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I live in a kind of dormitory and the next access point is 60 meters away from my room. So I bought a range extender (TP-Link WA730RE) and installed it into my room in the same height as the access point. But my problem is still not solved. The reception is slightly better but my connection still gets broken every two minutes.

The antenna that comes with this range extender was 4dB. My question is, can I buy an 8dB external antenna (like this one: http://www.amazon.com/TP-Link-TL-ANT2408C-Desktop-Omni-Directional-Antenna/dp/B0034CQSKW/ref=sr_1_14?ie=UTF8&qid=1332074993&sr=8-14) and replace it with the antenna that comes with the range extender? Or is this external antenna only suitable for the "receiver" end of the connection, i.e. the computer?

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Forcing a lower 802.11 connection speed can fix this problem (I used to support wireless barcode scanners and this fixed 90% of my problems, once I discovered it) (they were ROM-DOS though and only sending a few lines of text back and forth, so you may need more speed). If your internet connection is only, say, 6 Mbps forcing the LAN to be 54 Mbps or 11 Mbps won't cause an internet slowdown and will cause much better connectivity (no/greatly reduced signal drops and greater range). But I haven't been able to find out how to do that from the client side with a few minutes of googling. –  conspiritech Mar 18 '12 at 14:09
    
Real easy on the router side, at least with DD-WRT. –  conspiritech Mar 18 '12 at 14:09
    
The chipset of the router is not supported by DD-WRT. But maybe it already supports limiting the speed without any hack. I'll try this, thanks for the tip. –  ercan Mar 18 '12 at 14:26
    
No problem.. I think its a property of all radio data links, but I have no idea how to find the paper that gave me the idea (years ago). –  conspiritech Mar 18 '12 at 14:58

3 Answers 3

up vote 2 down vote accepted

There are no pure receiver or transmitters in a 802.11 network, all the devices have identical radio frontends (in principle). You can use any antenna you want for any part of the network as long as the interface between the antenna and the device is compatible.

However, by increasing antenna gain you might jump above the maximum allowed transmitting EIRP for unlicensed use of the frequency band where you live. If you care, you'll have to look into that yourself.

An "isotropic" antenna, like the one you linked might not be a good solution in your case, though. The value you want to increase is the SNR, not the power directly. An isotropic antenna with 4 dB higher gain, will increase the SNR by 4 dB for the access point so it will have an easier time receiving packets from you, but it will do nothing what so ever for packets going the other direction, which (hopefully) is most of them.

Since you apparently know where the AP is, you could get a directional high-gain antenna, or attempt to build one yourself. There are a number of "cantenna" projects that are easy to find on Google. A very simple and cheap solution (to gain just under 3 dB in both directions) would be to place a flat cardboard sheet covered with (wrinkle free) aluminum foil as a mirror (d = (n+0.5) 0.5 lambda) from your antenna on the side away from the AP. Iy would not have to be very big, the equivalent of a A5 sheet of paper would be more than enough.

distance d = ( n + 0.5 ) * 0.5 * lambda
n is a non-negative integer
lambda = c / f
c ~= 3 * 10^8 m/s
f is the frequency of the connection, probably close to 2.45 * 10^9 Hz

An example distance would then be (for n = 0 and f = 2.45 * 10^9 Hz)
lambda ~= 12.24 cm
d ~= 3.06 cm
(or with n=1, d ~= 9.18 cm)

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The antenna may help but have you looked at other devices that could be causing issues? You need to do a good site survey several times. Check for other devcies on the same channel. You may need a directional antenna if you cannot manage making changes to your range extender and the AP.

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Do you know anyone who lives between you and the access point. If so see if you can put the range extender in their room. Probably best about 1/3 distance from your room.

Problem with higher gain omni in cluttered environment is that it will increase unwanted as well as wanted signal. Plus my experience with them has been very poor. If you are going to buy an antenna you may be better off with a flat panel antenna. You should be able to get something with about 15dBi gain for a reasonable price (plus cost of coax).

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