IoT communications options explained

The Wikipedia definition of telemetry is the in-situ collection of measurements or other data at remote points and their automatic transmission to receiving equipment for monitoring. As new communication options develop, becoming more viable and economical, having a basic understanding of the network that will support your devices and the implications of making certain choices is fundamental in deploying an Internet of Things (IoT) solution effectively. This article focuses on one specific aspect of connectivity, licensed vs. unlicensed spectrum network options, and the impact it could have on the success of your project.

Licensed vs. unlicensed spectrum

Most IoT systems link networks of sensors via radio waves which transmit data from one place to another. Radio waves are a type of electromagnetic radiation that make up a small part of the electromagnetic (EM) spectrum.

In Australia most of the radio spectrum is licensed by the Australian Communications and Media Authority (ACMA). Companies are able to transmit on an assigned frequency by paying ongoing fees. Alternatively, organisations can still use the airwaves to transmit communications without getting permission from the ACMA, but they must transmit within those parts of the spectrum that are designated for unlicensed users. The amount of spectrum that is available for public and unlicensed use is very small.

With the exception of cellular devices almost all IoT devices operate in the unlicensed spectrum currently.

Licensed spectrum options:

Cell phone/Long Term Evolution (LTE)/4G

Long-range wireless radio networks have fixed location transceivers, operating on ultra-high frequency (UHF) radio frequencies.

Solutions based on cellular communications (2G/3G/4G/5G) usually provide good coverage but rely on land-based towers. When you are in a particular area, that cell is carried by the closest tower. When poor coverage occurs, this is usually because there isn’t a tower nearby or the topography of the area (such as mountains) may be blocking the electromagnetic waves.

• Advantages: Network management is carefully managed by the cell phone provider and as it is in the licensed spectrum contention for spectrum does not occur and congestion is well managed.
• Disadvantages: Not a good option for remote areas, or in the ocean, where distances to the closest radio tower is large.

Cellular (5G) LPWAN

Cellular Low Power Wide Area Networks (Cellular LPWANs) are built specifically for scaled IoT deployments to give better, cost-efficient coverage. Suitable for large-scale Narrow Band IoT (NB-IoT) deployments, this technology can co-exist with Global System for Mobile (GSM) communications and Long-Term Evolution (LTE) under licensed frequency bands (e.g. 700 MHz, 800 MHz and 900 MHz).

• Advantages: Range of approximately 50km. NB-IoT end devices are in sleep mode most of the time outside operation which reduces energy consumption. Moderate ongoing fees.
• Disadvantages: High ongoing fees.

Satellite based radio telemetry systems

Satellite – Equatorial (Geostationary): Telecommunications between ground antenna and a Geostationary Satellite, orbiting at the Earth’s equator at ~25,000 Km’s.

• Advantages: Offers a range of 50,000km and is carefully managed by the satellite provider.
• Disadvantages: High power needs, remote units need battery with solar. Fees are higher than cellular however they are decreasing. Long delay of ~250ms to satellite and back.

Satellite – Low Earth Orbit (LEO): Telecommunications between ground antenna and Low Earth Orbit Satellite(s), orbiting the Earth at ~1000 Kms. Full tow way IP service OR message based service available.

• Advantages: Short delay of ~10ms to satellite and back. Low power needs.
• Disadvantages: Only available when satellite is overhead, but this is most of the time and saturation of LEO Satellites is increasing.

Micro Satellite Networks: Telecommunications between ground antenna and micro satellite, orbiting the earth at ~600km.

• Advantages: Battery powered transmitters. Data Hub provided with capability for API connection. Low ongoing fees.
• Disadvantages: Significant restrictions on data volume. Coverage limitations, only available when coverage is overhead and communications are message based which arrive in a few hours.

Unlicensed Spectrum Options:

LPWAN (Low-Power Wide-Area Networks)

LPWAN is a low-power wide-area network that connects battery-powered devices over long ranges. LPWANs operate at a lower cost and use less power compared to mobile networks. They able to support a greater number of connected devices over a larger area. LPWAN’s communication range varies from 2 km to 1,000 km depending on the environment. LPWAN is highly suitable for IoT applications that need to transmit tiny amounts of data over a long range.

• Advantages: Can deliver messages over distances of 30-50km in rural areas, 3-10km in urban settings and up to 1000 km in line-of-sight applications. Suitable for large scale NB-IOT deployments.
• Disadvantages: As it is in the unlicensed spectrum, congestion and interference may occur.

LoRaWAN (Long Range Wide-Area Networks)

LoRa is a wireless technology designed for long-range wireless communication. A transmitter sends small data packages with low amounts of power. The communication works over long distances. LoRaWAN makes it possible for LoRa devices to communicate with each other via networks, platforms, and technologies across the Internet.

• Advantages: Extended range, less power, long battery life – LoRa end devices are in sleep mode most of the time outside operation which reduce the amount of consumed energy. Low fees.
• Disadvantages: As it is in the unlicensed spectrum, congestion and interference may occur.