5GHz has been the backbone of WISPs for a long time. 900Mhz is under assault in any urban environment meaning you are limited to Grizzly Adams neighbors and hope that most users only want to watch 70’s TV shows on NetFlix. 3.65GHz WiMax is tough on the budget and ulcers but it’s still the best option for long-range and vegetation, it’s just not magic. 2.4GHz is pretty much toast in any suburban area or city area. If you really want to see interference, I’ll show you the logs from our Xirrus router installed indoors that picked up 1400 APs. 2.4GHz still has value in remote areas for WISPs due to the 3-1 exception rule except that without Vivato, nobody has an AP that can take advantage of it any longer. I’m still holding out hope that with 802.11ac that the idea makes a comeback. Even though 802.11ac is specifically 5GHz, I’m not seeing the problem scaling it down to 2.4GHz in the future. A variation of this with dual-banding could bring back the mesh market.
The FCC is picking up the ball finally, and might grant another 195MHz in the band, with some limitations, to expand the use of unlicensed bands. With the only part of the band, UNI-II Upper, having sufficient EIRP to penetrate vegetation limited to 100MHz, it’s limiting the use of 5GHz as a backhaul frequency on a tower that already has 4 APs running at 20MHz. Another 100MHz will bring back the option of 5GHz as a backhaul frequency on the same tower without needing GPS. Coincidentally, that’s just in time for 802.11ac, meaning very high capacity unlicensed backhaul (see Chapter 43: Tales from the Towers – Galactus, Destroyer of Wired Worlds – okay, a cheap plug).
Many tower deployments that were originally installed with 5.8GHz backhauls had to change over to licensed backhauls since the 5.8GHz band was needed for the client connection. As Dolly Parton used to say, you can’t put 10lbs of potatoes in a 5lb. sack (wise woman that Dolly). 5GHz DFS frequencies simply don’t have the power output of a Nextel cell phone (You have to like a cell phone that can make CRT’s within 10’ scramble the screen when a call comes in. Now imagine what it was doing to your brain 2 inches away), UNI-II upper is the only band that makes tower deployments profitable. With 5.8GHz clients 10 miles away or more, that means towers that could be 20 miles apart. Unfortunately, 24GHz, the next unlicensed band over 5.8GHz, isn’t going that far unless it’s mounted on the moon.
So what do WISPS do for additional backhaul cost-effective backhaul in the U.S.? How about 10GHz? You have to like equipment that can be built from 802.11 chipsets and has almost the range of 5GHz. Ubiquiti sells a product like this for about $700 per radio/antenna. Although that’s a little expensive compared to 5GHz 802.11 backhaul radios, it’s still one of the cheapest radios around in that band. Unfortunately, we can’t use this radio in the United States.
Internationally, the 10.0 to 10.5 GHz band is in use with great success. Gateway Communications, a Nigerian ISP, uses it for their national frequencies. Much of Europe uses it for PTP backhaul links. In the United States, the International Amateur Radio Union uses it for ground and satellite communications. In reality, there is very little use in those bands. That means up to 500MHz of bandwidth could be used for WISPs and other data applications. At this point though, the only group that can grant that access is the FCC.
The problem was, nobody ever asked the FCC to open it up to the WISP community until Mimosa Networks came along. Brian Hinman, CEO of Mimosa, saw an opportunity and has formally applied to the FCC to open up the band. If the application goes through, we will all benefit from having another band to expand our backhaul options.
10GHz isn’t a perfect band by any stretch. Vegetation penetration is almost twice as bad as 5.8GHz which means forget getting through Grandma’s apple tree.