**4. Principles for positioning detection**

Radio-frequency EPTS are based on quite similar principles of use for positioning detection [13, 14, 21], however, UWB replace satellite navigation networks by a set of antennae installed in a known positioning around the field in which the data are going to be recorded. Thus, UWB system calculate position of devices using: (1) the antennae set (which act as a reference system), and (2) the devices tracked (**Figure 1**). The communication stablished between antennae allows a detection of each device enclosed in a tight-fitty garment commonly located between each player´ scapulae. So, UWB is based on a wireless technology, which establish a communication in the absence of a physical medium [23]. Concretely, the reference system is composed by a set of antennae located around the field in which the measurements are going to be recorded. Though an algorithm (see 4.2. section) (e.g. Time Difference of Arrival (TDOA)), at least three antennae stablished a circumference around themselves, whose radius is defined by the distance between an antenna and the object [13]. It is known that player positioning is in any place of the circumference's perimeter. When at least three antennae stablish their computation, the circumferences perimeters meet in a common place, where the player is (**Figure 1**).

These communication is stablished using electromagnetic waves which carry data [23]. The values of the electromagnetic waves that allow positioning computation are measured over time, and represented by curves, called sinusoids [24]. These curves appear in a certain shape according to their values. Mathematically, these sinusoids are the result of the number of beats or cycles per second (frequency), the power of each frequency component (amplitudes), and the delay or advantage of a signal (phase), which describe the angular displacement of two sinusoidal functions [23, 25]. The key to transmitting the information is through the use of waves with more complex shapes, as a result of a combination of different sinusoids [25]. Depending on the frequency of these waves, indoor positioning wireless technologies are classified into different types (see introduction section).

The distances between antennae (node located in known positioning) and device (held by each player and located in unknown positioning) are computed by UWB positioning algorithms, clustered into different categories: angle of arrival (AOA), received signal strength (RSS); time difference of arrival (TDOA); time of arrival (TOA), and a hybrid algorithm [13]. An understanding of the accuracy, environment, estimation technique, space, and purpose of use of these algorithms is critical because of their differences and the appropriateness of their use in different situations [3, 13]. In brief, despite the fact that AOA algorithm has valid accuracy, AOA and RSS are more suitable than other methods for those systems based on a narrowband signals than with a high UWB bandwidth [3, 13]. Instead, TOA algorithm is suitable for those systems with bandwidth such as UWB. Regarding to the accuracy, small errors in AOA will negatively impact precision when the target object is far away from the base station. However, TOA and TDOA are more accurate relative to other algorithms because of the high time resolution of the UWB signals. In addition, due to hybrid algorithms combine the advantages of all algorithms, it seems to be the most effective solutions for UWB positioning systems [13].

The receiver and transmitter devices that these technologies contain are interconnected to avoid communication with interference from other devices [13]. The communication of the UWB system occupies a very large frequency band, at least 0.5 GHz, as opposed to more traditional radio communications which operate on much smaller frequency bands. On the other hand, since UWB is only allowed to transmit at very low power, its signal emits little noise and can coexist with other services without influencing them (Bastida-Castillo, Gómez-Carmona, De la Cruz-Sánchez, et al., 2019).

## **5. Limitations and future ways of the use of UWB in team sport**

As was analyzed in this chapter, each manufacturer provides a different LPS based on different engineering specifications. Hence, the comparison between LPS provides a wide conclusion due to the comparison between two systems with

**101**

*Review of Ultra-Wide Band in Team Sports DOI: http://dx.doi.org/10.5772/intechopen.94591*

with the same characteristics, and context.

high speeds or involving different trajectories.

**6. Concluding remarks**

different standards is difficult. However, since LPS measurement seems to be sensible by several factors such as temperature, humidity gradients, air circulation, pitch dimensions or infrastructure condition, among others [3, 13], the comparison between the outcomes of two studies should be made with caution, even though both of them were performed with the same UWB device. In fact, the same device has resulted in different outcomes in outdoor and indoor context, even in two indoor environments (see **Table 3**). In order to open a research way with the aim of unification all possible information about the use of UWB technology (among others) in the scientific articles´ methodology description, a survey has been published [3] based on the following literature: [5–7, 13, 14, 21, 26–34]. Recently, the information provided in articles has been analyzed based on the survey, and it has been highlighted a need to more detailed descriptions [3]. Accordingly, the items provided by the survey belongs to five quality metrics: (1) system accuracy and precision; (2) coverage and its resolution; (3) latency in making location updates; (4) building's infrastructure impact; and (5) effect of random errors on the system such as errors caused by signal interference and reflection [35]. This fact makes that the comparison between two studies may be unsuitable, at least, while the narrow information is reported. The sampling frequency, computation methods for velocity and acceleration, data exclusion and inclusion criteria, high-intensity bias due to random error, the time at which the data were extracted, technology lock, and data synchronization, and other factors such as the athlete's clothes, the number of reference point, environmental and infrastructure conditions, antennae installation and position, and measurement methods have also been mentioned for the use and description for UWB technology. However, the most of these questions has been addressed in other context such as engineering, and this survey focused in sport settings was based on theoretical framework. The unification of these information will allow a summary of future systematic reviews comparing the outcomes extracted

