Ultra WideBand Positioning (UWB Positioning) is one of the most recent indoor positioning technologies to emerge. Prior to UWB Positioning, there were similar technologies referred to as a base-band, impulse, and carrier-free technology. The United States of America Department of Defense was the first to use the term “ultra wideband”. UWB indoor positioning became commercially available in the late 1990’s. UWB radio is a method of spectrum access that can provide high speed data rate communication over the personal area network space.
According to the Federal Communications Commission, UWB positioning is defined as an RF signal that occupies a portion of the frequency spectrum that is greater than 20% of the center carrier frequency, or has a bandwidth greater than 500 MHz. UWB is a communication channel that spreads information out over a wide portion of the frequency spectrum. This allows UWB positioning transmitters to transmit large amounts of data while consuming little transmit energy. UWB can be used for positioning by utilizing the time difference of arrival (TDOA) or the RF signals to obtain the distance between the reference point and the target.
UWB positioning systems rely on transmitting extremely short pulses and use techniques that cause a spreading of the radio energy (over a wide frequency band) with a very low power spectral density. This high bandwidth offers high data throughput for communication. The low frequency of UWB pulses enable the signal to effectively pass through common objects such as falls, furniture, and other objects.
There are three main areas of use for uwb localization:
- Communication and sensors
- Positioning and asset tracking
UWB positioning techniques can, in fact, give real-time indoor precision tracking for many applications such as mobile inventory and locator beacons for emergency services, indoor navigation for blind and visually impaired people, tracking of people or instruments, and military reconnaissance. UWB positioning signals provide accurate position and location estimation for indoor environments.
Why has Ultra Wideband Indoor Positioning Gained Attention Recently?
In general, the high data rate of UWB positioning systems can reach 100 Megabits per second (Mbps), which makes it a great solution for near-field data transmission.
Also, the high bandwidth and extremely short pulses waveforms help in reducing the effect of multipath interference and facilitate determination of TOA for burst transmission between the transmitter and corresponding receiver, which makes UWB a more desirable solution for indoor positioning than other technologies.
The length of a single pulse determines the minimum differential path delay while the period pulse determines the maximum observable multipath delay in order to unambiguously perform multipath resolution.
In addition, the low frequency of UWB pulses enables the signal to effectively pass through obstacles such as walls and objects which improves the UWB positioning accuracy. In fact, UWB provides a high accuracy rate that can minimize error to sub-centimeters. Therefore, UWB positioning can be considered as one of the most suitable choices for critical positioning applications that require highly accurate results.
UWB indoor localization technology, unlike other positioning technologies such as infra-red and ultrasound sensors, does not require a line of sight and is not affected by the existence of other communication devices or external noise due to its high bandwidth and signal modulation. Also, the cost of UWB equipment isn’t as expensive and consumers less power than other comparable technologies such as beacons.
Many indoor positioning systems were implemented commercially using UWB technology. One well known positioning system example is the Ubisense system. In a Ubisense system, a user carries tags that transmit UWB signals to fixed sensors that use the signals to determine the user’s positions using the time of arrival (TOA) method.
According to a report published by TechNavio market research company, the market of indoor positioning services grew at a compound annual growth rate of 29.7% over the period of time between 2014 to 2019. Indoor positioning systems today, in 2021, are now being used for various applications in hospitals, shopping malls, airports, museums, athlete training, and others. Due to the increase in market demand, other companies, such as Mapsted are starting to explore new opportunities of this new market to leverage the advantages of UWB technology in providing more innovative solutions.
Legal Concerns with UWB Indoor Localization
While UWB indoor localization does have its advantages, UWB applications must limit their operation to short ranges of frequencies with wide frequency range of UWB to reduce the probability of interference. In order to regulate the use of the wide range of UWB indoor localization, license-exempt (unlicensed) and individually licensed frameworks were developed. Many countries and administrations have adopted license-exempt frameworks for UWB positioning such as the United States, European Union, and many Asia-Pacific countries. These frameworks require application of special masks and operational conditions. The Federal Communications Commission, European countries, Korea, and Japan are aligned in having the entirety or parts of the 3100 to 10,600 MHz band for such extensive applications.
