Innovative Dual-Carrier Solution from Cactus Computer Eliminates Dead Zones, Keeps Operations Flowing for Grand Prairie Water

Cactus Computer
"Digi was clearly the best choice. They have a long history of smart connectivity and a thorough engineering footprint in the 4G space."

Jake Smith, President of Cactus Computer

For over 28 years, Texas-based Cactus Computer has been the go-to supplier for both enterprises and municipalities seeking innovative network solutions, consulting and systems integration. The boutique firm specializes in customized design, development, manufacturing and support of electronic and computer-based products and systems.

Business Challenge

For the Grand Prairie Water Department in Texas, maintenance and repair work is a high priority and a daily logistical challenge. From fixing broken water meters to tackling emergency water main repairs, skilled GPWD teams crisscross the city every day in a fleet of specially equipped vehicles that can cost $300,000-$500,000 each, which means coordination and efficiency are paramount. Out in the field, armed with laptops loaded with specialized software to track work orders, GPWD techs can submit job information, get schedule updates, look up information, minimize unnecessary travel time, and coordinate resources.

But that only happens if the onboard computers stay connected to the GPWD operations center.

Unfortunately, the utility found that cellular carrier “dead zones” and “drop-outs” were translating into wasted time, lost productivity and worker frustration – as well as slower service and higher costs. “These are expensive assets and a highly skilled workforce,” said Jake Smith, president of Cactus Computer. “Improving efficiency by even a small amount has a direct impact on the utility’s bottom line. GPWD needs to tightly track who is doing what and where. And they want to optimize the routes for each truck and each team.”


Too often, however, crews sat idly in truck cabs and at job sites, waiting to connect to the operations center. That’s when Cactus Computer proposed a new alternative: a dual-router that could seamlessly failover from one carrier to another in a few seconds in the event of a lost signal. “After buying all of their laptops and software, GPWD was frustrated by the single-carrier experience, so we introduced them to the ‘Cactus 2x4GLTE’ dual-radio router,” said Smith. “We turn each of their 61 trucks into a mobile hotspot that can effortlessly switch between Verizon and AT&T for instant internet connectivity.”

The heart of the 2x4GLTE product is a pair of high-performance Digi TransPort® WR21 routers that provide primary and backup connectivity for wide area network (WAN) connections over 4G networks and beyond. Flexible power and connectivity options and extended temperature ranges make Digi TransPort WR21 a versatile product for Grand Prairie’s use on the roads, often in harsh environments with extreme temperatures. The Digi TransPort routers are mounted onto a single mounting plate and bolted onto the truck frame with external antennas on the roof. If a carrier signal fails for more than five seconds, Cactus-developed embedded software automatically and transparently routes the inbound and outbound traffic from one router to the other. “Except for a few seconds of delay, the user won’t even notice the failover on his or her laptop,” Smith explained. “It happens flawlessly in the background, so he or she can continue with their computing task, uninterrupted.”

In designing and building the Cactus 2x4GLTE, router selection was pivotal. “We tried several different 4G radios,” Smith said. “Some cost more, some cost less. Some had great reputations; some were new to the market. We were willing to give just about any alternative a careful look, but ultimately, Digi was clearly the best choice. They have a long history of smart connectivity and a thorough engineering footprint in the 4G space. Beyond the standard configuration parameters, we liked that we could write some powerful custom programs that extended the functionality significantly. When you have a scalable, customizable and stable router, that’s the best go-to-market strategy I can think of. And the Digi TransPort also has all the carrier certifications, so the performance is better.”


“Without connectivity, there are significant impacts to productivity and service for the Grand Prairie Water Department,” Smith said. “The ability to redeploy repair teams on the fly, to increase the pace and speed of vital repair work, and to improve the overall performance of the city’s water system – these are the kinds of benefits that happen when trucks and people are constantly and reliably connected. Now, a driver can jump into the truck cab, grab the laptop, update service orders, and get the latest assignments – without enduring the delays and lost connections. The rugged reliability of the Digi TransPort WR21 is an essential reason for the Water Department’s success.”

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