UWB Positioning Explained – Everything You Need to Know About it Before Implementing

February 16, 2021

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uwb positioning explained
uwb positioning explained

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 enables the signal to effectively pass through common objects such as falls, furniture, and other objects.

How Does Ultra-Wideband (UWB) Positioning Work?

UWB gives a sixth sense to your devices. These signals work on a spatial scale ranging from NANO to Personal Area Network (PAN). It is intended to operate in close proximity and over a wide bandwidth due to its low pass spectral density. The UWB adheres to the 802.16.5 standard and communicates with peer devices. 

The UWB employs pulse radio to transmit a large bandwidth in short cycles while consuming very little power. UWB uses high pulse repetition rates to increase localization accuracy and data rates by transmitting more pulses per second. 

The pulse repetition rates are reduced to improve ranging performance, making the technology suitable for radars and imaging. 

Rather than the received signal strength indicator, the measurements are based on Time of Flight (ToF) and Angle of Arrival (AoA) (RSSI). To improve trilateration accuracy, three or more receivers are required, but the line of sight is more vital. When UWB tags are tracked, they emit pulses containing ID, ToF, and timestamp data. The signals are picked up by nearby nodes and sent to the tracking source for processing. ToF measurements are used to determine the distance and orientation of tags within a few centimeters.

There are three main areas of use for localization:

  1. Communication and sensors
  2. Positioning and asset tracking
  3. Radar

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. 

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Technical Features of Ultra-Wideband

The spectral density of UWB in comparison to other short-range communication protocols is shown above. UWB stands out due to its high bandwidth of 500Mhz. It operates efficiently in a signal dense environment with almost no interferences. It performs at frequencies ranging from 3.1 to 10.6 GHz and requires transmission power ranging from 0.5mW to 41.3 dBm/MHz. Within a 10-meter radius, UWB signals have an effective line of sight range of 10-150m and a high data rate of 1Gbit/s.

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 the 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 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 have 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 for 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 in 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 a 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 the 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 directional 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 complaints or any equivalent requirements in other developed countries.

Strengths of Ultra-Wideband Indoor Positioning 

strengths of ultra wideband indoor positioning

One advantage of using a 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 allow transmitters to send only during the pulse transmission which in turn produces a 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 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 for indoor positioning systems penetrate better through 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 the 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 at 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 tracking 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.

How is UWB Different From Other Positioning Technologies?

To answer the question of ‘how does UWB positioning work’, let’s look at how it contrasts with GPS. Today, indoor positioning technology is almost a curiosity due to its use in a wide range of military and civilian applications. While GPS is synonymous with outdoor navigation, indoor navigation presents a unique set of challenges that most other technologies have yet to address. That is precisely why the emphasis has shifted to UWB. Whereas traditional short-range communication protocols have flatlined, UWB has remained consistent and adaptive. While immovable obstacles, people, and other signal interferences reduce Bluetooth and Wifi range and data rate, they have no effect on UWB devices or their ability to perform trilateration on indoor objects, and that sets UWB apart from any positioning technology known today.

Frequently Asked Questions

Q1. How does UWb location technology work?

Ans. During UWB transmission, closely spaced pulses are broadcast across a broad spectrum, and these pulses are parsed in the exact order in which they were transmitted at the receiver station. For ranging, Time of Flight measurements are used, and the accuracy is within centimeters rather than meters as with other positioning technologies. This is why an ultra-wideband location system is a better choice.

Q2. What is UWB used for?

Ans. The UWB localization excels over other similar technologies because it helps in enforcing social distancing by warning tag bearers when they are closer to peer devices. The technology can also unlock and lock doors being completely immune to signal spoofing attacks. UWB technology is found in newer Apple gadgets to securely share data with nearby devices.

Q3. Does UWB interfere with Wi-Fi?

Ans. UWB devices can operate effectively in a signal jungle without becoming susceptible to interference or interfering with other narrowband signals operating at the same or nearby frequencies.

Q4. How secure is UWB?

Ans. UWB technology employs robust security protocols that discourage hackers from employing signal spoofing techniques. The technology is at the pinnacle of precise positioning and provides fine-ranging measurements, increasing its efficiency in indoor localization.

Q5. Are UWB systems expensive?

Ans. The cost of implementing a UWB system can be several times of BLE and Wi-Fi systems. They require specialized tags and peer devices that can send short-range pulses without being power-starved.

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