Wireless connectivity between 2 buildings

I need to get two buildings hooked up through a wireless connection and have a fair bit of concrete (not real worried about), steel and insulation. Now, there is a high amount of security that is needed to be in place, which is what's making me lean away from a standard omni-directional

802.11G antenna. I was thinking that a pair of low power directional antennas may do the trick and for them to just be placed on the out side of the buildings, or even inside if the signal reaches.

My question is how narrow is the wireless field? The building is about

50ft away, not real far, but I want to be very careful that the wireless signal is not going right down the block. My other ocnsideration was using an infrared connection between the two buildings, but have found little in terms of products that will have an "ease of use" in terms of connecting to the existing network.
Reply to
I_AM_Raptor
Loading thread data ...

On 12 Jul 2006 07:44:52 -0700, I_AM snipped-for-privacy@hotmail.com wrote in :

Wi-Fi signals can be greatly attenuated by concrete, depending on construction. Insulation is a serious problem if foil backed. Steel can cause problematic reflections. Etc.

Antennas don't have any real bearing on security -- bad guys have better antennas than you do. Use WPA with RADUIS or strong passphrases.

OK.

I'd personally use external panel antennas over that distance.

In addition, infrared can be a problem in bad weather.

Reply to
John Navas

I_AM snipped-for-privacy@hotmail.com hath wroth:

That's going to be difficult. Most antennas have side lobes that can be heard from off axis. Even if the side lobes were perhaps 30dB (1/1000th the power) lower than the main beam, a 30dB direction antenna in the hands of an evil wireless hack (like me) would bring the signal back to a usable level. In addition, 2.4Ghz bounces around and not all the RF that arrives is absorbed by the receive antenna. Lots of it hits the building and bounces to who knows where. It's a good idea to limit your beamwidth to reduce interference and enhance security, but it's not a guarantee.

As a rule of thumb, the antennas -3dB beamwidth is dependent on the type of antenna and the antenna gain. For example: Type Gain -3dB BW dBi degrees Biquad 10 60 Panel 19 18 Dish 24 8 Yagi 15 30 Dish 15 19 coffeecan 10 60

Using the 19dBi panel as a practical example, with an 18 degree beamwidth at 50ft, the beam will be 16.2 feet in diameter. That means that HALF the RF will end up in a 16.2ft diameter circle. Since the antenna is only about 1 ft square aperture area, something like 1/415 of the transmitted power actually hits the antenna. The rest is reflected off the target building.

At 50ft, you could probably reduce your transmit power to the absolute minimum necessary to communicate. However, you're not going to be able to prevent anyone from hearing the signal.

For 50ft, I suggest using an FSO (free space optical) bridge. See:

formatting link
they're MUCH more expensive the 802.11g wireless.

Reply to
Jeff Liebermann

Okay. I think my plan right now is to use approx a 8dbi gain antenna(DLink Pico) hooked in place of the standard router/AP antenna. And see what that gets me for signal strength in the other building. If its not enough, depending on how much is lacking, I will add what I need there in terms of AP or possibly another directional antenna.

For someone to pick up the wireless signal it would have to travel a good distance to get out to the street. With the way the directional would be facing, there is a good 100-150 yards to the closest street/public lot. And even with the signal bouncing there is not much in close proximity to the buildings for someone to sit and pick up a signal.

So a semi powerful signal is not going to get far enough to reach to the public. I was just concerned about possibly overpowering the signal needed and allowing the broadcast to reach all the way out to where I don't want it. I am not very familiar with how far a directional antenna will reach with its rated power. DLink claims about 500M for their Pico antenna, but I don't know if this is really accurate or if its extremely ideal and I should really expect much less than that. Particullarly with structures involved.

Reply to
I_AM_Raptor

On 12 Jul 2006 09:55:06 -0700, I_AM snipped-for-privacy@hotmail.com wrote in :

Never make assumptions like that without a careful site survey. I've shocked clients that had made assumptions like yours by picking up and cracking into their networks (with their permission) using cheap equipment.

