indoor geo location system
TRANSCRIPT
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1. INTRODUCTIONRecently, there is an increasing interest in accurate location finding techniques and
location based applications for indoor areas. The Global Positioning System (GPS) and
wireless enhanced 911(E-911) services also address the issue of location finding. However,
these technologies cannot provide accurate indoor geo location, which has its own
independent market and unique technical challenges.
Despite extraordinary advances in global positioning system (GPS) technology, millions
of square meters of indoor space are out of reach of GPS satellites. Their signals, originating
high above the earth, are not designed to penetrate most construction materials, and no
amount of technical wizardry is likely to help. So the greater part of the world's commerce,
being conducted indoors, cannot be followed by GPS satellites.
1.1.What is indoor geo location?
Indoor Geo location is the process of findinggeo locationof an electronic device inside
a building. Since technologies used for indoor geo location are substantially different from
technologies used for outdoorgeo locationthis area is considered as a separate area of
science and technology.
1.2. Need for indoor geo localization:
Consider some everyday business challenges. Perpetual physical inventory is needed
for manufacturing control, as well as to keep assets from being lost or pilfered. Mobile assets,
such as hospital crash carts, need to be on hand in an emergency. Costly and baroqueprocedures presently track and find manufacturing work-in-process. Nor is the office
immune: loss of valuable equipment such as laptop computers has become a serious problem,
and locating people in a large office takes time and disrupts other activities.
1.3. Tracking:
What these systems share is a need to find and track physical assets and people that
are inside buildings. The design differences between an efficient asset-tracking system and
GPS arc more basic. First and foremost, control of the situation shifts from users of GPS
receivers, querying the system for a fix on their position, to overhead scanners, checking upon the positions of many specially tagged objects and people. In GPS, each receiver must
determine its own position in reference to a fixed infrastructure, whereas inside a building,
the tracking infrastructure must keep tabs on thousands of tags.
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2. ARCHITECTURE OF INDOOR GEOLOCATION SYSYTEMThe architecture mainly consists of 3 parts.
1. Geolocation base station (GBS)
2. Geolocation control station (GCS)
3. Mobile station (MS)
Similar to the cellular geo location system, the architecture of indoor geo location
system is mainly classified into 2 categories. Mobile based architecture and network based
architecture. Most of the indoor geo location techniques proposed to date have been focused
on network based system architecture. The geo location base station(GBS) extract location
metrics from the radio signals transmitted by the mobile station and relay the information to a
geo location control station(GCS). The communication between GBS and GCS can be either
wired or wireless. Then the position of the mobile station is estimated, displayed and tracked
at the GCS. With the mobile based system architecture the mobile station estimates self
position by measuring received radio signals from multiple fixed GBS. Compared to mobile
based architecture, network based architecture system has the advantage that mobile station
can be implemented as a simple structured transceiver with small size and low power
consumption that can be easily carried by people or attached to valuable equipments like tag.
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3. TYPES OF VARIOUS INDOOR GEOLOCATION TECHNIQUESIt is not easy to model the radio propagation in the indoor environment because of
severe multipath, low probability for availability of line-of-sight (LOS)path, and specific site
parameters such as floor layout, moving objects, and numerous reflecting surfaces. There is
no good model for indoor radio multipath characteristic so far. Except using traditional
triangulation, positioning algorithms using scene analysis or proximity are developed to
mitigate the measurement errors. Targeting different applications or services, these three
algorithms have unique advantages and disadvantages. Hence, using more than one type of
positioning algorithms at the same time could get better performance.
Fig.1.Types of various indoor geo location systems
3.1. Direction-Based technique:The direction-based technique consists of the Angle of Arrival Method (AOA) which uses
the Ling of Sight (LOS) approach.
