M2M communications: extending Ethernet for remote access
01 July 2009
Everyone seems to be making big claims for their individual approaches to machine-to-machine (M2M) communications. Paul Herron cuts through the marketing hype and technology predictions to focus on the use of Ethernet based M2M technology for remote monitoring of control and automation applications
During a recent web search for M2M related information I noticed that just about every technology and communication company had a reference to M2M, and how that company was perfectly placed to “help businesses increase efficiency and improve productivity while reducing operating costs.” Quite a claim!
M2M is an acronym for machine-to-machine. From this name, you can probably guess that human involvement is not exactly at the forefront in the M2M arena. It is claimed the idea behind the technology is to streamline the way data is collected from physical devices and incorporated into IT systems - without having to rely on people to do anything manually along the way. No bad thing, but I’d go further and say that M2M enabled devices or machines offer greatest benefit when the functionality extends beyond the communication link to the action that the device or machine initiates or takes itself.
For example, a silo level switch that can tell an operator when to re-fill with raw materials is all well and good. It would be so much better if the level switch could automatically contact the raw materials supplier and schedule a delivery. Now that is usefulness beyond the value of the data!
This ‘untouched-by-human-hand’ philosophy can bring benefits to many control and automation applications. What better than having machines or devices talk to each other, make decisions and take actions; the ideal control and automation scenario - no labour costs.
In reality, current technology and cost remain barriers to removing humans completely from the loop. Therefore, the current aim of M2M must be to reduce the reliance on operators as much as practicable and to give other involved personnel all possible assistance. But cost and technology barriers are rapidly diminishing.
Internet, GSM, GPRS et al
It has long been accepted that the best way to integrate the many business applications found in a modern manufacturing facility or utility plant is to build a scalable and resilient communications infrastructure based on Internet Protocol (IP) with logical segmentation. The simple and cost effective extension of such an IP network to the control and telemetry end-points (devices) significantly increases the benefits. The network reach is also extended due to the underlying physical infrastructure, whether it is wireless, cellular mobile communications or wired Ethernet, being transparent to the attached applications.
For remote access applications, cellular based M2M is a very good method of connecting assets over great distances using already established, robust, and proven networks. Also, cellular technology is effective across widely varied industries because it’s easy to integrate and cost effective to deploy.
For readers unfamiliar with cellular M2M technology, it simply means equipping devices with cellular embedded modules (the engine of a mobile phone) or installing communication modems with the appropriate cellular technology. The latter is a good way to add M2M capability to machines and devices that are not already equipped with this functionality.
By using various techniques such as data-tunnelling and protocol translation, most legacy equipment can be integrated into the IP network. A different modem is used to support each cellular network format using Global System for Mobile Communications (GSM), General Packet Radio Service (GPRS) or Universal Mobile Telecommunications System (UMTS or 3G). The modems, of course, require an appropriate SIM card.
As the mobile phone handset market has become saturated, airtime providers and network carriers are now offering attractive pricing packages to the industrial M2M space. Some SIM card contracts can be as little as £2.50 per month including 1MB of data transmission. Another rapidly diminishing cost barrier.
By using cellular modems and Internet services, remote access is cheap, easy and very effective. And if you add some additional features to the modem, such as industrial hardening, SMS messaging, I/O, IP routing and Virtual Private Network (VPN), it then adds more value than just the connection (remember our M2M philosophy already outlined above).
These modems are often connected to logic controllers in machine control or building management applications. As control system vendors put more communication features in their equipment, remote access is becoming easier and more beneficial. For example, a very small PLC costing less than £350 can contain an Ethernet connection, web-server and email capability. Add a remote access modem and a wide variety of functions are economically achieved.
A simple example of further added value gained from some remote access modems is the ability to trigger SMS messages from inputs to the modem. A pulse signal applied to the input can trigger (up to 20) pre-configured SMS messages to create a tactical response plan with targeted notification to various locations, systems or service personnel. Some modems can respond to in-coming SMS text messages to trigger corrective actions without going to the plant or machinery.
GPRS mobile communication offers direct connection to IP networks, and is somewhat faster than the older GSM technology (voice and text). GPRS also offers an ‘always on’ connection where the charges are applied based on the amount of data transferred, not the call time, so it is particularly suitable for continuous monitoring or surveillance.
Not as prevalent as GPRS is the UMTS or 3G communication service. This provides a much faster data rate, potentially 3.6 Mb/s (compare that with a 56Kb/s telephone modem), which brings applications such as video surveillance into the cellular arena.
Cellular communications inherently use the internet. One potential negative is the insecure nature of Internet transmission, whether this applies to the sensitivity of data transmitted or the potential for malicious hacking. With a little extra planning and the correct modem, appropriate security measures can be achieved. For example, ‘Call-back’ is a function whereby the modem identifies incoming calls and then automatically establishes an IP connection to a previously determined remote terminal. The caller, who triggers the connection set-up, can identify themselves via a PPP authentication method, or a telephone number.
Combined modem, router and Ethernet switch devices (see Figure 2) include firewalls and VPN capability to provide the best security methods available. VPNs can use Public Key Infrastructure (PKI) authentication involving static keys, a certificate with user name and password, or just a certificate.
Whatever your approach, undoubtedly the big pay-off comes when IP networks are extended to allow M2M enabled machines and equipment to initiate or take action beyond the immediate environment in order to maintain or restore their best possible performance.
Paul Herron is support manager, Insys Microelectronics
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