SENSORCOMM 2014 : The Eighth International Conference on Sensor Technologies and Applications

Ultra Wideband Positioning:

An Analytical Study of Emerging Technologies

Suheer Alhadhrami, Abdulrahman Alarifi, Mai A. Al-Ammar

AbdulMalik Al-Salman Ahmad Alnafessah
and Hend S. Al-Khalifa and Mansour Alsaleh

Computer Science Department, Computer Research Institute, Department of Computer Science,

King Saud University, King Abdulaziz City for Al-Imam Mohammad bin Saud
Riyadh, KSA Science and Technology, Islamic University,
Riyadh, KSA Riyadh, KSA
Email: 430204094@student.ksu.edu.sa Email: aarifi@kacst.edu.sa Email: mai.alammar@ccis.imamu.edu.sa
salman@ksu.edu.sa aalnafessah@kacst.edu.sa
hendk@ksu.edu.sa maalsaleh@kacst.edu.sa

Abstract—In recent years, indoor positioning has emerged time [5]. IPSs use numerous positioning approaches, which
as a critical function in many end-user applications; including vary greatly in terms of accuracy, cost, precision, technology,
military, civilian, disaster relief and peacekeeping missions. To scalability, robustness and security [2]. There are five main
cope with this surge of interest, much research effort has focused
on meeting the needs of these applications and overcoming quality metrics of the indoor positioning systems, which
their shortcomings. Ultra WideBand (UWB) is an important should be considered: (1) accuracy and precision of the sys-
technology in the field of indoor positioning and has shown tem; (2) coverage and resolution of the coverage; (3) latency
great performance compared to others. In this work, we identify in producing location updates; (4) impact of a building’s
and analyze existing ultra wideband positioning technologies infrastructure; and (5) effect of random errors on the system
and present a detailed comparative survey. We also provide
a Strengths, Weaknesses, Opportunities, and Threats (SWOT) such as errors caused by signal interference and reflection [6].
analysis, a method generally used in management science to Indoor positioning has many applications such as indoor
evaluate the strengths, weaknesses, opportunities, and threats navigation systems for blind and visually impaired people,
involved in a product or technology, to analyze the present state locating devices through buildings, aiding tourists in museums,
of UWB positioning technologies. finding an emergency exit in a smoky environment, tracking
Index Terms—Ultra wideband; localization; positioning; in- kids in crowded places, and tracking expensive equipment.
door positioning; wireless sensor networks; networking; SWOT
Indoor positioning applications may require different quality
attributes and thus IPSs should be carefully selected to meet
I. I NTRODUCTION the requirements of the application.

Positioning is the process of determining a position of Indoor location-based services are an important application
people, equipment, and other objects. Recently, it has been of indoor ubiquitous computing. Accurate position measure-
an active research area where much of the research focuses ment is a critical requirement for indoor positioning tech-
on utilizing existing technologies to address the problem of niques. Given that UWB is one of the key techniques that is
positions’ determination. Positioning can be classified, accord- proven effective in indoor positioning, a comparative analysis
ing to the environment where the positioning is conducted, of the state-of-the-art UWB indoor positioning systems is
into two types: outdoor positioning and indoor positioning. indeed required. Furthermore, due to the U.S. Federal Commu-
Outdoor positioning is performed outside buildings and indoor nications Commission (FCC) recent allowance for the use of
positioning is performed inside buildings such as houses, unlicensed UWB communications, UWB civilian applications
hospitals, malls and others. Different applications may re- have been studied and explored intensively worldwide. Also,
quire different types of positioning technologies that fit their the development of international wireless communication stan-
needs and constraints. For example, Global Positioning System dards that adopts UWB technology has encouraged research
(GPS) is a technology that is suitable and efficient for the and development efforts on UWB. Consequently, developing
outdoor rather than the indoors since satellite radio signals new algorithms to improve UWB positioning performance is
cannot penetrate solid walls and obstacles [1][2][3][4]. becoming an active research area [7].
Indoor Positioning Systems (IPSs) determine the position This work is motivated by the fact that UWB is the most
of something in a physical space continuously and in real- promising technology for indoor positioning and tracking.

