The Internet of Things (IoT) describes the network of electronic devices (air quality monitors, purifiers, motion detectors, cameras, etc.) that are embedded with sensors, software, and other technologies for the purpose of connecting and exchanging data with other devices over the Internet.

In this article, I am going to describe some of the available networks and physical layers that are used by Air Quality Monitors (AQM), mainly for consumer-based products, and discuss which technologies make more sense in 2021+ for Smart Homes/Buildings and Businesses.

Wi-Fi IEEE 802.11

IEEE 802.11 is part of the IEEE 802 set of local area network (LAN) protocols and specifies the set of media access control (MAC) and physical layer (PHY) protocols for implementing wireless local area network (WLAN) Wi-Fi computer communication in various frequencies including 2.4 GHz, 5 GHz, and 6GHz.

IEEE 802.11a/b/g/n

This standard wireless network protocol is among the most common protocols for communication between the devices and the internet/cloud. Most devices even today use the ~20 years old 802.11b or 802.11g with a linkrate between 1 to 54 Mbit/s and a frequency of 2.4 GHz for power conservation reasons and good wall penetration. The 802.11n transmits the highest data throughput, but at the cost of high-power consumption at 5GHz.

IoT AQMs do not need a high-speed data throughput because the information they transfer is very little and in the range of a few kilobytes. So protocols like the IEEE 802.11ac and IEEE 802.11ax don’t make a lot of sense because they demand energy and they don’t offer good wall penetration in order to cover an entry house/apartment.

IEEE 802.11ax aka WiFi 6 or 6e

There are some claims that IoT devices will adopt the new WiFi 6e (e stands for enhanced) but I don’t think we will see that happening as bandwidth isn’t relevant for AQMs but the range is more essential and the WiFi 6e is designed to cover approximately 30m/98ft indoors. The 6e operates at 6Ghz, as a result, the highest the frequency the shortest the distance a signal can travel within walls. A positive feature of this protocol is that it supports a Low Power Indoor (LPI) mode. In the multi-user scenario, the WiFi 6 module consumes only one-third of that of the Wi-Fi 4 (802.11n) module and they achieve that by shortening wake-up time.

IEEE 802.11ah

Now the Sub-1 GHz IoT 802.11ah protocol makes much more sense as it can cover a broader area in and out of a house in case the user has AQMs indoors and outdoors. Bandwidth-wise it offers speeds up to 8.67 Mbits/s.

LR-WPAN

Low Rate Wireless Personal Area Networks (LR-WPAN) are implemented by several competing technologies including ZigBee, Z-Wave, EnOcean, Bluetooth LE, Wibree, CSRMesh, and 6LoWPAN.

Thread IEEE 802.15.4

Thread is an IPv6-based aka 6LoWPAN, low-power mesh networking technology for IoT devices. It is designed to be future-proof which means it will be around for a long time. It provides simplicity, security, reliability as it is a self-healing mesh network protocol, low power as devices can sleep and operate on battery power for years, and it can easily support hundreds of devices.

I believe it is the future of smart homes for two big reasons. Apple, Google, Samsung among other big tech companies support it and it is a royalty-free standard with open-source code. Additionally, it supports already existent communications protocols like WiFi or Bluetooth or even Zigbee as it is at the bottom of the stack right above the radio.

In order to have a functional Thread network in homes or businesses, we need a Thread Border Router which will talk via WiFi or Bluetooth or Ethernet, etc to the internet. Apple HomePod mini is a thread border router and uses WiFi in order to connect to your ISP router. Then we have Router devices. Routers also provide joining services for devices trying to join the network. Routers are not designed to sleep like an AQM which is always measuring the air quality and it is plugged on the wall. Finally, we have Host devices which are the end devices and sensors that are connected to the Thread network and most likely are operate on batteries like Eve Door & Window wireless contact sensor or a simple humidity/temperature sensor. The host devices are also called sleepy end devices because they can hibernate and save energy.

