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The IEEE 802.11e Enhanced Distributed Channel Access (EDCA) is designed to provide differentiated services without real hard performance guarantees, such as bandwidth and delay bounds in wireless LANs. In this paper we design a measurement-assisted, model-based call admission control (MM-CAC) scheme to support guaranteed QoS in the EDCA. For this purpose, we first develop an accurate analytical model of the legacy IEEE 802.11 DCF under non-saturation conditions; then using this model, we define the concept of equivalent number of competing entities, to convert a heterogeneous (multi-class) EDCA network into an equivalent homogeneous network and study traffic classes in isolation. Our analytical model is then invoked to decide to admit a new flow or reject it with much little computational complexity as compared to a fully fledged EDCA model. Numerical results validate our model and analysis, and simulations demonstrate the effectiveness of our MM-CAC scheme.

This paper addresses the optimization of handovers in a Wireless LAN/Mobile IPv4/v6 environment by controlling the link layer handover process directly at the mobile node's side. One successful way to improve system performance of mobile clients in Wireless LAN multimedia networks is to use efficient and fast handover mechanisms when users move between different access points. We implemented some quality parameters of the wireless link provided by Network interface Card (NIC) firmware into a network-management software running on the mobile node. This concept allows a mobile user to automatically decide about when to start a handover and to which access point to connect to. The experience shows that our multimedia-enabled solution provides the necessary guidance to monitor and control the handover process without adding new extensions to the already existing Mobile IP standards.

In this paper, we describe a novel architecture to enable a secure communication among mobile devices using different wirelesstechnologies like wireless LAN, Bluetooth, cellular systems or even infrared. Making use of the combination of these technologies for the data transmission and for the signaling of the communication, we analyze several scenarios with increasing complexity. The complete picture appears in the last scenario where all technologies are involved and the network is composed of heterogeneous mobile nodes. The paper also presents a solution for the setup of a secured communication channel (i.e. a Virtual Private Network connection) between several heterogeneous mobile nodes controlled by the cellular network operator. The mobile nodes can be either cellular aware or non-cellular aware in this framework. We propose to setup the heterogeneous network communications via the cellular network using the cellular aware nodes.