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Do WiFi Range Extenders Work?

Posted on 2014-01-05
Medium Priority
Last Modified: 2016-01-31
My mother lives in an apartment complex. There is a free WiFi network in the building but my mother seems a bit too far away to reliably connect to it. Do range-extenders work? Any suggestions as to which one to purchase? Where should it be placed?
Question by:johnb121
LVL 35

Expert Comment

by:Dan Craciun
ID: 39757584
Wireless repeaters (or range extenders) do work, but you'll have reduced throughput.

Cheapest way is to buy a router that can use open source firmware and install DD-WRT on it. Here's the guide for that: http://www.dd-wrt.com/wiki/index.php/Repeater .

As for position, you'll have to do some testing. It varies greatly, depending on building materials, signal interference etc.

LVL 24

Expert Comment

ID: 39757589
Yes. They work. Look for an inexpensive one.

(Not using one personally, I have no recommendations about the products and models; I generally use Netgear router products, however.)
LVL 14

Expert Comment

ID: 39757617
Have a look at this one from newegg.

TP-LINK TL-WA850RE 300Mbps Universal Wi-Fi Range Extender. Wi-Fi Booster

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LVL 44

Expert Comment

ID: 39757686
If you go with an inexpensive WRT-type router and DD-WRT, you could replace one of the DD-WRT router's antennae with an L-Com RE09P-RTP patch antenna facing the nearest AP from the apartment complex's provided WiFi (it's not really "free" - you can be sure its cost is included in the rent/lease price), then create your virtual interface for the repeater's separate SSID which would use the remaining rubber duck antenna to connect the local client[s] to the internet.

Once you get it all setup, be sure to backup the DD-WRT configuration in case someone finds and uses the 'restore defaults' option in the DD-WRT menus, or tries to 'hack' into accessing the repeated signal by using the recessed reset button (I do not advise disabling that button in DD-WRT's settings)... that way all the settings can be easily restored.
LVL 47

Expert Comment

by:Craig Beck
ID: 39758119
+1 for DD-WRT.

Just be careful if you do mix antenna types... IIRC DD-WRT only supports the ability to use either both (or all) antenna connectors to transmit and receive, or to choose which antenna to transmit and which to receive.  Therefore it's not a good idea to use one connector for the link to the main AP, then the other for the client.  If there's no option to use separate antenna connectors for different SSIDs, don't separate the antennas, and don't just use one antenna either.
LVL 44

Expert Comment

ID: 39758421
I'm not sure what is meant by "Therefore it's not a good idea to use one connector for the link to the main AP, then the other for the client."

I've setup numerous DD-WRT repeaters exactly like that, where the RE09P-RTP is connected to one RP-TNC connector and 'aimed at' the main router/AP, and the stock rubber ducky is on the other RP-TNC connector making local connections to the virtual interface with the repeater SSID. Some have been in place for years without a hiccup.

That patch antenna delivers full speed both TX/RX for a good 60 yards, in my experience, while the stock rubber ducky is lucky to detect the main router/AP's SSID at that distance.

Unless the internet connection on the main router/AP is faster than 12Mb/s or so, the speed reduction, incurred by the radio spending half its time connected to the main SSID and half its time connected to the virtual interface's SSID, is unnoticeable.
LVL 47

Expert Comment

by:Craig Beck
ID: 39758832
The way antenna diversity is supposed to work is to work out the difference in what it hears from the two antennas.  This helps to reduce the effects of noise and interference.

So if you have one antenna which is a 14dBi patch, and a 3dbi ducky you'll lose a lot of what's heard from the patch as the same data was never received on the ducky.

If you think about it, you're connecting two different antennas to one radio.  The radio isn't designed to listen to two clients at the same time - only one as it's using CSMA/CA.  Therefore it's better if you don't do this, especially if the link to the main AP is over a large distance.

To be fair it does give you a service though to a fashion, but it's best to not do this.

Here's Cisco's explanation...

LVL 44

Assisted Solution

Darr247 earned 1000 total points
ID: 39759987
I see... good info, though I think that type of diversity depends on MIMO, which I'm not sure the 802.11g WRT routers employed. Still, the problem specifically described in that technote is using two directional antennae, not one directional and one omni... also they are both using the same SSID; DD-WRT repeaters use a different SSID on the virtual interface to repeat the signal, so the client should not get confused and try to talk directly with the signal to/from the main SSID while 'connected' to the SSID of the virtual interface.
LVL 47

Accepted Solution

Craig Beck earned 1000 total points
ID: 39760018
I get what you mean with the virtual SSIDs, but it's still the same physical access media, so it doesn't work how you'd expect it to work.  The AP still expects to send or receive data on both antennas simultaneously.  In some situations this has been known to break broadcast and multicast transmissions as some APs only transmit out of one antenna.

MIMO on the other hand relies on antenna diversity, so you don't have MIMO unless you have more than one antenna.

If you use one directional antenna and one omni (or even two directional antennas pointing in different directions) you'll see issues as diversity is specifically designed to help with issues arising from multipath, etc.  It's not meant as a means to extend your cell's coverage area.

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