3 'must-haves' for successful smartphone and IoT design

As we enter the era of IoT and build smaller and smarter connected devices, the task of meeting a design's most fundamental needs becomes more challenging.

Smartphone design Internet of Things IoT
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Wireless has become so commonplace we now take it for granted. It is essential not only for phones, but it is also unleashing the new universe of connected devices known as the Internet of Things (IoT). The IoT has taken off and will grow exponentially in the next few years. It is certain to bring embedded connectivity to all types of equipment and products used in industries, business, and society, and it is already opening up compelling new product categories, such as smart wearables.

You'd think that with ubiquity a wireless product developer's work would become routine. But, in fact, the opposite is the case. As we enter the era of IoT and build smaller and smarter connected devices, the task of meeting a design's most fundamental needs becomes more challenging. The traditional must-have characteristics for successful devices—high performance, low power and low electromagnetic interference (EMI)—are more important than ever.

In addition, it's necessary that interfaces used to connect these components support—and even improve—a product's ability to meet these needs.

Must-Have No. 1: High Performance

Take smartphones, for example. Smartphones are becoming pervasive, but they are still not easy to build. Each generation of smartphones that comes to market uses an increasingly complex assortment of components, including multiple high-speed modems, faster application processors, high-resolution cameras and displays, a dozen or so sensors and more. The physical layer interfaces between components must meet very stringent requirements to facilitate high-performance computing, as well as the high wireless data speeds that 4G/LTE and 802.11ac Wi-Fi technologies can bring.

IoT devices have fewer components and more modest overall performance requirements when compared to smartphones, but in many ways it is more challenging to deliver the needed capabilities with IoT because these products must often operate multiple radios, processors and sensors while running on coin-sized batteries. When it comes to interfacing components in IoT designs, the classic mobile design challenge—the need to do more with less—takes on added difficulty and significance.

Must-Have No. 2: Low Power

Low-power operation is always required in a mobile or mobile-influenced device. For smartphones, the design must consume minimal power even while delivering PC-like performance so customers can enjoy extended feature-rich operation while preserving battery life. Low-power operation also protects the device from getting too hot.

IoT devices can get by with fewer radios and other components because these products are often designed into very small form factors for wearables or other narrowly defined use cases. The challenge with IoT products is to keep power requirements as low as possible while maintaining connectivity and controlling sensors to gather and transmit information. A fitness tracker, for example, might employ sensors for counting steps or tracking location via GPS, and must feed that information efficiently via a wired interface to an application processor or radio.

The majority of smartphones and IoT products today employ I2C interfaces to integrate sensors efficiently. The forthcoming MIPI I3C interface—which is compatible with and broadens the use of I2C—introduces sensor sleep mode capability, a duty-cycle approach to collecting and sending data, and high-speed transmissions to further improve performance while minimizing power requirements. (Note: In full disclosure, I serve as chairman of the technical steering group for MIPI Alliance.)

IoT devices will also need to employ power-efficient wireless standards to connect to hub devices, such as smartphones. While an IoT device can use a variety of wireless standards depending on the use case, practical options that support low-power operation include Bluetooth Smart; the forthcoming low-power, extended range version of Wi-Fi called 802.11ah; and ZigBee.  

Must-Have No. 3: Low EMI

EMI refers to the interference created by multiple radio interfaces in a device as well as the interference from displays and other components.

EMI is more of a concern in smartphones than it is in IoT devices, because the RF front end of a smartphone can have 10-20 RF components, including multiple radios operating in multiple frequency bands along with a power amplifier, switches, and filters. But there can be multiple radios in IoT devices like wearables, too, and in both smartphone and IoT products the design must minimize interference between the components.

Designers need to understand these issues and identify methods to reduce interference. In general, interfaces that employ slew-rate controls and low-voltage swings will make it possible for multiple radios to coexist in devices. These techniques will also prevent interference from impacting displays and other features.

Recommendations for Engineers

Developers who are interested in the ever-expanding world of mobile and mobile-influenced devices need to leverage the ecosystem of technology interfaces for their designs. Whether you are employing physical wires to interface internal components or wireless communications protocols to provide an air interface to the network, make sure your design observes the three key principles of successful mobile designs: high performance, low power, and low EMI. The dedicated focus on these principles has enabled developers to find success in smartphone designs, and by maintaining focus on these design must-haves, developers will establish the best foundation for success in burgeoning IoT markets too.

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