One of the factors which may delay some internet of things (IoT) progress is the lack of agreement on standards for wide area machine-to-machine connectivity. As the pros and cons of licensed cellular versus long distance WiFi versus proprietary sub-1GHz solutions are debated, one of the would-be standards, Weightless, has extended its platform into new spectrum bands to boost its relevance.
Weightless was originally developed by UK-based Neul to harness the TV white space (TVWS) license-exempt frequencies. Trials have been run and Neul makes chips, but progress has been limited by the uncertainties over this spectrum. Outside the US, few countries currently allow use of the TVWS for commercial wireless data and so the economies of scale of a global platform seem far off. “We hoped that there would be an opening up of white spaces around the world,” said Professor William Webb, CEO of the Weightless SIG, in an interview with GigaOM. “That simply hasn’t happened.”
So the SIG or industry group which controls the Weightless specifications has announced a new implementation, Weightless-N, targeted at the UHF 800MHz-900MHz spectrum, which include the US’s 900MHz ISM frequencies and the 868MHz band in Europe. Although these frequencies cannot support the speeds of the white spaces version (now called Weightless-W), they are internationally open and have a wide ecosystem already.
These are also target bands for the UltraNarrowBand (UNB) technology which underpins several IoT-focused technologies, also hoping to become de facto standards. These include Sigfox, which has signed partners to deploy M2M networks in several countries already; and Senaptic, a start-up deploying systems based on Plextek’s UNB platform.
So a battle is brewing in the UHF band, which has the good coverage and penetration qualities needed for many wide area M2M networks. Weightless will have some catching-up to do, having originally made a bet on the TV white spaces taking off more rapidly than they have (and in many cases, the momentum behind them is being driven by rural broadband rather than M2M, as seen in Google’s and Microsoft’s trials in Africa). It has started work on a new air interface, necessary for the very narrow ISM bands, and the project is “being progressed systematically through the Weightless SIG working groups and is anticipated to be completed rapidly”, within a 3-6 month timeframe, with trials scheduled for the first half of 2015 and commercial deployments targeted for the end of next year.
Any would-be standard needs scale and broad support to make an impact, and Weightless is seeking this in two ways –by inviting new contributors to its effort, even perhaps rival narrowband solutions; and by extending into as many low frequency bands as possible, potentially offering a solution which IoT-minded cellcos might adopt.
In the first respect, the SIG said in its statement that it “welcomes new members to contribute to the evolution of this important new standard and invites proposals from non-members in the drafting of the specification”. More significantly, it added that it “invites companies that currently have proprietary solutions in this space to engage and adapt these to comply with the new standard”. This is presumably a call to organizations like Plextek and Sigfox to consider joining forces and creating a harmonized solution for the UHF band, dedicated to IoT rather than an adaptation of general purpose standards like WiFi and GSM.
As for additional spectrum options, Weightless will seek to steal a march by going after licensed frequencies in this band too, something it could achieve by acquiring spectrum itself or with partners; or (more likely) by licensing its platform to existing licence holders. In theory, at least, that could provide a licensed spectrum option below 1GHz which would be more optimized for IoT requirements than current licensed solutions – GSM in 900MHz and LTE in 700MHz and 800MHz. The body said: “Weightless-N will typically be deployed in unlicensed spectrum in the region 800-900MHz … It is also designed to work in licensed spectrum around these frequencies.”
There is a potential market for such a solution in IoT markets, such as smart metering, whose requirements are so different from the mobile broadband assumptions behind the design of LTE. These applications revolve around absolute reliability and ubiquity, but often transmit only small amounts of data on a periodic basis. Platforms such as Sigfox’s are optimized for that type of usage, but they are confined to unlicensed frequencies.
Many applications would do best in licensed spectrum, for security and QoS reasons, but the cellular technologies come with many question marks. GSM fulfils some coverage, cost and low-power requirements, but is unlikely to last for 10 years or more in most areas and has issues with penetration through walls and pavements. LTE has longer shelf life, and can support the minority of M2M services that require broadband, but it is optimized for mobility, which is generally unnecessary in M2M. Neither of the cellular options have driven terminals down to the cost levels claimed by Sigfox and Plextek, despite their scale. And although the 3GPP is working on LTE adaptations optimized for M2M, with low cost terminals and simplified protocols, this is part of Release 12 and so commercial availability will be at least another year to wait.
Then there is WiFi, also unlicensed-only, but with many extensions to improve its security and QoS. The 802.11ah effort is pushing WiFi from its traditional high frequency bands into the 900MHz ISM spectrum, though the standard is unlikely to be included in mainstream commercial products until the second half of 2015. However, companies are already working on pre-standard developments – for instance Greek start-up Antcor showed off silicon IP for 900MHz WiFi at this year’s Mobile World Congress. It will target home and industrial automation and will cooperate with Bluetooth or ZigBee for the “last few centimetres”.
The 11ah specification supports data rates from 150Kbps in a 1MHz band to as much as 40Mbps over 8MHz. Because of the low frequency, it can achieve at least 50% longer distances than conventional 11n Wi-Fi in 2.4GHz or 5GHz. Among the giants involved in the effort are Broadcom, CSR, Huawei, Intel, LG, Marvell, NEC, Panasonic, Qualcomm, Samsung and ZTE.
To ensure that Weightless takes its place in the pantheon of wireless IoT standards, rather than becoming a curiosity like some of its predecessors in the UHF spectrum, it will need to secure the interest of a similar line-up of silicon makers, though the real breakthrough might well be a major operator partnership, allowing it to turn its licensed spectrum developments into real differentiation.
Webb said in a statement: “Enabling the vision of 50bn connected devices requires chipset costs below $2, battery life of 10 years or more and a range of five kilometers or more to ensure ubiquitous coverage from a low cost network. The current Weightless standard delivers on this promise using the TV white space spectrum and provides a feature rich solution, but is subject to regional licensing limitations. Weightless-N aligns with Weightless values and offers geographical ubiquity, right now.”