The Weightless SIG is working on a new standard for a low-power wide area network (LP-WAN) scheme targeting a class of applications for the Internet of Things (IoT) that cannot be served by established wireless networks such as WiFi or ZigBee. The Weightless-P standard aims to provide bi-directional communications between mobile, battery-powered devices and base stations over distances up to 2km in a challenging urban environment. Based on field-proven technology developed by SIG member M2Communication (M2COMM), the standard is expected to be ready for release in Q4 of 2015 with first hardware available in early 2016.
The Weightless story originally began with a scheme that targeted re-use of television “white space” as its operating frequency, The SIG's CEO, William Webb, told EE Times in an interview. “That was Weightless-W,” said Webb, “but the availability of whitespace hasn't developed around the world and so that protocol has been shelved until such time as the channels become available.” The SIG subsequently developed the Weightless-N standard, which went live in May, targeting lowest-cost, one-way communications at low data rates from IoT devices to a base station over a distance up to several kilometers.
“But there is a whole set of applications that need two-way communications,” Webb said, “for acknowledgement of messages, software updates, and the like. Or they need a higher data rate than –N provides. Weightless-P is aimed at these markets.”
According to the Weightless SIG website, Weightless-P will operate in the unlicensed, sub-GHz ISM bands using narrow-band channels and FDMA+TDMA modulation in 12.5 kHz channels. The base stations with which IoT devices communicate will be time-synchronized to manage radio resources as well as handle handover to allow device roaming. The data rate available for communications will be adaptable, from 200 bps to 100k bps depending on link quality and resource availability.
When asked about the aggressive timeline proposed for the standard's readiness, Webb pointed out that many of the technical elements are already in place. “Weightless-P will reuse a lot of the principles in the –W MAC layer,” said Webb. The physical layer, he added, is based on the RF technology of M2COMM, but with expanded range.
Fabien Petitgrand, technical spokesperson for M2COMM, told EE Times that its original technology aimed at a medium range of about 100m, to provide indoor coverage for its IoT devices: digital price tags. These tags replace paper price markers on store shelving with e-ink or LCD displays so that stores can adjust product pricing wirelessly. Other active applications for the technology include informative displays on production batches in a factory, indicating their status and next steps needed. Because the communications are two-way, these displays can also incorporate sensors that monitor the environmental status of items. Two-way communications also allows for authentication of message traffic and other security features that one-way communications cannot support.
Although the Weightless-P stems from M2COMM's technology, Petitgrand said, it's not a wholesale copy.