wireless / physics question

[RabbieBurns]

Our buildings are in residential areas, and are seperated by houses and other buildings. We cant link them with fiber as its too expensive to dig up the public roads. So we use wireless directional antenna on the roofs with netgear bridges. (802.11g)

 

From building A to B it works absolutely perfectly, and normal network usage it is almost impossible to tell that your not plugged in.

 

But from building B to C, even though the signal strength is reported in the AP, packet loss is astranomical.

 

The only thing different is that between B and C it goes over treetops and roofs whereas A - B is pretty clear.

 

Am I correct in thinking the wavelength on 2.4Ghz is about 12.5cm? So should the trees and rooftops be having an effect?

 

Its so unusable accross at building C its not funny.

[FN-GM]

Do you have anything else local operating on the same channel?

[Psymon]

Do you have anything else local operating on the same channel?

 

What i would suggest also. Ideally you would have 4 wireless stations creating 2 bridges.

 

A Wireless to B on Channel x

B wired to C

C Wireless to D on Channel y

 

Si

[SYNACK]

Trees are awful for wireless as like people they are full of water, 2.4ghz is a microwave frequency which is closely coupled to water and so lovely green leaves act as an impressively effective cone of silence for wireless traffic as the signals are absorbed rather than bounced. I suspect you may need to try and route the signal around the obsticals differently or use a more focused antenna that can be targeted directly at the receiver.

 

Your other options would be to try using 802.11a ad it 5.something ghz band may be more resilient to both the obsticals and any electronic interference in the way or to use 802.11n with dual or tripil antennas on each side that can use multiple path and a wider frequency band to transfer the data.

[RabbieBurns]

What i would suggest also. Ideally you would have 4 wireless stations creating 2 bridges.

 

A Wireless to B on Channel x

B wired to C

C Wireless to D on Channel y

 

Si

 

Yup thats the excact setup. There are 2 AP's on building B, one at the front linking to A and one round the back on the side linking to C.

 

Ive been through every channel on the B-C link to see if it makes a difference.

 

We have a company coming tomorrow to demonstrate WiMax or something along those lines, but 11a and 11n is two of the other options I have been thinking along.

[Gerry]

Check these websites out:

What is the best WiFi antenna for me? | Do-It-Yourself Wireless Antennas Update

Wireless - Technical Discussion Document

 

Yup, anything that retains water is going to affect wi-fi signal. 5GHz band is much better, but will still suffer some degradation, and if you are going to use it, will have to be registered with Ofcom (for a small fee) as the military and emergency services also use the same band.

 

I would recommend directional antennas, mounted on poles to have a clear line-of-sight, or you trim the trees back a little.

[kylewilliamson]

YouTube - Heineken - Road works

 

Have you waited for something like to happen?

 

Kyle

[Domino]

why not ask a wireless specialist company for a survey...?

 

Might be able to swing a freebie - there might be things you haven't considered....

[User3204]

Laser costs about £3k - £5k, but this will start at 100mbps, you do need line-of-site.

 

We have a 11mbit directional wireless, and found we had to trim a few trees to get the signal through, and if it really buckets it down, to the extent we can't see the building, neither can then wireless...

 

I have been trying to get our SLT to approve replacing the wireless with something the kids don't aim footballs at, and fibre is the best option (for us), it's just not cheap.

Other options I considered:

a) an additional phone line with SDSL, that we could get a VPN through - but no SDSL in the area (apparently).

b) pay the LA, who provide our Internet access, to link to it (at 8mbit), and let us have a straight VPN through - but they said no chance.

c) fibre across the road - no-one was able to get me a price on a mole...

 

Contact a local network cabling company to see what they can do, ask for a survey.

[kmount]

but no SDSL in the area (apparently).

 

If you don't believe there's no SDSL provision given the apparently, check for yourself at Samknows.com.

[mac_shinobi]

What i would suggest also. Ideally you would have 4 wireless stations creating 2 bridges.

 

A Wireless to B on Channel x

B wired to C

C Wireless to D on Channel y

 

Si

 

side tracking a bit but how do you create a wireless bridge ( presuming this is between 2 wireless access points ) or how do you do it exactly ?

[User3204]

If you don't believe there's no SDSL provision given the apparently, check for yourself at Samknows.com.

 

Samknows.com tells me there is SDSL service.

But when I talk to actual phone companies, Redstone, BT, they can't tel me who... I suspect samknows.com knows about the LA connection, but this is somehow reserved by them, and not available to anybody else. Which is why I went to the LA and asks them about another connection, and they said no.

[kmount]

Without being facetious is your LA connection SDSL?

[john]

BT have services which allow you to link buildings together, enquire with them, they can do them for you for a price, Kilostream I think was one going back years ago that was popular for linking remote offices back to central ones, but it will no doubt have been superceded by now. They were all about direct P2P links though which would do the job you need.

[webman]

Try pointing B and C antennas slightly to the side or above the trees; or both towards any other high buildings in line of sight of both sites - it might just bounce

[RabbieBurns]

tried mucking about with the antennas loads, no change. Cant chop trees as they are all in private gardens. The expense of a dedicated leased p2p line isnt an option really. ADSL with a VPN will be the only other option I think.

 

Got a company coming today who say they can do a wireless solution that doesnt require a line of sight - so will be interested to see how this pans out!

[RabbieBurns]

CableFree Solutions - Broadband Wireless - Free Space Optics - High Performance Wireless Networks

 

anyone used anything from there before?

[SYNACK]

There is the mad scientist route, attaching a magnatron from an old microwave to one of the antennas will crisp those nasty leaves, birds and anything else out of the way it is something that you operate from a safe distance and a couple of brick walls away though

 

Have you tried aiming the antennas both slightly upward above the tree line as there is an effect 'freznel zone' or something along those lines that causes signals to drop in angle slightly but it may only be over water. I heard a wireless engineer talking about it regarding wimax links over open ocean to an island located near Auckland.

[steveg]

If you do want to try and go down the cable route, then def worth speaking to BT, as you can rent pairs of copper off of them connected to both buildings. Main disadvantage of this is the length of copper is from building 1 to phone exchange back to building 2 - so if the exchange is 2 miles away, you're never going to get much accross it.

 

Can't remember what the service was called, or if they still offer it - last time i did this was about 6 years ago, but it worked out at something like £350 per year for the lines, and the install wasn't hugely expensive. You just put your own sdsl routers at each end.

 

I'm pretty sure they do the same thing with fiber as well, but no idea of the costs, and if you haven't already got bt fiber into both buildings, its gonna be expensive!

 

If not, are the tree's on the schools land, or somewhere else? I it feasable to loose a few of them? We've round trees really kill a wireless signal - obvoius question is does it improve in a month or so's time when they loose their leaves?

 

Steve

[RabbieBurns]

Nope the trees are in about 6 different houses' gardens

[rhyds]

Time for some nocturnal chainsaw action?