Wireless exterior connection of 500 meter apart 2 networks

[yemulss]

Hello,

We are small software development company in India. We wish to setup wireless network for our new development centre about 500 meter away from the existing office.

I am searching which is best wireless Access Point/Router for us to connect two buildings 1st has network of 6 PCs and second will have about 8 Pcs. Both the networks have switches for LAN.

The distance between two buildings is about 500 meters and these are across the road, not in a straight line. Both the buildings are 3 storied and there are few 3-4 storied buildings in between.

Also I wanted to know do I need to keep the Access point at both the buildings at the top on Terrace ? Do I need to use Antena/Extenders ?

About 10-12 mbps speeds will be sufficient.

When I was going through few Access Points of LinkSys/Dlink the Range was not specified, I am curious to know, where do we get this information ?

Please suggest which will be best Access Point/Router for us ? Thanks in advance.

Regards
[Sham]

 

[Brandon]

I've done a lot of things in my days, including connecting buildings via WAPs, even set up two WAP54gs to span over a mile and a half. It's really a hard question to respond to.

I would suggest going for AP's that have detachable antenna, then replace them with something like this.

I really don't want to give you the wrong equpment ideas however. I know a few good directional antenna's will do what you want though.

 

[corndog]

I set up a couple campus networks like this a couple years ago using the Proxim 4000AP with Hyperlink 5.8GHz patch antennas (about the size of a couple drink coasters) and 802.11a wireless technology. They have performed flawlessly ever since installation.

A couple of suggestions. Use PoE to get your AP as close as possible to the antenna, but keep the AP inside. Try to use less than 12 feet of antenna wire, so you don't lose all your signal strength to cable signal loss. If possible, try to use 5GHz 802.11a for your link, as there is much less busy traffic on this band. Also, be careful to get an AP with an external plug for the 5GHz antenna. Proxim has been shipping dual band APs recently with internal only on 5GHz, and lacking the external plugs for 5GHz antennas.

 

[thiggins]

Forget picking products based on range specifications. They don't tell you how the products will behave in real life.

You should assess the wireless environment before you even attempt this. If there are many busy wireless networks in the 2.4GHz band, then your throughput might not be acceptable. This will tell you whether you must move to the 5GHz band.

I agree with the other suggestions, 5 GHz band if possible, keep the antenna cable short.

If this is for business and you want it to be reliable, then you should look for products that are specifically built for backhaul / wireless bridge use.
Linksys, D-Link, Netgear make products for consumer use.
Proxim Tsunami QuickBridge Series

PePWave PolePoint

Finally, you might want to consider an optical link (but not cheap):
http://www.lightpointe.com/products/enterprise.cfm
http://www.usa.canon.com/html/industrial_canobeam/canobeam/index.html

 

[yemulss]

Hello,

Thanks for the responses.

1. There are no Networks, wireless in this area. This will be the first in this area, probably in my city.

2. There are cell-phone/mobile towers in the range of 2-3 km from my office and development centre.

Regards
[Sham]

 

[thiggins]

Sounds like you're ok to use 2.4 GHz. The cell/mobile phone networks won't bother you.

 

[Foggy_UK]

You can do wonderful things with standard "off the shelf" kit as long as you use external antennas and try to get line of sight or near line of sight. You of course would need to pick kit which has removable antennas in the first place, as this is easier alround than trying to retro fit connectors yourself. I personally used to get my broadband connection this way using Linksys, Hyperlink and Senao kit over a 14.2km near line of sight link before DSL was availible in my area. Some history here: http://victory4wifi.co.uk/history.html

Generally, radio signals require a clear path between antennas. This is not 100% true. Sometimes a signal will go from point to point by a route which is by reflection (e.g. from a neighboring building). In fact reflection is generally the only way to make a wireless link when you don't have clear line of sight. It's also worth noting that 5GHz radio reflects a lot better than 2.4GHz and is generally a much better method for NLOS (non-line-of-sight) connectivity.

It is therefore necessary to know the requirements of a clear path (known as 'line of sight').

Line of Sight (LOS) means a bit more than the words say. Of course the first condition for a LOS link is that the two antennas can be connected with an imaginary straight string. There should never be any object blocking this line. Achieving this with a short link is fairly easy. Long links, however, can cause problems.

Besides the LOS there is the Fresnel zone. This zone is an elliptical area immediately surrounding the visual path. It varies in thickness depending on the length of the signal path and the frequency of the signal. The necessary clearance for the Fresnel zone can be calculated, and must be taken into account when determining the height of the antennas.

For each link a 'link budget' needs to be made. The link budget will calculate the signal level through the link, and predicts the signal level at the receiver's side. Example: (2.4GHz, 802.11b wireless): We want to bridge a point-to-point distance of 6 Km over average terrain in a dry climate using 11b wireless. The bridge must perform at full speed (e.g.11Mbps).

To be able to do this, we first select the components we need. Let's assume that you will use 'standard' access power devices (c.100mW, 20dbm) and 14dbi gain Yagi antenna at each end.

The output power of the Transmitting Access Point, Pout: 20dbm
Cable loss and connector loss, assume approx. 0.3db for each connector plus gain loss in the cable (e.g. HDF200 cable is 0.5db/m), CT: 4.5 dB
Antenna gain, Gt: 14dbi

FSL (free space loss), from above example: -115.67db

The receiver sensitivity is (typical sensitivity value for a decent access point) Rin: -83db
Cable loss and connector loss, assume approx. 0.3db for each connector plus gain loss in the cable, Cr: 4.5 dB
Antenna gain, Gr: 14dbi

Add this lot up: 20 - 4.5 + 14 - 115.67 - 4.5 + 14 + 83 = 6.3dbm

So we have a margin of about 6db on the link. This is a good margin giving you plenty of excess to cope with unforeseen losses for example due to rain! Generally, we would not advise trying a link with a margin lower than about 5db. This signal is a calculation under ideal circumstances.

A solid mechanical installation of the antenna is the base of a quality link. An outdoor mounted antenna is exposed to extreme weather conditions. Metal brackets oxidise, and vibrations will cause slack on connections. Therefore, the mechanical connection between the antenna and its carrier needs to be solid. Use locktite on screws. The connector between the cable and the antenna needs to be sealed with threading tape. Corrosion on the connector will cause signal losses due to changing impedance of the connection.