Cellular networks do more than voice

Industrial Embedded Systems — November 18, 2009

3It's easy to overlook, but it's not news that cellular wireless networks carry data traffic nicely, and that is exactly what many industrial applications need when operating over a wide geographic range.

Networked sensors can bring new intelligence to industrial infrastructure, enabling everything from environmental or food quality monitoring and oil field telemetry to systems that monitor the conditions of roads, tunnels, railways, and other systems. Because these assets can be broadly distributed, located in remote areas, or moved from place to place, wireless is the only networking technology that makes sense from a technical standpoint.

But what’s the right wireless technology for the job? One wireless technology that’s almost everywhere might work best for specific industrial situations.

Assets near or far drive the choice

The first decision about which wireless technology to use depends on what is being monitored, where it is located, and whether the object is moving from one location to another.

For example, if the job involves building a one-off wireless data network at one location – such as tracking pallets or bins as they move around an assembly operation – and the system will never grow beyond that, then one option is to implement RFID tags and other sensors that use either unlicensed Wi-Fi or ultra-wideband technology networks.

Device and local area network wireless technologies are particularly well-suited to building a quick network in a warehouse environment because they are relatively inexpensive, can be built using standard, off-the-shelf technology, and can be managed with well-established scanning and tracking hardware and software. RFID technology has been around for a few years, and large retailers and trucking operations are using it for logistical tracking. RFID tags can cost as little as a few cents apiece, and Wi-Fi access points and controllers cost a few hundred dollars.

However, tracking and managing assets that move between several different facilities, contractors, or suppliers requires a wireless technology that is much more ubiquitous and has frequency allocations already in place to alleviate coverage interference. With a wireless network that spans multiple locations (some of which belong to partners or other third parties), an infrastructure that is maintained and managed by someone else is best, avoiding the cost of “doing it yourself” across multiple locations.

For this kind of architecture, cellular data technology provides the optimal solution. Cellular monitoring networks include sensors, cellular modems (or an in-building wireless network system such as the ADC InterReach Fusion system pictured in Figure 1), and cellular networks that carry traffic. While the sensors that simply identify an asset or monitor vibration, wear, and temperature are the same as those used in local area networks, they must be linked to a cellular data modem that maintains the connection to the larger geographic network.

Figure 1: The InterReach Fusion in-building system offers multiband spectrum wireless capabilities that span multiple locations.

The freedom to innovate

By using a carrier-owned and -maintained cellular network that provides ubiquitous coverage over a large geographical area and modems with highly reliable links to that network, engineers can stop worrying about wireless coverage, interference, and capacity or the range of local area networks and concentrate instead on how networked wireless sensors can improve industrial operations. Wireless is already in use in many different scenarios.

For example, cellular-based wireless networks are being used to remotely manage and monitor beverage vending machines, as shown in Figure 2. These machines can report back to a central location when they have an operational problem or when they’re low on inventory. This simplifies maintenance and makes it easier and less expensive for the vending company to maintain the right inventory on route trucks.

Figure 2: Cellular-based wireless networks can enable vending machines to report problems to a central location.

Many companies in other fields are now designing and providing remote cellular-based monitoring and management technologies for trucking, oil field asset tracking, refineries, chemical plants, and manufacturing.

In airplane manufacturing, for example, a huge ecosystem of subsystems goes into the plane – turbines, generators, instrument pods, engines, seats, and so on – all parts that are built at different locations by different contractors. The whole ecosystem needs to function cohesively, and the logistics are complicated in terms of bringing the right systems together at the right time at the airplane assembly plant. These are high-value assets that one wouldn’t want sitting around in inventory, but also wouldn’t want to delay production waiting for. In a situation like this, cellular-based asset tracking can enable the electrical manufacturer as well as the airplane maker to track all of the facilities and manufactured goods and know where everything is at any point in time.

The food industry is another example. One of the critical issues with food is managing the temperature at which it is stored as it moves from the plant through the distribution chain. Recent salmonella outbreaks confirm the importance of tracking food temperatures and being able to prove them during any subsequent investigation. If a company wants to monitor food temperatures at the plant, on trucks, and in warehouses and maintain a central log that stores continuous time-stamped readings, a cellular data network can deliver the reliability and reach to enable these functions.

Automotive telematics is another field being tested by major manufacturers. Sensors monitor wear and operations of various subsystems in a vehicle, reporting back to the manufacturer to alert the company about potential problems before the customer even knows there is a problem. The customer can receive an e-mail from the manufacturer asking for a service visit.

Making cellular networks work

Cellular tracking devices today cost in the tens to hundreds of dollars each, so it’s wise to reuse them. If the application involves tracking movements or the condition of manufactured goods in transit, users should track objects at the case, pallet, or truckload level rather than by the individual item, and the sensor and modem should be recovered and reused once the item is delivered.

Another consideration is indoor cellular coverage. Companies might need to conduct a site survey of coverage inside the plant, warehouse, or other facility to ensure that cellular service is reliably available. In some situations, companies should deploy in-building cellular coverage systems because the signal from outside the facility might not adequately penetrate the building to provide reliable service.

Designers should consider a checklist of issues when selecting and implementing a particular wireless network technology for asset monitoring or tracking:

·    Application: Is the asset or process fixed or mobile? Can things work with a static network at a single facility, or is something needed to provide a connection for multiple sites?

·    Interference: Will the network use licensed or unlicensed technology? Licensed technologies such as Wi-Fi might have problems with interference from other equipment at the site, nearby Wi-Fi networks, or different access points in the same network.

·    Capacity: Wi-Fi networks potentially offer far more capacity than do cellular data networks, on the order of tens of megabits per second for Wi-Fi versus up to a megabit per second for cellular. However, typical applications for wireless asset tracking and monitoring traffic are relatively low volume, so it is possible to use low-bandwidth cellular services such as GPRS or even SMS to reduce service costs.

·    Management: Who will manage the wireless network? If it is a single-site solution like a Wi-Fi network, the site owner will likely manage network operations and connectivity. With a cellular network, the carrier manages operations, thus freeing the end user from the management burden.

·    Cost: The wireless infrastructure and tracking solution must be inexpensive enough to return its investment in terms of lower logistics costs or savings from other improved operations. A network that performs reliably for many years makes it easier to return the investment than does one that must be continually tweaked or upgraded.

Cellular moving into M2M

With wireless cellular networks virtually everywhere and other wireless networks available for modest investments, it is clear that wireless monitoring and tracking systems will become common throughout industry.

Industrial embedded systems designers should consider how these cellular technologies can improve the functionality, cost, manageability, and longevity of the equipment they design and begin planning for their use. As evidenced by trends in fields as diverse as health care, basic research, transportation, defense, and financial services, it’s not a question of whether cellular networks will arrive, but rather when they will arrive.

Michael Day is VP of technology and strategy and Chief Technical Officer for ADC, based in Eden Prairie, Minnesota. His responsibilities include corporate business strategy, technology policy and strategy, and managing ADC’s India BPO and software development center in Bangalore. His experience includes roles at Alcatel, Ameritech, Telecom New Zealand, and AT&T Bell Labs. He has authored numerous articles and presentations and has chaired a variety of industry conference sessions in network architecture and technology, with a particular focus on network evolution, transmission systems and network architectures, protection, restoration and survivability, and mission-critical communications networks. Michael received his BS with honors in Physics from the University of Missouri and his PhD in Theoretical Physics from the University of Wisconsin. He is a member of the IEEE and the IEEE Communications Society.