Security in wireless networks has traditionally been considered to be an issue to be addressed at the higher layers of the network.IEEE 802.16, known as WiMAX, is at the top of communication technology drive because it is gaining a great position in the next generation of wireless networks. Due to the evolution of new technologies wireless is not secured as like others networking technologies. A lot of security concerns are needed to secure a wireless network.Secure communication can only be provided after successful authentication and a robust security network association is established. By keeping in mind the importance of security, the WiMAX working groups has designed several security mechanisms to provide protection against unauthorized access and threats, but still facing a lot of challenging situations. WiMAX security architecture deals with all of the basic wireless security requirements like authentication, authorization, access control, data integrity, confidentiality and privacy.This paper examines the threats which are associated with MAC layer and physical layer of WiMAX and also proposes some enhancements to the existing model for improving the performance of the encryption algorithm and proposes some techniques in the existing model to enhance its functionality and capability.