Reply to
John Navas

As I said, I am unfamiliar with the ranges that I am going to be dealing with so not much would shock me on how far it is going to go. And of course full encryption and codes would be in place on the wireless signal, I am just wanting to avoid broadcasting the network availability across half the city. :D

Some of the stuff that we are doing requires an absolute measure of security, so anything involving that immediately rules out wireless and even connectivity to the standard network. The area involved with the wireless I am trying to setup is confidential, but is not to a degree that is going to be of any interest to most people. I just want to keep the knowledge of the network lower key as to not to attract to many unwanted attempts. I assumed with wireless that there is no sure fire way to protect your transmissions, but I never assumed that no one would be able to pickup the signal from out of the compoud.

Reply to
I_AM_Raptor

you are trying to make a wrench out of a hammer. itdoesnt sound like wireless fits the application very well, so you should at least look at alternatives.

if you are paranoid even on different networks, if your security folks are as paranoid as mine, they will not agree to working wireless even on a different network in the same building (to be fair, theyare worried about what happens, when someone comes along and alters the network and joins them up in some way, or there is access between control networks etc.

So you need to check if your assumptions about wireless and the security level are acceptable, whether there is a duct inplace, or enough height for a wire support between buildings.

if possible use fibre or rent a telco Ethernet WAN link -which would also give you a lot more useful bandwdith, and probably be more reliable.

>
Reply to
stephen

Security seems to be your main focus so why have doubt and checkout running fiber between the two buidings?

Reply to
George

Fiber and anything involved installing an underground line isn't feasible right now. The lot was just redone and the fundage providers don't want to have to redo it again. And there are no available conduits that a line can be fed through.

However, one option we are looking at is running fiber to yet another building from the one we want the connection as we already have the third building connected to the main building.

Reply to
I_AM_Raptor

Forgot to add that an over head line is out of the question as well. It would not work with the equipment that needs to get moved around here.

Reply to
I_AM_Raptor

stephen snipped-for-privacy@xyzworld.com:

We are in a similar situation, can't go under the street or through the air and would like to dump the wireless bridge we currently have. I tried Googling this "rent a telco Ethernet WAN link" and couldn't come up with anything that explains it in layman's terms. Could I trouble you to explain what this is exactly or point me in the direction of a good resource?

Thanks much, ~Jacy

Reply to
jacy77

On 18 Jul 2006 19:17:07 -0700, snipped-for-privacy@gmail.com wrote in :

Call your telco and ask about leasing a circuit between the two buildings.

Reply to
John Navas

| if you are paranoid even on different networks, if your security folks are | as paranoid as mine, they will not agree to working wireless even on a | different network in the same building (to be fair, theyare worried about | what happens, when someone comes along and alters the network and joins them | up in some way, or there is access between control networks etc.

If security can't even trust WPA, then what I'd do is isolate the wireless with a Linux box on each end that transports all the packets in a VPN that goes over that wireless. So if a hack breaks through the WPA, he next has to break that VPN. And with programming, I could pile on some heavy TLS on that. OTOH, a DoS attack (e.g. interference) would be way easy.

Reply to
phil-news-nospam

i am based in the UK, so can only give you product names i am familiar with - but they will probably be similar elsewhere.

these things are fairly common here - when they 1st arrived it was just dedicated point to point fibre links limited to 25 Km (due to fibre drive distances), but more recent versions use SDH.

BT Lan extension service (LES), also WES - wholesale flavour, BES, for backhaul.... part of short haul data services. BT have a strategy to replace basically all their customer tails with DSL for "low" speed and Ethernet / fibre got high speed - oh and also convert all the core / edge network to IP. should keep them busy for a few years - frankly i think the whole idea is scary, but it is making Ethernet "pipes" mainstream here as a side effect...... (21CN)

Also seen National Ethernet Ethernet private circuit / line and a few similar layer 2 MPLS, VPLS and so on tend to be for longer distances.

although it isnt the same, you might find a wayleave (duct space for your own wire, although the telco might insist they install / maintain it), lambda, or dark fibre - but these tend to cost more......

you can also get an Ethernet link bundled with other things - latest one i stumbled across is a CCTV link with associated 100 Mbps Ethernet meant for security use.

Reply to
stephen

Cabling-Design.com Forums website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.