SIM cards and avoiding stranded IoT assets

Since pennants, drums, smoke, and horses fell out of favor to more advanced communication technology, network operators have struggled to find balance. Too few subscribers interested, and infrastructure investments completely fail. Just the right number of paying users, revenue streams provide profit and ability to invest in growth. Too many connections, and a network clogs, and subscribers curtail use or flee for alternatives.

In the early days of the electrical telegraph, three innovations provided the breakthrough. One wire systems made pulling cable relatively inexpensive compared to early six wire attempts. Relays provided signal boost needed to span more than a few kilometers. Morse code created a compact, standard message format.

With popularity came the next challenge. Operators restricted telegraph messages to a 10 word limit, with overage charges for verboseness. It wasn’t entirely because they were money-grubbing capitalist pigs; there was a practical reason. Only one message could be on a given segment of wire, so longer messages meant increased wait times for network access. Advances in the harmonic telegraph – an early use of frequency division multiplexing – and switching stations providing multiple routes to get to a destination helped.

A similar problem arose with the early generation mobile telephone, “0G” in telecom parlance. There was one big transmit tower with 12 frequency slots for a given city. Perhaps there were a couple thousand people with radios, but only 12 could get on the network at a time. Waits were typically 30 minutes to place a call. Part of the problem was spectrum allocation, and part was computational power needed to encode and decode more connections.

Video content drove 4G, and even with cell tower proliferation, more spectrum, improvements in DSP, and denser LTE encoding, we still don’t have enough bandwidth to keep up. Wi-Fi offload saves users from hitting their data plan cap, but it also keeps the network from total congestion.

Now, all these IoT devices show up. Fixed sensor clusters can use wired gateways. Personal clusters based on smartphones hang on the 4G network. Agile clusters – think connected cars, trucks, buses, trains, airplanes, ships, anything that moves – also rely on a cellular M2M gateway. Wi-Fi does not address mobility, and it does not look like WiMAX will achieve wide scale deployment. With 2G networks sunsetting, individual IoT devices may not need 3G or 4G bandwidth for data, but nonetheless they consume spectrum for a connection to the cloud.

Devices resembling connected cars also need to be portable across markets, for original sale, use, and resale. The solution to that in mobile phone space was the SIM card, and there are now those thinking we need a similar idea for IoT devices. SIMs carry the international subscriber mobile identity (IMSI) and an authentication key plus other info.

courtesy GSMA

A SIM would keep unauthorized IoT devices off the network, and enable services network operators can monetize. The user-installable SIM form factor seen in smartphones is less than ideal for IoT use. A solderable, embedded SIM form factor such as embedded universal integrated circuit card (eUICC), can add SIM-style functions to IoT devices. For instance, there is a Gemalto implementation of an MFF2 machine identity module.

Gemalto MFF2 package for embedded SIM

One-time programmable memory would play a key role in embedded SIMs, just as in mobile SIM cards. It would prevent tampering and enable secure provisioning of IoT devices. However, in cases such as the connected car, transition of service to new ownership is important. OTP can emulate multiple time programmability by using replicated blocks and pointers, allowing reprogramming of keys. Or, creative applications could emerge such as a device locked for a contract period, then unlocked for its remaining life.

The GSMA in conjunction with Beecham Research Ltd. has produced a study on the use cases for eUICC in M2M or IoT markets. Their points on connected cars are well taken; proprietary solutions could slow adoption and reduce portability upon resale or service termination, perhaps to the point of leaving allegedly connected assets “stranded” off a network. The text narrative and reasoning in this study is worth a look, even if the forecasts don’t come to pass as shown. Also worth noting: Apple is all over eUICC.

If network operators are going to embrace IoT devices to the degree people are projecting, the use case for the entire lifecycle needs careful consideration. It would be a shame to lose the benefits of connectivity of a thermostat, car, or other long life IoT device over not incorporating ID/key reprogrammability or unlocking in some form. Embedded SIMs may be part of the answer.

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• Rekeying the IoT with eMTP