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How does a WISP work?

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Hi,

 

I hope this is an appropriate question for this forum. Please let me know if there is a better forum/site/book to get this info. I can't find anything in a web search on this.....

 

I'm trying to understand how a WISP system operates, particularly between the hardware at the local provider's tower to how it connects to the transceiver/dish on my roof. I'm an electrical engineer (IC designer), so I'm looking for basic technical details as much as possible. I currently use a WISP for all my internet/phone/entertainment needs, and this understanding will help me if I ever need to intelligently talk with my WISP if/when things go bad.

 

My understanding is that one local WISP tower can communicate with "hundreds" of customers in the area at the same time. This is the main area I'd like to understand. How is this accomplished?

Are there generally multiple transceivers/dishes on one tower to talk with all these customers? (I'm guessing that there isn't one transceiver/dish per customer on the tower, correct?)

I'm guessing that there must be multiple customers assigned each transceiver/dish on the local tower, with each customer assigned to a 'channel' on that dish? (one channel per customer?). Is this similar in concept to an 'ethernet switch' built into each of the tower's transceivers to allow it to communicate with multiple customers at the same time? How many channels are generally on each of the tower's transceivers? 8? 16? or?

 

Does the tower's transceiver need to be 'pointed at' a customer, or is it broadcast in all directions (or 180 degree view?, or?) from the tower? Then it's up to each customer's dish to point to the tower? (this is my bet)

 

What stops a person (a non-customer) from simply pointing a dish at a tower and 'pirating' a connection? The hardware does not look proprietary. Simply a password protects this? Do they use public-private key encryption on each channel? Just curious.

 

I'm just guessing at most of this.

Probably have more questions, but this would help greatly.

Comments?

 

thanks!

Rod

 

 

 

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Some of the wireless internet service providers (WISPs) that operate here in Ireland operate on the 5GHz Wi-Fi band.  This is basically like a home Wi-Fi set up, but on a much bigger scale.  The purpose of the dish is provide a high enough gain to pick up and transmit the signal over a several mile radius.  The tower usually consists of several sector antennas, typically three aimed 120 degrees apart operating on separate channels.  Customers on one sector generally share the same channel like on a home Wi-Fi network.

 

The last WISP I was with used Ubiquiti hardware.  When I changed provider, I was curious myself to check out its web interface and to my surprise they never changed the default password on the dish hardware's web interface.  Its configuration was very similar to home Wi-Fi, mainly an SSID, WPA2 passphrase and internal IP address set.  Their service end likely had a gateway server that throttled the up/down bandwidth according to whatever package was ordered, while also metering the usage from the assigned IP address.

 

Ubiquiti has a training book freely available on their website which goes into detail on how enterprise Wi-Fi works including on a large scale that WISPs use:

https://dl.ubnt.com/guides/training/courses/UEWA_Training_Guide_V2.1.pdf

 

A few other WISPs here use LTE on the licenced 3.6GHz band.  This basically works the same as a mobile phone LTE service, but where the operator has exclusive control over its assigned spectrum, LTE hardware and installation.  As this is a managed network, it generally performs a lot better than a mobile phone LTE network as each LTE client device (i.e. that dish antenna on the roof) is professionally installed, maximising the signal encoding efficiency.  The weaker the signal quality, the more airtime is required to transmit the same amount of data. 

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Here in Ireland WISPs advertise packages anywhere from 4Mbps up to 150Mbps.  The price also varies a lot from one WISP to another and most have multiple price tiers according to the ordered speed.  So it's hard to say what speed to expect, a bit like asking what kind of speeds do you get on a motorway.  Which city? Rush hour? Tollway? etc... it's the same with a WISP. 🙂

 

As wireless is a shared medium, the actual real world speed varies according to the number of users online on the local mast.  For example, with the WISP Imagine that advertises 150Mbps, I've seen people post speed tests anywhere from under 2Mbps to over 100Mbps in the evening, i.e. those lucky to get the high speeds likely have very few subscribers on the local mast, e.g. just recently installed.

 

When an ISP goes live in your area, you'll likely get the best speeds from it in the first few months of it going live.  The amount it drops off will depend on how many others in your area join the service. 

 

As for the text colour, click this icon in the toolbar and choose 'Automatic': 😉

TestMy change text colour.png

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Thanks Sean, I didn't realize that WISP were so popular ocer there. I thought maybe they were more like Cell service providers here where there are only a handful (3-4) with a multitude of Virtual providers reselling service. I was reading up on WISPs here and they seem to still be in their infancy. They appear to have formed an association to deal with bandwidth and other regulatory issues. Their primary focus is building in rural areas where major isps don't find value in building out their systems. The higher end values you show are quite impressive, considering most of our cell service providers with peak reception and prime time can only provide 20 to 40 Mbps.

One thing I've not been able to ascertain is the use of a receiver dish and does it need an unobstructed line of sight to the transmitter like a satellite dish to the satellite?

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The line of sight will depend on the distance from the transmitter.  If it's nearby such as within a mile or two, it will may work fine with minor obstructions such as a tree or wall in the path, much like how 5GHz Wi-Fi can still penetrate walls.  Most WISPs here operate on 3.6GHz (licenced) or 5GHz (using the 5GHz Wi-Fi band.)

 

If the transmitter is far away such as 10+ miles or operates above 6GHz, it will need clear line of sight of the transmitter.  This is a problem the new wideband 5G cells face where anything in line-of-sight blocks the signal, such as going indoors.  For example, all the 5G speed test demos are carried out either outdoors or in a cellphone shop that has an indoor 5G node. ;) 

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