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ABSTRACT802.11i is an IEEE standard designed to provide enhanced MAC security in wireless networks. The authentication process involves three entities: the supplicant (wireless device), the authenticator (access point), and the authentication server (e.g., a backend RADIUS server). A 4-Way Handshake must be executed between the supplicant and the authenticator to derive a fresh pairwise key and/or group key for subsequent data transmissions.We analyze the 4-Way Handshake protocol using a finite-state verification tool and find a Denial-of-Service attack. The attack involves forging initial messages from the authenticator to the supplicant to produce inconsistent keys in peers. Three repairs are proposed; based on various considerations, the third one appears to be the best. The resulting improvement to the standard, adopted by the 802.11 TGi in their final deliberation, involves only a minor change in the algorithm used by the supplicant.

Resource Reservation is very important for handoff control in wireless networks. Now many researches have aimed to predict the user's destination cell based on its movement pattern for efficient resource reservation. In the future networks with small size cells, handoffs will occur more frequently and the user's movement will be more like random processes, so it is not practical to predict the accurate destination of a user. We propose a statistical strategy for resource reservation through the estimation of a user's Transfer Probabilities, which represent the possibilities of the user leaving the current cell and entering the neighboring cells. The resources reserved for a user in each base station are proportional to the user's Transfer Probabilities. A mathematical model is proposed to obtain the Transfer Probabilities of a user from the initial states (position, velocity and direction) through simulation of the user's movement. Neural Networks are developped to predict the Transfer Probabilities of a user from the initial states and facilitate efflcient resource reservation.

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