Wireless bridge

Thu Jun 18 15:16:53 UTC 2009

We're a WISP, so I have lots of experience with this kind of thing. The problem with using 2.4GHz equipment is that there's a whole lot of noise out there (run Network Stumbler sometime on a laptop with a wireless card, and you'll be shocked by just how many wi-fi APs are floating around).

You didn't mention your bandwidth requirements, but I'm assuming that you're trying to get more (and spend less), so I'll only recommend unlicensed gear. For that distance, you might want to consider using a 5.2GHz radio. The FCC limits their transmit power, so they only work well in short-range applications (>2 miles or so), and 5.2GHz doesn't propagate the way that 2.4GHz does, so there tends to be much less noise in that band.

The Motorola PTP400 series (http://www.motorola.com/Business/US-EN/Business+Product+and+Services/Wireless+Broadband+Networks/Point-to-Point+Bridges) is very good (Asymetric Dynamic Frequency selection means that each side can pick the best frequency to transmit on, and ARQ means that scrambled packets get handled at the wireless layer), and throughput tops out about 45Mbps (300Mbps for the PTP600 series), but they are expensive. They can be purchased in many different bands.

On the lower end, we've been using Ligowave (http://www.ligowave.com), and had good results from them, for the price. They also come in many bands, and run about $3000 (for the model with an integrated panel antenna), support throughput up to 45Mbps, and also support ARQ.

Hope this helps.

Tim Huffman
Director of Engineering
Business Only Broadband, LLC
O (630) 590-6012
C (630) 340-1925
tim at bobbroadband.com
www.bobbroadband.com

> -----Original Message-----
> From: Peter Boone [mailto:NANOG at Aquillar.com]
> Sent: Thursday, June 18, 2009 8:06 AM
> To: nanog at nanog.org
> Subject: Wireless bridge
> 
> Hi NANOG,
> 
> I'm looking for some equipment recommendations for a wireless bridge
> between
> two locations approximately 500-800 meters apart. The current setup for
> this
> company has been extremely unstable and slow. I don't have a lot of
> experience in this area so I was hoping someone could give me a few
> pointers.
> 
> Currently, both locations are using Linksys WRT54GL's flashed with DD-WRT
> firmware (Yes, 802.11g. All extra bells and whistles are disabled in the
> firmware. They were set up for WDS so other wireless clients could connect
> to the same access point, with varying degrees of success. Not very
> important). They are connected to SmartAnt 2300-2500 MHz 14 dBi
> directional
> antenna mounted on the roof (extended pretty high for perfect line of
> sight). I'm not sure when they got these antenna exactly but I'm told it
> was
> when WiFi was very new. The network is very small so both locations share
> the same subnet (192.168.1.0/24).
> 
> They have gone through numerous Linksys access points over the years. The
> wireless settings are tweaked as best as possible, and we have found the
> connection to be most stable when the TX is limited to 6-9 Mbps.
> 
> We have explored other options as well. An internet connection at each
> location + VPN is out due to very slow upstream speeds (the buildings are
> in
> an industrial area, ADSL is the only option.) The max they offer on
> regular
> business accounts is 800 kbps up. T1 lines are even slower and even more
> expensive. They won't offer us any other solutions such as fibre. We have
> considered running fibre/coax but there is too much construction activity
> and other property in the way.
> 
> I'm looking into RouterBOARD right now, considering a RB433AH and R52H
> wireless card, but I'm not sure this will actually solve the problem. It's
> difficult to determine if the issue is with the antennas or access points
> (for example, after a good thunderstorm, the wireless link will be down
> for
> at least 12 hours, but will fix itself eventually. Resetting either access
> point will keep the link down for at least 30 minutes. Using an airgun on
> the access points tends to make them more reliable, even if they are clean
> and dust free. From the admin interface, each access point will report
> seeing a very good and strong signal from the other, yet they refuse to
> communicate until they feel like it a few hours later.)
> 
> Any suggestions welcome. I'm sure you can tell cost is a bit of a factor
> here but it will be easy for me to justify a higher price if I'm confident
> it will be effective.
> 
> While I'm at it, I've been reading along on the list for over a year now;
> thanks everyone for sharing your real world experiences :)
> 
> Peter
> 