Professor William Webb, chief executive of the Weightless SIG, discussed this during his presentation to the recent New Electronics conference at the Electronics Design Show. In his view, the IoT is about three things: collecting data, transmitting that data, then processing it. “Sensors are no problem,” he said, “neither is cloud computing. The problem is how to get data from the sensor to the cloud.”
Prof Webb noted that wireless is the obvious way to transmit data and that it should present few problems to application developers. But he highlighted four issues that constrain the solution. “Devices need extremely long battery life, they need to be low cost, they need to access good coverage and they have to applicable globally.” In his opinion, there are no agreed standards that will help the IoT to move forward.
“At the moment,” he said, “deployment is slow and it doesn’t look like we’ll see 50bn devices deployed in the near future. But something will happen to bring this exponential growth – and that will be coalescence around one wireless standard.”
He believes when this happens, developers will be able to select ‘Chip X’, which will cost $1 or less and which meets a wide range of application needs. “But we have to decide on that wireless standard first,” he warned. “Writing standards is easy; getting competitors to collaborate is much harder.”
In Prof Webb’s opinion, a standard will only become successful when companies believe in it. Before that happens, he told the conference, there will be standards battles between ‘bad standards, multiple standards and proprietary standards’.
One company which is taking the latter approach is Sigfox. The French company, established in 2009, had come to the same conclusion as Prof Webb. According to vp of communications Thomas Nicholls: “All the pieces were coming together, except for connectivity. It was still too complex, too expensive and too power hungry. We wanted to lower these barriers and maybe to get rid of some.”
Nicholls said Sigfox had evolved from the M2M sector, founded by people who were frustrated with technology and the fact it didn’t get to the expected volumes. “The founders started from a blank sheet of paper to develop an ideal connectivity solution. Telecomms companies or Wi-Fi providers can’t start from that point.”
Where the Sigfox approach differs from others is in its business model. “There are no borders in the IoT,” Nicholls asserted. “What users need is integration and the ability to connect from anywhere. What they don’t need to worry about is the network.”
Sigfox is a subscription based service, with data handled by a network rolled out by partners in various countries; in the UK, the company is working with Arqiva. “Partners roll out the physical network,” Nicholls continued, “then become distributors of subscriptions. And the subscription gives users access to the same service.”
The US is a major target for the company, but it has yet to find the right partner so has started rolling out the network itself. “We have recently signed a subscription for 1m connections with company which monitors 120m utility meters,” Nicholls said.
While Sigfox continues to roll out its network, it claims users can expect good coverage. “There are three elements,” Nicholls explained. “Where the device is, whether it’s indoors or not and how well the antenna has been designed. We provide a tool that lets users know what coverage they can expect.”
The Sigfox network is created as a collaborative star. “That’s the opposite to the mobile network,” Nicholls pointed out, “where the network decides everything and instructs devices how to behave. In a Sigfox network, devices have no knowledge of the network; the messages they transmit will be picked up by all basestations in proximity.”
Data is transmitted using ultra narrow band communication in the 868MHz band in ETSI countries and 915MHz in FCC areas. “The ISM bands are used for all kinds of things,” Nicholls continued, “but we only need a small part of the spectrum.”
While Sigfox might have created a proprietary solution to the IoT challenges it perceives, the solution takes advantage of readily available hardware. If users want to access the network quickly, they can buy Sigfox modules from the likes of Telit. “If you want to optimise communications, you might want to use an SoC from a company like Atmel,” Nicholls noted, “and if you want to go all the way to a device that costs less than $2, you can go to companies like Texas Instruments, Silicon Labs and ST, for example. All have transceivers available that weren’t built for Sigfox, but which can run a compatible software protocol.”
And it’s possible to retrofit Sigfox capability to existing devices. “Securitas in Spain monitors more than 1m alarm systems using 3G communications. The systems also feature a TI chip for local connectivity. Securitas has used the 3G channel to send a firmware upgrade which contained the Sigfox protocol and installed this over the air.”
While it’s still relatively early days for Sigfox, Nicholls claims the company’s network is now handling data from ‘hundreds of thousands’ of connected devices and adds that it has sold 5m subscriptions, not all of which are live yet.
“Companies care about service, cheap connectivity, longer battery life and knowing their device can communicate,” Nicholls concluded.
Low power WAN developments Two low power wide area network approaches are also being developed and both take advantage of the sub GHz ISM spectrum. The Weightless-P specification – expected shortly – will use a narrow band modulation scheme to offer bidirectional communications and what is being called ‘best in class QoS’ for the industrial IoT sector. The approach will support time and frequency division multiplexing in 12.5kHz channels, with adaptive data rates of up to 100kbit/s. It will run across all sub GHz ISM bands, allowing global deployment, and transmit power will be up to 17dBm. Weightless-P uses narrowband transmission, rather than ultra narrow band, which the Weightless SIG says could be vulnerable to frequency offset and drift. LoRaWAN is intended for wireless battery operated devices in regional, national or global networks. A LoRaWAN network will typically be a star-of-stars, with gateways relaying messages between end-devices and a central network server. Gateways connect to the network server via standard IP connections, while end devices use single hop wireless communication to one or many gateways. LoRaWAN transmits 256byte packets at data rates ranging from 300bit/s to 50kbit/s and devices will have a transmit power of up to 19dBm at the antenna. |
