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LPWA: Things in Search of a Network

Marco Hogewoning — 20 Jun 2016
Last week I had the opportunity to visit the LPWA IoT Networks Event in Amsterdam, a two-day conference dedicated to the use of low power wide area (LPWA) wireless networks that lie behind many Internet of Things (IoT) solutions that are entering the market.

 

Both the conference programme and the accompanying trade show offered a complete overview of the different technologies available alongside countless examples of successful deployments as well as innovative pilots. Inside the conference a lot of time was spent highlighting the benefits of the different technologies and how to establish the best match between radio technology and specific applications based on technical and business requirements.

Two ends of the spectrum

The principal divider among the available solutions is spectrum management, where you have the choice of using a licensed spectrum band or making use of the license-exempt frequencies available in the ISM (industrial, scientific and medical) radio bands. These are the frequencies that also power your Wi-Fi connection and probably - if you have one - the remote control of your garage door.

Most of the licensed spectrum for IoT connected devices is available in the form of GSM appointed frequencies and, with a limited number of license holders in each country, usually requires using an established GSM operator for the connectivity requirements. This is in strong contrast to the ISM unlicensed applications, with which you could build and operate your own network, provided you adhere to the published technical regulatory constraints.

A broad band of standards

The two main standards developing organisations active in the physical world of wireless connection are the 3 rd Generation Partnership Project (3GPP) , who develop mobile phone standards, and the IEEE 802 working groups who, among other things, maintain Bluetooth, Wi-Fi and a variety of other protocols that make use of the license-exempt spectrum.

Most noticeable among these standards are the IEEE 802.15.4 standard, upon which most of the license-exempt solutions are based, and in 3GPP the recent emergence of the NB-IoT standard that is due to be released. Next to those, there is the IEEE 802.11ah standard that by using sub 1 GHz bands extends the range of the Wi-Fi protocol, and specific amendments such as Extended Coverage GSM (EC-GSM) that aim to re-purpose existing GSM networks for use in long range and low power environments.

Power is the primary factor

Many IoT applications rely on small battery-powered sensors and actuators that require a life expectancy of five to ten years. In such applications the power used to send or receive radio transmissions has to be limited, with devices going into some form of hibernation for prolonged periods in between scheduled activity. This is where most of these dedicated IoT standards make the difference, as they allow devices, using a limited burst of energy, to transmit a small data packet over a relatively long range that can extend to 20 km or more depending on a number of external factors.

Bandwidth and other communication requirements

In addition to reducing power consumption, the decisive factors in choosing a particular technology or protocol are the amount of data transported, the frequency of those transmissions and sometimes the transmission time. While most network technologies offer some form of acknowledgement that a transmission was received on the other side, the actual guarantees of the speed of delivery and reliability vary greatly. One can naturally expect that the use of licensed bands offers a greater level of control, which is translated in products that are supposed to support a higher quality of experience. This is a claim that is subject to much debate.

Pick your technology

Where the three main technology leaders all offer solutions in long range and low power, there are significant differences in their business models.

While the 3GPP standards are open, the use of licensed spectrum in practice means that you will always have to partner with a network operator that has a license. This dependency is balanced by the fact that the network can offer additional services towards authentication and authorisation of devices.

Of the technologies that operate in license-exempt bands, the two main leaders are the LoRa Alliance and Sigfox . Both are based on IEEE 802.15, and the most significant difference between the two is that LoRa allows you to build a network using your own transceivers, whereas Sigfox only operates with a select group of partners that provide the carrier service. It has to be noted that while LoRa allows you to deploy your own network of base stations, several large carriers in Europe provide a nationwide network of receivers on which capacity can be acquired.

Both technologies operate in a similar fashion where the messages received from the devices are transported over the Internet to a cloud platform where they are stored and made available to the application provider for further processing.

Does it run IP?

Naturally, as it is called the Internet of Things, one would expect that these technologies incorporate the Internet Protocol. While it is true that many of the narrowband solutions offer support for 6lowpan, a variant of IPv6 that is especially designed for use in these resource-constrained environments, it is often left as optional for the application provider. This means that, despite a passionate call from one of the LoRa founders about the need to support IPv6, not many of the LoRaWAN based applications do support IPv6. Often the role of IP is limited to providing the transport between the base station and the central server cluster, where the limited deployment of IPv6 in networks means that many choose to build their applications based on IPv4.

A positive exception is formed by the Wi-SUN alliance, a group that develops smart utility applications based on IEEE 802.15.4 and who support and deploy IPv6 by default in their networks and applications.

Finding a business

In conclusion, there appears to be a number of choices that from a technical perspective all offer a very similar set of properties. With endless possibilities to develop new innovative applications, it means that the choice for a particular solution has to be made on the business side. Questions such as dependence on carriers or suppliers, coverage in potential markets and, ultimately, cost are likely the more decisive factors in picking one.

Of course, there remains the choice to future-proof any solution by building in support for IPv6: a choice that unfortunately many have yet to make.

 

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