Mobile phone users are not, as a rule, at the North Pole, in a sandstorm, or underwater. Machine-to-machine (M2M) communications, on the other hand, often need to function in extreme conditions. Even in extremes of heat, cold, or humidity they must be failsafe on a long-term basis and transmit data without interruption.
M2M offers developers a basis for countless new applications and for all manner of industries. Around 81 million machines are already connected in wireless networks all over the world, but that is nothing in view of the rapid growth forecast by researchers. According to market analysts Berg Insight, the number of communicating machines is set to rise to around 270 million by 2015.
The M2M market is booming thanks to the unlimited uses for M2M communications. These include vehicles in a car-sharing pool relaying their location or fuel level, freight cars that send their position autonomously to a tracking service, and vehicles that warn of dangers ahead and automatically call out the emergency services. The more areas of life and work that rely on M2M, the more important failsafe and reliable data transmission becomes.
A typical smartphone is designed for use in temperatures between -10°C and +40°C. But in humidity, dust, or dirt, most devices cease to function in next to no time. M2M solutions must withstand much more. For example, the automotive industry has extreme requirements for automatic emergency calls. These are based on fixed M2M solutions installed in vehicles, which must be resistant to both extreme fluctuations in temperature, shocks or severe changes in speed. The device must not fail in the event of an accident and should be able to make an emergency call automatically.
Many designs, one function: the SIM cardThe core of every wireless M2M solution is a SIM (Subscriber Identity Module) card. The SIM card handles network allocation and authentication and is the switchboard for security and access control in connecting to the mobile network. While the other electronic components of an M2M solution can be made suitably robust, the contact between the chip card and the circuit board electronics is the real challenge in extreme conditions.
Different SIM designs are used in industry, but the classic design is the 2FF SIM, or plug-in SIM card. At 2.5x1.5cm it is especially popular in the M2M sector, while the micro-SIM (1.5x1.2cm) – also known as the 3FF SIM – is the most common type used in smartphones.
These SIMs have a major advantage in that they can be fitted simply and swiftly into M2M applications of all kinds and are ideal for use in conventional conditions. Plug-in SIMs also enable low-cost production of M2M solutions that are required in small numbers and are suitable for limited use in extreme conditions. In both, the transitions between the SIM contact surfaces and the contact springs of the rest of the electronics are seen as potential sources of faults.
However, shocks, humidity and corrosion can interrupt contact between the circuit board and the SIM card, impairing an M2M application’s failure safety. Deutsche Telekom uses special M2M SIM chips, known as MFF SIMs, in its solutions. Depending on the type used, these SIMs are impervious to temperatures of -40°C to over 100°C.
Furthermore, MFF SIMs are smaller than plug-in SIMs and can be inserted in automated production lines. In this way, robust and compact M2M solutions can be manufactured in bulk. An MFF SIM with its corrosion-resistant contacts is permanently integrated into the M2M electronics – in other words, soldered onto the circuit board. This makes it more robust and longer lasting than solutions that use plug-in SIMs – even in terms of write and erase cycles.
The SIM memory is accessed during each and every network authentication process and ‘ages’ accordingly. MFF SIMs are designed for up to 500,000 accesses, or five times as many as for plug-in SIMs, and their permanent integration into the electronics provides protection from manipulation and theft.