7 rules for designing wearable devices

March 01, 2014

The past year has certainly been an exciting time for the semiconductor industry. The shared enthusiasm among silicon companies has been on the rise b...


A main driver behind this phenomenon is wearable technology. Familiar items such as clothing, glasses, jewelry, and watches are being fitted with sensors, processors, and displays – technologies you wouldn’t have expected to find inside these everyday objects before. The potential for this market is quite impressive; ABI Research projects that 32 million sports and fitness wristbands will have shipped in the past twelve months alone.

So if wearable devices are what everyone is raving about, why does it seem like so few companies actually know how to design them? This guide outlines how to address the current issues facing the wearables market for designing the next generation of wearable technology.


Rule 1: Augment, don’t replicate

An important aspect of wearable devices is the user experience and interface. Designing interfaces for wearables should be based on how consumers will use them, not on replicating smartphone or tablet experiences.

Even though using a popular, off-the-shelf operating system like Android might sound like a quick and easy fix for devices with a screen, it’s best to design a customized, fully skinned interface that fits within the confines of a miniature display surface.

More importantly, wearables should augment other mobile devices, not try to replace (part of) their functionality. Trying to cram features in by using a checklist approach will lead to underpowered devices that users will quickly abandon.

Instead, designers should focus on optimizing user and machine interfaces to ensure that wearable devices work well together and with other mobile devices.

Rule 2: Design, don’t reuse

Every engineer has heard of the “design and reuse” approach. However, the principle can only apply to devices that have proven to work universally; this is not the case for wearables.

Even though wearables are mobile devices at heart, they have different and specific requirements to smartphones and tablets (more on this later).

Reusing mobile SoCs for every wearable category out there (smart watches, smart glasses, smart wristbands, etc.) is unsustainable not only because these devices come in distinct shapes and sizes, but mainly because their power profiles can vary radically.

Today’s wearable devices are generally a magnitude off in terms of battery life. Most current wearable fitness devices usually last for two to three days when they should last weeks or months. Reports have placed some smart watches at battery life of less than one day; most consumers would expect at least one week. People have different expectations between smartphones/tablets and wearables and don’t usually factor a charging regimen into their daily habits for a these ultra-portable devices.

Plus, if a smart watch is supposed to act as a regular watch during the day and a sleep health monitor at night, when would users charge them?

Rule 3: One size does not fit all

Wearables have different features and require specific type of SoC. If you are creating computing platforms for smart devices, there are two main categories to consider:

Input wearables

Input wearables are devices such as fitness bands, heart rate monitors, sleep monitors, and Near Field Communication (NFC) rings. They are essentially smart, connected sensors with minimal or no displays that have extremely low power requirements. Their main role is to collect raw data, then filter and send it to a central hub, be it a mobile device (smartphone or tablet) or a residential gateway in your connected home. On the hub, this data is translated into usable information. Additional functionality can then enable automatic actions or alerts based on that information.

For this category, the essential element is designing for the lowest power connectivity possible. These devices typically require a high-performance 32-bit MCU-class processor for fast, efficient processing, ideally a compact-footprint, unified MCU/MPU and DSP embedded processor core. Designers will also need to select a solution for baseband communications; combining Bluetooth LE (low energy) with FM in one small, integrated radio solution is ideal for ultra-low-power wearable applications.

Depending on the application area, designers can also include dedicated hardware to support a gyroscope or motion sensors.

Output wearables

Output wearables are devices such as smart watches or smart glasses that provide quick and easy at-a-glance access to immediate information. This information usually can fit on a small screen and is available to the user quickly and in real-time. Output wearables are aimed at accelerating daily tasks, and offer a more intuitive way of interacting with technology.

When it comes to designing chipsets for output wearables, designers need to make sure that each processor inside the SoC is used as efficiently as possible. Low power is still the dominant factor when architecting the underlying system but the focus should be on creating a general-purpose platform that performs a subset of the tasks a smartphone or a tablet might do.

