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x3lq

WLAN Long distance

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Posted · Original PosterOP

Hey guys,

so a friend and I had a really interesting Talk. During that talk we talked about Access Points that can reach a distance of 2km. You can normally connect to them and we understand that receiving data ist easy, but how can the client, in this case the phone, send data to the access point. In our perspective the phones antenna shouldn't be strong enough. So how can the phone "Upload" Data?

Hope you guys can help me. Couldn't find anything during my Research. 

Thanks for some enlightment :)

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Most systems that can go that sort of distance are actually a pair of devices, not a single access point. You basically send the information to the close AP, which sends it long distance to the other AP. 

 

As a note, there is definitely a difference between devices in how far away they can pick up a signal from an AP. I live in the middle of flat farmland and have an outdoor AP to cover the entire garden. Even across the river and halfway down a massive field, I can still pick up the WiFi signal probably about 160m away, but my sister's iPhone can't pick it up any further than about 100m away. 

 

EDIT: Like this: 

 

fresnel_zone.png

 

Some of the coolest implementations I've seen of this are in big cities, where the APs are located at the top of tall buildings. I think there was actually a guy that posted on the forums a while back showing his long range Gigabit WiFi setup he installed to get a fast internet connection from a (relatively) nearby town, as the wired options to their remote property were terrible. 

 

EDIT2: Long range WiFi installs are actually pretty cool when you consider the distances. A lot of remote places have long distance WiFi, where running a cable is too expensive or not possible. 

 

This install covers 19km of ocean to get from one island to another. 

Map.jpg

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Our phones can connect to cellular antennas easily enough from quite a distance. Even if the nearest tower is 30km away, you'll still get signal. I believe modern phones can do that, but many routers don't have the range due to being consumer grade or being poor quality (or both!).

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4 hours ago, x3lq said:

Hey guys,

so a friend and I had a really interesting Talk. During that talk we talked about Access Points that can reach a distance of 2km. You can normally connect to them and we understand that receiving data ist easy, but how can the client, in this case the phone, send data to the access point. In our perspective the phones antenna shouldn't be strong enough. So how can the phone "Upload" Data?

Hope you guys can help me. Couldn't find anything during my Research. 

Thanks for some enlightment :)

You cant. The long range wireless solutions are site to site. They are not built in to devices. They are made to be stationary on a building and send data via line of site to each other. The Ubiquity items linked above are solution you might use if you have two business sites that you need to have a network connection with. Or if you have an out building on your property and have no way of running a cable to it. 

 

4 hours ago, infered5 said:

Our phones can connect to cellular antennas easily enough from quite a distance. Even if the nearest tower is 30km away, you'll still get signal. I believe modern phones can do that, but many routers don't have the range due to being consumer grade or being poor quality (or both!).

Cellular signals are sent out at a much higher power level. Some of the frequencies used by providers are on the lower side such as 700Mhz used by ATT for LTE service in my area. Again they are sent out at with a large amount of power. Ive read that if you stood directly in front of a cellular transmitter for enough time, that it could literally start cooking you. Which is part of the reason they are on towers, the other reason is being higher up gives them better range.  

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Posted · Original PosterOP

Of course consumer Grade Hardware cannot achieve those lengths. But there ist buisness Hardware that can achieve those distance. And yes it works. Actually in labconditions standard wlan already achieves 1km or so. I believe Sophos sells those. So basically it is supposed to be possible.

So I know that cellular works cause of wavelengths which are below 1 GHz  and WLAN works with 5ghz at larger distances.

If you say that a Phones antenna ist powerfull enoguh to send a Signal Off <1 GHz Up to 30km, the wlan should in my Theory with a wavelengths 5 Times smaller reach 1/5 of that distances so around 6km. So taking loss into consideration it still makes total Sense To be able to send with ur Phone Up to 2 km or even 1.5 km , since it uses the Same antenna for WLAN. Hope I am Not mistaken in that.

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55 minutes ago, x3lq said:

Of course consumer Grade Hardware cannot achieve those lengths. But there ist buisness Hardware that can achieve those distance. And yes it works. Actually in labconditions standard wlan already achieves 1km or so. I believe Sophos sells those. So basically it is supposed to be possible.

So I know that cellular works cause of wavelengths which are below 1 GHz  and WLAN works with 5ghz at larger distances.

If you say that a Phones antenna ist powerfull enoguh to send a Signal Off <1 GHz Up to 30km, the wlan should in my Theory with a wavelengths 5 Times smaller reach 1/5 of that distances so around 6km. So taking loss into consideration it still makes total Sense To be able to send with ur Phone Up to 2 km or even 1.5 km , since it uses the Same antenna for WLAN. Hope I am Not mistaken in that.

There are laws governing maximum signal output. Cellular tower operators have to get a radio license to transmit with those output power levels. They also use restricted frequency bands to ensure clean signal transmission.

 

It is very illegal to output any wifi signal at the same output power or on those frequencies, you will get a fine and a big one.

 

Enterprise grade indoor access points actually have no more output power than a consumer one. Where they differ is they have much better and more antennas with complex signal processors that use those antennas to noise filter and beam form. Enterprise outdoor access points are basically the same with weather resistant casing and slightly higher output power.

 

One of the biggest issues when deploying enterprise wireless solutions is actually the client devices, weakest link in the chain. They have far worse antennas and lack any decent signal processing so they are worse at both sending and receiving signals.

 

Long range wireless use directional antennas which means far greater range with the same output power, much more than a client device would be able to transmit back. This is why these are point to point with an omni-directional access point paired with it for example.

 

Ubiquiti for example sells long range wireless equipment that don't require a license and some that do.

 

Also if you go out and just setup a long range wireless signal without doing a signal survey you might end up pissing off an ISP or business, while you aren't doing anything illegal your another person taking up a frequency band which potentially could have been one they were using.

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