GEOLOCATION
TECHNIQUES
DIRECTION -
BASED
DISTANCE -
BASED
ARRIVAL TIME
METHOD
SIGNAL
STRENGTH
METHOD
RECEIVED SIGNAL
PHASE METHOD
FINGERPRINTING -
BASED
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3.1.1.Angle of arrival:The angle of arrival geo location technique the direction of arrival of the received
signal to determine the location of the mobile station. The direction of the incoming signals
are received and measured from the target transmitter to a direction using directional
antennas or antenna arrays. If the line of sight signal path is blocked, then the angle of arrival
being used is a reflected or scattered signal for its direction estimation. This technique is not
feasible when dealing with indoor geo location because often times there will be walls or
objects blocking the line of sight signal path.
Direction is determined from the AOA (angle of arrival) of received signal. Receiver
(GBS) measures the direction of the received signal from the target transmitter (MS) using
directional antennas / antenna array. Accuracy depends on where the transmitter is located
with respect to the receiver. More than 2 receivers are needed for accuracy.
In AOA, the location of the desired target can be found by the intersection of several
pairs of angle direction lines, each formed by the circular radius from a base station or a
beacon station to the mobile target.AOA methods may use at least two known reference
points (A, B), and two measured angles 1, 2 to derive the 2-D location of the target P.
Estimation of AOA, commonly referred to as direction finding (DF), can be accomplished
either with directional antennae or with an array of antenna.
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3.1.1.1. Advantages:
A position estimate may be determined with as few as three measuring units for 3-D
positioning or two measuring units for 2-D positioning, and that no time synchronization
between measuring units is required.
3.1.1.2. Disadvantages:
The disadvantages include relatively large and complex hardware requirement(s), and
location estimate degradation as the mobile target moves farther from the measuring units.
For accurate positioning, the angle measurements need to be accurate, but the high
accuracy measurements in wireless networks may be limited by shadowing, by multipath
reflections arriving from misleading directions, or by the directivity of the measuring
aperture.
Some literatures also call AOA as direction of arrival (DOA.).
3.1.1.3. Application:
Can be used in next generation cellular system where smart antennas are used to
increase capacity.
3.2. Distance Based Technique:The Distance-Based Techniques involve the following methods:-
-Time of Arrival (TOA)
-Time Difference of Arrival (TDOA)
-Signal Strength
-Received Signal Phase
3.2.1.Time of Arrival:The time of arrival technique uses the distance between the mobile station and
receiver to estimate location.At least three measurements are necessary to calculate the
possible position of the user. The measurements estimate the position in two dimensions and
four measurements estimate the position in three dimension. By estimating the distance
between the receiver and the mobile to be d, the mobile is located on a circle with radius d
centered on the receiver. Distance is equal to the velocity of light multiplied by the time taken
by the signal to reach the base station.
The distance from the mobile target to the measuring unit is directly proportional to
the propagation time. In order to enable 2-D positioning, TOA measurements must be made
with respect to signals from at least three reference points, as shown in Fig. For TOA-basedsystems, the one-way propagation time is measured, and the distance between measuring unit
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and signal transmitter is calculated. In general, direct TOA results in two problems. First, all
transmitters and receivers in the system have to be precisely synchronized. Second, a
timestamp must be labeled in the transmitting signal in order for the measuring unit to discern
the distance the signal has traveled. TOA can be measured using different signaling
techniques such as direct sequence spread-spectrum (DSSS) or ultrawide band (UWB)measurements.
A straightforward approach uses a geometric method to compute the intersection
points of the circles of TOA. The position of the target can also be computed by minimizing
the sum of squares of a nonlinear cost function, i.e., least-squares algorithm. It assumes that
the mobile terminal, located at (x0, y0), transmits a signal at time t0, the N base stations
located at (x1, y1), (x2, y2), . . . ,(xN , yN ) receive the signal at time t1, t2, . . . , tN . As a
performance measure, the cost function can be formed by
fi(x) is given as follows.
fi(x) = c(ti t) sqr root((xi x)^2+ (yi y)^2)
where c is the speed of light, and x = (x, y, t)T.
