Why out-of-band communications is essential for the next generation of Wireless Power Transfer solutions


by Sanjay Gupta, AirFuel Alliance President

I recently had a very interesting discussion with AirFuel Alliance Technical Steering Committee Chair and Samsung Research and Development Institute Director, Clint Chaplin about the role of out-of-band communications in wireless power transfer. In this post, I’m going to share much of what we talked about as it’s become an important factor in the industry’s collective success.

Let’s start with what consumers really want from wireless power
While our industry is working hard to incorporate wireless power in products, we need to work a little harder to put consumer and end user needs at the very heart of our innovation. At the beginning, it was all about providing a means to eliminating cords, but as wireless charging has evolved, end users’ needs have too. They want a reliable, universal system that is simple to understand and easy to use – safe, interoperable, and smart. A single wireless power transmitter should be able to charge all of our mobile devices simultaneously from wearables to laptops without worrying about pesky details such as size, battery sizes, power levels, or exactly where the device is placed. Speed is also an issue. Wireless charging should be as fast or faster than wired charging in all aspects. As Clint so aptly put it: “Consumers want cordless power to ‘just work’, they shouldn’t even need to think about powering their devices – ever.”

Re-engineering for success
Clint emphasized that for the system to operate satisfactorily, there must be constant communication between the wireless power transmitter and the receiving circuitry, before, during and after completion of power transfer. For example, the wireless power transmitter must know the amount of power to deliver to a receiver embedded in a device and/or how many devices are being powered at any given time. Additional information is frequently communicated between the transmitter and receiver – this may include, among others, authentication parameters, device capabilities, etc. These are critical to improve the overall experience, enable new use cases, and enhance efficiency.

The limitations of in-band communications
Today, the most common inductive wireless power technology deployed uses what is commonly referred to as in-band communications. In in-band communications, the data being sent is typically piggy-backed on the wireless power transmission. The system has the following limitations:

  1. This is unidirectional from the receiver to the transmitter, i.e., only the receiver can send information to the transmitter (and no information can be communicated from the transmitter to the receiver).
  2. It only works when a single receiver is associated with a single transmitter; meaning that only one receiver can be associated with a given transmitter.
  3. The type of information that can be transmitted through the in-band method is regulated by regional agencies and is restricted accordingly.

These issues ultimately result in performance issues for end users. Bottomline: most of the experiences and features that consumers want from wireless power technology aren’t enabled by the current in-band solution — they require an out-of-band communication mechanism.

Introducing out-of-band communications
An out-of-band communication scheme can allow the data to be sent between the transmitter and the receiver independently of the power transmission. This enables high speed bi-directional communication using an off the shelf communication solution needed for delivering on the experiences consumers demand.

As Clint pointed out, there are a number of existing technologies available to us to enable out-of-band communication; for example, NFC, ZigBee, Bluetooth and so on. Bluetooth Low Energy (BLE) is a good option because it easily meets the growing needs of wireless power systems, minimizes impact on existing devices given the ubiquity of BLE in all of our devices – from IOT sensors, wearables, smartphones, and laptops, and overall cost.

The out-of-band communication scheme developed by AirFuel, and that Clint and the rest of the technical committee are working on, therefore recommended Bluetooth LE, which already naturally supports the requirements. For wireless power specifically, it allows simultaneous support of multiple receivers for a given transmitter and support of devices with multiple power level needs, increased spatial freedom and distance, authentication security, low power consumption, as well as many other user-friendly features for the next generation of IOT devices.

Taking the next steps
We’ve already got many of the technical building blocks in place to both meet and exceed some of the consumer demands mentioned at the outset of this post. At AirFuel, for example, we’re working with resonant and RF technologies to deliver:

  • A single technology specification and interoperable standard to charge ALL mobile devices, anywhere in the world. And while we are at it, charge them simultaneously as well
  • The ability to power devices on a variety of different surfaces e.g. wood or metal. This means wireless power charging could be done anywhere – from furniture to countertops to vehicle interiors
  • The ability for devices when charging to not be displacement by surface movement or a vibration and to instead carry on charging e.g. when a car navigates a pothole
  • Assurance from a safety standpoint that you won’t get burnt from objects (metal or otherwise), including coins, keys, etc. overheating.

In fact, many mobile device developers, robotics companies, wearable designers, IoT makers, and others are integrating out-of-band technology into their products as they see the benefits of the next generation of wireless power which consumers are demanding. AirFuel is in fact including out-of-band with both resonant and RF. The technology is here – our industry just has to embrace it.

If you’re interested in finding out more there’s an opportunity to find out more about out-of-band communications at our Wireless Power Mini Conference on 11 September in Los Angeles which we’re organizing in partnership with Mobile World Congress Americas. It’s free to attend and you can find out more information as well as register here.