We analyze the link-layer handoff process in wireless LANs based on the IEEE 802.11b standard and suggest how to reduce its duration. Firstly, we divide the process into three phases: detection, search and execution. Our performance measurements indicate that the detection and search phases are the main contributors to the handoff time. We show that the linklayer detection time can be reduced to three consecutive lost frames. We also show that the search time can be reduced at least by 20% using active scanning with the two timers that control its duration set to 1 ms and 10.24 ms. Several simulations illustrate the achieved reduction in handoff time.

We propose a load-balancing scheme for overlapping wireless LAN cells. Agents running in each access point broadcast periodically the local load level via the Ethernet backbone and determine whether the access point is overloaded, balanced or under-loaded by comparing it with received reports. The load metric is the access point throughput. Overloaded access points force the handoff of some stations to balance the load. Only under-loaded access points accept roaming stations to minimize the number of handoffs. We show via experimental evaluation that our balancing scheme increases the total wireless network throughput and decreases the cell delay.

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The mobile radio systems beyond third generation (3G) will evolve in all-IP systems, integrating Internet and mobile systems advantages. BRAIN project is developing a system architecture which combines local coverage broadband radio access systems based in HIPERLAN/2 with several wider coverage mobile radio systems, enabling full coverage of seamless IP-based services for users in hot spot areas and on the move. End to end quality of service (QoS) provision is one of the mayor challenges in the design of such a system and must be supported by the application, network and wireless access layers. This paper proposes a QoS system architecture, including the terminal architecture, the IP based access network and the main characteristics of the enhancements to the air interface based in HIPERLAN/2 focusing on its wireless QoS support.

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