Theoretically, UWB seems to be the most promising technology for team sports tracking monitoring, however, since it has not been compared against another LPS in team sport setting, it should be considered with caution. In any case, the devices based on UWB technology have shown a high degree of validity for all variables based on positioning (static positioning, time-motion, high speed running and collective tactical behavior). Specifically, Realtrack Systems (6 antennae/18 Hz) = bias (distance covered): 0.55–5.85%, bias (velocity): −0.56 - 0.67, and difference with other EPTS (collective tactical analysis): 8.31%; Realtrack Systems (8 antennae/33 Hz) = bias: 0.28%; KINEXON ONE = TEE: 1.0 ± 6.0%; Ubisense = bias: 8.25 ± 4.07%). Hence, all Realtrack Systems´, KINEXON ONE's and Ubisense systems´ UWB are considered a valid technology for sport settings. Moreover, Realtrack Systems´ and KINEXON ONE's UWB showed to be reliable (KINEXON ONE = TE: 1.7 cm; Realtrack Systems (6 antennae / 18 Hz) = ICC: 0.65 (x-axis) and 0.88 (y-axis); Realtrack Systems (8 antennae / 33 Hz) = %CV: <1%). Therefore, UWB is considered a valid and reliable EPTS in the field of load monitoring of team sports in both indoor and outdoor environments. However, although UWB has usually resulting in greater accuracy than other radio frequency systems at high intensity drills [10], special care should be taken when analyzing load indicators at

To date, due to the low amount of information reported in the articles´ methodology sections [3], the comparison between outcomes extracted from devices with

### *Review of Ultra-Wide Band in Team Sports DOI: http://dx.doi.org/10.5772/intechopen.94591*

*Innovations in Ultra-WideBand Technologies*

The distances between antennae (node located in known positioning) and device (held by each player and located in unknown positioning) are computed by UWB positioning algorithms, clustered into different categories: angle of arrival (AOA), received signal strength (RSS); time difference of arrival (TDOA); time of arrival (TOA), and a hybrid algorithm [13]. An understanding of the accuracy, environment, estimation technique, space, and purpose of use of these algorithms is critical because of their differences and the appropriateness of their use in different situations [3, 13]. In brief, despite the fact that AOA algorithm has valid accuracy, AOA and RSS are more suitable than other methods for those systems based on a narrowband signals than with a high UWB bandwidth [3, 13]. Instead, TOA algorithm is suitable for those systems with bandwidth such as UWB. Regarding to the accuracy, small errors in AOA will negatively impact precision when the target object is far away from the base station. However, TOA and TDOA are more accurate relative to other algorithms because of the high time resolution of the UWB signals. In addition, due to hybrid algorithms combine the advantages of all algorithms, it seems to

The receiver and transmitter devices that these technologies contain are interconnected to avoid communication with interference from other devices [13]. The communication of the UWB system occupies a very large frequency band, at least 0.5 GHz, as opposed to more traditional radio communications which operate on much smaller frequency bands. On the other hand, since UWB is only allowed to transmit at very low power, its signal emits little noise and can coexist with other services without influencing them (Bastida-Castillo, Gómez-Carmona, De la

be the most effective solutions for UWB positioning systems [13].

**5. Limitations and future ways of the use of UWB in team sport**

As was analyzed in this chapter, each manufacturer provides a different LPS based on different engineering specifications. Hence, the comparison between LPS provides a wide conclusion due to the comparison between two systems with

**100**

**Figure 1.**

*Positioning using UWB technology.*

Cruz-Sánchez, et al., 2019).

different standards is difficult. However, since LPS measurement seems to be sensible by several factors such as temperature, humidity gradients, air circulation, pitch dimensions or infrastructure condition, among others [3, 13], the comparison between the outcomes of two studies should be made with caution, even though both of them were performed with the same UWB device. In fact, the same device has resulted in different outcomes in outdoor and indoor context, even in two indoor environments (see **Table 3**). In order to open a research way with the aim of unification all possible information about the use of UWB technology (among others) in the scientific articles´ methodology description, a survey has been published [3] based on the following literature: [5–7, 13, 14, 21, 26–34]. Recently, the information provided in articles has been analyzed based on the survey, and it has been highlighted a need to more detailed descriptions [3]. Accordingly, the items provided by the survey belongs to five quality metrics: (1) system accuracy and precision; (2) coverage and its resolution; (3) latency in making location updates; (4) building's infrastructure impact; and (5) effect of random errors on the system such as errors caused by signal interference and reflection [35]. This fact makes that the comparison between two studies may be unsuitable, at least, while the narrow information is reported. The sampling frequency, computation methods for velocity and acceleration, data exclusion and inclusion criteria, high-intensity bias due to random error, the time at which the data were extracted, technology lock, and data synchronization, and other factors such as the athlete's clothes, the number of reference point, environmental and infrastructure conditions, antennae installation and position, and measurement methods have also been mentioned for the use and description for UWB technology. However, the most of these questions has been addressed in other context such as engineering, and this survey focused in sport settings was based on theoretical framework. The unification of these information will allow a summary of future systematic reviews comparing the outcomes extracted with the same characteristics, and context.