This function is formed for each measuring unit, i = 1, . . . , N , and fi(x) could
be made zero with the proper choice of x, y, and t. The location estimate is determined by
minimizing the function F(x).
Fig.3.Position Based on TOA method
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There are other algorithms for TOA-based indoor location system such as closest-
neighbor (CN) and residual weighting (RWGH). The CN algorithm estimates the location of
the user as the location of the base station or reference point that is located closest to that user.
The RWGH algorithm can be basically viewed as a form of weighted least-squares algorithm.
It is suitable for LOS, non-LOS (NLOS) and mixed LOS/NLOS channel conditions.
3.2.2.Time difference of arrival:Some outdoor geo location applications use the time difference of arrival technique.
This is where the differences of the time of arrivals are use to locate the mobile. The time
difference of arrival technique is similar to that of the time of arrival technique but instead of
using circles, the time difference of arrival uses hyperbolas on which the transmitter must be
located with foci at the receiver. At least three measurements are needed to calculate a fixed
position at the intersection of the hyperbolas.
The idea of TDOA is to determine the relative position of the mobile transmitter by
examining the difference in time at which the signal arrives at multiple measuring units,
rather than the absolute arrival time of TOA. For each TDOA measurement, the transmitter
must lie on a hyperboloid with a constant range difference between the two measuring units.
Fig.4.Positioning based on TDOA measurement
Except the exact solutions to the hyperbolic TDOA equation shown in through
nonlinear regression, an easier solution is to linearize the equations through the use of a
Taylor-series expansion and create an iterative algorithm. A 2-D target location can be
estimated from the two intersections of two or more TDOA measurements. Two hyperbolas
are formed from TDOA measurements at three fixed measuring units (A, B, and C) to
provide an intersection point, which locates the target P. The conventional methods for
computing TDOA estimates are to use correlation techniques. TDOA can be estimated from
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the cross correlation between the signals received at a pair of measuring units. Suppose that
for the transmitted signal s(t), the received signal at measuring unit i is xi(t). Assume that
xi(t)is corrupted by the noise ni(t) and delayed by di, then
xi(t) =s(t di) + ni(t).
Similarly, the signal xj(t) = s(t dj)+nj(t), which arrives at measuring unit j, is
delayed by dj and corrupted by the noise nj(t).
The TDOA estimate is the value that maximizes Rxi, xj( ), i.e., the range differences. This
approach requires that the measuring units share a precise time reference and reference
signals, but does not impose any requirement on the mobile target. Frequency domain
processing techniques are usually used to calculate . Except the previous TDOA methods, a
delay measurement-based TDOA measuring method was proposed in for 802. 11 wireless
LANs, which eliminates the requirement of initial synchronization in the conventional
method.
3.2.2.1. RLS Algorithm:
It is used when there are errors in the distance measurements. Let the distance di from the i th GBS ,
di=c*t
where c velocity of light
t time taken by the signal to reach the GBS.
Location ofi th GBS(xi , yi) Location of mobile(x , y) We have N equations of the form:
fi(x , y)= (x-xi)^2 + (y-yi)^2-di^2 for i= 1,2,3,,N
.
3.2.3.Signal Strength Method:The signal strength technique uses the transmitted power at the mobile station and the
received signal strength at the base station to provide an estimate of the distance between the
transmitter and the receiver. Similar to the time of arrival technique, the distance gives the
circle centered on the receiver which the mobile transmitter is on.
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Fig.5.Received Signal Strength Method
The above two schemes have some drawbacks. For indoor environments, it is difficult
to find a LOS channel between the transmitter and the receiver. Radio propagation in such
environments would suffer from multipath effect. The time and angle of an arrival signal
would be affected by the multipath effect; thus, the accuracy of estimated location could be
decreased. An alternative approach is to estimate the distance of the mobile unit from some
set of measuring units, using the attenuation of emitted signal strength. Signal attenuation-
based methods attempt to calculate the signal path loss due to propagation. Theoretical and
empirical models are used to translate the difference between the transmitted signal strength
and the received signal strength into a range estimate, as shown in Fig.5.
