The most recent flagship smartphones are making a move towards always-on technology. We have already seen quite a few phones offering voice activation while the screen is on or while the phone is plugged into a power source. Nonetheless, full-fledged, touchless, always-on handheld devices remain quite rare and relatively new. The trend started with Motorola's Moto-X featuring always-listening voice activation. The Apple iPhone 6S, released half a year ago, features always-listening Siri. The brand new Samsung Galaxy S7 is a double member of the always-on club, with S-voice activation as well as a perpetual low-power date and time display. These flagship phones are the pioneers, but it's a safe bet that these features will quickly become standard for all handheld devices.
The challenge of always-on portable devices
The main challenge for portable devices with regard to adopting always-on technology is the limitation on battery life. Always-on static devices, like the highly acclaimed Amazon Echo, are quite common; having a constant power supply allows for leeway in the implementation. Portable devices, on the other hand, need to have extremely efficient designs so they won't drain the battery and significantly reduce the standby time or normal use time of the device.
The newly released Amazon Echo Tap is a small, portable version of the Echo. Now you can take Alexa with you wherever you go, but this comes at a price. Instead of the excellent, responsive always-listening technology in the full sized Echo, the Tap, as its name suggests, requires a tap every time you want to talk to Alexa. Obviously, the logic behind this is to conserve battery life, but is it really necessary? It's probably safe to assume that the same factors that forced the Echo to be plugged in are responsible for the Tap not being touchless — namely expensive, hefty, and power-hungry processors, as I described in this post last year. The Echo Tap has no screen and far less power-consuming features than any smartphone on the market. In that light, it's pretty disappointing that the always-listening implementation isn't efficient enough to get rid of the need to tap Alexa to wake her up. So, what does it take to have great always-on features, and not drain your phone's battery?
Looking under the hood
Motorola claims that the battery of the Moto-X is not drained by the always-listening feature because it uses a “super low-power natural language processor.” The iPhone 6S boasts the same type of efficiency and, surprisingly, the battery is slightly smaller than the previous iPhone 6 battery. Despite this, standby time remains unchanged, even with Siri always listening. Apparently, one of the major design changes that enables this is the integration of the sensing processor into the main processor. By acting as a power island within the main processor, the sensing module can be alert and listening for the “Hey, Siri” activation, while the more power hungry main processor is kept on standby.
Samsung Galaxy S7 Edge with always-on display
(Source: flickr; Author: Răzvan Băltărețu; License: CC2.0)
According to multiple reviews — like this one on cnet.com — Samsung's Galaxy S7 has a long battery life. This might come as a surprise, since it is both always listening and always displaying the date and time. The display is kept efficient by utilizing the Super AMOLED technology, which enables each pixel to be controlled separately. This means that only the small portion of the screen showing the date and time is on while the rest of the screen is off. This would not be possible with popular backlit displays, like the ones used in the Apple iPhones.
The always-listening feature is supported by the ultra-low-power DBMD4, an always-on voice DSP that offers the industry's lowest power always-on solution, according to DSP Group. This tiny platform, powered by a CEVA DSP, is extremely low-power and specifically designed for battery operated devices. The same logic that enables control over every pixel in the Samsung displays is implemented in the design of CEVA's programmable solutions. Each module is controlled separately, and used only when necessary using a dedicated Power Scaling Unit, as described in this recent post.
DSPG's DBMD4 has a tiny 1.8 x 2.1mm form factor (Source: DSPG)
Another interesting point about always-on technology, which may be contrary to intuition, is that — in some cases — it might actually reduce battery usage. By controlling the precise features that are always on, a user could reduce the amount of times a day that the device is woken up. For example, if a user constantly checks the time every few minutes, an always-on clock might be more efficient than waking the entire screen each time. In the same manner, voice operation that is used frequently to get updates, control a smart home, or other uses could be more efficient with always-listening technology. The key for this to work, of course, is a very low-power, highly-efficient platform that only wakes up the other components when they are required.
The future of always-on: always-everything
The race for cool new features is always exciting and unpredictable. Some features come and go and are forgotten for eternity. But when a feature is as intuitive as natural language (literally), you know it will be here to stay. In the case of always-on technologies, it's pretty clear that this is just the beginning.
Instead of just one always-on feature per device, we could be seeing more multi-function always-on devices. With the right design strategy, always-on displays and always-listening mics will be joined by always-seeing, always-sensing features enabling our devices to respond to voice, gestures, glances, and other input, without the need to touch them. Freeing our hands is just the first step in revolutionizing the ways in which we interact with our devices.