Copyright (c) IARIA, 2014. ISBN: 978-1-61208-374-2 66

SENSORCOMM 2014 : The Eighth International Conference on Sensor Technologies and Applications

Further, to the best of our knowledge, this paper is the first provides a high accuracy rate in which error can be minimized
analytical study of the state-of-the-art UWB indoor positioning to sub-centimeters. Therefore, UWB is considered to be one of
systems. Our study analyzes a wide range of positioning al- the most suitable choices for critical positioning applications
gorithms that have empowered UWB positioning systems and that require highly accurate result.
tackle different aspects of applications needs and requirements. UWB technology, unlike other positioning technologies
The nature of the application in question plays a major role such as infra-red and ultrasound sensor, does not require
in determining the appropriate solution for achieving certain line-of-site and does not get affected by the existence of
quality attributes. Hybrid positioning approaches have future other communication devices or external noise due to its high
potentials as they combine features of different approaches to bandwidth and signal modulation [13][14]. Furthermore, the
improve the performance. UWB equipment cost is low and it consumes less power
Our contributions in this paper are twofold. compared with other competitive solutions.
• We provide an updated literature review for existing Many IPSs were implemented commercially using UWB.
and recent research in UWB positioning systems (see One of the most known positioning systems that use UWB is
Sections II and III). Ubisense system. In Ubisense system, a user carries tags that
• We conduct a Strengths, Weaknesses, Opportunities and transmit UWB signals to fixed sensors that use the signals to
Threats (SWOT) analysis for UWB technology, which determine the user’s positions using Time of Arrival (TOA)
provide new directions and deeper insights into the state method [15].
of this technology beyond its well-known pros and cons B. Signal Modulation
(see Section IV).
Signal modulation is the process of carrying information
II. UWB P OSITIONING on the impulse signal (the carrier signal) by modifying one or
more of the signal properties. In general, signal modulation can
UWB is one of the most recent, accurate, and promising be categorized based on the signal state into three categories;
technologies [8]. The precursor technology of UWB is referred binary modulation, ternary modulation, and M-ary modulation.
to as a base-band, impulse, and carrier-free technology. The Also, signal modulation can be categorized based on signal
US Department of Defense is the first to use the term ultra properties that need to be modified into four categories; am-
wideband. At the late of 1990, the UWB was commercially plitude modulation, frequency modulation, phase modulation,
available [8]. UWB radio is a method of spectrum access and hybrid modulation.
that can provide high speed data rate communication over the
Signal modulation is a crucial phase in signal transmission,
personal area network space. UWB is based on transmitting
which can greatly improve the quality of transmitting signals
extremely short pulses and it uses techniques that cause a
to achieve certain quality criteria. For example, UWB signals
spreading of the radio energy over a wide frequency band with
are usually transmitted in the existence of other signals in
a very low power spectral density [8]. This high bandwidth
the air as well as reflected signals which may cause multi-
offers high data throughput for communication. The low
path interference. Thus, UWB must have high modulation
frequency of UWB pulses enables the signal to effectively
efficiency as signals must be recognized correctly in the
pass through obstacles such as walls and objects.
presence of noise and interference [9].
There are three main application areas for using UWB, There are various signal modulations that are used for
namely (1) communication and sensors; (2) positioning and UWB, such as Pulse Position Modulation (PPM), On-Off
tracking; and (3) radar [8][9]. UWB positioning techniques Keying (OOK), Pulse Amplitude Modulation (PAM), and
can provide real time indoor precision tracking for many Pulse Width Modulation (PWM) [9][16]. Signal modulation
applications such as locator beacons for emergency services is utilized to enhance the accuracy of UWB localization [9].
and mobile inventory, indoor navigation for blind and visually In UWB, Time-Hopping Spread Spectrum (TH-SS) impulse
impaired people, people or instruments tracking, and military radio could be used to solve multipath problems and generate
reconnaissance. The characteristics of UWB signals provide UWB signals with relatively computational cost. There are
the potential of highly accurate position and location estima- other modulations that are used by UWB such as Pseudo
tion for indoor environments [10][8]. Random (PR) time-modulation, Binary Phase Shift Keying
(BPSK), Time-Hopping Binary Phase Shift Keying (TH-
A. Why UWB has recently gained attention?
BPSK), Time-Hopping Pulse Position Modulation (TH-PPM),
In general, UWB has different features that are explored and Minimum-Shift Keying (MSK) [6][17]. Further details
in the literature [8][3][11]. The high data rate of UWB can about using these modulation technologies in positioning are
reach 100 Megabits per second (Mbps), which makes it presented in the next sections.
a good solution for near-field data transmission. Also, the
III. UWB P OSITIONING A LGORITHMS
high bandwidth helps in reducing the effect of multipath
interference, which makes UWB a more desirable solution for UWB technology is well-suited for indoor positioning
indoor positioning than other technologies [12]. In fact, UWB applications. In order to employ this technology, different

