Weightless-W

Ultra high performance IoT connectivity

The Weightless-W open standard is based on a low power wide area (LPWAN) star network architecture operating in TV white space spectrum*. Weightless-W offers best in class signal propagation characteristics leading to excellent range of several kilometres even in challenging urban environments. Very low power consumption provides for exceptionally long battery life measured in years from small conventional cells and leading edge innovation in design minimises both terminal hardware and network costs.

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.

Functional specification

System

Modulation methods from 16-QAM to differential BPSK coupled with spreading codes of up to 1024 allows massive range of link budgets

Terminals can be sited in a wide range of different locations and environments from easy to reach to deep within buildings. They can also vary widely in the quality of their antenna and the power they have available to transmit.

Rather than restricting operation to smaller ranges or demanding expensive terminals, Weightless is able to trade off data rate in order to increase range. Having a huge range of data rates (a difference of 10,000 between the lowest and highest) allows immense flexibility in terminal design and deployment.

Uplink narrowband FDMA channels using 24 parallel 128kbit/s channels (rest of world) or 16 interleaved "comb" channels (Americas)

The narrowband uplink allows for a balanced link budget — this means that the range of transmissions from the base station to the terminal (downlink) is the same as the range from the terminal to the base station (uplink) despite the terminal having 1/100th of the power (20dB less) than the base station. This is because a narrowband transmission has a lower noise floor than a wideband one, and reducing the bandwidth by a factor of around 24 results in about a 20dB lower noise floor, thus enabling a balanced link.

Time division duplex (TDD) with flexible uplink/downlink boundaries on a frame-by-frame and per base station basis

TDD means that the downlink and uplink share the same frequency, transmitting in turn. This helps in white space since there may not be two channels available with good spacing between them to enable the more normal "frequency division duplex" operation.

It also has the benefit that the balance between downlink and uplink capacity can be adjusted simply by giving more or less time to each within each frame. This provides great flexibility which is valuable as at present it is far from clear whether an M2M system will have more uplink than downlink traffic or not.

Inbuilt error detection and correction with packet re-transmission as required

Error detection and correction ensures that packets with errors are detected as such and can be re-transmitted if appropriate. This results in the application layer being sure that any information it sends or receives is correct.

Terminal sleep modes fully integrated into system design

Sleep modes enable long battery life. Careful integration into the network ensures that the network is aware when the terminal will be awake and will schedule traffic for it accordingly.

Very low complexity terminal enables low cost implementation using minimal memory and processor power which in turn extends battery life

Weightless shifts the core network functionality away from the terminal in order to minimise complexity of terminal design and components. This enables the terminal hardware to be minimised and less powerful processing hardware to be specified resulting in a lower cost.

Less complex processing at the terminal end of the link also significantly reduces power consumption further contributing to longer battery life.

Network

Ultra-low out-of-band emissions and reduced impact on TV receivers through waveform shaping enabling access to high amounts of unlicensed spectrum compared to other systems

The amount of unlicensed spectrum that a technology can access is contingent upon the level of interference it causes to TV receivers. Well designed systems have minimal emissions outside of their selected channels and therefore cause little interference. This enables them to access more spectrum than would otherwise be the case.

Weightless specifically utilises a modulation and encoding technique for best- in-class emissions, enabling the greatest possible availability of white space.

Makes use of free spectrum — no auction fees or licenses required

Weightless is designed primarily to operate in unlicensed spectrum including the white space spectrum, frequencies between 470MHz–790MHz previously allocated solely for TV broadcast and wireless microphone applications. Dynamic spectrum access techniques make a large proportion of this spectrum available for use in M2M applications. Unlike 3G and LTE spectrum, these frequencies are not being auctioned by government communications regulators and are being offered license and cost free for use. This

significantly reduces the cost of deploying and using a white space network when compared to technologies operating in licensed spectrum.

Entire core network run as a software service and can be cloud-hosted

A Weightless network, like a cellular network, consists of multiple cells connected back to a core network that links them all together and allows the system to function, handling areas like billing, security, routing, terminal management and operations maintenance. In a cellular system this is often implemented on large, bespoke switches requiring a high upfront cost.

Because Weightless has much longer allowed latency it can move all of the core network into software which can be run either on a self-owned general purpose platform or even in the cloud, allowing the entire core network to be delivered as a service to the operator. This results in very low cost and high flexibility.

Extremely wide range of modulation schemes and spreading factors, providing great flexibility in network design and enabling coverage of 5km to indoor terminals

Terminals can be sited in a wide range of different locations and environments from easy to reach to deep within buildings. They can also vary widely in the quality of their antenna and the power they have available to transmit.

Rather than restricting operation to smaller ranges or demanding expensive terminals, Weightless is able to trade off data rate in order to increase range. Having a huge range of data rates (a difference of 10,000 between the lowest and highest) allows immense flexibility in terminal design and deployment.

Interference avoidance through frequency hopping and intelligent frequency planning enabling use of white space even when congested

Operation in unlicensed spectrum requires good interference tolerance. Weightless employs a frequency hopping regime at a frame rate of 2s to avoid interference on congested networks and to limit the impact of interference to a single hop rather than degrading the entire transmission.

Weightless also employs intelligent frequency planning to remove frequencies with persistent interference from a cell hopping sequence.

