Microsoft explains it as under:
"The 802.11b standard permits Wired Equivalent Privacy (WEP) encryption. Depending on the manufacturer and the model of the network adapter and access point, there are two levels of WEP typically available: 64-bit encryption based on a 40-bit encryption key, and a 24-bit initialization vector, and 128-bit encryption based on a 104-bit key and a 24-bit initialization vector. In addition to enabling WEP, there are other steps that you can take to make your home local area network (LAN) more secure."
It looks like that WAP is not supported by 802.11b