Copyright (c) IARIA, 2014. ISBN: 978-1-61208-374-2 67

SENSORCOMM 2014 : The Eighth International Conference on Sensor Technologies and Applications

TABLE I. C OMPARISON OF UWB S YSTEMS

No. Authors Year Accombined Technology Algorithm Environment

1 Ch’oliz et al.[26] 2011 TOA LOS/NLOS
2 Guangliang Cheng[10] 2012 TOA LOS/NLOS
3 Gunter et al.[27] 2010 TOA LOS/NLOS
4 Sivanand et al.[14] 2007 TDOA NLOS
5 Rowe et al.[29] 2013 TOA LOS
6 Jiang et al.[34] 2010 GPS AOA, TDOA NLOS
7 Jiang et al.[34] 2010 TDOA, TDMA LOS
8 Pittet et al.[31] 2008 MEMS AOA, TDOA
9 Shahi et al.[11] 2012 AOA, TDOA LOS/NLOS
10 Segura et al.[12] 2012 TOA, TDOA and TDMA LOS/NLOS
11 Cao and Li[47] 2012 ROA, TDOA and DOA
12 Mucchi et al.[37] 2010 AOA, TOA LOS
13 Liu et al.[48] 2012 GPS TDOA, RSS NLOS
14 Kuhn et al.[17] 2011 GPS, RFID and WLAN
15 Zhang et al.[49] 2010 TDOA
16 Deissler et al.[38] 2012 TOA
17 Tuchler et al.[50] 2005 TOA LOS
18 Digel et al.[39] 2013 LOS/NLOS
19 Jiang et al.[40] 2012 TOA,RSS LOS/NLOS
20 Tome et al.[28] 2010 TOA LOS
21 Arias-de-Reyna and Mengali[13] 2013 TOA LOS
22 Kilic et al.[51] 2013 TOF LOS
23 Mahfouz et al.[52] 2011 TDOA LOS
24 McCracken et al.[53] 2013 RSS Sensor RSST
25 Jiang et al.[54] 2013 TOA, TDOA
26 Yang et al.[55] 2013 STBCS-TDOA LOS/NLOS
27 Mirza et al.[56] 2012 Ultrasound sensor and compass AOA,TDOA
28 Ubisense[57] 2010 AOA,TDOA LOS/NLOS
29 Ubisense[58] 2011 TOA,TDOA LOS/NLOS
30 Ubisense[59] 2010 TOA,TDOA LOS/NLOS
31 Ubisense[60] 2010 TOA/TDOA LOS/NLOS

positioning algorithms have been developed in which position environment, estimation technique, range, purpose of use and
information is extracted from radio signals traveling between others. A summary and comparison of UWB positioning
the target node and the reference nodes as well as position algorithms is presented in Table I.
information of the reference nodes. There are many positioning
algorithms that can be classified into five main categories A. AOA-based Algorithms
based on estimating measurements: (1) Angle of Arrival In AOA technique, the estimation of the signal reception
(AOA); (2) Time of Arrival (TOA); (3) Time Difference of angles from at least two sources are compared either with
Arrival (TDOA); (4) Received Signal Strength (RSS); and (5) signal amplitude or carrier-phase across multiple antennas.
hybrid algorithm. In this section, we give a detailed review From the intersection of the angle line for each signal source,
of these algorithms for UWB indoor positioning. Also, we the location can be found. AOA estimation algorithms are
compare the algorithms in different aspects such as accuracy, very sensitive to many factors, which may cause errors in

