Wireless M2M increases value of wired infrastructure
The IT world started to standardize network infrastructures back in the 1990s, pursuing interoperability in everything from cabling and connectors to the seven-layer Open System Interconnection model. Costs per connection plummeted and performance skyrocketed. But the industrial world sat on the sidelines for years, trapped in single vendor communities with proprietary Fieldbus systems as a result of a general belief that Ethernet was too fragile for manufacturing environments. Eventually, however, the enormous cost differential between an “IT” network connection and an “industrial” connection led to a tipping point. Vendors started to provide ruggedized equipment, and Ethernet has become an integral part of industrial automation.
We’re approaching another tipping point now. Like the early incarnations of wired Ethernet, wireless Ethernet was long perceived as being too unreliable for industrial applications. A failure or interruption in the wireless connections at a local coffee shop is normally a mere an inconvenience, but in the industrial world it can be a catastrophe. So, like wired Ethernet, wireless Ethernet had to make some changes before it could be used for machine-to-machine (M2M) automation.
Reliable Wi-Fi connections
Wi-Fi’s interoperability and low-cost chipsets make it a natural choice for wireless IT applications. But the early Wi-Fi standards struggled with issues like multi-path propagation, the phenomenon that occurs when radio waves are absorbed or reflected by obstacles in the local environment. The obstacles may be anything from ordinary building materials to vegetation, and each one interacts with radio in its own way. The end result is that Wi-Fi signals arrive at the receiver at different times and out of sequence. A connection that worked at one moment might fail five minutes later, simply because someone moved a forklift or relocated a stack of cartons.
The Wi-Fi 802.11n standard addresses that problem with multiple-input multiple-output (MIMO) technology. The standard employs multiple antennas at both the transmitting and receiving sides of the wireless connection and splits the data into numerous spatial streams. The streams are transmitted through separate antennas and collected by corresponding antennas in the receiving devices, where onboard software uses signal processing algorithms to correct and interpret the incoming data.
MIMO 802.11n devices also employ precoding and postcoding techniques like spatial beamforming. Spatial beamforming modifies the phase and relative amplitude of the signal to create a pattern of constructive and destructive interference in the wavefront, which simplifies interpretation on the receiving side. The 802.11n standard adds frame aggregation to the MAC layer, and makes it possible to specify management information less frequently by grouping several data frames into a single, larger frame. The ratio of payload data to total data volume is higher, allowing for better throughput. 802.11n also adds 40 MHz channels to the physical layer (PHY), twice the bandwidth that was available under the older 20 MHz standard. Together, 802.11n’s many modifications to the Wi-Fi standard have resulted in a wireless technology that is reliable enough for industrial applications.
Obsolescence isn’t an option
If you buy a new desktop computer these days it will come with multiple USB ports as standard equipment. But if you want a serial port you’ll probably have to install an expansion card. Serial communications have become irrelevant in the home/office world, where the inability to connect to some old dot matrix printer is hardly a cause for concern. Things are a bit different in the industry. Companies and organizations all over the world still have enormous capital investments in serial equipment. In fact, the low cost and rugged reliability of the serial protocols continue to make serial installations quite attractive, and the number of installed serial devices continues to grow. So how do you get those serial devices to communicate across modern networks, and how do you make them wireless?
Wired serial servers and media converters have been around for a long time. So one option would be to Wi-Fi enable them by connecting them to an external wireless device. But there’s another way to go about it.
Vendors are now producing wireless routers and bridges that provide the serial to Wi-Fi conversion in a single box solution.
You can use these devices to wirelessly network-enable either new or legacy serial equipment. There will normally be an Ethernet port as well, which will let you connect local networks or stand-alone Ethernet devices to the same wireless router or bridge.
Another option is the wireless access point. Connecting it to your serial device gives the serial device its own Wi-Fi hotspot, allowing technicians to communicate via laptops, tablets, or even smartphones. If you’re designing new serial equipment you can build in all of the same functionality by adding embedded modules that duplicate the features of the external routers/bridges/access points.
Wireless router/bridge/access points can also be used to network-enable mobile equipment like forklifts, which will connect to networks or handheld devices any time they are within range. Dual band Wi-Fi devices will let you choose between the 2.4 Ghz and 5 Ghz license free bands in environments where the airwaves are cluttered with transmissions from competing equipment.
Long range communications
The 802.11n standard can provide for line-of-sight ranges measured in kilometers, with throughputs of up to 150 Mbps. That’s very useful when you need to cross a barrier like a river or a superhighway. But as the network edge continues to expand, there is an increasing need for wireless connections in areas where there is no Ethernet infrastructure and where even the newest and most advanced Wi-Fi equipment would have insufficient range.
Cellular M2M data networking can solve the problem. Like some of the industrial Wi-Fi routers, today’s cellular routers will often include support for serial devices. A model with I/O ports, Ethernet ports, and Wi-Fi would let you connect a broad array of equipment to the Internet via the cellular telephone network while supporting the older serial protocols. Through Virtual Private Networking you can use the cellular networks as securely as if they were proprietary infrastructure.
And this is just the beginning. The buildout of the 4G LTE networks is nearing completion. Network designers will soon be able to combine 4G’s enormous bandwidth and low latency with enhanced Wi-Fi to give networks incredible wireless capabilities. And there will be no need to abandon your existing equipment or wired infrastructure. Wired networks aren’t going to go away—they’re only going to get better.
Mike Fahrion is director of product management at B&B Electronics
More on wireless Ethernet:
Webcast: Industrial Ethernet, Part 1: Technologies. Archived version of this new Webcast now available on demand.
Video and article: PINA General Assembly looks ahead to growing industrial Ethernet deployments
E-Guide: Industrial Ethernet Best Practices