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I thought radios in the unlicensed bands were capped to really weak TX power levels which would make them useless for broadcasting to large areas.
by guelo 11y ago
I thought radios in the unlicensed bands were capped to really weak TX power levels which would make them useless for broadcasting to large areas.
- dboreham 11y agoNot true in most countries (including USA). There is a whole service provider industry (WISP) with sizable equipment vendors (Miktotik and Ubiquity) that depends on using the unlicensed bands over wide areas and long range.
- venomsnake 11y agoI think that new 5GHz carrier cells may have some very powerful directional transmitters aimed at them if they interfere with wifi.
- nitrogen 11y agoIn the absence of a license, aren't those long range and wide area systems still subject to the same power caps as consumer gear?
- jauer 11y agoThere's a big difference in how they use the available power. WISP-type equipment generally uses very directional antennas so the available power is used more efficiently. A laptop and a home WiFi router are like people talking in a crowded room. Long-range systems are like talking into a unpowered megaphone while the other side is listening with a megaphone on its ear.
- guelo 11y agoIf what the carriers are talking about is highly directional links for backhaul then I don't see what the fear is. Directional is not going to interfere with nearby WiFi.
- dboreham 11y agoThey're talking about handset to base station, split band -- using licensed frequencies for downlink and unlicensed for uplink. So, not backhaul.
- dboreham 11y agoYes, but a) those caps are not so small as to be useless as stated by the parent, and b) there are sub-bands of the 5GHz unlicensed band that allow higher txpower in the US only when deployed "outdoor". This page provides a decent summary: http://www.wisp-router.com/page.php?11 http://www.wisp-router.com/page.php?11 fwiw fear of overwhelming interference from well-funded entities such as carriers is not new. In fact it was very common until the extra capacity in 5GHz was opened up 10 years ago or so. Prior to that you could find a cell carrier in your area decided to backhaul a tower with a T-1 on 2.4GHz, lighting up the entire band with impenetrable noise. Since that time the carriers' backhaul capacity needs increased significantly, driving them to fiber-feed their sites or use 23GHz licensed. At the same time the available channels in 5GHz expanded (through re-use of space previously allocated for military use). So things have been reasonably quiet (sic) on the interference front until this new challenge. Disclosure: I built and run a very small WISP due to owning a home in a place with no Internet service, in conjunction with making my living writing software (oops!)
- ghshephard 11y agoDepends on your receiver sensitivity and desired throughput. Smart Grids operating at 1 watt dBm with receivers at -98 RSSI routinely have mesh-hops of 5km+ @ 100 kbits.
- leoedin 11y agoWhat does "1 watt dBm" mean. Do you mean 1 dBm (1.3mW) or 1 Watt (30 dBm)? Presumably the former?
- spacecowboy_lon 11y agoUp to a point "professionals" can go over the 200mw limit but this is for PTP links using wifi tech.