What is the advantage of using WPA over WEP security?
In WPA, the encryption key is changed after every frame using Temporary Key Integrity Protocol (TKIP). This protocol allows key changes to occur on a frame by frame basis and to be automatically synchronized between the access point and the wireless client rather than using a static key (using the same key on every frame) like WEP.
The result of this is that it is more difficult for a malicious party to gain unauthorised access to a secure network.
Starting with 802.11n (or Draft-11n), WEP is no longer supported; using WEP on devices that support Draft-11n will limit them to the lower speed of 54 Mbps.