Due to severe multipath fading and shadowing present in the indoor environment,
path-loss models do not always hold. The parameters employed in these models are site-
specific. The accuracy of this method can be improved by utilizing the premeasured RSS
contours centered at the receiver [7] or multiple measurements at several base stations. A
fuzzy logic algorithm shown in [8] is able to significantly improve the location accuracyusing RSS measurement.
3.2.3.1. Advantages:
Low complexity receiver.
3.2.3.2. Disadvantages:
Very unreliable due to shadow fading (fluctuations around the mean value and expected
value caused due to signal being blocked from GBS).
GBS do not distinguish between signal strength in los path and reflected path
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3.2.4. Received Signal Phase Method:
The received signal phase technique used with reference receivers measures the
carrier phase. Differential Global Positioning System improves location accuracy within
twenty meters to one meter as compared with Global Positioning Systems which uses range
measurements. In indoor geo location systems, it is possible to use signal phase methods with
time of arrival, time difference of arrival or received signal strength techniques to better
estimate the location.
The received signal phase method uses the carrier phase (or phase difference) to
estimate the range. This method is also called phase of arrival(POA). Assuming that all
transmitting stations emit pure sinusoidal signals that are of the same frequency f, with zero
phase offset, in order to determine the phases of signals received at a target point, the signal
transmitted from each transmitter to the receiver needs a finite transit delay. In Fig., the
transmitter stations A up to D are placed at particular locations within an imaginary cubicbuilding. The delay is expressed as a fraction of the signals wavelength, and is denoted with
the symbol i = (2fDi)/c in equation Si(t) = sin(2ft + i),
where i (A, B, C, D), and c is the speed of light. As long as the transmitted signals
wavelength is longer than the diagonal of the cubic building, i.e., 0 < i < 2, we can get the
range estimation Di = (ci)/(2f). Then, we can use the same positioning algorithms using
TOA measurement. The receiver may measure phase differences between two signals
transmitted by pairs of stations, and positioning systems are able to adopt the algorithms
using TDOA measurement to locate the target.
For an indoor positioning system, it is possible to use the signal phase method
together with TOA/TDOA or RSS method to fine-tune the location positioning. However, the
received signal phase method has one problem of ambiguous carrier phase measurements to
overcome. It needs an LOS signal path, otherwise it will cause more errors for the indoor
environment.
3.2.4.1. Advantages:
Differential GPS can improve location accuracy from about 20m to within 1m.
3.2.4.2. Disadvantages:
Ambiguity resulting from periodic property of the signal phase. Multipath condition causes more errors.
3.2.4.3. Application:
Used in indoor geo location system, along with TOA/TDOA or RSS method to fine-tune the location of MS.
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3.3. Finger-print Based Technique:
Another technique that estimates position location is signal fingerprinting. The
multipath structure of the channel is unique to every location and may be considered
fingerprint or signature of the location if the same radio frequency signal is transmitted from
that location. This technique may be used in indoor geo location applications where a
location pattern develops from multipath rays in a multipath structure in an area. Develops a
signature database of a location grid in specific service areas. The received signal is
measured as a vehicle moves along this grid in specific areas and recorded in signature
database. When another vehicle moves in the same area, the signal received from it is
compared with the entry in the database, thus its location is determined.
RF-based scene analysis refers to the type of algorithms that first collect feature
(fingerprints) of a scene and then estimate the location of an object by matching online
measurements with the closest a priori location fingerprints. RSS-based locationfingerprinting is commonly used in scene analysis. Location fingerprinting refers to
techniques that match the fingerprint of some characteristic of a signal that is location
dependent. There are two stages for location fingerprinting: offline stage and online stage (or
run-time stage). During the offline stage, a site survey is performed in an environment. The
location coordinates/labels and respective signal strengths from nearby base
stations/measuring units are collected. During the online stage, a location positioning
technique uses the currently observed signal strengths and previously collected information to
figure out an estimated location. The main challenge to the techniques based on location
fingerprinting is that the receivedsignal strength could be affected by diffraction, reflection,
and scattering in the propagation indoor environments.
