Low Power Wide Area Networks for IoT: SigFox, LoRa, LTE-M, 5G LP-WAN

[In collaboration with guest blogger Marc Espinosa]

The important topic of connectivity protocols was discussed in our previous IoT post, it is time to dive deeper into the telecommunications protocols underneath. The fact is that the technologies that enable the IoT architecture need to assume low power at the same time as the transmission via the long distances (meaning - lower frequencies). 

For example, if we need to cover a field, a campus, an entire building or turning a city smart, we will need a specific communication protocol. The truth is that ZigBee and 6LoWPAN do create a low-power and low-cost WPANs, but since the assets can be distributed in an pretty wide area - we need to include another variable to the equation: the range.

The following networks/technologies are called Low Power Wide Area Networks (LP-WAN). Regardless of the fact that the consumption of devices they are connecting is low, they actually cover a wide area network, making things easier and better to connect from one point to another:

As you can appreciate, there are two new agents in the network ecosystem: LoRaWAN and SigFox. Both are called LPWAN and as you can realise they cover from 150 to 500 times in suburban or rural areas (respectively) the maximum range that ZigBee is offering. 

These two characters have been competitors in the LPWAN space for several years. The business models and technologies they use are different, but the targets are very similar: mobile networks adopting their technology to deploy IoT solutions.

Even though LoRa and SigFox serve similar markets, the first option is more likely if you need bidirectionality, because of the symmetric link (if you need to command-and-control functionality, like an electric grid monitoring). 

However, for applications that send only small and infrequent bursts of data (like alarms and meters) I would recommend the second one or ultra-narrow band technology that can hold a 2-way transport message as well (3*).

When we talk about mobile networks we can’t forget talking about NB-IOT: a LPWAN Narrow-Band radio technology standard that has been developed to enable a wide range of devices and services to be connected using cellular telecommunications bands. It has been designed for the IoT, standardised by the 3rd Generation Partnership Project (3GPP), a collaboration between groups of telecommunications associations.

To sum up all this content let’s group it into a table that explains qualitatively the LPWANs takeaways (4*).

To conclude, let’s highlight the key takeaways for the 3 low-power networks:

• SigFox : extremely low power and bandwidth, kind of open standard due to you have to use their own network, easily tradable, limited security but it’s got some and lot of deployments.
• LoRa: driven by a chip company (Semtech) so they want you to but the maximum number of chips. Not quite as low power as SigFox but pretty good too, it has more bandwidth to make control functions and send good data streaming, not an open standard as commented because you have to use compulsory the Semtech chip (in my opinion I consider this point as weakness because you are forcing your client to buy your product instead of you understanding the market needs), there are a lot of suppliers willing you to use Semtech chips, pretty good security (they do all the basic authentication), and several deployments
• NB-IoT: a technology that mobile operators carry on, very low-power and bandwidth, similar to SigFox but not as deployed as the ultra-narrow band network, it is an open standard because it is part of the 3GPP, lots of suppliers because it is open, solid security and authentication and some deployments (Vodafone with Huawei did the  first commercial PoC that took place in Madrid using Vodafone Spain’s network on the September 19th 2016). There is another network called LTE-M (Long Term Evolution-Machine) that is pretty similar (open standard as well) to NB-IoT: not as power efficient as NB-IoT but best security. Low deployments but they are going to grow exponentially hand in hand with NB-IoT.

The question is: which of these is the IoT network of the future? Will LoRa and SigFox be able to survive if 5G standard includes the IoT-WAN? IoT is a big market, in our opinion - there´s a place for everyone, we just need to wait and see what happens.

Understanding the IoT Protocols: MQTT, CoAP, ZigBee

[In collaboration with the guest blogger, Marc Espinosa]

Let's start with the messaging protocols, MQTT and CoAP, and consider which of the following open standard protocols should be considered for your implementation.