An example of such a platform for smart glasses can be designed by pairing a low-power, high-performance CPU with the smallest available OpenGL ES 3.0/OpenCL GPUs, H.264-capable hardware video transcoders, a configurable OpenVX-ready ISP pipeline, and a connectivity processor that supports Wi-Fi 802.11n 1x1 and Bluetooth.

Rule 4: Think always on, think low power

The small form factors of wearable devices dictate the use of extremely small batteries, which limits the battery life of these devices. Because of this, wearables need smart technologies that implement low-power methodologies in various points of the design. This is to ensure that the processors operate as efficiently as possible and in ways that suit short bursts of intense activity followed by longer periods of idleness. Designers must implement (or choose processors that already implement) advanced power management techniques such as automatically enabled clock gating, the ability to intelligently turn power on/off for specific cores or clusters, and intelligently using the Microkernel firmware to offer lower latency workload feedback into the DVFS and power management decision process.

To complement the hardware, wearables need to support the appropriate low power standards that enable a prolonged “always on” functionality. Although there are many options to choose from, the main contender to the title is Bluetooth LE.

Bluetooth LE is a power-friendly version of the Bluetooth wireless technology designed to provide practical connectivity for the mass market. The power efficiency of Bluetooth LE enables devices needing to run off a tiny battery for long periods of time; even better, Bluetooth is compatible with existing smartphones and tablets for device-to-device communication.

Rule 5: Security above all

Wearables require multiple layers of security due to the sensitive nature of the data they have access to:

  • Device security: Wearable devices need to run operating systems and applications securely; this requires support for multiple secure environments
  • Link security: Transmission of information between wearables and a central hub must be protected and encrypted
  • Cloud security: Storage of personal information is another delicate area; consumers want to know that their details are kept away from unwanted intruders

These security layers should be enabled both in hardware and software and can scale from the core level all the way up to the system level. An example of implementing core-level security is a virtualization-based approach where multiple operating systems can co-exist in multiple security contexts, thus supporting secure content delivery, secure payments, identity protection and more, across multiple applications and content sources.

Rule 6: Build a viable ecosystem

More and more companies are waking up to the reality of how important a developer ecosystem is to the success of any consumer platform. The same rule applies to wearables: Developers need to see the value added factor of wearables, otherwise they won’t create more than a few apps.

Another important element in creating a thriving environment for wearables is an open approach to APIs and device intercommunication. For example, limiting compatibility to only certain brands of devices means consumers will have no incentive to buy a wearable unless they own that particular brand. Efforts such as the recent AllSeen Alliance are steps in the right direction in order to create an open standard for platforms and APIs.

Rule 7: Get the price right

Finally, wearables need to adopt a three tier pricing model similar to their smartphone and tablet brethren that makes them accessible to the largest possible number of consumers. There is so much buzz around wearables that even fashion brands like Nike are getting in on this new product category. By creating entry-level, mid-range and high-end devices, companies can create an instant, compelling, and complete line-up of devices that addresses the growing consumer demand.

Designing the future of wearables

The sensible approach when designing SoCs for any market is to use proven solutions. For the past decade, Imagination Technologies has been creating multimedia, processor, and connectivity IP that has shipped in billions of mobile and embedded devices from some of the industry’s leading silicon vendors. Imagination provides all the required IP, design services, and software tools and platforms required for building connected devices. On top of these IP system-optimized technologies, Imagination can offer value-added solutions like FlowCloud – a platform that helps companies deliver a complete IoT-ready solution, including all the security/device-to-device and device-to-cloud communication/back-end services.

Given their potential, there is a clear opportunity for wearable devices to succeed considering everyone from chip makers and OEMs to consumers and carriers believe this category of devices will be in high demand in the coming decade. Once it reaches critical mass, wearable technology will become embedded within every aspect of our lives, allowing us to do everything better, faster and simpler.

Kevin Kitagawa is Director of Strategic Marketing for Imagination Technologies.

Imagination Technologies


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