Copyright (c) IARIA, 2014. ISBN: 978-1-61208-374-2 68

SENSORCOMM 2014 : The Eighth International Conference on Sensor Technologies and Applications

their estimation of target position. Furthermore, AOA estima- transceiver chipset for UWB to use them in indoor localization
tion algorithms have a higher complexity compared to other systems where TOA techniques have been used for position
methods. For instance, the antenna array geometry has an estimation [27]. The system was implemented for Line-of-
important role in the estimation algorithm [18]. Increasing Sight environment and its accuracy was estimated to be 8.3
the distance between the sender and receiver may decrease cm. On the other hand, Tom’e et al. designed and built a large-
the accuracy [19]. AOA technique can be used with other scale deployable UWB-based Local Positioning System (LPS)
techniques to increase the accuracy [20]. in which TOA is used for position estimation [28].
AOA based algorithms have been used in many literatures.
Xu et al. presented a new cooperative positioning method C. TDOA-based Algorithms
based on the AOAs, which utilizes pairwise AOAs information TODA is based on measuring the time difference of arrival
among all the sensor nodes rather than relying only on anchor of a signal sent by an object and receive by three or more re-
nodes [21]. Lee proposed the using of signal model and ceivers. In this manner, the location of the object (transmitter)
weighted-average to estimate AOA parameters for Low data will be determined. Also, the scenario can be flipped where a
Rate UWB (LR-UWB) [22]. A Kalman filter based AOA single receiver can determine the target location by measuring
estimation algorithm was introduced by Subramanian, which the difference in arrival times of two transmitted signals [19].
rely on a new linear quadratic frequency domain frequency
invariant beamforming strategy [23]. Typically, only one transmitter is available that requires the
multiple receivers to share the data and cooperate to determine
Furthermore, many studies have been conducted to evaluate the location of the transmitter. This cooperation requires
the performance of AOA for different applications, environ- significant bandwidth in comparison with other algorithms.
ments, hardware, and configurations. Mok et al. studied the
feasibility and performance of AOA for UWB in Ubisense Krishnan et al. have used TDOA for UWB indoor posi-
Real-Time Location System (RTLS) when integrated with tioning system where the site has been divided into cells and
GPS to facilitate resource management in underground railway each cell has four UWB readers mounted on the top corners
construction sites [24]. The influence of UWB directional to have line-of-sight with user tag. In this manner, the readers
antennas on the performance of AOA estimation was presented will be able to receive the signals from the user tag then send
in detail by Gerok et al. [25]. Gerok et al. presented a corrected the time of arrival to a central processing unit to determine
AOA estimation algorithm, which mitigates the error resulting TDOA and find user location [14]. Rowe et al. designed
from the UWB directional antenna. one dimensional system with two sensors and one tag using
TDOA based algorithm to determine the tag location [29].
B. TOA-based Algorithms On-Off Keying (OOK) modulation was used to overcome the
collision deduced by synchronous tag transmission, increase
TOA is based on the intersection of circles for multiple the performance, and decrease the cost and power at the same
transmitters. The radius of those circles is the distance between time.
the transmitter and receiver. This distance is calculated by
finding one-way propagation time between them [19]. The D. RSS-based Algorithms
time synchronization of all transmitters is required while the
receiver synchronization is unnecessary so that any possibility In RSS-based algorithms, the tracked target measures the
of significant delays must be accounted for during calculation signal strength for received signals from multiple transmitters
of the correct distances. in order to use signal strength as an estimator of the distance
between the transmitters and receiver. This way, the receiver
Choliz et al. identified a realistic indoor scenario, defined will be able to estimate its position relative to the transmitter
by a layout of walls and corridors, and a specific indoor nodes. Although RSS is sensitive to multipath interference and
UWB ranging model to evaluate different kinds of TOA based small scale channel effect, which cause a random deviation
algorithms for UWB such as Trilateration, Weighted Least from mean received signal strength, it is used frequently
Square with Multidimensional Scaling (WLS-MDS), Least with unrealistic assumptions such as transmitted power and
Square with Distance Contraction (LS-DC), Extended Kalman path loss exponent are known, and transmitter antennas are
Filter (EKF) and Particle Filter (PF) [26]. isotropic [19][30]. According to Pittet et al., the accuracy of
TOA based algorithms have been used to locate targeted RSS for Non-Line-Of-Sight (NLOS) and multipath environ-
objects for various applications and environments. Cheng et ment is low, which shows clearly that RSS is not the right
al. designed TOA-based personnel localization system for coal estimation method for indoor positioning systems [31]. Gigl et
mine using UWB technology, which can be very helpful al. explored the performance of RSS algorithms for positioning
to locate workers effectively in case of accidents [10]. For using UWB technology [32]. They also studied the effect
mobile robot tracking, Segura et al. proposed a novel UWB of small scale fading on the system accuracy; however, a
navigation system for indoor environment, which employ a simulator based on the UWB channel model 802.15.4a was
TOA based estimation algorithm to accurately locate mobile used to evaluate the algorithms rather than relying on real
robot [12]. Fischer et al. designed a monolithic integrated scenarios for indoor environments.