There are at least five location fingerprinting-based positioning algorithms using
pattern recognition technique so far: probabilistic methods, k-nearest-neighbor (kNN), neural
networks, support vector machine (SVM), and smallest M-vertex polygon (SMP).
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4. PERFORMANCE MEASURENT OF GEOLOCATION SYSTEM:
It is not enough to measure the performance of a positioning technique only by
observing its accuracy. Considering the difference between the indoor and outdoor wirelessgeo location, we provide the following performance benchmarking for indoor wireless
location system: accuracy, precision, complexity, scalability, robustness, and cost.
4.1. Accuracy:
Accuracy (or location error) is the most important requirement of positioning systems.
Usually, mean distance error is adopted as the performance metric, which is the average
Euclidean distance between the estimated location and the true location. Accuracy can be
considered to be a potential bias, or systematic effect/offset of a positioning system. The
higher the accuracy, the better the system; however, there is often a tradeoff betweenaccuracy and other characteristics. Some compromise between suitable accuracy and other
characteristics is needed.
4.2. Precision:
Accuracy only considers the value of mean distance errors. However, location
precision considers how consistently the system works, i.e., it is a measure of the robustness
of the positioning technique as it reveals the variation in its performance over many trials. We
also notice that some literatures define the location precision as the standard deviation in the
location error or the geometric dilution of precision (GDOP), but we prefer it as thedistribution of distance error between the estimated location and the true location. Usually,
the cumulative probability functions (CDF) of the distance error is used for measuring the
precision of a system. When two positioning techniques are compared, if their accuracies are
the same, we prefer the system with the CDF graph, which reaches high probability values
faster, because its distance error is concentrated in small values. In practice, CDF is described
by the percentile format. For example, one system has a location precision of 90% within 2.3
m (the CDF of distance error of 2.3 m is 0.9), and 95% within 3.5 m; another one has a
precision of 50% within 2.3 m and 95% within 3.3 m. We could choose the former system
because of its higher precision.
4.3. Complexity:
Complexity of a positioning system can be attributed to hardware, software, and
operation factors. In this paper, we emphasize on software complexity, i.e., computing
complexity of the positioning algorithm. If the computation of the positioning algorithm is
performed on a centralized server side, the positioning could be calculated quickly due to the
powerful processing capability and the sufficient power supply. If it is carried out on the
mobile unit side, the effects of complexity could be evident. Most of the mobile units lack
strong processing power and long battery life; so, we would prefer positioning algorithmswith low complexity. Usually, it is difficult to derive the analytic complexity formula of
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different positioning techniques; thus, the computing time is considered. Location rate is an
important indicator for complexity. The dual of location rate is location lag, which is the
delay between a mobile target moving to a new location and reporting the new location of
that target by the system.
4.4. Robustness:
A positioning technique with high robustness could function normally even when
some signals are not available, or when some of the RSS value or angle character are never
seen before. Sometimes, the signal from a transmitter unit is totally blocked, so the signal
cannot be obtained from some measuring units. The only information to estimate the location
is the signal from other measuring units. Sometimes, some measuring units could be out of
function or damaged in a harsh environment. The positioning techniques have to use this
incomplete information to compute the location.
4.5. Scalability:
The scalability character of a system ensures the normal positioning function when
the positioning scope gets large. Usually, the positioning performance degrade when the
distance between the transmitter and receiver increases. A location system may need to scale
on two axes: geography and density. Geographic scale means that the area or volume is
covered. Density means the number of units located per unit geographic area/space per time
period. As more area/space is covered or units are crowded in an area/space, wireless signal
channels may become congested, more calculation may be needed to perform location
positioning, or more communication infrastructure may be required. Another measure ofscalability is the dimensional space of the system. The current system can locate the objects
in 2-D or 3-D space. Some systems can support both 2-D and 3-D spaces.
