WiFi range extender (repeater)

just wondering - since this topic frequently pops up -

How well do these types of devices work in the real world ?

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If it has to receive, process, and then re-transmit the air frames, what kind of delay/latency do you encounter - ie gaming ? What SSID does the "extender" transmit ? How can you tell if you are connected to the "extender" vs the real AP ?

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I presume that you are asking about the "repeater" mode for this not the AP mode.

As Jeff or anybody else will tell you, one big issue is that they cut thruput in half since they are store-and-forward repeaters trying to do it all with one radio.

They are not universal and usually require specific matched routers to work at all. Linksys to certain Linksys, D-link to certain D-link, etc.

In my experience, using DD-WRT (the most robust and flexible) routers in this mode, it is very hard to get the repeater to work with WPA security. Some claim to and others don't. But mine got caught up a lot and only really worked right with WEP or no security That was a deal killer for me.

Also, they don't seem to work consistently. I had that DD-WRT repeater installed for a distant client and they were always calling that it didn't work, wasn't connecting. I'd go out and reboot various things in different orders and it would work again. Then I installed a two radio repeater (-)-)-) ethernet client ----AP -)-)-)-), and everything became reliable.

Some people HAVE reported success with repeaters and swear by them.

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sounds like a better antenna is best bet over repeaters then?


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Well, it will cut your pipe in half, so it depends on your traffic. If your traffic is just internet traffic, you probably won't notice too much of a difference, but if you have a lot of heavy LAN traffic, you will definetly notice a big difference. Also, this repeater can only be used with certain WAP's. Read the fine print.

I played around with "repeater mode" in my WAP's a while back, but for the reason mentioned above, I stopped using them as "repeaters". I'm not sure about latency, but heavy LAN performance was horrible. I ended up stringing "repeaters" by simply cabling new WAP's, using the same SSID/channel. Also, I have an other "repeater" that is two devices working together: a wireless-ethernet bridge connected to a WAP using the same SSID/channel as the SSID it is "repeating". This basically gives you an "over-the-air repeater" without the pipe cut in half. (I'm using 802.11a, hence the reason for the several repeaters throughout my house.)

The same SSID as the AP being extended. Same channel too. In "repeater mode", they are transparent. Garbage in, garbage out.

By the connected MAC BSSID...

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Reading seaweedsl's post reminded me something about all my DWL-7100AP's (mentioned above), they don't support WPA in "Repeater Mode". They only support WEP. A quick look at the "emulator" for the DWL-G800AP shows that it also does not support WPA in "Repeater Mode".

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You are better off runing a second WAP cabled directly to a router or through a wireless-ethernet bridge... If you want it to be a "repeater", simply just use the same SSID/Channel. This is how my WAP's are setup and it works fine. My laptop, PDA, etc automatically (and seamlessly) reconnect themselves to the stronger AP's as I move them around my house. I'm using (mainly) all D-Link...

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If it appears frequently, then perhaps using Google Groups search to read the comments might be useful? My rants under "repeaters suck" at:

In case you missed the obvious, methinks that repeaters suck and no better than wi-fi jammers.

They don't. I have a pile of assorted boxes in my office junk pile, from customers, that were once used as repeaters. Fortunately, most are multi-function devices, which can also act as access points, so they're not totally wasted.

Short summary of problems:

  1. Half your *MAXIMUM* thruput. Actually, your maximum speed will be considerably less than half. Typical is about 30% of maximum speed.
  2. Downloads are erratic as connecting directly to your access point still causes the repeater to resend everything it hears.
  3. Airtime used is doubled. For every packet you send, you use twice the airtime. That's not a problem if you only have a few wireless clients, but it's fatal in high traffic (coffee shop, convention, hotel) environments.
  4. Only a few repeaters will do WPA encryption. The lack of WPA support is a security problem.

Here's an experiment you can easily try. Setup a wireless router and wireless client in a room. Short range, good signal, lots of speed. Also setup some kind of computer plugged into the wired ethernet port on the router. Run some benchmarks with IPerf to download and upload between the two computers. It should be quite good.

Now, plug in a repeater in the same room. The idea is to insure that the wireless router, wireless client, and repeater can all "see" each other. Configure the repeater to repeat on your SSID. Try the benchmarks again. It will be far less than half the thruput, even if you are allegedly directly connected to the wireless router.

The delays will be erratic and depend on the connection speed. They won't be because of the 50% loss in max thruput. The latency will be from lost packets due to collisions. If you can ping your wireless router and get typically 2-3msec responses, with a repeater in the room, it will vary from 2 to perhaps 100msec, all due to packet loss. Again, the problem is not the actual added latency. It's the erratic and unpredicable latency caused by packet loss that will drive you nuts.

They filter packets based on SSID and only retransmit those with the correct SSID. If you have more than one SSID, you will need two repeaters. If you are trying to change the SSID in the network, in order for you to chose which device to connect, you can't do it.

Methinks your wireless client manager should have a status page, that shows the connecting SSID and it's corresponding MAC address. Check the MAC address. (I'm not 100.0% sure about this and too busy to double check.)

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Jeff Liebermann
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Ok, I understand the problems with the "repeaters" that reuse the same frequency as the original access point.

How's about something that I could put in my window (or roof) that would "see" the original access point using, say, channel 1, and then re-feed it out into a second fcaility on channel 11? (and vice versa).

I've done this using a Mac Mini [a] on the window shelf, taking that signal and "sharing it via ethernet" out to an Airport on a different channel.

[a] it has a built in 802.11 card

I haven't been able to do complete speed diagnostics, but I know it works...

Is there a commercial grade "box" that has this all built in? I've looked around a bit and haven't found one, but it's such an obvious applicaation I must be missing the obvious.

Price, within reason, isn't a concern.


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danny burstein

Sure. No problem. Two boxes and two antennas. One box is a wireless client, that connects to whatever on Ch 1. The other is a common wireless access point (or wireless router with the router section ignored), to which you connect to on Ch 11. They are connected together with an ethernet cable between LAN ports. (You might need a crossover cable).

However, if you're going put all this stuff on the roof, you might as well just put the wireless client radio on Ch 1 on the roof, use PoE to deliver power via CAT5, and put the wireless access point on CH11 inside the house.

No problem. Basically, you're using the Mac Mini as a wireless ethernet client radio. See the FAQ at:

Not all of these will work. Verify that it has a "client mode" feature.

Back to back radios work just fine. No self-interfernce, no slow down, and tolerable flow control (due to ethernet).

Probably, but methinks you could easily build your own out of commercial hardware. If not, look for a box that has dual radios.

Yeah sure. That's what they all say just before they start negotiating the price downwards.

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Jeff Liebermann

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