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SENSORCOMM 2014 : The Eighth International Conference on Sensor Technologies and Applications

RSS based algorithms can be classified into two main types: Several other systems have been developed for critical
trilateration and fingerprinting [33]. Trilateration algorithms missions to help in tracking people and object. An UWB
use RSS measurements to estimate the distances to three dif- indoor/outdoor NLOS localization system has been imple-
ferent reference node and hence estimate the current location. mented for disaster aid, in which GPS is used for outdoor
On the other hand, fingerprinting requires collecting a dataset localization while UWB is used for indoor localization [36].
of RSS fingerprints of a scene, which is later used to match TDOA and RSS are used to improve localization performance.
on-line measurements with the closest fingerprint in the dataset Another UWB tracking system for athlete has been presented
in order to estimate the location. by Mucchi et al. in order to determine the athlete’s speed
and acceleration and analyze his/her performance after med-
ical surgery [37]. They have implemented their system for
E. Hybrid-based Algorithms outdoor environments with different cell sizes and for indoor
environments using 4 sensors. The system was implemented
When multiple positioning techniques are used, they can
for Line-Of-Sight (LOS) environment setup and uses TOA and
complement each other or target different parts of the site that
AOA for positions’ estimation with good accuracy. Another
fit with their strengths. Overall accuracy will increase and the
system was designed by DeiBler et al., which tackles the
complexity and cost will increase, too. Jiang et al. presented a
problem of simultaneous localization and mapping in an
tracking system for staff, patients, and instruments in a hospital
emergency like an earthquake, fire, or terrorist attacks [38].
environment [34]. They used GPS for outdoor tracking and
The system was designed to perform UWB indoor mapping
UWB for indoor tracking. Furthermore, the site was divided
using a mobile antenna array with two receiver antennas and
into cells where each cell has at least 4 UWB readers and GBS
one transmitter between them. DeiBler et al. used Kalman
repeater. They used PDA, which has built-in GPS receiver and
filter for position estimation and Rao-Blackwellized particle
it was connected to UWB tag in order to work with both GPS
filter for data association and initialization of new objects.
and UWB at the same time. The UWB subsystem uses both
AOA and TDOA received by UWB readers to estimate the user Furthermore, a new UWB indoor navigation system was
position. Similarly, Kuhn et al. designed a multi-tag access proposed by Segura et al., which includes two sub-systems: the
scheme for UWB localization system, in which Minimum- location system and Mobile Robot (MR) control system [12].
Shift Keying (MSK) modulation was used with 2.40-2.48, They detect the first arrival of signal by designing a novel
5.40-10.6 Gigahertz (GHz) frequency and refresh rate of 1- dynamic threshold crossing algorithm and using TOA/TDOA
20 Hz in the range of 1m-100m [17]. Also, they have used for estimation. Time Division Multiple Access (TDMA) is
Time Division Multiple Access (TDMA) for channel access used to avoid multi-users interference.
control. TDOA was used to discover new tags and identify its Several other efforts have been done to improve positioning
position in 3D. Experimentally, it uses two tags and switches in UWB using hybrid based algorithms. Digel et al. designed
between them 20 times per second. and improved a digitizer of no-coherent Impulse Radio Ultra
A new pedestrian navigation solution has been introduced WideBand (IR-UWB) [39]. Jiang et al. designed a technique to
by Pittet et al., which combines UWB localization system and mitigate NLOS error by using Biased Kalman Filtering (BKF)
Micro Electro Mechanical Sensors (MEMS) to improve the and Maximum Likelihood Estimation (MLE) where both AOA
performance of pedestrian positioning [31]. AOA and TDOA and RSS were used [40]. Srimathi and Kannan made a
were used to know the presence of multipath and position comparison between Time-Hopping Spread-Spectrum (TH-
estimation. Furthermore, they used an Extended Kalman Fil- SS), Time-Hopping Binary Phase-Shift Keying (TH-BPSK),
ter (EKF) based algorithms to couple the measurement of and TH-SS coded and un-coded scheme UWB systems [41].
these two subsystems in order to combine the complementary Zebra is a commercial UWB positioning system, that offers
advantages of UWB and MEMS. Another system has been a UWB Real-Time Location System (RTLS) integrated with
introduced by Shahi et al., which consists of a network of other RTLS, which can use technologies, such as GPS, Radio
tags and receivers communicating over 68 GHz signals [11]. Frequency Identification (RFID) and Wireless Local Area
The path from transmitter to receiver is measured to locate the Network (WLAN) [17].
tag. The true location is determined by the direct path signals;
however, the error was produced by reflections of the signals. IV. SWOT A NALYSIS
The direct path signal can be distinguished from reflection
using UWB, so the accuracy increases. The computation is SWOT analysis is a useful analysis tool to understand and
calculated in one master server, which uses AOA and TDOA evaluate a technology, solution or business. SWOT analysis
for estimation. Also, FuCheng and MingJing designed UWB aims to identify the key internal (strengths and weaknesses)
localization and tracking system based on Kalman, linear H and external (opportunities and threats) factors that may affect
and extended H filters to accurately estimate the target position the success of an analyzed target. SWOT analysis has been
using DOA and TOA [35]. Their system was implemented in applied in many areas such as; industry, management and
30x30 meter cell with one access point, which is equipped engineering. Here, we apply the SWOT analysis to evaluate
with 4 elements array and noise statistics. UWB in terms of strength, weakness, opportunities and threats

