think

I >    know the concept of the diversity antenna to help the card >    differentiate >    between signals, but will it make a difference to the kind of setup I >     have described? I have noticed and expected that people close to the >    gateway, in the effective dead zone of the omni based on it's >     height get >    poor performance from their connections. Would a diversity antenna >    help >    out with this dead zone?

> /This is always the difficulty of how to get a radio shot over a good > distance, but still get the signal down into where its needed. All of > us use a variety of tools to achieve this, from antenna on the roof > connected to AP's in client mode, through to putting more mesh in. / > /I'd be wary of using diversity in the way that you describe. The > purpose of it is to provide two places where the signal can be > received, to account for the fact that the signal often bounces off > other objects, and the more antenna you have, then the more likely > that you are going to pick up a strong signal. The trouble with > Diversity is that it is not very intelligent. Simplistically it > switches off the antenna that is picking up the weakest signal. I > would not be sure until I had tried it, but it may cause issues with > meshing and talking to different customers, as you may end up meshing > on the wrong antenna. / / > /If you have good line of site, and good height to account for the > fresnel zone, then a diversity antenna is probably not going to make > much difference./ /Now MIMO - or 802.11 Pre-n - that looks interesting, as that receives > on all antenna similtaneously, then adds the signal together so that > the resultant signal to the receiver is that much higher./

>    I know this sounds like a long mail with lots of questions, but I have >    been sort of storing them all up and thought I would try and get >    advice >    on the whole setup, rather than just asking one question when not all >    facts are available.

> /I note from your email address that you are in South Africa. I > believe that you have a 3Gb cap on standard ADSL. The 2100 > software, may be worth a closer look for the volume based user > accounting. In other words, you can set volume caps on your users, > also the PPoE authentication may be of some use, as I understand that > this is the way that you athenticate to ADSL in SA / > > /PS I'm not on commision from LW;-)/

>    I would appreciate any information on or off list on these questions, >    and thank everyone in advance for any assistance.

Many thanks for the detailed reply. I will stick with the Omni for now, and give the diversity a miss, as it sounds more hassle than anything else. I am only using the open mesh software as this is not a commercial venture and just an experiment on my side of things. The 2100 would be overkill and expensive. We are in South Africa and the cap on ADSL is not quite 3Gb, but bandwidth is expensive, so that needs to be controlled. For those who want to be shocked, we pay monthly about 50 pounds sterling to have a 512k ADSL line to a house, and then about 23 pounds sterling for a 3gb shaped account. So for about 75 pounds sterling, we get up and going, so it is expensive. We do you PPoE to connect, but in terms of connecting to the mesh, that doesn't really have much play on things.