4.6. Cost:
The cost of a positioning system may depend on many factors. Important factors
include money, time, space, weight, and energy. The time factor is related to installation and
maintenance. Mobile units may have tight space and weight constraints. Measuring unit
density is considered to be a space cost. Sometimes, we have to consider some sunk costs.
For example, a positioning system layered over a wireless network may be considered tohave no hardware cost if all the necessary units of that network have already been purchased
for other purposes. Energy is an important cost factor of a system. Some mobile units (e.g.,
electronic article surveillance (EAS) tags and passive RFID tags, which are addressed later)
are completely energy passive. These units only respond to external fields and, thus, could
have an unlimited lifetime. Other mobile units (e.g., devices with rechargeable battery) have
a lifetime of several hours without recharging.
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5. COMPARING GEOLOCATION TECHNIQUES
The time of arrival technique estimate location by calculating the position of the
mobile by using circles centered on the mobile or the fixed transceivers. The time difference
of arrival does a similar technique using hyperbolas and does not require the knowledge of
transmit time from the transmitter. To create estimates of time, TOA and TDOA techniques
employ pulse transmission, phase information, or spread spectrum to arrive at locations of
mobile stations The time of arrival techniques are seen as superior to angle of arrival
techniques because the AOA method is not appropriate for indoor geo location systems. The
angle of arrival is suited for outdoor geo location but has poor accuracy. It has a low delay
but may be costly due to the need for antenna arrays that need to be installed in areas. The
signal strength method cannot be used in situations where the precision of the location needs
to be within accuracy of a few meters.
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6. EXAMPLE OF AN INDOOR GEOLOCATION SYSTEM
Commercial indoor geo location products have already appeared in the market. The abovefigure shows the example of an indoor geo location system. It is a pin point local positioning
system.
The system architecture is shown in the above figure. The Pin-Point system uses
simple structured tags that can be attached to valuable assets or personal badges. Indoor areas
are divided into cells while each cell being served by a cell controller. The cell controller is
connected to at most 16 antennas located at known positions. To locate tag position, cell
controller transmits 2.4GHz spread spectrum signal through different antennas in TDD mode.
Once receiving signals from the Cell Controller antenna network, tags simply change the
frequency of the received signal to 5.8GHz and transmit back to the Cell Controller with tag
ID information phase-modulated onto the signal. The distance between the tag and antenna is
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determined by round trip time of flight. With the measured distances from tag to antennas,
the tag position can be obtained in the same way as in TOA method. A host computer is
connected to cell controller through TCP/IP to manage the location information of the tags.
Since the cell controller generates the signal and measures the round trip time of flight, there
is no need to synchronize the clocks of tags and antennas.
The multipath effect is one of the limiting factor of the indoor geo location system.
Without multi path signal components, the time of arrival(TOA) could be easily determined
from the triangular auto-correlation function of the spread spectrum signal.
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7. APPLICATIONS
Positioning and tracking applications:
Commercial: finding in-demand equipments, in-need personnel, such as elderly, children
and patience
Military and public safety: positioning and guiding soldiers, firefighters in mission
Location-aided techniques:
Location-aware routing, location-aided handoff, location-aided network planning
Location-based services:
Location sensitive billing, location aware services, location specific advertisement
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8. FUTURE TREND
Future trends of wireless indoor positioning systems are as follows.
1) New or hybrid position algorithms are needed. A few of the works have already been
started supporting such algorithms. For example, a calibration-free location algorithm based
on triangulation, triangular interpolation and extrapolation (TIX). A hybrid algorithm is
presented in for indoor positioning using WLAN that aims to combine the benefits of the RF
propagation loss model and fingerprinting method. The selective fusion location estimation
(SELFLOC) algorithm infers the user location by selectively fusing location information
from multiple wireless technologies and/or multiple classical location algorithms in a
theoretically optimal manner.
