The IETF NEtwork MObility (NEMO) working group has considered how to enable an entire network to move from one location to another. Mobile Virtual Private Network (VPN) has been developed to secure mobile user's communication between untrusted external networks and the protected private internal network. However, the IETF's mobile VPN does not address how to support NEMO. In addition, it is not suitable for real-time applications. In this paper, we propose architecture and protocols to support VPN in NEMO, which is called Secure NEMO (SeNEMO). The proposed SeNEMO, based on Session Initiation Protocol (SIP), is specifically designed for real-time applications over VPN. It allows an entire network to move and still maintains session continuity. In addition to analyzing the security vulnerabilities, we also propose analytical models to evaluate the performance of the proposed SeNEMO. The analysis is validated by extensive simulations. The results show that the proposed SeNEMO can reduce signaling cost significantly.

This paper presents an energy conservation scheme, Maximum Unavailability Interval (MUI), to improve the energy efficiency for the Power Saving Class of Type II in IEEE 802.16e. By applying the Chinese Remainder Theorem, the proposed MUI is guaranteed to find the maximum Unavailability Interval, during which the transceiver can be powered down. We also propose new mathematical techniques to reduce the computational complexity when solving the Chinese Remainder Theorem problem. Because the computational complexity is reduced significantly, the proposed MUI can be practically implemented in real systems. The proposed MUI is fully compatible with the 802.16e standard. It provides a systematic way to determine the start frame number, one of the important parameters defined in the standard. In addition to analyzing the computational complexity, simulations and experiments are conducted to evaluate the performance of the proposed algorithms.

Mobile virtual private network (MVPN) has been developed to secure mobile user's communication between untrusted external networks and protected private internal network. The IETF's solution, however, leads to some problems: where should we put the external home agent (HA), how could we trust the external HA, and overhead of three tunnels. In this paper, we propose an alternative SIP-based MVPN. Because the proposed architecture is based on SIP, the problems inherited from mobile IP are not problems in our architecture. In addition, there is no need to tunnel a packet three times as that in IETF MVPN. In this paper, we also propose analytical models to evaluate and compare the performance of the proposed SIP-based MVPN with the IETF MVPN. The results show that the proposed SIP-based MVPN can reduce packet delivery cost significantly. It is especially suitable for real-time applications.

This paper presents an energy conservation scheme, maximum unavailability interval (MUI), to improve the energy efficiency for the Power Saving Class of Type II in IEEE 802.16e. By applying the Chinese remainder theorem, the proposed MUI is guaranteed to find the maximum Unavailability Interval, during which the transceiver can be powered down. The proposed MUI only dynamically adjusts one parameter defined in the standard. In addition, it is fully compatible with 802.16e standard. We also propose a new technique to reduce the computational complexity when solving the Chinese remainder theorem problem. Simulation and analysis have been conducted to evaluate the performance.

IEEE 802.11 wireless LANs have been widely deployed. How to efficiently balance the traffic loads among access points (APs), which will lead to improved network utilization and higher quality of user experience, has become an important issue. A key challenge is how to select an AP to use during the handoff process in a way that will achieve overall load balance in the network. The conventional approaches typically use signal-to-noise ratio (SNR) as the criterion without considering the load of each AP. In this paper, we propose two effective new AP selection algorithms. These algorithms estimate the AP traffic loads by observing and estimating the IEEE 802.11 frame delays and use the results to determine which AP to use. The algorithms can be implemented in software on mobile stations alone. We will show that better performance can be achieved when the APs provide assistance in delay measurements; however, the improvement is not significant. There is no need to exchange information among APs. The proposed algorithms are fully compatible with the existing standards and systems and they are easy to implement. We will present extensive simulation results to show that the proposed algorithms can significantly increase overall system throughput and reduce average frame delay.