IEEE 802.16m is now under consideration by the International Telecommunication Union (ITU) to become the International Mobile Telecommunications (IMT)-Advanced standard. However, handover authentication is a critical issue in this area. In this paper, we propose an efficient group-based handover authentication mechanism, named as GHAP, for correlated mobile stations (MSs) in IEEE 802.16m networks. In our scheme, the correlated MSs who have the similar Signal to Interference-plus-Noise Ratio and history handover information etc. are divided into the same handover group. When the first MS of the handover group members moves from the service base station (BS) to a target BS, the service BS transmits all the handover group members' security context to the target BS utilizing the security context transfer (SCT) method and then all these MSs in the same handover group can easily perform the handover authentication with the target BS. Different from the conventional SCT schemes, our scheme uses the MSs' security context as a symmetric key of Cipher-based message authentication code (CMAC) but not the key material of deriving new session key. Therefore, the proposed scheme can effectively resist the domino effect existing in the previous SCT schemes. Moreover, security analysis shows that the proposed scheme also meets the other security requirements in handover authentication semantics. Furthermore, performance analysis demonstrates that the proposed scheme is very efficient in reducing average handover latency. [ABSTRACT FROM AUTHOR]