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Wireless technology aids workzone communications

First publishedin ITS International
May June 2012
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Chandler’s MWAN wireless network
Chandler's MWAN wireless network consists of mesh radios at each of three intersections, with a modem wired into the city's fibre network linking back to Chandler's traffic management centre

Need for a temporary communication fix during a construction project has led  to rapid deployment of a permanent but simplistic wireless broadband network  in Chandler, Arizona

When a major construction project was expected to disrupt highway communications in the city of Chandler, Arizona, the city’s engineers went looking for a simple solution. They needed a way of maintaining data connections with three consecutive intersections along Arizona Avenue in Chandler while construction necessitated the severing of trunk communication cables. “And they wanted something that they could quite easily configure and maintain themselves,” says Siemens product manager Matt Zinn.

Chandler traffic engineers had previously made use of wireless communications when cable networks were planned to be temporarily disrupted. “This was a point to multi-point radio system. The city experienced some difficulty with it and found it time consuming to set up and configure each time it was required to be in use,” Zinn says. Chandler’s engineers were keen to try something new, to explore more advanced technology. Additionally, the city has aspirations for a bus rapid transit (BRT) system on key corridors including Arizona Avenue. The primary role of new wireless communications was to solve the temporary disruption due to construction, but the city also saw an opportunity for the system to provide or at least demonstrate a permanent function for the BRT system.

Setting an example

“In consideration of the BRT lanes and the communications for that, the city and transit authority in the area hope to see connectivity provided for riders of any new BRT system developed,” Zinn says. As the wireless technology for solving the temporary disruption was being considered, the city and transit authority had eyes on installing a good example of what they hoped a developer would subsequently adopt for the whole BRT system. “If it was to be the city’s responsibility to maintain the wireless system (which was the case for the initial installation at least), then the city’s engineers wanted it to be something they knew how to install and configure,” says Zinn.

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Arizona Avenue
Each node on Arizona Avenue is equipped with 5.8GHz and 2.4GHz radios. The former communicates between intersections. The latter provides connectivity for external devices and additional services. A BRT system, if developed, will make use of the 2.4GHz frequency
The city of Chandler entered into a strategic partnership with Siemens and Motorola for development and delivery of the new wireless communications. After considering a number of options, including modern point to point and point to multi-point systems, the solution selected was a mesh wide area network (MWAN). This would consist of mesh radios – wireless routers, or ‘access points’ – at each intersection, with a modem wired into the city’s fibre network at one intersection to link the wireless network back to Chandler’s traffic management centre.

Resilience and reliance

Overall this would serve to give a broadband connection for all communications from the three intersections including video. According to Motorola sales director Bill Cusack, it also provided necessary resilience. “The city wanted to maintain connectivity and it wanted that to be as resilient from interference as the normal fibre connection at intersections. The wireless system had to be equally reliable,” he says.

A ‘dual radio Mesh 4300 series network’ was selected for the Chandler installation. Each node is equipped with 5.8GHz and 2.4GHz radios. The 5.8GHz would be used for communication between each intersection. The 2.4GHz radio provides connectivity for external devices such as laptops and smartphones, or for providing additional services for local businesses, libraries or emergency services. A BRT system, if developed, will make use of the 2.4GHz frequency.

Siemens claims the radios installed to have ‘five nines’ reliability; the explanation being the radios are claimed to work for 99.999% of the time. Motorola’s patented MeshConnex routing engine contributes significantly to the reliability of the company’s mesh networks. This is Motorola’s proprietary development of technology originally developed by the US military for secure and reliable communications. According to Motorola, MeshConnex provides a combination of reactive and predictive routing, using patented ‘layer 2’ routing technology to ‘find and establish throughput optimised connections’. Importantly, the MeshConnex system allows radios to automatically reconfigure communication links for maintaining constant connectivity.


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The MWAN network
The MWAN network was installed and operational within a day and a half. Chandler City personnel fixed the radios and antennas with assistance from a Siemens and Motorola team which provided on-site training, assembly of cable arrays and assistance with cabinet equipment and programing

Demonstrating simplicity

The construction project on Arizona Avenue is now finished and the road’s cable network fully reinstated. The wireless MWAN network remains in place and in use as a complementary communication system. “Such technology serves very well to provide additional hot spot connectivity and for maintaining communications during construction projects. The performance and reliability of modern MWAN systems are such that deployments initially considered or intended as temporary solutions are now usually becoming permanent installations. Fibre networks are no longer needed everywhere,” Bill Cusack says. “With LTE 4G technology and systems developing rapidly, wireless broadband networks will soon become a lot more prevalent across local and city regions and wider areas. The Chandler deployment is a perfect example of a complementary wireless network at a local level. It has also demonstrated how simple and straightforward it can be to establish such a system.”

Chandler’s MWAN infrastructure was installed and operational at the three intersections within a day and a half. According to Siemens, the greatest effort required in the deployment was in the attaching of the radio equipment to traffic signal poles. Chandler personnel fixed the radios and antennas – with one Cat 5 cable and one NEMA 5 conductor – at each intersection, with assistance from a Siemens and Motorola team which provided some on-site training while assembling cable arrays and assisting with cabinet equipment and programing the radios.

The latter simply involved programing an IP address and a few further parameters. This was followed by a series of systems tests to confirm the links – visible on a single computer screen with Motorola’s One Point Wireless Manager software – and to determine whether communications including video were accessible at the desired speed and quality. Motorola staff gave Chandler personnel additional training on how to interface with the radios and how to reprogram them if necessary for other locations.

“The city of Chandler was pleased with the installation, particularly the speed of the deployment and the fact that it caused no disruption, and with the performance of the MWAN system since,” Matt Zinn says. The next step for Chandler may be extending its MWAN wi-fi connectivity for transit riders, as a number of other cities and counties have or are seeking to do. “There are some exciting things to come,” Zinn adds.

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