Sigfox and the S2-LP: To improve the accessibility of our content, please find the audio version of this blog post.
Since the release of ST’s physical distancing SDK, new solutions are using our technology in conjunction with our S2-LP Sigfox transceiver. It is thus essential to delve into the motivations that are driving engineers to rely on this Sub-Gigahertz network. Indeed, there are primarily three reasons that make a Sigfox wearable a very attractive proposition in the context of contact tracing: privacy, energy efficiency, and cost. Moreover, many companies chose the S2-LP because it offers unique advantages, such as the ability to drive the power amplifier and adjust the frequency bands to work in any Sigfox’s Radio Configuration (RC) Zone.
There Isn’t Always A Good App for That
There are a lot of questions around applications that can help with physical distancing and contact tracing. Smartphone makers and operating system developers try to make it as intuitive as possible. The problem is that relying on mobile phones for large-scale projects has inherent issues. Not everyone has a smartphone, nor wants one. Using a cellular network to transmit data can be expensive, and some older demographics don’t always carry one. A Sigfox wearable in the form of a clip or bracelet can thus become an answer to many of these concerns. It can also send notifications when a person comes into contact with someone that tested positive. The downlink channel may even send an alert if someone enters a high-risk area or when there’s an anomaly.
Engineers are also wondering how they will get a return on their investments after the global pandemic is over. Using a simple mobile app on a smartphone can have a short lifespan. On the other hand, a Sigfox wearable can support so many other applications. We are already talking with our partners to see how they can offer badges for concerts or sporting events in massive stadiums. A similar device could alert students on a university campus or track patients with medical conditions. There are also industrial applications for assisting workers and enforcing zoning requirements in manufacturing plants or other business settings. Hence, let’s take a look behind the scenes to understand this new trend better and help professionals consider whether they too should jump on the bandwagon.
Sigfox and the S2-LP: Privacy
Privacy in the Sigfox Layer
To prepare this blog post, we sat down with Ajay Rane, VP Global Ecosystem Business Development at Sigfox. He explained that the network he represents has characteristics that make it easier to protect people’s privacy. Using the Sigfox 0G protocol means engineers don’t rely on a SIM card and a mobile operator that can triangulate an individual’s geographical locations. The Sub-gigahertz network doesn’t also depend on the same precision as GNSS. A traditional GPS will pin-point a position on a map within a few centimeters to provide directions, for example. Sigfox works great with an approximation in the hundreds of meters. Tracking assets benefits from the energy efficiency of Sigfox, and most IoT applications prioritize a robust, wide, and cost-effective network over geographical precision.
Privacy in the ST Reference Design Implementation
The ST reference design (STDES-MONARCH) uses a Bluetooth SoC to determine the physical distance between two devices. The system only stores Bluetooth MAC addresses and can send them to the cloud using the Sigfox network. Hence, there’s an additional layer of privacy since the default system doesn’t track Sigfox IDs. An employer may decide to bypass all this and assign a device to a specific user and keep their Bluetooth MAC address in a database. However, this is a lot of work that will produce diminishing returns, especially with larger-scale projects. Ultimately, engineers are using a cloud infrastructure that relies on Sigfox to benefit from the inherent privacy, not circumvent it.
Sigfox and the S2-LP: Efficiency
The Inherent Efficiency of a Sigfox Transceiver
Ajay Rane emphasized that energy efficiency was another factor that pushed companies to rely on Sigfox. The energy requirements to drive a transceiver like the S2-LP are significantly lower than those necessary for a cellular module. Additionally, to conserve battery, manufacturers can poll the network only a few times a day and still be efficient. The system simply checks to see if an ID flagged by the system is in the local database. Hence, the time the transceiver is active is reasonably short, and users can enjoy a longer battery life. For instance, a wristband from Traksens designed to help with physical distancing and contact tracing has a battery life of approximately one month. However, this is a realistic estimate, and the band can last longer in some real-world cases.
The Inherent Efficiency of the S2-LP
The S2-LP is also unique in the industry since it can drive a power amplifier. Engineers don’t need an external microcontroller operating this particular component. Hence, it lowers the overall consumption. It also makes it easy to create a system that will work in every Sigfox RC. Indeed, the S2-LP can adapt the transmit power to the various specifications around the world on the fly. Put simply, the ST transceiver can detect the Sigfox region and decide whether to turn the external power amplifier on or off. The STDES-MONARCH is also the first ST solution to officially cover all of Sigfox’s RC (from RC1 to RC7).
Sigfox and the S2-LP: Cost
The Cost-Effective Nature of Sigfox
The Sigfox network doesn’t require a SIM card or a partnership with a mobile network operator. Additionally, subscription fees are much lower than cellular plans. Hence, it is an exciting proposition, whether we are talking about a startup or a large city. Sigfox data packets are also small, making interactions with the cloud efficient. It thus becomes possible to combine a Sigfox transceiver and inexpensive memory storage to poll a local database.
Let’s imagine an engineer trying to determine the memory capacity for such a design. Let’s also take the example of a global pandemic and a virus with an incubation period of about 14 days. One would need a system that effectively stores tens of thousands of IDs and erase entries older than 21 days. A few megabytes should thus be more than enough in nearly all cases.
After all the advantages listed above, it’s easy to see why Inocess is coming out with a Sigfox version of its Nextent Tag.