1. Fault Tolerance – WLAN for Factory Network
Month Year
doc.: IEEE yy/xxxxr0
November 2005
Fault Tolerance – WLAN for Factory Network
Date:
Authors:
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Takashi Sakakura, Mitsubishi Electric Corp.
John Doe, Some Company

2. Month Year
doc.: IEEE yy/xxxxr0
November 2005
Abstract
Factory Automation is seeking wireless technologies to eliminate their cabling cost while WLAN is the most popular wireless solution today.
Some links need sub-10ms constraint in latency despite of tough radio communication conditions such as spattering , multi-path fading, absorb by metal made machines.
Redundant APs on a same channel is proposed in this presentation.
Takashi Sakakura, Mitsubishi Electric Corp.
John Doe, Some Company

3. Problems on Cabling in a factory
November 2005
Problems on Cabling in a factory
Cabling tethers equipments to fixed locations
Cabling material and labor cost
Disrupts operations while cable is accommodated
Cable run length is quickly exceeded if devices increased
→Wireless solution is needed
Takashi Sakakura, Mitsubishi Electric Corp.

4. Requirements for WLAN in the Factory
November 2005
Requirements for WLAN in the Factory
Reliable link
Low latency (<10ms)
Takashi Sakakura, Mitsubishi Electric Corp.

5. Redundant APs on a Same Channel to Realize Reliable Low Latency Link
November 2005
Redundant APs on a Same Channel to Realize Reliable Low Latency Link
Place more than one APs on one channel
The APs are connected a controller
Keep the association remained
Fast handover by the switching controller
Controller PC
Takashi Sakakura, Mitsubishi Electric Corp.

6. Handover Control Every AP on the channel watches the RSSI of the STA
November 2005
Handover Control
Every AP on the channel watches the RSSI of the STA
The controller executes handover if the RSSI goes weaker than the threshold
Signal strength
AP1
AP2
Handover
Threshold ｔ
Takashi Sakakura, Mitsubishi Electric Corp.

7. November 2005
Proposal to TGV
Define a controller which selects an AP with the strongest signal strength from a STA among APs on a channel
Define an AP which reports signal strength each time when that receive a packet from a STA
Takashi Sakakura, Mitsubishi Electric Corp.

8. November 2005
Conclusion
Factory automation needs wireless communication to eliminate cabling cost
WLAN is a candidate of wireless communication
Proposed redundant APs on a same channel to shorten handover overhead to keep the latency requirement (sub-10msecs)
Takashi Sakakura, Mitsubishi Electric Corp.