Wireless Communication Options: Part 3

[Joel_Weder]

Low Earth Orbiting Satellites

The LEO broadband and IIoT (Industrial Internet of Things) satellite market is very new, but is growing incredibly quickly. The satellite industry overall is in the midst of a dramatic shift, and definitely bears watching. Previously, satellite offers for SCADA and telemetry were primarily limited to geostationary (GEO) satellites. The data rate provided by GEO satellites is limited unless very large dish antennas are used. Also, costs are high, and latency is significant due to the distance of satellites from Earth. In contrast, the new LEO broadband satellite systems will offer multi-megabit data rates with latency of under 60 milliseconds, terminal costs similar to cellular modems or license-free radios, and low monthly fees.

Currently there are several companies developing LEO satellite constellations. Foremost among them is SpaceX’s Starlink system, which is already in operation with over 2,000 satellites, and has over 250,000 customers as of February 2022. The customers are primarily residential at this time. SpaceX has plans to grow their system to include up to 30,000 satellites, though this massive number is being hotly debated and current authorization is for about 4,400. Also, satellites will communicate directly with each other via laser channels to avoid the need for repeated up/downlinks.

Similarly, OneWeb and other smaller players are growing their own systems. OneWeb is intending their system be primarily offered to commercial customers. Their smallest Earth terminal is the size of a briefcase, and cost is expected to be very reasonable. The flat panel antenna will (as with Starlink) be electrically steerable – no need for physical movement. Early testing has shown data rates of up to 400 Mbps, with latency as low as 35 ms. They currently have nearly 400 satellites of a planned 648, and were expected to begin offering service to customers before the end of 2021.

Swarm Technologies, a small player with tiny (eg 30 cubic in.) SpaceBEE satellites, was recently acquired by SpaceX. Swarm’s approximately 150 satellites are designed to enable low-speed communication of IoT devices to their global communication terminals. Their “Tile” earth terminals may be embedded into a circuit board, and are quite inexpensive at (approx.) $119 USD. A network subscription is as low as $5 a month. Services are being offered to agriculture, maritime, energy, environmental, transportation etc. This IIoT communication provider may be of particular interest to Schneider Electric’s customers.

In contrast, Telesat Canada is aiming for 300 large satellites in the several-hundred kilogram range. They will begin to launch in 2022. These satellites will offer broadband speeds to commercial and industrial customers, with latency of 30-60 ms. Testing performed so far has  included HD video, encrypted file transfer, VPN use and video conferencing.

Inmarsat already has several geostationary satellites, and aims to grow a LEO constellation called Orchestra of about 150 satellites. Terminals may be installed on ships, in moving vehicles, or be stationary. The intent is to provide a least-cost communication link, where the terminal will choose LEO, GEO or a terrestrial 5G network if available. Also, one terminal may provide connectivity for another nearby terminal.

In many cases when developing a wireless system using existing licensed or license-free radio options, certain sites cannot be reached economically due to distance or challenging terrain. Any system designer encountering such an issue would be well advised to consider a Low Earth Orbiting satellite option.

Low Power Devices

There are many wireless companies providing low power solutions at relatively short range, whether they be data loggers, cameras, weather stations or microcontrollers. The cost of these devices has plummeted due to greatly increased integration of features into tiny low-cost packages, and much-increased sales volume. A wide variety of technologies are available providing high or low data rates. A general term for most such devices is LPWAN (Low-power wide-area network). LPWAN devices typically communicate at 50 kbps or less, though other technologies provide higher speeds. Typically these devices will operate on battery power.

LoRaWAN protocol is transported using a LoRa module, which typically operates in license-free bands below 1 GHz, such as 433-434 MHz, 863-867 MHz or 902-928 MHz depending on the region. Data rates are low (300 bps to 50 kbps), but range is good considering the small power consumption. Distances of 5 to 15 kilometres may be spanned, depending on obstacles. The technology uses chirp spreading, and includes Forward Error Correction (FEC) to reduce interference concerns. LoRa may be of interest for battery-powered devices which must send relatively small amounts of data over significant distances.

Zigbee is still popular, but the newer-technology CHIP (Connected Home over IP) project is worth watching. CHIP doesn't replace Zigbee, but rather replaces its transport protocol with an IP layer, and adds its own application layer. Data rates are between 20 and 250 kbps, with transmission distance typically 30-100 metres. The formal brand for CHIP tech is “Matter,” and display of its logo states interoperability with other CHIP-tech devices. This standard is worth watching, as it seeks to bring vendors together to provide interoperability. Schneider Electric is a member of the Connectivity Standards Alliance (CSA).

Sigfox is a technology offered by the French company of the same name. As with LoRa, Sigfox uses internationally-recognized ISM (Industrial, Scientific & Medical) license-free bands. This LPWAN technology is intended for use where data traffic will be very low, no more than 140 messages sent from the remote device each day, with payloads of just 12 bytes per message. The data rate is very low, at 100 bps. Extremely low power consumption is offered, with good range. However, Sigfox does require communication with an existing mobile system network, so its use in remote areas is limited. This technology might be suitable for (eg) a low-budget municipal water system.

The use of Bluetooth, typically for short-range point-to-point links, has expanded over the years. The technology is mature, but there are variants worth investigating further. For example, a Class 1 Bluetooth device may transmit at up to 100 mW, providing a range of approximately 100 metres. Bluetooth Low Energy (BLE) is at the other end of the scale, able to operate on a very low power budget, though providing a lower data rate and shorter range than other variants. It may be considered, for example, to be included with a SCADAPack or other device for local wireless configuration or diagnostics.

Industrial WiFi has become significantly more popular as a new generation enters the workforce who grew up with the technology. Many factories include WiFi networks, providing very low latency with high data rates throughout a facility. The use of both the 2.4 and 5 GHz frequency bands, and MIMO wireless technology, have increased reliability. WiFi routers are also being optionally included in the same housing as wireless devices of other types, for example 900 MHz license-free data radios. A WiFi module might also be considered for network access at larger remote sites.