In order to realize the ubiquitous communication, it is essential to make fast handover systems.

When a Mobile Node(MN) moves from one access network to another, the MN has to search candidate networks and then, it tries to connect to one of them. Then the MN starts IP setting and restarts the communication. We call these processes as "handover". And during handover, the MN cannot continue communications.

So we are trying to short this time by using cross-layer architecture.

We are proposing cross-layer architecture called inter-Layer Information Exchange System (LIES).

By using LIES, a MN can use abstracted informations of the Link Layer (L2). For example, LinkDown is the signal which means the link connection is disconnected. LinkUp is opposite.
And by using LinkConnect request, the L3 can control the L2.
The figure is a ideal procedure using LIES.

We are now proposing the Internet-Draft "draft-irtf-mobopts-l2-abstractions-02.txt" at mobopts, which is one of the research groups of IRTF.

In this draft, we propose several abstracted primitives of the L2. By abstracting the L2 information, it is possible to conceal the difference of link media, such as Wi-Fi, WiMAX, 3GPP or various comming wireless technologies. Primitives are devided into three types as follows:

• Type 1: To provide the L2 information to the upper layers immediately.
• Type 2: To notify the upper layers of the L2 events asynchronously.
• Type 3: To contorl the L2 actions from the upper layers.

And to obtain L2 information or to control L2 condition from other layers, nine primitives are defined.

Primitive	Type	Detail
L2-LinkStatus	1	Request current link information
L2-PeerList	1	Request available peer list
L2-PeerFound	2	Indication of new peer discovery
L2-PeerLost	2	Indication of lost
L2-LinkUp	2	Indication of link establishment
L2-LinkDown	2	Indication of link disconnection
L2-LinkGoingDown	2	Indication of link quality degradation
L2-LinkConnect	3	Instruction of connection
L2-LinkDisconnect	3	Instruction of disconnection

References

• draft-irtf-mobopts-l2-abstractions-02.txt

We implemented the L3-Driven Fast Handover mechanism with LIES over FreeBSD.

We experimented fast handover performance of our implementation at Yokosuka Research Park (YRP) on April 2005. We allocated Access Points(IEEE802.11a) at intervals of 100 meters as you can see in the map below. We drove the car around the park at 30km per hour and the MN send a streaming video from the car.

By using LIES, the MN could perform handovers so fast that the CN was able to receive the video with few disruption.

• Demonstration Video

Experiment Environment
Network	8 IEEE802.11a APs with 8 IPv6 subnets
AP Channels	All APs use the same channel
Distance between APs	80 m in average
MN's Moving Speed	40 km/h by the car
Streaming	15 Mbps DVTS Video Streaming from the MN (in a car) to the CN (static node)
L3 Mobility protocol	LIN6

We also experimented in our campus testbed on September 2006.

We allocated Access Points(IEEE802.11a) at intervals of 25 meters in the building. Unlike previous experiment, each AP uses different channels. Thus the MN has to scan for the L2 handover. Normally this process takes more than handreds milliseconds. However, we implemented background scaning mechanism and realized handover in 15 milliseconds.

• Demonstration Video

Experiment Environment
Network	7 IEEE802.11a APs with 7 IPv6 subnets
AP Channels	Each AP uses the different channel
Distance between APs	25 m (in average)
MN's Moving Speed	Walking Speed
Streaming	10 Mbps DVTS Video Streaming from the MN to the CN (static node)
L3 Mobility protocol	LIN6