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The reasons why it is expensive to connect IoT devices to a mobile telephone network
The capabilities of the new LoRa technology, which operates in licence-free bandwidth
The choice of components and modules available to OEMs for developing LoRa-certified equipment
The vision for the Internet of Things (IoT) sees billions of devices connected to the internet, each with its own IP address. A connection to the universal network enables even the simplest of devices, such as sensors in a factory or LED lights in a home, to continually upload small bursts of data in real time, and to act on commands sent by a remote controller.
The technology to accomplish this exists today. The IPv6 protocol supports a practically unlimited number of individual IP addresses. And through wired and wireless communications, a connection to the internet can be made in almost every inhabited place on the planet, and in many that are not inhabited.
One barrier to the realisation of this vision, however, has so far received too little consideration: the economic model for connecting wire-free, mobile or hard-to-reach devices to an internet access point. While mobile telephone network coverage might be almost universal in the industrialised world, a mobile data service plan comes at a high price. That’s fine for expensively employed humans such as sales people or field service technicians, and for expensive assets such as shipping containers.
But for millions or billions of tiny devices such as sensors or actuators? Today, the cost of a mobile telephone connection is totally out of proportion with the cost of the device. And that is why device OEMs should take note of a proven new technology for wide-area wireless networking, and ensure that new device designs are able to take advantage of the much cheaper connectivity option which it is set to provide.
The high cost of service plans
The internet is transport-neutral. A device may connect via a wired Ethernet network in an office, a Wi-Fi® access point in a home, or through a mobile telephone mast from a farmer’s field: the internet treats them all equally.
In a wireless sensor network or similar IoT application, therefore, users will normally want to choose the lowest-cost feasible means of connection. This will normally be a Wi-Fi or ZigBee® (wireless) or Ethernet (wired) connection where available. These are not available to remote or mobile devices, which today rely on a mobile telephone network to provide access to the internet.
But when a typical cellular telephone data service plan costs some $25 per month per device, the financial model for wireless sensor networks might not add up. In fact, the situation promises only to get worse, as Mobile Network Operators (MNOs) are keen to switch off their legacy 2G GSM networks. Consumer demand drives the business strategies of the MNOs, and this demand is for very high download rates to support video streaming, file sharing, photo sharing and other popular applications. So MNOs are pouring investment into the roll-out of 4G LTE networks, which offer wide-area mobile broadband capability.
By contrast, the old 2G networks offer far less attractive revenue opportunities: MNOs would prefer to eliminate the cost of maintaining and operating old 2G equipment and carry all data traffic on the newer 3G and 4G networks. But the higher data-rate service plans available on 3G and 4G networks are even more expensive than the basic offerings, putting mobile telephone airtime even further out of the reach of wireless sensor networks.
Today, then, some device manufacturers are tending to implement a compromised version of the IoT. In a gateway architecture, remote or wire-free devices connect wirelessly to a fixed gateway. The connection to the gateway may be via a technology such as Wi-Fi, Bluetooth® Low Energy or ZigBee: licence-free, and with no airtime cost.
The gateway might have a fixed-line link to the internet, or it might require a mobile telephone connection to access the internet, but in this case the high cost of the service plan is shared among the tens or hundreds of devices which use the gateway.
This architecture may be suitable for some applications, but it has its drawbacks. The chief one is the limited range of the link between the node and the gateway: Wi-Fi, Bluetooth Low Energy and ZigBee all have a limited point-to-point range of typically less than 100m. A complex mesh network topology, which is supported by the ZigBee protocol, might be able to extend this to some extent, but only if one node is never more than 100m from another node.
Applications in which nodes are widely distributed or mobile over a wide area, therefore, cannot rely on this gateway architecture. They need their own, dedicated, long-range link to internet access points. And today, this is normally provided by a GSM module interfaced to a mobile telephone network, as shown in Figure 1.
Low-cost wide-area wireless networking
Today, then, the problem for the industrial device OEM is that there is only one wireless technology which provides practically universal coverage: the mobile telephone network. Other existing technologies, such as Wi-Fi, Bluetooth and ZigBee, provide local patches of coverage, but are not universal.