2) Internetworking of different wireless positioning systems is a research and practical topicin order to extend the positioning range.
3) Wireless combined with other technologies such as optical (e.g., IR), inertial, dc
electromagnetic and ultrasonic for indoor location is another trend. How to combine these
technologies into a practical system is a topic of sensor fusion.
4) How to deploy sensors to improve the positioning accuracy, how to finish deploying
wireless positioning system in a short time, especially for emergency responder application.
5) Wireless indoor location using UWB (from 3.1 to 10.6 GHz) techniques and indoorpositioning using mobile cellular network are other promising research topics.
6) How to integrate indoor and outdoor positioning system is another area of research. This
integration may help in developing more efficient and robust detection systems for
positioning of mobile computing nodes. In this case, a mobile node will be tracked indoor or
outdoor using the same detection system.
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9. CONCLUSION
This paper surveys the current indoor positioning techniques and systems. Different
performance measurement criteria are discussed and several tradeoffs among them are
observed. For example, the one between complexity and accuracy/precision needs careful
consideration when we choose positioning systems and techniques for different applications
environments such as warehousing, robotics, or emergency. Usually, location fingerprinting
scheme is better for open areas while Active RFID is suitable for dense environments. In
terms of scalability and availability, these positioning techniques and systems have their own
important characteristics when applied in real environments. The choice of technique and
technology significantly affects the granularity and accuracy of the location information.
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10. REFERENCES
[1] J. Hightower and G. Borriello, Location systems for ubiquitous computing Computer,
vol. 34, no. 8, Aug. 2001.
[2] K. Pahlavan, X. Li, and J. Makela, Indoor geo location science and technology, IEEE
Commun. Mag., vol. 40, no. 2, pp. 112118, Feb. 2002.
[3] C. Drane, M. Macnaughtan, and C. Scott, Positioning GSM telephones,
IEEE Commun. Mag., vol. 36, no. 4, pp. 4654, 59, Apr. 1998.
[4] B. Fang, Simple solution for hyperbolic and related position fixes, IEEE Trans. Aerosp.
Electron. Syst., vol. 26, no. 5, pp. 748753, Sep. 1990.
[5] M. Kanaan and K. Pahlavan, A comparison of wireless geo location algorithms in the
indoor environment, in Proc. IEEE Wireless Commun. Netw. Conf., 2004, vol. 1, pp. 177
182.
[6] D. Torrieri, Statistical theory of passive location systems, IEEE Trans. Aerosp.
Electron. Syst., vol. 20, no. 2, pp. 183197, Mar. 1984.
[7] J. Zhou, K. M.-K. Chu, and J. K.-Y. Ng, Providing location services within a radio
cellular network using ellipse propagation model, in Proc. 19th
Int. Conf. Adv. Inf. Netw.
Appl., Mar. 2005, pp. 559564.
[8] A. Teuber and B. Eissfeller, A two-stage fuzzy logic approach for wireless LAN indoor
positioning, in Proc. IEEE/ION Position Location Navigat. Symp., Apr. 2006, vol. 4, pp.
730 738.
[9] M. Kossel, H. R. Benedickter, R. Peter, and W. Bachtold, Microwave backscatter
modulation systems, IEEE MTT-S Dig., vol. 3, pp. 14271430, Jun. 2000.
[10] A. Gunther and C. Hoene, Measuring round trip times to determine the distance
between WLAN nodes, in Proc. Netw. 2005., Waterloo, ON, Canada, May 2005, pp. 768
779
[11] B. D. Van Veen and K. M. Buckley, Beamforming: A versatile approach to spatial
filtering, IEEE ASSP Mag., vol. 5, no. 2, pp. 424, Apr. 1988.
[12] P. Stoica and R. L. Moses, Introduction to Spectral Analysis. Englewood
Cliffs, NJ: Prentice-Hall, 1997.
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