On Tue, 8 Apr 2008 20:51:33 -0500, "P.Schuman"
<pschuman_no_spam_me@interserv.com> wrote:
>just wondering - since this topic frequently pops up -
If it appears frequently, then perhaps using Google Groups search to
read the comments might be useful? My rants under "repeaters suck"
at:
<http://groups.google.com/groups?as_q=repeaters+suck&num=50&as_ugroup=alt.in ternet.wireless=&as_uauthors=Jeff+Liebermann>
In case you missed the obvious, methinks that repeaters suck and no
better than wi-fi jammers.
>How well do these types of devices work in the real world ?
> http://www.dlink.com/products/?pid=267
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.
>If it has to receive, process, and then re-transmit the air frames,
>what kind of delay/latency do you encounter - ie gaming ?
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.
>What SSID does the "extender" transmit ?
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.
>How can you tell if you are connected to the "extender" vs the real AP ?
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.)
--
Jeff Liebermann
jeffl@cruzio.com
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
WiFi range extender (repeater) 
Linear Mode