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SENSORCOMM 2014 : The Eighth International Conference on Sensor Technologies and Applications

TABLE II. S UMMARY OF SWOT ANALYSIS FOR UWB TECHNOLOGY

Internal
Strengths Weaknesses
• License free • Potential interference to the existing systems ( ex
• Low power consumption Wimax in USA)
• Does not interfere with most of the existing radio • Affect GPS and aircraft navigation radio equipment.
systems • Potential interference to the existing systems
• High level of multipath resolution • Very short pulses in UWB may take long time for
• Large bandwidth synchronization
• High data rate communication
• High processing gain in communication system
• Involve very short pulses
• Carrierless transmission property offers the advantage
of hardware simplicity.
• Work well with low SNR
• Low Probability of Intercept and Detection
• Resistance to jamming
• Penetration through different kinds of material
External
Opportunities Threats
• Robot guidance • Commercially expensive compared to other technolo-
• Tracking systems gies
• Medical and surgeries that require sub-millimeters of • They are in some cases not totally immune to multipath
accuracy effects
• Indoor localization systems • Design and implementation of UWB antennas can be
• UWB short pulses. This short pulses signals can be more challenging
utilized in non-communication purposes
• Sensor, positioning, and identification network (SPIN)
• Industrial warehouses applications
• Shipboard environment application
• Military applications.
• Application for noisy environments
• Video streaming

to have a deep understating of UWB. A summary of SWOT law, where is the channel capacity is proportional to the
S
analysis is shown in Table II. bandwidth (B) and the log of Signal to noise ratio N plus
one.  
A. Strength S
C = B log2 1 + (1)
N
One advantage of using UWB is being licensed free because
of its low power. UWB is not classified as a radio equipment In addition to the advantage of large bandwidth, it is
as its low power signal does not interfere with most of the potential for high processing gain in communication systems.
existing radio systems [42]. In addition, UWB has a very high Processing gain for real Direct-Sequence of UWB (DS-UWB)
level of multipath resolution because of its large bandwidth. modulation systems is defined as two times ratio of noise
Large bandwidth provides frequency diversity that makes Time bandwidth at the front end of the receiver to the noise
Modulated Ultra WideBand (TM-UWB) signal resistant to the bandwidth of symbol rate. Here is the formula of DS-UWB
multipath problems and interference [42]. Time Modulated processing gain [43]:
UWB has a low probability of interception and detection, Noise Bandwidth
which it is used in some applications, particularly in the PG = 2 × (2)
Symbol Rate
military.
The large processing gain offers a greater immunity distortion
The large bandwidth is the main feature of the UWB wire-
and noise. It allows negative Signal to Interference and Noise
less systems. This feature offers an improved channel capacity
Ratio (SINR) to be recovered [43].
and high data rate communication in digital communication
systems [43]. The channel capacity is defined by Shannons UWB signals have greater penetration of obstacles (such as

