Hi, I wish to connect LWAPP AP on a remote office. The controler will be reachable through on OSPF L3 network. Moreover, I wish to define my WLAN VLAN on the remote office so as the WLAN client have a remote IP and are switched by the remote switch.
Sounds like you are wanting H-REAP... Normally the AP does a LWAPP Join to the controller, and the SSID is bound to a Dynamic Interface (Subnet/VLAN) connected to the controller. If you run H-REAP, all authentication is still LWAPP tunneled back to the controller, but the AP assigns a remotely defined IP address to the remote clients.
If you have Gig between the AP and controller, then I'd classify that as LAN :) I would not worry about LWAPP traffic.
The only way I'd recommend H-REAP is if you have resources at the remote site that need to be accessed directly from the wireless clients. Let's say you have a Cisco Call manager GW at the remote site. It would be inefficient to encapsulate the voice traffic via LWAPP and send back to the controller in the data center, only for the controller to send the packets back to the Call Manager GW on the remote network. It all depends where your resources are located. If I needed to keep traffic local to the remote site, then I might think about a 2006 or a small 4402. Remember if the link goes down with H-REAP, then so does any dot.1x authentication. I believe only static WEP and WPA-PSK will survive when H-REAP is cut off from the controller.