What is Weightless?
Weightless is one of many viable players in the low power, wide-area network (LPWAN) space. The Weightless Special Interest Group (SIG) offers three different protocols— Weightless-N, Weightless-W, and Weightless-P—that support different modalities and use cases. Below, we’ll introduce and discuss each of these protocols, examine a few benefits and considerations, and look at some differences and similarities between Weightless and its competitors in the LPWAN space.
The Weightless Standards
The Weightless-W Standard
This Weightless-W open standard is designed to operate in TV white space (TVWS) spectrum. Weightless-W is an offshoot of what Neul was trying to develop before they were acquired by Huawei. Using TVWS is attractive in theory, because it takes advantage of good ultra-high frequency (UHF) spectrum that’s not otherwise in use. However, in practice, it can be quite difficult. For one, the rules and regulations for utilizing TVWS for IoT vary, and it isn’t available everywhere. Also, end nodes are typically designed to operate only in a small part of the spectrum, and it’s simply impossible to build a small antenna that can go anywhere from 400 mHz to 800 mHz. In one city you might have a 500 mHz channel available, while in another you might have a 700 mHz one available, and the RF system cannot adapt to accommodate both of them (antennas, front ends, etc). Therefore, TVWS sounds good in theory, but can be lacking when it comes to application.
TVWS aside, the Weightless group uses a lot of pretty sophisticated modulation for the Weightless-W standard, including quadrature amplitude modulation (QAM), with spreading codes that allow for a large range of link budgets. Together, these modulations provide an interesting service layer with really high data rates, which makes it a very interesting standard.
Weightless-W is ideal for use in the smart oil and gas sector, because there is likely TVWS available.
The Weightless-N Standard
Weightless-N is an ultra-narrowband system that is very similar to SigFox. You can think of it as a LoRa Alliance-based version of SigFox. Instead of being a complete end-to-end enclosed system, it’s made up of a network of partners. It uses the same modulation type—differential BPSK—in narrow frequency channels, and is intended for uplink sensor data.
Nwave—an IoT hardware and software developer—is the driver behind the Weightless-N line. Some of the disadvantages of Nwave over, for example, a LoRa based system, are the requirement for the temperature compensated crystal oscillator (TCXO) and the relatively unbalanced link budget. This can be problematic because you’re getting much higher sensitivity going up to the base station than you are coming down to the end node. These types of systems generally need to rely on a simpler FSK downlink message.
The Weightless-P Standard
Weightless-P—which is expected to launch in early 2016—is the latest Weightless technology. It offers two-way features and quality of service tiers, which we think is very important. In terms of the underlying technology, it’s 12.5 kHz channel is relatively narrowband. Weightless uses Gaussian minimum shift keying (GMSK), which is a more standard modulation, and quadrature phase shift keying (QPSK), which is much more advanced. Unlike Weightless-N and -W, Weightless-P doesn’t require a TCXO because of the wider-band MSK.
ubiik—an industrial IoT technology company— has emerged as a leader the development of Weightless-P. The range for Weightless-P is currently quoted at roughly two kilometers, and unlike Weightless-N, it probably won’t be suitable for wide-area networks. This is because the receiver sensitivity of a 12 kHz minimum-shift keying (MSK) channel is not going to be anywhere close to what you get in a narrow BPSK channel.
Weightless-P is ideal for private networks, more sophisticated use cases, and things where both uplink data and downlink control are important.
Benefits & Considerations
Cost, Capacity, & Oscillation
The base station for narrowband signals is more complex in Weightless protocols, because it’s based on software defined radio (SDR) hardware. This creates hundreds to thousands of small binary phase-shift keying (BPSK) channels. This allows you to get lot of capacity out of the architecture, but it creates a more expensive base station.
The Weightless-N end nodes can also be more expensive, because they may require a temperature compensated crystal oscillator (TCXO) instead of a simple crystal. The TCXO is required so when the temperature varies at the end node, the frequency remains stable and doesn’t drift. LoRa, on the other hand, is very forgiving to bad oscillators (or crystals with a lot of drift).
The ranges of Weightless-N and Weightless-W are around five kilometers in urban environments. You need a positive signal-to-noise ratio (SNR) to detect these signals, but there is much lower noise in small channels, which makes this kind of range possible. Coded signals with processing gain generally need a wider channel, so they have a higher noise level, but you can detect signals that are below the noise floor, which leads to other advantages. Weightless-P will offer a range of around two kilometers.
According to the Weightless group, “It is critical that the technology is an open global standard rather than a proprietary technology in order to guarantee low cost and low risk, and to maximize user choice and ongoing innovation.”
While we believe standards are important, the most important thing is to get customers to market. Whether you use Weightless, SigFox, LoRa, Symphony Link, or LoRaWAN, the most important thing right now is getting an end-to-end solution out the door.
Weightless-N vs. SigFox
Weightless-N and SigFox are similar from a technology perspective, but they’re very different from a go-to-market perspective. Weightless is a standard, so it’s up to another company to create an IoT solution around it. (As we mentioned, N-Wave is the leader in this space, and it sells a lot of hardware for Weightless-N to companies trying to create a Weightless network.) On the other hand, SigFox offers a complete out-of-the-box solution.
Weightless vs. LoRa & LoRaWAN
Weightless and LoRa offer very different means to an end from a technology perspective. But functionally, LoRaWAN and Weightless-N are very similar, particularly because both are uplink-focused data systems.
If LoRa is not attractive to a user because the radio silicon is solely sourced from Semtech, Weightless is a good alternative of something based on an available standard. The challenge for engineers or firms will be determining how to build an IoT system around it.
Weightless-P vs. Symphony Link
Link Labs and Weightless-P are both going after very similar use cases, like private networks, with their Symphony Link and Weightless-P standards. Symphony Link’s range performance is arguably better because it uses LoRa instead of MSK.
Frankly, we don’t know as much about Weightless as we’d like to—and we’re really interested in learning more. If you’re an expert in the space, get in touch with us, because we’d love to fill in some blanks and learn more.
We hope this article has helped you answer the question, “What is Weightless?”. If narrowband solutions are attractive to you, Weightless-N is certainly a technology to consider. If you know your market will have available TVWS, Weightless-W is really interesting, and it is worth looking at. Weightless-P looks like an exciting new LPWAN protocol as well, and we’ll be watching its launch in 2016. The only caveat: It is unclear to us just how much of Weightless is about standardization, and how much is about pushing the agenda of a specific vendor over another. This is always a risk in open standard organizations, and it should thus be carefully considered.