In the United States, there are very strict requirements for the bandwidth and power spectral density of UWB positioning systems. The prescribed transmit frequencies are regulated by the National Telecommunications and Information Administration (NTIA).
One of the challenges of UWB Positioning system implementation is avoiding transmission of the signals at the prescribed frequencies according to the country’s regulation regarding the frequency in which it will be used. Many countries do not provide UWB frequency allocation for a new device unless it achieves the NTIA guidelines on spectrum complaint or any equivalent requirements in other developed countries.
Strengths of Ultra Wideband Indoor Positioning
One advantage of using an UWB indoor navigation system is that it is license-free because of its low power. UWB is not classified as radio equipment because its low power signal does not interfere with most of the existing radio systems. UWB consumes low power in comparison with other positioning systems that enable power efficiency for better battery life of devices. UWB localization uses pules that allows transmitters to send only during the pulse transmission which in turn produces strict duty cycle on the radio in order to minimize the baseline power consumption.
Also, the complexity of ultra wideband localization communication is implemented in the receiver rather than in the transmitter. This feature offers low power consumption for senders and shifts complexity as much as possible to the receiver. In addition, UWB has a very high level of multipath resolution because of its large bandwidth. Large bandwidth provides frequency diversity that makes time modulated ultra wideband (TM-UWB) signal resistant to the multipath problems and interference. Time modulated UWB has a low probability of interception and detection and it is used in some particular applications such as in the military.
UWB indoor positioning systems have greater penetration of obstacles (such as walls, furniture, and people) than conventional signals, and they achieve the same data rate. However, due to power restrictions, common UWB positioning systems may face difficulty to penetrate walls.
UWB transmissions involve very short pulses, which have recently received significant interest. Very short pulses offer an advantage in terms of resolvability of multipath components. Many received signals in an environment that are characterized by multipath is a superposition of the delayed replicas of the signal. This has been avoided in UWB because the reflections from objects and surfaces near the path between the transmitter and receiver tend not to overlap in time because of the very short pulses of UWB. This means UWB has a desirable direct resolvability of direct multipath components.
Ultra Wideband Indoor Positioning Weaknesses
Although uwb localization systems have their strengths for many applications, it does have some weaknesses. For example, the possibility of interference with nearby systems that operate in the ultra wide spectrum due to misconfiguration. In the United States, the UWB frequency range for communication applications is 3.1 to 10.6 GHz, which operates in the same frequencies as popular communication products such as Worldwide Interoperability for Microwave Access (WiMAX) and digital TV. in some countries, it may also interfere with systems such as third-generation 3G wireless systems.
There are some concerns that many UWB positioning devices may cause harmful interference to GPS and aircraft navigation radio equipment. To overcome those concerns, various techniques have been developed to eliminate harmful interference with other sensitive services, such as Detection and Avoidance.
Interference may also occur from the existing system to the UWB positioning system. The UWB indoor positioning system’s signals may spread over other bandwidths that contain the existing frequency of a narrowband system. This interference can be elevated by using minim mean-square error (MMSE) multiuser detection schemes to reject strong narrowband interference. Also, simultaneous ranging among many UWB tags may cause some problems to channel access control which may lead to weakened UWB positioning accuracy.
Although using very short pulses in UWB has many advantages, the UWB receiver requires signal acquisition, synchronization and tracking to be done with very high precision in time relative to the pulse rate. These steps are time-consuming. Positioning is one of the most important and challenging phases in navigation systems where different technologies have been developed to improve performance. While UWB positioning provides high accuracy positioning in addition to many other features (E.g., license free, low power consumption does not interfere with most of the existing radio systems, large bandwidth, and high data rate communication), UWB positioning technology may affect GPS and aircraft navigation radio equipment and can also cause interference to the existing systems that operate in the ultra wide spectrum. In comparison to other technologies Mapsted has analyzed, UWB positioning systems have emerged as one of the leading technologies for indoor positioning and have been used in a plethora of applications. Thankfully, Mapsted uses a revolutionary algorithm to leverage a variety of positioning systems and provide the world with the only indoor positioning system that doesn’t rely on the use of Bluetooth beacons, WiFI, or UWB signals.