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Making a "Smart City" smart with cellular gateways

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March 27, 2018

Daniel McCormackMichael Morscher,-March 27, 2018

"Smart cities" comprise increasingly dense networks of remote sensors, providing levels of insight never before achievable and made even more valuable by allowing the correlation of diverse sources. The promise of smart cities can only be unlocked with real-time data access, yet many urban sensor applications prohibit wired connectivity and cannot be supported by short-range WiFi. The use of industrial cellular gateways eliminates the barrier between data and cloud databases in systems where measurements would otherwise be stored only on disconnected local storage. Cellular gateways retrofit to existing sensor deployments, and as such, a gateway can be used in lieu of installing an entirely new connected sensor system. Further, specialized gateways reserve flexibility for the end user to adapt to certain design decisions such as the use of independent power versus wired power, and the type of battery to be used in accordance with the deployment environment. For functionality, cost-effectiveness, ease of integration, and security, cellular gateways are a sound choice to implement and complement scalable SCADA systems used for remote monitoring.

SCADA and Cellular Gateways

Automating the acquisition of data is critical, especially in the modern world of aging infrastructure. That’s where supervisory control and data acquisition (SCADA) comes into play. Systems administrators can reduce costs and increase insight regarding urban metrics, such as the integrity of structures such as roadways and bridges, by using well-designed SCADA systems.

Properly selecting hardware is a crucial process in the SCADA development cycle, affecting later business decisions such as ROI time and scalability. While off-the-shelf programmable logic controllers (PLCs) with connectivity modules work for many industrial applications, they can be insufficient for exceptional use cases. Applications that are demanding on hardware, such as distributed agriculture monitoring, marine sensing, and urban networking, are much better served by packages known in the IoT industry as cellular gateways.

There are currently two approaches to connected systems design, both having serious flaws in sustainability. The first approach is to rely on custom engineering as the solution to any and all hardware needs. Some deployment scenarios demand this research and development, but in most scenarios, contracting custom engineering solutions is akin to reinventing the wheel. A PLC/connectivity solution can be built from scratch, and it will get the job done, but it is grossly wasteful in terms of time and financial investment. In the worst case, if a municipality is designing a connected system and contracts a custom engineering firm for a solution, they might find they are subject to a restrictive exclusive technical relationship, thus barring them from integrating with suitable existing products in the future. While the work done by engineering firms is undoubtedly valuable, designers should first look to work with IoT product manufacturers to source proven solutions at a lower cost, and have custom solutions developed only when existing solutions are incompatible with client needs. The customer will benefit by having a stronger device that is easily maintained.

The second misguided approach to systems design is the polar opposite; in cases where custom solutions are not developed, designers turn to siloed products with little adaptability. Silo hardware providers are well established and create rigid hardware products that do one task very well, but are designed (in terms of geometry, application layer logic, power requirements, etc.) to perform best in the situation it was designed for, and only in that specific situation. These systems might not have been designed for your current application, might not contain device health self-reporting capabilities, might not be able to meet complex mixed-material RF environments, and perhaps most important, might not effectively balance price points to make scaling the solution economically feasible. A device that measures only groundwater levels is not as valuable as a device that measures groundwater levels today and can also measure volatile organic compounds (VOCs) next week and a new metric the next through simple sensor swaps. Large-scale deployments thrive, in functional and economic terms, when built around reuse and modularity. Siloed networks and siloed systems are less valuable networks and less valuable systems than their adaptable counterparts.

When considering design choices, take a step back, look at your long term goals of your connected system, and weigh the cost of having an Engineering Development Model constructed and having a design transfer performed versus modifying an off-the-shelf solution. Give extra consideration to existing solutions that are designed for adaptability and customization—while you’re best off not working at the circuit board level, you also don’t want to invest in what are essentially plastic bricks that are completely inflexible. Proven solutions that have a durable form factor but also allow for reconfiguration have an immense long-term value. The hidden consideration in solution comparison is providing for intuitive device maintenance and servicing. Maintainers will likely be parties other than the manufacturer or the owner of the device—and if you think servicing can be done quickly and easily on a poorly integrated piecemeal system, you haven’t thought deeply enough.

Analyzing the Needs of a Smart City

Smart cities are complex feats of engineering, requiring good design to be safe and valuable.  Good design stems from experience and is reflected in a uniform and tested product, proven to work in several sectors while maintaining best practices for security, device health, and user safety. The ability to maintain best practices, and ensure the longevity of the device, is a direct benefit of purchasing an industry-proven IoT product as opposed to having a custom one-off solution made. A product will have a support and integration team, whereas a custom solution typically loses that support rather quickly after the contract is complete; this is why dependability problems have risen with custom engineering firms in the smart city space working without a product provider partnership.

Resiliency and cost reduction are often said to be two of the most important traits of sustainable IoT, and they are best ensured by proper hardware and network selection. Network selection remains more challenging than hardware selection, but the use of cellular gateways provides for additional flexibility in network implementation. In many applications, complex RF environments require custom-modified solutions to improve RSSI in mixed-material urban environments; in some cases, embedding cellular transmitters in the soil or in monitoring wells beneath sidewalks offer the only viable connectivity solution able to provide access to the desired data and overcome the limitations of infrastructure surrounding the sensing system.

Industrial off-the-shelf SCADA solutions sometimes don’t have the proper specifications to function and survive in smart city environments, whether that is due to issues in connectivity, durability, or scalability (pricing, maintenance time, and expandability). Using a well-designed cellular gateway hardware and software framework as starting point for your solution allows for a great amount of customization in order to overcome challenges and problems that can’t be foreseen before deployment:

  • Data streaming can be modified. This allows for easy adjustment of simple dynamic settings such as time between samples, more complex behavioral changes redefined by updating the firmware of the unit to support new complex features, or even rollback capabilities in the event of a budget cut.

  • Additional hardware can be retrofitted. With easy remote updates, this opens an area for city workers or third party contractors to easily go out and modify the devices. When developing smart city infrastructure, maintenance is key, just like it is for infrastructure in general. Any smart city solution, cellular or otherwise, needs an easy-to-upgrade system for sensors. Ultra low-cost sensors often need to be replaced entirely, as they lack the ability to be effectively calibrated after a relatively short expiration date. Even higher-end sensors often need to be replaced as the equipment required for field calibration is rather unwieldy. Therefore, any solution needs to be able to have its firmware updated to support changes to sensor specifications from third party vendors.

  • Distant devices can be coordinated. Mesh networks have the benefit of not requiring payment to a third party network provider, and are thus a common solution. Local area connections such as these can suffer from interference if badly designed, and many others draw a surprising amount of energy and so the benefit of not paying for a network is offset by the operational and business expenses incurred by operating an isolated mesh. But, they lack some of the great remote diagnostic and security capabilities that a cellular network provides. Mesh networks coupled with farther reaching networks such as cellular or satellite networks are a great hybrid approach that give you the costs savings of mesh with the reliability of the cellular system. Frequently, cellular gateways are used as ports to the Internet for large swaths of local area sensors that connect to the gateway via a local mesh strategy. Coordinating devices securely on the implemented network enables correlation of localized data for unparalleled insights, and choosing a cellular network enables remote access and coordination.

And, by the top-down perspective, cellular gateways can easily be retrofitted to existing sensor systems to make them remotely accessible and controllable, making a city smart with minimal redesign and reengineering.

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