Atmel Tap Dances with Handover Protocol for WLAN Terminal Devices

2/6/2004 - Atmel® Corporation (Nasdaq: ATML) announced a new roaming and handover protocol named "Tap-DanceTM". Tap-Dance, an Atmel patent-pending solution, is easily integrated into the Wireless Local Area Network (WLAN) protocol, extending WLAN roaming capabilities by offering uninterrupted service even to time critical applications due to its seamless and smooth handover. Tap-Dance will be offered and supported by only wireless router/Access Points based on Atmel's AT76C511, VNET-2 access point component. This component provides advanced networking capabilities for the entire infrastructure needed to support the Tap-Dance protocol. With Tap-Dance, on-going services experience very little to no performance or quality changes, making it especially suitable for Voice-over-Internet-Protocol (VoIP) or streaming applications. Tap-Dance offers extended mobility with an unmatched list of advantages over the other currently available proposed protocols. These advantages include seamless handovers between different subnets, preservation of open IP sessions, lower latency, and zero reconfiguration requirements from the stations.

One of the most important issues in the area of wireless and mobile communications technology is the ability to maintain an IP-connection while roaming. Roaming, unfortunately, has not yet gained much attention in the current IEEE 802.11 standards. The result is insufficient support of important functionality's such as preservation of the wireless station's (STA's) IP connectivity upon a Layer 3 (L3) handover (A L3 handover occurs when a STA has moved out of its home IP subnet and gets connected to an AP of a foreign IP Network). Today, the IEEE 802.1f Inter Access Point Protocol (IAPP) addresses L2 handovers (roaming between Access Points (APs) inside STA's Home Network), but not L3 handovers. Mobile IP, on the other hand, addresses roaming but not without considerable reconnection time (latency). For applications such as voice and video, this may be prohibitive.

Tap-Dance extends the capabilities of the 802.11f IAPP that is used for Layer 2 (L2) mobility management of STAs when roaming between Access Points (APs) inside their Home IP Network (HN). With IAPP when a wireless node enters a foreign network/subnet, a new IP address is required for the routing of STA's IP data. This is because after changing the point of attachment (AP), a STA cannot be identified by its original home IP address anymore. Consequently, any on-going connections are disrupted and IP connectivity is lost. For applications like wireless VoIP phones or streaming applications, this is not acceptable.

With the implementation of Tap-Dance, a STA can roam across WLAN's of different subnets (networks or L3 handover) while preserving its original IP-connection (address acquired inside its HN). In other words, a STA is able to perform a seamless and smooth L3 handoff between APs of different IP networks, maintaining the active session as well as quickly restoring IP connectivity. This enables routing of IP data to/from their current foreign location using their original IP address. Unlike other protocols that address L3 handovers, Tap-Dance's latency (time to reconnect and restore the original IP connection) is as low as 20 msec to 50 msec on average (under real traffic conditions), which is many times faster than other competing protocols. This is well within the 82 msec required for wireless VoIP applications for the user not to notice any variations in the quality of the call.

Furthermore, the beauty of Tap-Dance is that it runs on the AP (Atmel's AT76C511 based AP's come with the Tap-Dance protocol). Thus it requires no manual set-up, no reconfiguration or software upgrades to the STA, and no specific networking devices, that increase the network architecture cost, to control roaming. Therefore, VoIP phones such as ones based on Atmel's recently announced AT76C901 or STA cards (based on Atmel's reference designs or any other chip suppliers) are able to benefit from the roaming capabilities provided by Tap-Dance.

"Tap-Dance, the result of our research in the area of IP roaming in WLAN provides surpassing characteristics when compared to any other available protocols. We consider IP roaming, continuous connectivity and preservation of open traffic sessions, as the factors that add "real mobility" to WLAN. In the end, what's the need for wireless if you are confined to a given area. Tap-Dance is ATMEL's answer to this." said Dr. Theodore Karoubalis, System Concepts Group Manager of Atmel's Multimedia Communications Product Group.

About Atmel
Founded in 1984, Atmel Corporation is headquartered in San Jose, California with manufacturing facilities in North America and Europe. Atmel designs, manufactures and markets worldwide, advanced logic, mixed-signal, nonvolatile memory and RF semiconductors. Atmel is also a leading provider of system-level integration semiconductor solutions using CMOS, BiCMOS, SiGe, and high-voltage BCDMOS process technologies.

Atmel, the Atmel logo and combinations thereof are registered trademarks, Tap-Dance and others contained herein are trademarks of Atmel Corporation.

Atmel's product information may be retrieved at:

Previous Page | News by Category | News Search

If you found this page useful, bookmark and share it on: