The recent years have witnessed a surge of interest in wireless ranging and localization complementary to GNSS to navigate or geo-reference objects in areas without satellite coverage, provide higher precision or reactivity, or to circumvent the cost of additional chips, their excessive size or power consumption. Apple and Samsung smartphones have paved the way by including Ultra-Wideband (UWB) solutions, assessing the commercial promises of applications such as indoor real-time localization systems (RTLS), asset tracking, smart locks, and keyless car entry.
Several ranging methods are available for use in wireless systems based on received signal strength (RSSI), time of flight (ToF) and channel sounding (CS). Other localization techniques such as time difference of arrival (TDoA) or angle of arrival (AoA) typically exploit multiple antenna configurations. These are supported by a wide range of wireless technologies, targeting different applications, and suited for use with different ranging and localization techniques.
This work focuses on the evaluation of localization techniques based on two wireless standards intended for battery operated devices and short to medium range, Bluetooth and Bluetooth Low Energy (LE) and UWB (IEEE802.15.4z), comparing them in terms of power consumption, accuracy, latency, and cost. The connectivity champions Bluetooth and Bluetooth LE are now being extended by more performant ranging and localization capabilities, competing with UWB. The UWB is dedicated to higher data rates and optimized for precise and secure ranging, at the typical cost of an order of magnitude higher peak power consumption, larger silicon area and lower link budget. Nevertheless, the two-way ToF employed in UWB devices provides a time and energy efficient means to determine distance with a cm-level precision. The CS technique employed by Bluetooth, requires a long time to sample the different frequencies and convert them to time-domain response, making it slower and requiring more energy. In addition, the available bandwidth of 80 MHz in the ISM band limits the achievable resolution to more than 1 m. However, with the planned allocation of the new 6 GHz band to Bluetooth, the performance is expected to approach that of UWB, albeit at an additional cost in power consumption and complexity.
Depending on the application requirements, either Bluetooth or UWB will have an edge. UWB is a technology of choice when precision and efficiency are paramount, while Bluetooth can be seen as a smaller and cheaper alternative, offering connectivity to many devices. The ranging speed, and support for TDoA make the UWB better suited for scaling, allowing to quickly localize many devices. The two technologies can also be perceived as complementary and merged to leverage the Bluetooth connectivity and the UWB localization capabilities, expanding on the concept of narrowband-assisted UWB localization and paving the way for future applications.