Other mechanisms to remove interference include the base station directing antenna nulls towards strong sources of interference, intelligent scheduling of transmissions to avoid frequencies exhibiting the strongest interference and the use of spreading to realise interference resistance.

Very low overhead on small packets

M2M traffic is often characterised by very short messages, for example a 30 byte meter reading. The MAC protocol is designed to add minimal signaling overhead to such messages to avoid highly inefficient transmissions. This is achieved through flexible small packets with highly optimised header information and typically results in a less than 20% overhead on small data packets.

Advanced scheduling system, enabling most communications to be pre- planned and resulting in very high efficiency of loading

Most applications have periodic transmission requirements — e.g. smart meters may send a reading once a day. Rather than requiring the meter to wake up and request resources when it has a message to transmit, it is pre- assigned its next slot at the end of its previous transmission. This allows the network to plan ahead its loading in a very efficient manner as well as reducing the signaling load needed to request transmission time.

Terminal

Data rates from 1kbit/s to 10Mbit/s depending on link budget

Terminals can be sited in a wide range of different locations and environments from easy to reach to deep within buildings. They can also vary widely in the quality of their antenna and the power they have available to transmit.

Rather than restricting operation to smaller ranges or demanding expensive terminals, Weightless is able to trade off data rate in order to increase range. Having a huge range of data rates (a difference of 10,000 between the lowest and highest) allows immense flexibility in terminal design and deployment.

Ultra-secure using 128-bit encryption and authentication based on a shared secret key

Weightless provides certainty that a message has come from the terminal identity claimed (authenticity), that the message has not been tampered with en route (integrity), and that no eavesdropper can view the message contents (confidentiality). It also guarantees message freshness, i.e. rejection of replayed messages. 128-bit encryption is used and high quality random number generation is a provided by central control.

Data packet sizes from 10 bytes upwards, no upper limit

The majority of M2M transmissions consist of very small amounts of data when compared to voice or data traffic on a telephony based cellular network.

A utility meter reading for example can be completely defined in a few tens of bytes.

Weightless provides a very lightweight, efficient protocol to minimise data packet overhead for small data transmissions — a 50 byte transmission will carry an overhead of around 20%. For larger transmissions Weightless is infinitely flexible with no upper limit on data packet size.

Acknowledged or unacknowledged message transmission modes

In most cases M2M messages will require an acknowledgement that they have been correctly received — for example a meter reading. However, other cases exist where acknowledgements are less important, e.g. a stock-market update that is repeated every 15 minutes so if one is missed it is preferable to await the next rather than force re-transmission. An unacknowledged mode allows for this and removes the signaling traffic needed to support acknowledgement where not required.

Mobility fully supported including high-speed transport

Terminals that move within cells, between cells and across different networks are supported with no loss of connectivity or extra complexity within the terminal. Terminal speeds of up to about 100mph can be accommodated (depending on actual network topology).

Multicast call capability sending the same message to multiple devices

Some applications may require the same information to be sent to multiple terminals. This might be a software upgrade sent to all terminals, a media item sent to those registered, etc. Weightless offers a method to significantly improve the network's efficiency by addressing the same sequence of messages to multiple terminals.

Multicast messages can only exist in the downlink, being exclusively sent from the network to terminals. A multicast session may either be an Acknowledged Multicast Session or an Unacknowledged Multicast Session. The two types of session differ in the network load required to offer the service and the type of messages that may be carried. An Acknowledged Multicast Session offers greater flexibility and is suitable for applications requiring guaranteed delivery. An Unacknowledged Multicast Session is less demanding in its use of network resources, and allows terminals to operate with lower power consumption.

Interrupt capability, able to handle alarms raised by devices including advanced load management when multiple devices simultaneously raise the same alarm

Some Weightless applications may be characterised as regular data transmissions with occasional uplink interrupt events. Within a cell there may be many terminals reporting the same or similar interrupt events. The Weightless network offers the ability of terminals to transmit data from interrupt end points over multiple instances of interrupt logical channels.

The terminals that have interrupt end points may be grouped by the network so they can use dedicated contended access, as well as general contended access or direct addressing from the network to transfer interrupt data. This grouping of the terminals allows the network to efficiently manage multiple applications interrupt channels and provide more, but contended, opportunities for the terminals to send interrupt data.

A terminal may support multiple interrupt end points. Each interrupt end point can be open or closed. When an interrupt end point is opened data transfer is possible from the end point. When the interrupt end point is closed interrupt data from it shall not be transmitted to the network by the terminal.

Service provision layering enabling worldwide contracts and automated change of network provider

Weightless network structure is divided into network operators who build and run networks (base stations, network management systems, etc) and service providers who offer service to end users. Service providers can negotiate service arrangements with multiple network operators and thus offer a multi- country service to their clients. They can also decide to change the network operator they are contracted with in any given region without needing to make any changes to the terminals providing flexibility and enabling competition.

Terminal can run multiple applications allowing different priorities per application

The Weightless module within a terminal can act as a multiplexer, allowing more than one application to run on the terminal. This can add flexibility to the terminal designer who may wish to separate out different applications (e.g. engine management compared to location update) or can allow more than one differing application to be supported on the same terminal. It also enables, for example, a long software update message to be interrupted by a more urgent message should that be required.

*Please note that shared access to white space spectrum for IoT use cases is currently only available in a limited number of regions. We recommend that you consider Weightless-P technology.