If you're looking for the right guide to gain a solid perspective of the IoT business, these lines might just be what you need. The IoT can be defined as the a system of interrelated devices (such as sensors) that are provided with unique identifiers and the ability to transfer data over a network without requiring human-to-human or human-to-computer interaction.

So, how do all these "Things" speak among them? Which are the languages/communication protocols they use and which one should we choose? The answer might surprise you... it depends!

There are 2 types of open standard protocols that work for small devices:

• Message Queuing Telemetry Transport (MQTT)
• Constrained Application Protocol (CoAP)

MQTT and CoAP are two of the most promising protocols for small devices such as sensors. Both are:

1. Open standards lightweight protocols very useful to cover the IoT needs
2. They suit to constrained environments better than HTTP does
3. Provide mechanisms for asynchronous communication
4. Run on IP
5. Have a range of implementations

The main differences between these two protocols are shown in the table below:

None of these protocols applies to all the cases, both have their pros and cons. Choosing the correct one depends on your application.

Let's proceed with a second group of Protocols: ZigBee and 6LoWPAN for sensor Networks

As a curiosity, the name ZigBee comes from the communicative erratic patterns that the bees do. This looks back on the invisible networks and their respective connections. ZigBee is an IEEE standard 802.15.4 (a technical standard that defines operation of low-rate WPANs) based specification for high-level communication protocols used to create WPANs, operating at 2.4 GHz targeting applications that require relatively infrequent data exchanges at low date-rates over a restricted area and within a 100m range.

The technology defined by ZigBee is simpler and less expensive than other WPANs such as Bluetooth and WiFi. ZigBee is a low-cost, low-power, wireless mesh network standard 3 targeted at the wide development of long battery life devices in wireless control and monitoring applications. Their devices have low latency, which further reduces average current. The following diagram shows the ZigBee meshed architecture and all sort of devices on the network

To sum up, ZigBee was developed to satisfy and provide a standards-based protocol for interoperability (applications do not need to know the constraints of the physical links that carry their packets) of sensor networks. And guess what? A competitor came up in the market: 6LoWPAN

On the other hand 6LoWPAN which is an acronym for IPv6 3 over Low-Power Wireless Personal Area Networks, originated from a working group in the IETF.

Their products have entered the marketplace as ZigBee’s competition, as it can utilize 802.15.4. Moreover, it can run on other PHYs (physical layer of the OSI model, and it refers to the circuitry required to connect a link layer often called MAC to a physical medium such as a cable).

Let’s make a more detailed comparison to be able to see which fits best or the most used connectivity protocol nowadays and why.

On the one hand, ZigBee’s wireless interoperability protocol defines the communication between 802.15.4 nodes and then defines new upper layers all the way to the application. This means ZigBee devices can interoperate with other ZigBee devices, creating in my opinion a bit more constrained network at a glance.

On the other hand, 6LoWPAN offers interoperability with other 802.15.4 wireless devices in addition to any other IP network link (Wi-Fi or Ethernet) with a simple bridge device. Although bridging between non-ZigBee and ZigBee networks requires a more complex application layer gateway. The key requirement for IPv6 over 802.15.4 is that the maximum transmit unit (MTU) must be at least 1280 byte packets.

In terms of security, both connectivity protocols benefit from built-in AES128 encryption, which is part of the IEEE 802.15.4 standard.

Finally, and trying to get a conclusion of which goes first on the race, we can affirm that all the major players in the semiconductor industry promote and supply 802.15.4 chips which can be used for either ZigBee or 6LoWPAN, but these same companies even offer free ZigBee stacks. So, the support for 6LoWPAN stacks seems to be trailing behind ZigBee. 

Concluding, 6LoWPAN is pretty attractive, since it is IP based. Nevertheless, ZigBee appears to be more popular and has been adopted by major players in multiple industries, and the ZigBee alliance just introduced ZigBee IPv6 end-to-end networking to create a cost-effective and energy-efficient wireless mesh network.