Do you have an Apple iOS or Google Android phone? At a high level, the answer hints at which you might prefer for your long-range, low-power IoT network deployment: LoRaWAN or Sigfox. Both are battling hard to get the attention of IoT solution providers.
As discussed previously, LoRaWAN’s LoRa Alliance had a big gathering in Philadelphia to showcase its technology and partners, but Sigfox has been busy too. Last month it announced a partnership with WND-UK to deploy Sigfox technology across up to 95% of the UK, and it’s currently preparing for its first Sigfox IoT World Expo in Prague, Czech Republic (September 25-26).
Sigfox and the LoRa Alliance are competing with cellular network providers’ LTE-M and Narrowband IoT (NB-IoT) to get low-power, long-range IoT connectivity into the hands of solution providers and out into the market to solve real-world problems, from smart agriculture to smart cities. They both have the advantage of being unlicensed but that’s where the commonalities end.
LoRaWAN started as an open platform but it meandered for a number of years, in large part because it had only a single IC provider, Semtech, which developed the technology. That has changed, with the addition of Microchip, Renesas and STMicroelectronics, to the ecosystem, thanks to an increasingly active LoRa Alliance.
On the other hand, Sigfox has been deploying aggressively, from its start in its home country of France (Figure 1).
Figure 1: The areas in blue show where Sigfox is actively deployed, most densely in Europe, but spreading quickly across the Asia, Australia, New Zealand and the United States. (Image source: Sigfox).
Its model is to enable independent network operators to get up and running quickly using a “coverage as a service” model while supporting them with clearly defined technology and operator exclusivity for an agreed-upon region. For example, Thinxtra has an exclusive Sigfox operator for Australia, Hong Kong and New Zealand, and currently covers 70% of the Australian population and 91% of New Zealand.
Digital Matter, a developer of telematics solutions, recently announced its partnership with Thinxtra to provide its $100 (AU) Oyster GPS tracking device across Thinxtra’s Sigfox coverage area for developers of IoT solutions.
The Oyster operates for 5 years off three AA 1.5-V lithium batteries using 2G or 3G networks, but it is likely that battery life will be extended using Sigfox’s network technology. The Oyster comes in a rugged IP67-rated housing and can be managed through the Telematics.guru platform, or through the customer’s cloud platform, via a simple API from the Sigfox back end.
As a result of the deployment agreement, Digital Matter has attracted interest from the Europe, South America and the United States.
Link Budget is Critical for Wireless Networks
Besides an aggressive rollout and unique business model, Sigfox’s approach to technology is also interesting. At a base level, it uses ultra-narrowband, very-low-bit-rate D-BPSK modulation for the uplink to transmit at 100 or 600 bits/second, depending on the region of operation. With D-BPSK, one Hz is used to transmit 1 bit, so 100 bit/s will require 100 Hz.
Where Sigfox really differs from LoRaWAN is that the bulk of the complexity and component cost required for signal transmission and detection is pushed to the highly signal-sensitive basestation, so the remote nodes can be very simple, low power and low cost. The sensitivity ranges from -142 to -134 dBm, for 100 bits/s and 600 bits/s.
At 100 bits/s, when radiating at 16.15 dBm EIRP from the transmitter, and with a basestation antenna gain of 5.15 dBi, this translates to a theoretical link budget of 163.3 dB. The theoretical link budget for LoRaWAN is 157 dB. That’s a big difference (+3 dB = 2x power level increase). Note, this difference between LoRaWAN and Sigfox link budgets depends on the regional EIRP power-emission limits.
While there is much that can be done to improve performance, the link budget for any wireless interface is a critical consideration, and it depends upon the operating frequency, modulation scheme, coding rate and receiver sensitivity. LoRaWAN and Sigfox differ in the latter three, hence the difference in link margin.
However, everything involves a tradeoff. IoT solution providers need to look closely at what they’re giving up for that larger link budget, both technically and from a business model point of view. Engineers and developers tend to like the freedom Android provides to innovate, while business leaders prefer the simplicity of an Apple iOS-like walled garden with controlled, deterministic, technology roadmaps. Both have pros and cons, but we’re in the early days of IoT and devices need to get connected, so don’t get too stuck in analysis paralysis.