Zigbee IEEE 802.15.4

Zigbee has some advantages in complex systems offering low-power operation, and robustness as it supports up to 6500 nodes approximately. It is used by many sensor networks in IoT applications. One of the disadvantages is that Zigbee is not secure like a Wi-Fi based secured system and it is prone to attack from unauthorized people. The transmission distances range from 10 to 100 meters depending on power output and environmental characteristics (walls, trees, etc).

Z-Wave ITU-T G.9959

Z-Wave is similar to Zigbee but it uses the ITU-T G.9959 standard. Although it offers a better range of ~30 meters, it has a lower data rate between 10 to 100kbs. Z-Wave was designed for home automation and it supports up to 232 nodes. There are some variations of the protocol, the Z-Wave and Z-Wave Long Range (Z-Wave LR). Most notable Z-Wave LR’s use of a star network topology vs. the traditional mesh topology found within Z-Wave networks. Finally, Z-Wave uses proprietary technology.

Bluetooth LE IEEE 802.15.1

Bluetooth LE (LE stand for Low Energy) uses the 802.15.1 standard which is designed for short-range communication, typically in a star configuration. Wearable IoT devices like health and fitness trackers, often use BLE. Although BLE offers a higher data rate the area coverage is worse than Zigbee, Z-Wave, and Thread. The worst disadvantages in my opinion are the lack of native IP addressability and the network size limit at only 10 devices.

LPWAN

Low Power Wide Area Network (LPWAN) is a category of technologies designed for low-power, long-range wireless communication. They focus on large-scale outdoor deployments of low-power IoT devices such as wireless air quality monitors. LPWAN technologies include LoRa, SigFox, LTE-M, and NB-IoT. These technologies are used in cities, industrial sites, and forests for air quality monitoring.

LoRaWAN

LoRaWAN is designed to provide low-power wide-area networks with features specifically needed to support low-cost mobile secure communication in IoT, smart city, and industrial applications. LoRa uses unlicensed sub-gigahertz radio frequency bands like 868 MHz (Europe), 915 MHz (Australia and North America), and 923 MHz (Asia). It features a low data rate between 290bps and 50 kbps and a long communication range between 2 and 5 km in urban areas and up to 15 km in rural areas.

SigFox

SigFox is similar to LoRa but uses different modulations (BPSK). It can achieve a longer communication range of 3 to 8 km in urban areas and up to 50 km in rural areas but with a data rate of approximately 100bps. It can support up to 1M devices per access point.

NB-IoT

NarrowBand-Internet of Things (NB-IoT) is a licensed spectrum low power wide area (LPWA) technology developed to enable a wide range of new IoT devices and services and it uses existing cellular networks. It comes with a higher cost for the end device and the deployment of a base station. It features a data rate of up to 250kbps.

LTE-M

LTE-M is similar to NB-IoT low power wide area ( LPWA) technology standard published by 3GPP. Its main difference is that supports data rates up to 1Mbps as it can operate in a higher licensed frequency band of 1.4Mhz.

Conclusion

Although WiFi is adopted within many prototype and current generation IoT AQMs, longer-range and lower-power solutions like Thread will become more widely available. The 802.11ah wireless networking protocol looks very promising and hopefully will become standard in upcoming routers.

For consumer-grade indoor/outdoor air quality monitors Thread makes total sense as it can be easily integrated across platforms (Homekit, Google Home, Alexa) and make automation solutions easier for the consumers. It can self-heal and reconfigure when a device is added or removed, and at the same time when a new device is added to the mesh the range of the network extends so more monitors can be added further away for example outside the house. Think of them as network repeaters.

For B2B air quality monitors, LoRa and SigFox can offer great signal penetration at low-cost and excellent battery life, a gateway is needed though. However, if you are looking for security and future-proof networking technology then NB-IoT and LTE-M are the technologies that are going to serve you most with a higher cost due to ongoing costs. Gateways for both NB-IoT and LTE-M are optional.