Extending Wearability

The market for wearable electronic products is fast growing and has undergone significant evolution over the past year. Certainly it is becoming an increasingly significant market: to cite some recent data from market research firm Futuresource Consulting, consumer demand for wearables is fast rising with expected shipments of 52 million units in 2014, up 32% from 2013 and increasing by 44% to 74 million units in 2015, with emerging sectors such as Smart Watches and activity trackers likely to grow even faster over the next few years. There is now an increasingly wide choice of products available with different use cases ranging from devices focused on health and activity, through to smartphone alerts and media control. 

Although this relatively new market is highly fragmented, a clearer landscape is slowly beginning to emerge with functionality previously found on discrete devices now being consolidated and integrated into the next generation of wearables, whether they are Smart Glasses or designed to be worn on the wrist. Importantly, the technology building blocks are now available for leading OEMs to realise the next phase of development in wearables and enable new use cases and applications in fitness and infotainment, as well as in healthcare, industrial and enterprise applications.

Requirements

The evolution in the market over recent years has meant makers and/or vendors of wearable devices are now gaining a much better idea of which types of product with which functions are the more likely to enjoy sustained success. This new knowledge is also filtering down to those in the supply chain such as the semiconductor vendors, which are obtaining a sharper understanding of the system-level needs for many different categories of wearables, each coming with their own package of requirements. For instance, there will be high-end devices that run a rich OS and complex user interface, down to very small and lightweight devices that have no user interface at all and are intended for use as a Smartphone appcessory (application accessory).

While there are a myriad of different products, there are key enabling technologies that will be common across all types. The absolutely critical factor for wearables — when compared to Smartphones, say — is even lower power consumption, or conversely greater processing efficiency. Which is not to say that power consumption is not an important ingredient in Smartphones, but in most or many cases the optimum balance between power consumption and processing performance will most likely need to be shifted toward the former, in addition to the paramount consideration of cost especially when considering the lower end of the wearables market. In terms of energy usage, a battery used in a wearable will need to be approximately 20 times smaller than that in a smartphone, perhaps offering 150mAh that will last for weeks and not days, versus the 3000mAh battery seen in larger Smartphones or other mobile devices.

Technologies

The reality is that most wearables devices available today largely utilise low-power ARM-based chips and technologies that pre-date the emergence of wearable devices. ARM and its partners are uniquely positioned to determine and optimise the underlying technologies to bring even greater battery life and better user experiences in wearable devices. This will be realised in the next phase of wearables development, which will be enabled by the development of bespoke application-specific SoCs that are tailored for wearable products and applications.

The availability of ultra-low-power silicon process technologies is an absolutely critical block to enable both highly integrated and low-power SoC solutions. The world’s leading foundry company TSMC, as an example, has recently expanded its ULP low-leakage technologies to offer manufacturing processes at the 55, 40 and 28nm nodes. This can mean a reduction in operating voltages by as much as 20 to 30%, resulting in both lower active and standby power consumption and enabling significant increases in battery life for wearables, potentially anything from doubling it up to a factor of ten times longer. Although the processes support speeds of up to 1.2GHz, it is much more likely that SoCs will be clocked to operate in the 500 to 600MHz range for lower power consumption. In addition, TSMC ULP processes - down to the 40nm node at least - also allow the implementation of embedded Flash memory and RF capabilities (and for wearables this is highly likely to imply the use of the BLE protocol) together with logic processing circuitry on a single chip, enabling high system-level integration and smaller form factors for products.

The second key component for SoC vendors is the selection of processing capability, architectures and the software development ecosystem, which commonly will be available from leading IP vendors such as ARM. In fact, ARM processors and architectures are already very well established in wearables, as the majority of current designs built with existing processors and MCUs are based on ARM technologies. The ARM ecosystem includes a rich range of processor cores, IP and architectures that can enable SoC vendors to tap into all the necessary requirements to produce optimised low-power wearable solutions. A wide selection of off-the-shelf ARM processors exist including the Cortex-M series of processor cores that offer a range of performance points and include the M0, M0+, M3, M4 and M7. These are highly suitable for deployment as the ultra-low-power core that can be used for the ‘always-on’ and ‘always-connected’ sensing system that processes the data locally, minimising wireless data traffic and preserving battery life. Whereas the Cortex-A5 or Cortex-A7 single-core application-class processors, both of which are very popular processors in low-cost Smartphones today, can handle a rich OS or complex user interface such as Android Wear. In addition, there is complementary IP for deployment for feature-rich devices with the ARM Mali range of graphics, video and display processors.

System Implementation

Chip vendors can use this IP and configure it in different ways for different functionality and price points, for example tuning processors for price and lower power consumption and not performance. For example, the Cortex-A5 and Cortex-A7 cores usually run at 1.2GHz when deployed in Smartphones, but it is entirely possible to configure the Cortex-A5 to run at only 500MHz in a 40nm ULP process; the result is a processor that will be very small, low cost and very low on power consumption, but retains the ability to run a rich smartphone-like OS if and when required by the system. In addition to this wide selection of IP, ARM has a robust and extensive software development ecosystem that has been built up over many years for mobile and consumer applications among many others. The ARM business model allows silicon vendors to focus on differentiation and application-specific functionality, while also gaining access to the industry’s broadest software ecosystems.

Chipmakers will need to take a holistic design approach and implement a broad range of technologies to develop these wearable-optimised SoCs that offer new capabilities in terms of extended battery life or higher levels of integration for a small form factor, which is essential in wearable devices. Critical for success in mid-range and high-end designs is a high level of integration and optimum system architecture partitioning in a multicore design that enables the efficient processing of real-time data from sensors, the waking up of an application processor only when needed to run a rich OS or user interface, in conjunction with an optimum combination of communication capabilities (see Figures 1 and 2 for high-end and mid-range architecture block diagrams). While at the lower end of the product spectrum, where the device has no need for a rich user interface and will work as an appcessory, for instance, devices may not implement the application processor. Key to this system arrangement (see Figure 3) is the filtering of data received from the sensory inputs, also known as ‘sensor fusion’, which is critical as the transmission of too much data to a Smartphone can be a killer in terms of power consumption — although use of the BLE protocol should make a significant contribution to extending battery life.

The processor in a low-end device will not be ‘always-on’. Typically it will be in a sleep state while sensor readings accumulate in memory before a burst of processing. Although sensing may appear to be continuous to the user, use of the processor will only be triggered by events such as user interaction or if a set of data is ready for processing.

The rapidly emerging and expanding wearables market - and today largely based on ARM technology - has matured and evolved and is now ready for the next step in its evolution. Next-gen wearable products will require the creation of a new breed of bespoke, highly integrated and low-power SoC solutions. All the building blocks are in place to realise this vision including the recent availability of ultra-low-power silicon process technologies, in conjunction with ARM’s extensive software development ecosystem and a wide range of low-power MCU- and application-class processors that are configurable for power-efficient SoCs for all categories of wearables.