The following task is assumed in the practical example described: In a machine control system, there is a slot for retrofittable expansion cards to connect the respective machine to the ISDN telephone or GSM mobile network if required. This connection is intended to enable certain remote maintenance tasks. This also includes remote level monitoring of various operating resources. Alternatively, an individual telephone number can be called automatically to establish an ISDN or CSD data connection and transmit the current fill levels and other operating data using a configurable character string. However, the ISDN and CSD services required for operation have been or are now being discontinued by practically all providers. An alternative is therefore required to retrofit existing installations and equip new machines with an IoT communication module that can be used worldwide.

On the one hand, the new retrofit solution to be developed should fit directly into the existing slot without any technical changes to the machine and, depending on the machine location, use a mobile network or IoT satellite network for bidirectional communication. In terms of data technology, at least one data record should be transmitted daily from each machine equipped with this retrofit technology to the IT of a service partner. Other important requirements are

• Minimal investment costs for the procurement and retrofitting of the required communication module in the communication slot of a machine.
• Minimal operating costs for daily data transmission via a wireless connection.
• Radio adaptability for worldwide operation, different locations, network operators and the associated national approvals.
• Flexibility in terms of data adaptation to the IT systems of various service partners.

In this example, the machine controller communicates with the modem module via AT commands (extended Hayes command set). As these commands are stored in the respective control software and such software may not usually be changed, the IoT retrofit module must reproduce the required AT commands and convert them into the individual communication actions for the respective mobile radio or IoT satellite networks in order to transmit machine data to an IT infrastructure and possibly enable further tasks.

IoT wireless alternatives

© SSV

The major challenge for this retrofit task is the completely different machine locations, the associated different mobile networks and, if there is no corresponding terrestrial network at a particular location, the connection to IoT satellites in orbit with antenna technology similar to LTE.

If 4G mobile network coverage is available, an LTE-A modem (LTE+) can be used, for example. This enables data transmission rates of 500 Mbps and more. The LTE-A data throughput is suitable for live streaming of relatively high-resolution camera images as well as for high-performance remote machine access, comparable to wired DSL access. At other locations, however, there may only be an LTE-M radio network with a fall-back to LTE Cat NB1 (NB-IoT). This is still sufficient to transmit small amounts of data (e.g. sensor measurement data) without any problems. However, interactive remote access to the command line, remote desktop (VNC) or web-based user interface of a machine controller is not possible.

The most demanding detailed task at the moment would be the use of an IoT satellite network with LEO satellites (Low Earth Orbit; swarms of miniature satellites at orbital altitudes between 200 and 2,000 km). The interfaces and the provider-specific use of radio technology in this market segment require extensive expert knowledge (there are currently no standards for extraterrestrial IoT communication).

Other challenges include the possible data volume per month, the location-dependent time offset between transmission and reception times and data integration in IT applications. On the cost side, however, increasing competition is already having an impact. In the fast-growing market environment for providers of LEO satellite communication, most business models are currently in the positioning phase. This has an impact on the established pricing models for data connections with geostationary satellites, which until now have primarily addressed high-end M2M applications. In this respect, it is not easy to make meaningful comparisons of operating costs, especially as the details and number of satellites in orbit and the resulting differences in message transmission times also play a significant role. There are new providers that enable the operation of IoT devices with up to 750 messages and a maximum of 192 bytes of user data for USD 5 per month. However, further restrictions include specified daily limits for the number of uplink and downlink packets and a maximum total limit of 60 downlink messages per month (example: SpaceX subsidiary Swarm). An established competitor charges a monthly line rental fee of USD 15 per IoT device and USD 0.15 per data package with 50 bytes of user data. Larger packages cost twice as much (Iridium Short Burst Data, provider: Ground Control Communications). Calculated over the year, there are already significant differences in operating costs.