Ultra-wideband communications and location detection applications are steadily increasing. As a designer, you have options and therefore must decide how to best integrate UWB into your IoT design.
Impulse radio ultra-wideband, commonly referred to as UWB, is a short-range, wireless communication protocol based on the IEEE 802.15.4z standard, operating at frequencies up to 9.5 GHz. UWB has significant benefits as a tracking and ranging technology, including high levels of accuracy, security, and immunity to jamming. With its ability to use large channel bandwidths of 500 MHz, UWB captures spatial and directional data with accuracy levels of less than 10 cm.
In this article, we briefly review UWB technology and the plethora of emerging use cases before considering the decisions and challenges facing the designer when starting a new UWB-based project.
UWB uses two positioning techniques: two-way ranging (TWR) and time difference of arrival (TDoA) (see Figure 1). TDoA uses a system of fixed-position anchors and movable tags, where the anchors detect UWB pulses emitted by the mobile tags. TDoA systems are used in smart factories or warehouses for asset tracking, for example, where smart tags attached to the asset transmit pulses to anchors installed in the facility. It is also possible, for example, for UWB-enabled phones to work with a set of anchors transmitting packets to ensure the location of the phone is available to users only and to protect privacy.
With TWR (Figure 2), two UWB-enabled devices start “ranging” or exchanging radio packets when they are in range. The distance between the two devices is calculated by multiplying the roundtrip time, or time-of-flight (ToF), of these radio packets by the speed of light.
UWB’s characteristics enable a range of compelling user experiences such as hands-free secure access and no-touch set-up and control of smart home environments. The three core UWB services can be found at the heart of each use case:
Hands-free access control
Figure 3 illustrates how UWB technology, combined with Bluetooth Low Energy (BLE) as wakeup, delivers a seamless, secure, hands-free entry experience to a user. The BLE receiver is used for discovery and channel establishment, minimizing the receive time and, hence, power consumption of the UWB device.
If the mobile device and smart lock are associated, they will trigger a credential verification, deriving the required session keys for the actual secure ranging. Once validated, the secure UWB ranging session is initiated, measuring the distance and angle of arrival (AoA) between the mobile device and the smart lock. This UWB-ranging session uses the session key on both ends derived in the previous step. The smart lock will trigger the unlock action for the person to enter — without needing key cards, PINs, or any specific user action.
UWB technology delivers highly accurate positioning within indoor environments and dense urban areas where the buildings and their structure can block satellite-based services such as GNSS. UWB technology provides precise positioning even in crowded, multi-path environments to support navigation in large spaces such as airports, shopping malls, and multi-story parking garages. UWB can also enable asset tracking in smart factories and warehouses, as well as tracking medical equipment, staff, or patients in hospital settings.
UWB’s AoA estimation technique lets two devices localize each other by sharing relative ranging and positioning data. This capability supports a wide spectrum of applications. For example, two people with mobile phones can locate each other with precision, parents can keep track of their children, and rideshare customers can find their driver in a sea of vehicles. This device-to-device capability enables a range of smart home use cases. Networked devices and appliances such as smart lighting and climate control systems can respond automatically as a person enters a room. UWB functionality embedded in smart speakers and TVs enables touch-free setup and control.
With more use cases constantly appearing across multiple markets, including smart cities, smart homes, industrial, and automotive, analysts are predicting strong UWB market growth over the next seven years.
As always, in such a fast-growing market, standards and interoperability are key, and the FiRa Consortium encourages the development of a complete UWB ecosystem. With a rapidly growing membership, including chip and device manufacturers, system integrators, service and technology providers, test tool designers, test labs, and academics, the FiRa website contains a wealth of information on UWB technology and solutions. The organization also provides a certification program, which ensures interoperability among chipsets, devices, and systems from different manufacturers.
Developing a fully featured UWB solution will require a designer to consider two primary factors: use case and end device. These two factors impact a variety of different design choices throughout the process.
First, designers must consider their use case. According to the FiRa Consortium, many use cases essentially rely on one or more of the three core services outlined above. The use case determines both the level of security and the antenna configurations, which affects the needed number and types of antennas. For example, enabling access control for a smart home requires secure ranging to have strong protection against relay attacks. In contrast, a smart home use case where one device locates another, such as locating a speaker, a tag, etc., doesn’t typically require secure ranging but will rely instead on the availability of angle of arrival information, requiring multiple antennas.
Different use cases also require different software features. To use our previous example, the device localization use case we discussed earlier would require the capabilities to range simultaneously to multiple devices, which might not be as necessary for a tag that is to be localized within the infrastructure.
You must also consider the end device to which you will integrate UWB. Coin cell batteries are commonly used in item trackers such as the Apple AirTags or Samsung Galaxy SmartTag+. The inclusion of coin cell batteries requires UWB designs that will not draw a too high peak current from the battery. You can, however, use a UWB IC specifically designed to these requirements. Meanwhile, wall plug-powered devices, such as speakers or televisions, will have fewer constraints on power needs.
Building a UWB-enabled device is ultimately a hardware and software integration. On the one hand, UWB ICs often provide software integration out of the box. In addition, UWB suppliers have started to offer a growing range of easy-to-use modules that can ease the development of UWB applications so you can reduce hardware-development time.
RF modules and off-the-shelf antennas
For companies developing UWB products with lower production volumes or companies that prefer not to do the full hardware development in-house, modules may be the best approach. Most module manufacturers provide development kits that let you perform rapid evaluation and prototyping before committing to developing the final product. This helps reduce the need for specialist skill sets. Furthermore, you can leverage pre-developed antennas and regulatory approval.
The development path
UWB is a popular technology, enabling a wide spectrum of applications across multiple use cases and sectors. With the UWB market currently snowballing, you must consider the use case, software, and other product requirements when selecting your UWB design. You can use UWB ICs with full software enablement and in some cases, UWB modules represent the best development approach for IoT applications.
Ultra-wideband (UWB) has emerged as a powerful wireless technology for positioning and ranging, offering considerable benefits, including accuracy and security, when compared with other technologies. The UWB market is set for rapid growth over the coming years, with use cases spanning multiple markets and applications, including smart cities, smart buildings, smart retail, smart home, mobility, and many more. Significant design opportunities exist for designers of new UWB applications, with critical success factors including cost and time to market.