Weightless is the name of a set of LPWAN open wireless technology standards for exchanging data between a base station and thousands of machines around it. These technologies allow developers to build Low-Power Wide-Area Networks (LPWAN).
There are currently two published Weightless connectivity standards, Weightless-N and Weightless-W. Weightless-N uses ultra narrow band technology operating in licence exempt sub 1GHz spectrum in what is commonly known as the Industrial, Scientific and Medical (ISM) bands. In Europe this includes a range of frequencies around 868MHz; in North America around 915MHz.
Weightless is managed by the Weightless SIG, or Special Interest Group, which was revealed to the public on 7 December 2012. An inaugural event for industry was held at the Moller Centre in Cambridge, UK by Cambridge Wireless on Friday, 30 September 2011. Representatives – mainly engineers – from many companies from around the world attended. Presentations were given by Neul, Landis+Gyr, Cable & Wireless, and ARM.
The intention is that devices must be qualified by the Weightless Special Interest Group to standards defined by the SIG. Patents would only be licensed to those qualifying devices; thus the protocol, whilst open, may be regarded as proprietary.
The name Weightless was chosen to reflect the lightweight nature of the protocol, meaning that the overhead per transmission is minimised for devices that need to communicate just a few bytes of data.
The Weightless logo is trademarked and appears as uppercase letters with the ‘W’ appearing in the top-right corner of a light blue box that has a solid blue line above it best running fanny pack.
One of the presenters at the inaugural SIG event in September 2011 stated jokingly, in reference to cellular communication standards, “Weightless is not 1G, 2G, 3G or even 4G – it is ZERO G“.
Weightless-N is designed around a differential binary phase shift keying (DBPSK) digital modulation scheme to transmit within narrow frequency bands using a frequency hopping algorithm for interference mitigation and enhanced security. It provides for encryption and implicit authentication using a shared secret key regime to encode transmitted information via a 128 bit AES algorithm. The technology supports mobility with the network automatically routing terminal messages to the correct destination. Multiple networks, typically operated by different companies, are enabled and can be co-located. Each base station queries a central database to determine which network the terminal is registered to in order to decode and route data accordingly.
Weightless-W uses Time-division duplex operation with frequency hopping and variable spreading factors in an attempt to increase range and accommodate low power devices in frequency bands, or channels, within the terrestrial television broadcast band. Channels that are in use by a nearby television transmitter are identified and left unaffected while channels not being used for broadcasting television can be allocated for use by Weightless devices.
A network of base stations communicate with the Internet, or a private network, in order to pass information from devices to a computer system; and to pass information back to the devices. The downlink to devices uses time slots (TDMA) and the uplink to the base station is divided into sub-channels so that several devices can communicate to the base station.
A base station transmits a Weightless frame which is received by a few thousand devices. The devices are allocated a specific time and frequency to transmit their data back to the base station. The base station is connected to the Internet or a private network. The base station accesses a database to identify the frequencies, or channels, that it can use without interfering with terrestrial television broadcasts in its local area.
Weightless is a wireless communications protocol designed to connect Smart Machines to the Internet – so-called Machine-to-Machine (M2M) communications – over distances ranging from a few metres to about 10 km.
Other technologies which use the white space – the channels not used for terrestrial television broadcast in a particular area – are also being developed. One is Wi-Fi under the developing standard IEEE 802.11af.
The IEEE 802.22 standard defines a MAC and PHY layer for TV WhiteSpaces that complies with the FCC and international standards for broadcasting in this spectrum. It also defines general protocol model for negotiating and selecting shared spectrum band for device operation. A Weightless Radio implementation would comply with this standard to cooperatively share the available TV WhiteSpace spectrum.
Currently the majority of the devices that are envisionsed to use the Weightless standard are mainly of industrial and medical type custom glass water bottles, such as smart electric meters, health monitors, vehicle tracking, etc.
The original Weightless specification, now called Weightless-W, was initially developed as an open standard machine-to-machine, low-cost, low-power communication system for use in the white space between TV channels in 2011 by engineers working at Neul in Cambridge, UK. The Weightless-W specification is based on Time-division duplex technology with Spread spectrum frequency hopping in an attempt to minimise the impact of interference and with variable spreading factors in an attempt to increase range (at the expense of lower data rate) and to accommodate low power devices with low data rates.
The specifications were finalised with the creation of version 1.0 in 2013.
The formal Weightless-W Standard was published in February 2013. The formal Weightless-N Standard was published in May 2015. Both Standards are available to Associate and Core members of Weightless SIG.
In networks using Weightless-W technology a base station queries a database which identifies the channels that are being used for terrestrial television broadcast in its local area. The channels not in use – the so-called white space – can be used by the base station to communicate with terminals using the Weightless-W protocol.
Terminal endpoints are designed to be low cost “fit and forget” devices – meaning that they are expected to use minimal power so that they could work autonomously for long periods close to the typical shelf-life of a battery (probably several years).
The protocol is designed to be at least as secure as GSM.
The Weightless-W protocol operates in the TV channels band. The Weightless-W protocol divides the band into channels. A database is queried by a base station to determine which channels are in use by terrestrial television broadcast stations in the area, and which ones are free for use by white space devices (such as those utilising Weightless). A range of modulation and encoding techniques are used to permit each base station to communicate at a variety of speeds with terminals, some of which may be nearby and others several km away. Data rates may vary depending on the distance and the presence of radio interference – the typical range is alleged to be between about 0.1Mbit/s and 16Mbit/s. The design of the air interface and protocol minimises the costs of the equipment and its power consumption. A broadband downlink from a base station to a terminal uses single carrier in an unused 6 MHz (for USA) or 8 MHz (for UK) TV channel.
The communications link between the base station and the devices is encrypted.