For the Edimax units to work together, one configuration would be having them both in AP Bridge-Point to Point mode. You could also have one in point to multi point, but without more of them there's not really a need for that. In that mode they should passthrough traffic to/from the RADIUS server, but you'll need 2 more wireless access points to generate that traffic, since the bridges will be talking only to each other via their wireless interfaces.
> because in DDRT tutorials, there was no bridge mode supporting Radius server.
There are so many different configuration options with V24's different builds and different platforms that if they wrote a tutorial for every possible combination the site would rival experts-exchange.com for server space to host it all.
If you have a couple old WRT54G or WRT54GS models, flash them (using the built in Linksys firmware updater) with the Vintage Standard build (WRT54GS could handle the Mega build, but it just adds extra features you don't need for this application), available here -
http://www.dd-wrt.com/dd-wrtv2/downloads/v24-sp1/Consumer/Linksys/WRT54GS_v4/vintage/dd-wrt.v24-9517_VINT_std.binIf they're v4, use the newer releases
http://www.dd-wrt.com/dd-wrtv2/downloads/v24-sp1/Consumer/Linksys/WRT54GS_v4/dd-wrt.v24_mini_wrt54g.bin or
http://www.dd-wrt.com/dd-wrtv2/downloads/v24-sp1/Consumer/Linksys/WRT54GS_v4/dd-wrt.v24_mini_wrt54gs.binhttp://www.dd-wrt.com/dd-wrtv2/downloads/v24-sp1/Consumer/Linksys/WRT54GS_v3/dd-wrt.v24_std_generic.binI'm fairly certain those 2 mini files are identical, but I have not downloaded them and compared them byte-by-byte.
I don't recommend starting your experiences of DD-WRT with a v5 because you have to use VxWorks Killer on them before flashing with DD-WRT, which makes it harder to recover from if anything goes wrong. With v4 and older models you can use DD-WRT's loader or even the Linksys TFTP application to reload the original Linksys firmware and revert if there are problems.
There are links to tutorials on the 'supported hardware' page... go to the model/version you have and look for links in the far right-hand box.
http://dd-wrt.com/wiki/index.php/Supported_Devices - once DD-WRT's loaded there are custom help pages for nearly every option... click the '...More' link in the 'Help' column... (default name/pw is root/admin by the way).