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SENSORCOMM 2014 : The Eighth International Conference on Sensor Technologies and Applications

walls) than conventional signals, and they achieve same data C. Opportunities
rate [44]. Furthermore, UWB transmissions involve very short
pulses, which have recently received significant interest. Very UWB becomes a choice for many systems that require high
short pulses offer an advantage in terms of resolvability of accuracy such in building robot guidance and tracking systems
multipath components [44]. Many received signals in an envi- to utilize its advantages. Furthermore, UWB is used for medi-
ronment that are characterized by multipath is a superposition cal applications that require sub-millimeters of accuracy [15].
of the delayed replicas of the signal. This has been avoided In addition, UWB is used in radars in order to improve their
in UWB because the reflection from objects and surfaces near high performance [45].
the path between transmitter and receiver tend to not overlap For indoor localization systems, there are multipath reflec-
in time because of the very short pulses of UWB. This means tions from objects inside rooms, which negatively impact radio
UWB has a desirable direct resolvability of direct multipath signals. However UWB signals have time resolution, which
components. offers a high resolution positioning applications to solve the
UWB technologys carrierless transmission property offers multipath problems [43].
the advantage of hardware simplicity and small hardware. As mentioned before, UWB communication signals have
UWB transceivers can be built with much simpler radio fre- short pulses. Those short pulse signals can be utilized in non-
quency architecture than narrowband systems with fewer com- communication purposes [44]. For instance, the low power
ponents. Also, there is no need for power amplifier because of UWB RFID tag transmitters have been used to locate objects
its low power consumption [44]. In general, UWB hardware is with an accuracy proportional to the inverse of the signal
considered to be simple and the hardware simplicity depends bandwidth.
on the application and operational scenario. For example, the
transmitter does not need Analog to Digital (A/D) converter, UWB could be beneficial for industry and service providers
digital pulse shaping filter, or equalizer to correct carrier phase in many applications such as Sensor, Positioning, and Identi-
distortion [44]. fication Network (SPIN) systems [46]. These systems need
a large number of devices (sensors and tags) in industrial
warehouses to transmit low-rate data combined with position
B. Weakness information. This allows the devices to operate over long
distance (around 100m) between mobile tags and sensors of
Although UWB has many strengths for different applica- UWB.
tions, it has some weakness. One of these weaknesses is the
There are some challenges for using Radio Frequency (RF)
possibility of interference with nearby systems [43]. In the
operation for the shipboard environment. Using UWB and
United States, the UWB frequency range for communication
network analyzer measurements offers good opportunities for
applications is 3.1 to 10.6 GHz, which is operating in the
NLOS communication for indoor and on ships [44]. It allows
same frequencies as popular communication products such as
signals to propagate well aboard ships and around objects,
Worldwide Interoperability for Microwave Access (WiMAX)
which provide reasonable accuracy to determine positions.
and digital TV. In some countries, it may also interfere
UWB is used in radar in order to improve its high perfor-
with some systems such as third-generation 3G wireless
mance [45].
systems [43]. There are some concerns that several UWB
devices may cause harmful interference to GPS and aircraft
navigation radio equipment [44]. To overcome those concerns, D. Threats
different techniques have been developed to eliminate harmful
interference with other sensitive services, such as Detection UWB usually does not have a negative impact on the
and Avoidance (DAA) [43]. neighbor’s devices because there are some techniques that
Also interference may happen from the existing system to are used to avoid the interference with other devices [15].
the UWB system. The UWB systems signals may spread However, UWB is still commercially expensive compared to
over other bandwidths that contain existing frequency of other technologies (see [9] for further limitations).
narrowband systems [44]. This interference can be elevated While UWB systems are known to be robust against multi-
by using Minimum Mean-Square Error (MMSE) multiuser path reflection issues, they are not totally immune to multipath
detection schemes to reject strong narrowband interference. effects [46]. One of these cases is when there is an extreme
ratio of link distance to antenna height. This may result in
Although using very short pulses in UWB has many advan-
signal losses and propagation delay that lasts to tens or even
tages, the UWB receiver requires signal acquisition, synchro-
hundreds of nanoseconds.
nization and tracking to be done with very high precision in
time relative to the pulse rate. These steps of processes are The design and implementation of antennas for UWB sys-
time-consuming and take a long time to be performed [44]. tems can be more challenging than the bandwidth and variable
There are some techniques for reducing this time such as using conditions of operation [46]. This may add some limitations
preamble sequence for rapid acquisition. to UWB systems in comparison with conventional RF.

Copyright (c) IARIA, 2014. ISBN: 978-1-61208-374-2 72

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