01-06-2012, 11:04 AM
Indoor Geolocation - Science and Technology
Indoor Geolocation - Science and Technology.pdf (Size: 100.04 KB / Downloads: 101)
ABSTRACT
This article presents an overview of the technical
aspects of the existing technologies for wireless
indoor location systems. The two major
challenges for accurate location finding in indoor
areas are the complexity of radio propagation and
the ad hoc nature of the deployed infrastructure
in these areas. Because of these difficulties a variety
of signaling techniques, overall system architectures,
and location finding algorithms are
emerging for this application.
INTRODUCTION
Recently, there is increasing interest in accurate
location finding techniques and location-based
applications for indoor areas. The Global Positioning
System (GPS) [1] and wireless enhanced 911
(E-911) services [2] also address the issue of location
finding. However, these technologies cannot
provide accurate indoor geolocation, which has its
own independent market and unique technical
challenges. In 1997, while engaged in the Defense
Advanced Research Projects Agency’s (DARPA’s)
Small Unit Operation/Situation Awareness System
(SUO/SAS) program, the lead author of this article
and his research group noticed the need for
fundamental research in accurate indoor geolocation
[3]. The follow-up initiative of the group
attracted the attention of Nokia and other Finnish
organizations to the commercial importance of
indoor geolocation. In recognition of this importance,
an NSF grant was awarded to establish a scientific
foundation in this field.
CHANNEL CHARACTERISTICS FOR
INDOOR GEOLOCATION
The indoor radio propagation channel is characterized
as site-specific, severe multipath, and low
probability for availability of a line of sight
(LOS) signal propagation path between the
transmitter and receiver [9]. The two major
sources of errors in the measurement of location
metrics in indoor environment are multipath
fading and no LOS (NLOS) conditions due to
shadow fading [3].
LOCATION SENSING TECHNIQUES
As discussed in the introduction, the location sensing
elements measure RSS, AOA, and TOA as
location metrics. The indoor radio channel suffers
from severe multipath propagation and heavy
shadow fading, so the measurements of RSS and
AOA provide less accurate metrics than does TOA
[4]. As a result, similar to GPS systems, independent
systems designed for indoor geolocation normally
employ the more accurate TOA as the
location metric. Systems using existing infrastructures
installed for wireless LANs or the third-generation
(3G) indoor systems may use RSS, AOA,
or less accurate TOA measurements to fully exploit
the existing hardware implementation designed for
traditional telecommunication applications [8]. In
indoor areas, due to obstruction by walls, ceilings,
or other objects, the DLOS propagation path is
not always the strongest; in some cases (e.g.,
NLOS), it may not even be detectable with a specific
receiver implementation [3].
CONCLUSIONS
Indoor geolocation is an emerging technology
that needs a scientific foundation. To provide
such a foundation we need to characterize the
radio propagation features that impact the performance
of the indoor geolocation systems. Two
classes of indoor geolocation systems are emerging.
The first class has its own infrastructure, uses
reliable TOA measurement using wideband,
superresolution, or UWB location sensing
approaches, and employs triangulation techniques
for positioning.
Indoor Geolocation - Science and Technology.pdf (Size: 100.04 KB / Downloads: 101)
ABSTRACT
This article presents an overview of the technical
aspects of the existing technologies for wireless
indoor location systems. The two major
challenges for accurate location finding in indoor
areas are the complexity of radio propagation and
the ad hoc nature of the deployed infrastructure
in these areas. Because of these difficulties a variety
of signaling techniques, overall system architectures,
and location finding algorithms are
emerging for this application.
INTRODUCTION
Recently, there is increasing interest in accurate
location finding techniques and location-based
applications for indoor areas. The Global Positioning
System (GPS) [1] and wireless enhanced 911
(E-911) services [2] also address the issue of location
finding. However, these technologies cannot
provide accurate indoor geolocation, which has its
own independent market and unique technical
challenges. In 1997, while engaged in the Defense
Advanced Research Projects Agency’s (DARPA’s)
Small Unit Operation/Situation Awareness System
(SUO/SAS) program, the lead author of this article
and his research group noticed the need for
fundamental research in accurate indoor geolocation
[3]. The follow-up initiative of the group
attracted the attention of Nokia and other Finnish
organizations to the commercial importance of
indoor geolocation. In recognition of this importance,
an NSF grant was awarded to establish a scientific
foundation in this field.
CHANNEL CHARACTERISTICS FOR
INDOOR GEOLOCATION
The indoor radio propagation channel is characterized
as site-specific, severe multipath, and low
probability for availability of a line of sight
(LOS) signal propagation path between the
transmitter and receiver [9]. The two major
sources of errors in the measurement of location
metrics in indoor environment are multipath
fading and no LOS (NLOS) conditions due to
shadow fading [3].
LOCATION SENSING TECHNIQUES
As discussed in the introduction, the location sensing
elements measure RSS, AOA, and TOA as
location metrics. The indoor radio channel suffers
from severe multipath propagation and heavy
shadow fading, so the measurements of RSS and
AOA provide less accurate metrics than does TOA
[4]. As a result, similar to GPS systems, independent
systems designed for indoor geolocation normally
employ the more accurate TOA as the
location metric. Systems using existing infrastructures
installed for wireless LANs or the third-generation
(3G) indoor systems may use RSS, AOA,
or less accurate TOA measurements to fully exploit
the existing hardware implementation designed for
traditional telecommunication applications [8]. In
indoor areas, due to obstruction by walls, ceilings,
or other objects, the DLOS propagation path is
not always the strongest; in some cases (e.g.,
NLOS), it may not even be detectable with a specific
receiver implementation [3].
CONCLUSIONS
Indoor geolocation is an emerging technology
that needs a scientific foundation. To provide
such a foundation we need to characterize the
radio propagation features that impact the performance
of the indoor geolocation systems. Two
classes of indoor geolocation systems are emerging.
The first class has its own infrastructure, uses
reliable TOA measurement using wideband,
superresolution, or UWB location sensing
approaches, and employs triangulation techniques
for positioning.