IoT Options by Beverly Owino July 22nd, 202I

Cellular IoT vs LPWANs

Currently, almost everything and everyone can communicate with each other through the internet. This makes connectivity, power, cost, size, security, and interoperability very important aspects to put into consideration while coming up with IoT designs. Low Power Wide Area Networks and Cellular technology are two major competitors in this aspect.

The intended IoT application not withstanding, services provided by LPWANs, cellular networks as well as other wireless network protocols such as RFID, Bluetooth, and Zigbee seek to allow periodic communication between sensors while ensuring low power consumption. How these communication technologies make this possible are different, much as the techniques applied are explicitly designed for IoT. For instance, each of the systems provides limits on the amount of data to be transmitted within a given period and tries as much as possible to use really low data rates which would require narrow bandwidths.

Cellular IoT

First of all, it is worth noting that LPWANs are a much more recent invention compared to cellular technology. Way before IoT was a thing, cellular technology existed through GSM (Global System for Mobile Communications), which provided 2G connectivity. Back then, however, GSM was more focused on offering voice, MMS and Short Message Services. Over time, GSM has evolved to be able to provide faster data communication and the ability to directly connect to the internet through improvements brought about by circuit-switched transport and later on by packet-switched networks such as GPRS and EDGE. The 3rd Generation Partnership Project (3GPP) has since developed 3G( UMTS), 4G(LTE), and 5G networks[2].

Improvements have been made to the existing technologies to come up with solutions that would, in the long run, impact battery life, reduce the cost of devices and consequently cost of deployment as has been witnessed through NB-IoT, LTE-M and 5G. To connect to a cellular network, IoT devices need a SIM card. Whichever cellular provider’s network you can access is determined by the SIM Card you use.

Advantages of Cellular IoT include the fact that it provides excellent coverage and global deployment is simplified. LPWAN providers would need to set up their systems in different areas for presence. Thankfully though, the setup of these systems is not as complicated as the one for digital cellular networks.

One major undoing of cellular technology as an option for IoT applications is its power consumption which is relatively higher than that of LPWANs. Cellular networks were traditionally not designed to accommodate the many new devices that would make bandwidth sharing essential. These networks are anticipatorily listening to radio signals, persistently staying on the watch for incoming calls, and periodically sending location area updates which explains why we would expect them to consume a relatively higher amount of power. LPWAN alternatives include LoRaWAN and SigFox.

LoRaWAN

LoRaWAN is an open standard administered by the LoRaWAN Alliance. It is a LoRabased networking protocol that connects devices wirelessly to the internet. It uses unlicensed ISM (Industrial, Scientific, and Medical) bands just like Sigfox ( 868MHz in Europe, 433MHz in Asia, and 915MHz in North America.) For connection to the internet, LoRaWAN makes use of a LoRaWAN Gateway which essentially connects IoT devices to the cloud. For instance, you may need to monitor water quality parameters at specific locations in a water basin; you could consider setting up wireless sensor nodes connected with LoRaWAN. Your data collection components (sensors) would be connected wirelessly to the LoRaWAN gateway, to which all data will be sent, and from which the received data packets would be forwarded to an IoT platform such as The Things Network. In LoRa, the modulation technique used is Chirp Spread Spectrum. This technique spreads a narrow-band signal over a wider channel bandwidth and as a result, noise levels are reduced. [3] The maximum payload length for messages sent over the LoRa network is 243 bytes.

SigFox

Sigfox claims to be a global leader in IoT connectivity services with its services available in 72 countries. It prides itself on its low power, long-range service that provides end-to-end connectivity service. Sigfox offers end-to-end connectivity allowing the transmission and reception of small data packets from sensors to its backend. From the Sigfox backend, the data can be routed to digital third-party applications. All networking complexity when working with a Sigfox board is managed in the cloud and for this reason, the Sigfox communications solution is quite effortless.
Sigfox technology works with the Ultra Narrow Band transmission technology, through which less energy is used to achieve longer distances of transmission. Exchange of radio messages over the air via Sigfox occurs at a frequency of 200kHz. Each message sent is 100 Hz wide and the rate of data transmission is about 100-600 bits per second (100bps for Europe and 600bps for the U.S.). Hence, reducing the problems of the noise over long distances and increasing its robustness. For modulation, Sigfox uses Differential Binary Phase-Shift Keying (DBPSK) in the uplink and Gaussian Frequency Shift-Keying (GFSK) in the downlink[3] [4].
Sigfox technology allows for uplink transmission of upto 140 messages a day by a single registered sigfox device, with the payload size for each message being 12 bytes. Downlink, only four messages can be transmitted in a day with a limited payload size of only 8 bytes. This technology uses unlicensed ISM bands.

Conclusion

After this brief introduction to cellular IoT, LoRAWAN and Sigfox as technologies for the deployment of IoT systems, the next step is going to be to perform experiments with the aim of developing comparisons based on factual information and provable experimental results to know which of the three mentioned technologies will serve the lower device cost, which one will provide the highest coverage, and which one will be more costly in terms of power consumption. This will be done through implementation of IoT based water resource monitoring systems using the three different technologies.

References

1. Mekki, Kais, et al. "A comparative study of LPWAN technologies for large-scale IoT deployment." ICT express 5.1 (2019): 1-7.
2. Mangalvedhe, Nitin, Rapeepat Ratasuk, and Amitava Ghosh. "NB-IoT deployment study for low power wide area cellular IoT." 2016 IEEE 27th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC). IEEE, 2016.
3. Reynders, Brecht, Wannes Meert, and Sofie Pollin. "Range and coexistence analysis of long range unlicensed communication." 2016 23rd International Conference on Telecommunications (ICT). IEEE, 2016.
4. Sigfox Technology. Available at https://www.sigfox.com/en/whatsigfox/technology#:~:text=Sigfox%20uses%20200%20kHz%20of,with%20DBPSK% 20and%20GFSK%20modulation.

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