In WPA, the encryption key is changed after every frame usingTemporary Key Integrity Protocol (TKIP). This protocol allows keychanges to occur on a frame by frame basis and to be automaticallysynchronized between the access point and the wireless clientrather 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 maliciousparty to gain unauthorised access to a secure network.
Starting with 802.11n (or Draft-11n), WEP is no longersupported; using WEP on devices that support Draft-11n will limitthem to the lower speed of 54 Mbps.