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Video Transmission over IEEE 802.11n WLAN for Bus Surveillance System

Location / Country : Hawaii, U.S.A.

Product Solutions:

Project Introduction

A transportation company in Hawaii serves thousands of travelers each day across well over 100 routes each week with approximately 50 bus vehicles operating out of 2 bus depots. The administration wanted to implement an intelligent surveillance system able to provide standard video recordings during normal operating conditions but also able to capture high-definition video footage when an emergency occurs aboard a vehicle. With multiple surveillance cameras installed throughout the bus, video surveillance is captured at 300 dpi under normal conditions. However, when an emergency is identified by the bus driver, the quality of pertinent video data will increase from 300 dpi to 720 dpi (HD) to provide enhanced imagery of the incident for a duration of 20 minutes. The enhanced recording of the event will then be tagged and stored on the bus until it can be extracted via a wireless connection when the vehicle returns to the depot.

System Requirements

• Substantial bandwidth will be required to upload highdefinition video via a wireless connection to the depot
command center.
• Wireless access points will need to withstand against humidity, constant downpour, and the rusting effects caused by the sea water.

Moxa Solution

Aboard each bus, video footage captured by the vehicle is stored on an onboard storage drive. When an unexpected incident/emergency is identified by the bus driver, image quality is immediately increased from 300 dpi to 720 dpi for 20 minutes and stored on the onboard storage drive. Control room operators at bus depot will then be notified of the recorded event(s) and will process request(s) for wireless transfer of video data when the bus arrives at the depot. The file size for 20 minutes of 720 dpi video is approximately 200 MB.

For this high-bandwidth wireless application, the AWK-3131 IEEE 802.11n wireless client was installed aboard each bus. While the bus is parked in the depot, it will connect with the AWK-4131 IP68-rated access points attached to the outer wall of the control center building, to maintain highspeed 802.11n wireless communications with MIMO (multiple-input multiple-output) capabilities to reach transfer speeds of up to 300 Mbps. Furthermore, the island is subjected to experience humidity, salty precipitation from the surrounding ocean and possible prolonged rain storms, all of which could cause corrosion and massive water damage to the outdoor wireless devices. The AWK-4131’s IP68-rated metal housing and corrosion-resistant connectors guaranteed constant and reliable wireless connection.

Why Moxa

• IEEE 802.11n transmission with MIMO capabilities provides data rates of up to 300 Mbps to provide efficient transfer of 720 dpi video footage from the bus to the control center.
• IP68-rated (AWK-4131 only) for outdoor protection against severe rain, and corrosion-resistant connectors to reduce maintenance efforts.


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Moxa’s comprehensive product line of WLAN and cellular solutions have been successfully implemented for various mission-critical industrial applications including transportation, factory automation, smart grid, and heavy industry. For more information, please click on the icon to download the Industrial WLAN success stories.