In the next two years, however, this is set to change. For instance, an alliance between semiconductor manufacturer Semtech and IBM is behind a programme to install low data-rate radio transceivers, operating in licence-free (ISM) frequency bands between 860MHz and 1020MHz, on mobile phone masts worldwide.
This new radio network will provide a wireless channel between devices and the mast, independent of any mobile telephone network. At the mast, traffic will be routed on to the same backhaul infrastructure used by the mobile telephone networks, providing a data pipe to the internet. Once on the internet, the data may be stored and processed in the cloud. Typically the cloud service will be provided by a third party such as Amazon, or a specialist M2M data service provider.
Crucially, the cost of using the Semtech/IBM network for periodic low data-rate communications is expected to be far lower than the cost of using mobile telephone networks.
A huge saving on the mobile telephone networks’ $25 monthly cost-per-device is possible because:
- the Semtech/IBM radio transmissions occupy licence-free bandwidth
- the network equipment is optimised for low data-rate sensor and actuator applications
- the radio concentrators can take advantage of existing masts, eliminating the need for major construction and commissioning costs, as shown in Figure 2.
At the heart of the new network is Semtech’s Long Range (LoRa™) technology: a patented modulation scheme that, at low data rates, provides a link budget of up to 157dB, and has been proven to work reliably in semi-rural environments over a range of 15km. Given that mast-mounted mobile phone transceivers in such environments are normally designed to serve cells with a maximum 10km radius, the range of LoRa transceivers is comfortably long enough to provide for universal coverage when mounted on existing mobile phone masts.
The possibilities opened up by this new LoRa network are exciting a great deal of interest in the industry. Already Microchip, MultiTech and IMST have announced that they are developing LoRa transceiver modules, and MultiTech and Kerlink are developing concentrators, for mounting on mobile phone masts.
And IBM itself has made its Mote Runner software development kit compatible with the SX127x series of LoRa transceiver ICs from Semtech. This means that OEMs’ LoRa-based systems will be able to use Mote Runner in their product development. Mote Runner provides an open and programmer-friendly platform for developing the software to connect and control wireless sensor and actuator nodes.
A 5,000-node trial LoRa network is already under way in France, and another 2,000-node trial is taking place in Swindon, UK. Outside Europe, several trial networks are taking place in the US, backed by the mobile telephone industry.
With the heavyweight backing of IBM, the technology seems highly likely to gain the support it needs from MNOs and others. Nationwide coverage in some European countries and in the US is expected to be achieved by the end of 2017.
Implications for device OEMs
So what does this mean for device OEMs? At a low monthly cost per device, many users of sensors, actuators and other industrial devices will derive enormous benefits from universal wireless internet access. There are applications in many fields:
- personal medical treatment, for instance tracking sufferers of Alzheimer’s disease when away from home
- forestry and agriculture, for instance implanted sensors in farm animals to alert farmers to bodily changes which indicate an animal is ill, distressed, or ready to give birth
- machine telemetry, to allow the virtual monitoring of the operation of machinery in remote locations
- transportation, for instance for asset or fleet tracking
And while the proposed LoRa network is not universally available, the technology to support it is available. Semtech’s SX127x LoRa transceiver ICs for devices are available in production volume from Future Electronics. LoRa transceiver modules from Microchip and MultiTech are also available from Future Electronics.
Therefore device manufacturers should consider carefully the case for future-proofing their products by building in LoRa capability now. Any device which today carries a mobile telephone transceiver module will also carry the high monthly cost of a mobile telephone data plan. A device with LoRa capability built-in can enable the user to switch from a mobile telephone network to a LoRa network as soon as the latter is available, and instantly start benefiting from very large monthly cost savings. This will provide a huge competitive advantage.
The alternative, of waiting until the LoRa network is fully operational before implementing LoRa in slave devices, ties today’s customers in to the mobile phone networks’ high data charges indefinitely.
The LoRa revolution is coming, and it makes most sense to prepare IoT products to use it now.
The LoRa™ name and associated logo are trademarks of Semtech Corporation or its subsidiaries.