Weightless-P Sacrifices Range and Power, Adds Speed and Flexibility

The Weightless SIG, one of a growing number of standards bodies in the market for Internet of Things (IoT) networks, is trying to balance power consumption and transmission strength with its latest wireless standard. The group recently published the Weightless-P standard, which it says provides the reliability and security of a "carrier-grade" network while consuming little power.

The new standard outlines a bidirectional network operates in the sub-GHz spectrum using FDMA/TDMA modulation and occupies 12.5 KHz narrowband channels to help reduce power consumption. To reduce interference and maintain the highest possible capacity, Weightless-P controls transmit power for the downlink and uplink. At the same time, data rates adapt between 200 bits/s to 100 kbits/s depending on the quality of the network connection. It has a roughly 2-km range.

Weightless-P has been under development since last August. Weightless SIG revealed that it had partnered with M2Communications (M2COMM), a Taiwan-based networking company, to lead the project. Development kits and hardware for Weightless-P, including base stations and endpoints, will be available in early 2016, according to a statement on the Weightless SIG website.

The Weightless-P standard belongs to a class of low-power wide-area networks (LPWAN) that are being designed for sophisticated industrial systems. In the future, these systems are expected to use thousands of wireless sensors to gather valuable data about manufacturing and infrastructure. Many industrial companies, including General Electric and Siemens, have spent the last few years working to connect machines with powerful servers that can analyze this data.

Weightless-P is the third low-power standard the Weightless SIG has developed. The first, Weightless-W, is designed to operate in the television “white space” spectrum. The more recent standard, Weightless-N, places an emphasis on an extremely wide area of coverage instead of high data rates. Though limited to one-way communications, Weightless-N supports farther range and lower power consumption than Weightless-P, which trades these benefits to a certain extent for higher performance.

In a presentation at the 2014 ARM Tech Symposia, Fabien Petitgrand, a technical staff member at M2COMM, said that low-power, low-cost, and highly reliable connections are the main requirements for industrial IoT systems. He stressed that cellular signals and mesh networks—such as those introduced by Bluetooth and Thread in recent years—consume too much power, and cannot scale as effectively as their LPWAN counterparts.

The low frequency signals used by the Weightless-P standard feed into these requirements of power and cost. With lower frequencies, network operators are able to design smaller, lower-power, and lower-cost antennas. Weightless-P operates with transmit power up to 17dBm to allow operation from coin-cell batteries. When idling, power consumption is below 100 uW.

In recent years, developments in the industrial IoT have caused a flood of new LPWAN standards. Other technologies include SigFox, Dash 7 Alliance Protocol, LoRaWAN, nWave, IEEE 802.11ah, and LTE Cat-M, among others still under development.