M2M standards group announces complete IoT over white space specification
The Weightless SIG today announced ratification of version 1.0 of the pioneering machine communications standard at its fourth Plenary Conference in Cambridge, UK.
The Weightless standard, optimised for machines, in development for more than two years with a group of industry leaders, now runs to over 600 pages and offers transformational competitive advantages over legacy technologies. Ultra low cost terminal hardware and license free frequency spectrum provides ground breaking cost savings comparable with PAN technologies such as Bluetooth. Ultra low power consumption allows operation of battery powered terminals utilising single primary cells for periods of more than ten years and high quality low frequency spectrum exhibits excellent signal propagation characteristics yielding ubiquitous coverage through superior range and in-building penetration.
At the terminal level data rates from 1kbit/s to 10Mbit/s are possible depending on link budget with data packet sizes from 10 bytes and no upper limit with an extremely low overhead – 50 byte packets have less than 20% overhead. Acknowledged and unacknowledged message transmission modes are supported and multicast call capability allows messages to be sent to multiple devices. Interrupt capability allows devices to raise alarms for specific events such as power outage. Service provision layering enables worldwide contracts and automated change of network provider capabilities. Terminals can run multiple applications and mobility is fully supported. An ultra secure 128-bit encryption and authentication model based on a shared secret key is provided. Extremely low complexity terminal architecture enables low cost implementation using minimal memory and processor power to further extend battery life.
At the network level careful scheduling enables transmissions to be planned in advance resulting in very high loading efficiency and both frequency hopping and intelligent frequency planning maximise throughput on congested networks. An extremely wide range of modulation schemes and spreading factors provides flexibility in network design enabling 5km coverage to indoor terminals. The entire core network is run as a software service and can be cloud-hosted. Ultra low out-of-band emissions through waveform shaping maximises white space bandwidth availability and license free spectrum significantly reduces network costs.
Modulation methods from 16-QAM to differential BPSK coupled with spreading codes up to 1024 enable an extremely wide range of link budgets to be configured. Downlink single carrier modulation of 6MHz bandwidth and uplink FDMA channels using 16 interweaved channels for the Americas and 8MHz bandwidth downlink and uplink narrowband FDMA channels using 24 parallel 128kbit/s channels for rest of the world enables truly global operation. Time Division Duplex (TDD) is used with flexible uplink/downlink boundaries on a frame-by-frame and per base station basis enabling dynamic balancing of uplink and downlink traffic. Error detection and correction with packet re-transmission capability is built in and terminal sleep modes are fully integrated into the system design.
What is “weightless”
The value in machines having wireless communications has long been understood and a large market is predicted for many years. That this has not transpired has been because of the difficulty of meeting all the requirements within the constraints of the available radio spectrum.
These constraints changed significantly with the advent of white space availability which provides near-perfect spectrum with free access.
However, the combination of the unique and unusual nature of that access and the very different characteristics of machine traffic compared to human traffic means that using any existing standard is far from optimal. Hence, the need for a standard designed specifically for machine communications within white space. Weightless technology has been optimised for this specific scenario and is now being delivered as a royalty-free open standard. The draft Weightless Specification, available to access on this site, provides detailed information about the standard and in essence provides for the following:
Great flexibility in the data rate provided depending on the application, range and environment. This includes the use of variable spreading factors which allow a trade-off of range against data rate for each terminal.
Time division duplex (TDD) operation since it may be difficult to find a pair of white space channels with appropriate duplex separation in all areas.
Relatively long frame duration of the order of 2s so that when high spreading factors are used on the frame header it remains a small percentage of the overall frame duration.
Frequency hopping at the frame rate to minimise the impact of interference – both received and caused.
A design that minimises costs and power consumption.
A broadband downlink using single carrier modulation within a 6-8MHz TV channel.
A narrowband uplink with 96 uplink channels per downlink channel to accommodate the lower terminal transmit power while maintaining a balanced link budget.
Highly efficient MAC-level protocols that result in small headers per transmission and hence little overhead even when the payload is only a few bytes long.