I'm too late on the scene to be helpful to the OP, but I had similar problems that stopped me from getting my Edimax EW-7416APn v2 AP in universal repeater mode working, and hopefully some of that experience will be useful to others.
The Edimax AP manual was indeed very poor, but Edimax have now posted an extra manual specifically for UR setup on their product support website -- I guess they were deluged with complaints about the original crappy documentation! This was the key to me getting the universal repeater mode set up correctly.
The extra setup guide is still not obvious to find: go to the product support page on the Edimax website, and in the FAQ section the final question "How to setup EW-7416APn V2 as a repeater (range extender) manually?" is linked to a PDF specifically answering that question. This document gives the necessary specifics about setting exactly the same security (type and password), channel, IP range, etc. and making sure that only the base router/access point is acting as a DHCP server.
What it still isn't clear enough about is that yes, you can and should use the same name (ESSID) for the network being repeated. The wifi protocol is (sensibly) designed that way, so that multiple physical APs can be used to implement one seamless network, with the attached devices automatically switching between APs depending on signal strength. I found it very useful on my Android phone to use the Wifi Analyser app, which shows the separate physical APs as sub-entries under my network's ESSID, and you can see the strengths varying and the device association switching between the APs as you walk around. On Linux (I just installed a copy of Xubuntu) the nm-tool and iwlist commands give similar useful information.
I also found out some weeks later that the enabled wireless protocols also need to be matched between base station and repeater. The extra setup guide wasn't clear about that either, and allowing the repeater to use a better protocol seemed to work until I got a new laptop with a better network card: at that point I could connect to the network and get a DHCP lease, but no pings or attempted local/internet traffic would work. So if the network being extended is a B+G network then the extender needs to be set to do that too, and not to allow wireless N: my suspicion is that when the extender is asked to use N by the client, it then attempts to do the same to the base AP and (if the base AP doesn't have that capability) fails.
Good luck -- it's certainly good once you've figured it out, but Edimax need to seriously improve the quality (and volume) of their documentation if they don't want to be a source of frustration to everyone who buys one of their products!
Does repeater mode imply that the repeated signal must be wireless as you suggest? Because I have a wired connection between the router and the AP. If the signal can be wired, what's the difference between AP and a repeater? So maybe I want a range extender that supports wired connection between the main router and the additional device? Or do I need network bridging? – Borek Bernard – 2011-10-01T17:07:32.427
The technical terms are not used in an exact manner. It all depends on the hardware and firmware, so don't trust the written terms - read instead what the black box can do. I would say that with a wired input and wireless output a box is an AP. With both wireless, it is more of a repeater. But the borders are thin, and many times a given box can do more than one role. – harrymc – 2011-10-01T17:36:14.447
1If you are not sure what to buy, go into a computer hardware shop, describe your setup and ask for a recommendation. Trying to judge by the terminology may be misleading. Ensure that if the vender makes a mistake you can ask for a replacement. – harrymc – 2011-10-01T18:43:49.983
The devices are Netgear WNDR3700 (main router) and Edimax EW 7209apg. I'd like to hear a generic answer because I have spent so many hours trying to figure out the setup that I think I should really try to understand what's going on. – Borek Bernard – 2011-10-01T21:47:07.040
See my edit above. – harrymc – 2011-10-02T10:58:03.210
Thanks, I know one thing for sure - I don't want to use the repeater mode because my AP is not even in the range of the original WiFi signal (the only connection between the two is an Ethernet wire). Then it has a couple of AP modes which kind of work but from my home devices I get frequent disconnects or sometimes I can't even connect (the phone, for example, says "obtaining IP address" but then goes straight to "disconnected"). I'm not sure if my setup is wrong or if the AP is malfunctioning. – Borek Bernard – 2011-10-02T12:08:45.907
The only thing that can go wrong with your setup is insufficient signal strength. If the devices have connected once then the parameters are correct. Interference can be a problem, so change your wireless channel to 11 (the strongest). If the neighbor is the problem, use a tool such as inSSIDer to map all signals around you. The problem can also be your microwave or even metallic cupboards near to the router.
– harrymc – 2011-10-02T12:20:44.837Neighbors aren't a problem, I've already measured that. Strange is that for example for 2 hours I am connected fine and then I get disconnected and can't connect back. I can see the wireless signal but the router / something wouldn't let me connect back to the network. (Is it correct that the router is responsible for assigning the IP address and letting my mobile device on the network, right?) – Borek Bernard – 2011-10-02T12:37:48.710
The router is responsible for its connections, but connecting thru the Edimax is actually 2-stage (2 connections). When a connection problem happens, you could try rebooting the boxes in various sequences to try to pin down the misbehaving one. – harrymc – 2011-10-02T14:39:30.117