The current mobile wireless standard 802.16e can provide data confidentiality, integrity and mutual authentication in wireless metropolitan area networks (WMANs). However, secure communication can only be provided after successful authentication and a robust security network association is established. In this paper, we propose our solution to patch the current 802.16e standard and address all vulnerable issues with a new simple authentication key-establishment protocol and an efficient way for privacy-preserving. In simple authentication, we smoothly apply the public-key cryptography-based key-establishment technique to the 802.16 MAC protocol. Our solution can provide link-layer data encryption in initial network entry procedure, separate session encryption keys to preserving privacy of different users, and protection for important frames such as management and Extensible Authentication Protocol (EAP) messages.