Basic m Basic m
of
methods methods
f Location Technologies
Teemu Heikkilä MIT9SY 4/2010
General about loc General about loc
An object can be located by measuring th
z An object can be located by measuring th
z The signals may be transmitted by the ob backscattered waves (as in radar or pass
z Active vs. Passive method:
− Active (a.k.a. network-based, remote pos
The target is a transmitter whose lo
z The target is a transmitter whose lo multiple fixed terminal receivers w
z e.g. Cellural networks
z The network sends specific signalsp g
− Passive (a.k.a. handset-based, unilatera
z The target receives transmission fr calculates its own position
z e.g. GPS
z A passive device does not transmit
z The target may choose not to repor
cation techniques cation techniques
he characteristics of received signals he characteristics of received signals.
bject to be located (active), or they may be sive RFID).
sition, multilateral)
ocation is calculated from measurements taken by ocation is calculated from measurements taken by whose positions are known.
s to estimate the location of a targetg
al)
rom multiple terminals, whose positions are known and
t any signal for location estimation purposes rt its location to the network
Basic of meas Basic of meas
z Triangulation requires knowing the angle
z In the two-dimensional (2D) case the loca d b d t i d b t il t ti
node can be determined by trilateration
z In case of 2 nodes of know location the de will be on either of the points that intersect p
with circle A (picture 2)
z 2D requires 3 nodes of known location (pi
z The 4th node of unknown location can be if the distance to the reference nodes is know if the distance to the reference nodes is know
z Three-dimensional (3D) determination req four reference node.
uring methods uring methods
between nodes (picture 1).
ation of an unknown
evice
cture 3). determined wn
wn
quires at least
Position relate Position-relate
Localization systems can employ various
z Localization systems can employ various
z RSS, TOF & AOA/DOA are three phy used to determine the location:
− Received Signal Strenght (RSS)
− Time-of-Flight (TOF)
z Time-of-Arrival (TOA)
z Time-Difference-of-Arrival (TDO
− Enhanced-Observed-Time
− The basic principle of oper Ph f A i l (POA)
z Phase-of-Arrival (POA)
− Angle-of-Arrival (AOA) or Direction-o
z Well known hybrid or standalone methods
− Cell of Origin (COO) a.k.a. proximity
− Location Pattern Matching (LMP) a.k
ed parameters ed parameters
s parameters from reveived signals s parameters from reveived signals.
ysical charasteristics of radio signal that are
OA) (explained more detailed in Kirsi's presentation)
-Difference (E-OTD)
ration of the E-OTD is the multilateration.
of-Arrival (DOA)
s of above mentioned techniques y
k.a. finterprinting
Signaling sc Signaling sc
R di f
z Radio frequency
− Signals can penetrate through obstac
− Work with long distances
− Widely used in various wireless syste
− Mainly used RF signaling waveforms
z Ultra-wideband (UWB)
z Ultra wideband (UWB)
z Code Division Multiple-Access (
z Orthogonal FrequencyDivision M
z Infrared
z Infrared
− Inexpensive
− Low signal power
R i Li f i ht(LOS) diti
− Requires Line-of-sight(LOS) conditio througth obstacles
− Commonly used indoor environment
chemes page1 chemes page1
cles
ems
s in localization:
CDMA)
Multiplexing (OFDM)
i th t i l t t t
ons meaning that signals cannot penetrate
Signaling sc Signaling sc
Optical
z Optical
− Inexpensive
− Low signal power
− Require LOS conditions
− Sunlight sensitive
− High accuracy (typically range is e.gg y ( yp y g g
z Ultrasound
− Inexpensive
A ti itt ti
− Acoustic emitters power consumptio
− Require LOS conditions, do not work
− High accuracy
− Short range
chemes page2 chemes page2
. 10m))
i hi h on is high
k certainly in Non-line-of-sight (NLOS) conditions
Received Signal Received Signal
z The received signal strength Indicator (RS transmitted power and dependence of sigp p g
z Active tracking using RSSI is a technique signal strength of a transmitter's packets location of the transmitter based on those
z The access points use the received signa phone to determine the phone's location.
l Strenght (RSS) l Strenght (RSS)
SSI) may be used to estimate distance if the gnal strength on distance is known
g g
e in which a measuring device detects the and determines its own location or the e measurements.
al strength of packets transmitted by the
Angle of Arrival or Angle of Arrival or
AOA/DOA techniques seeks to determine
z AOA/DOA techniques seeks to determine the angle at which signals transmitted fro
z If the mobile is not on the direct line throu intersect at the node position
intersect at the node position.
z The AOA estimation technique requi antennas to measure incoming signa
z If the mobile device is connected two mobile device can be calculated.
Direction of Arrival Direction of Arrival
e the location of a mobile device based on e the location of a mobile device based on om the device arrive at the base station(s)
ugh two different base stations, both lines
res that the base stations use specialized als from the mobile terminals.
o or more base stations, the location of the
Time Difference o Time Difference o
At least two TDOA measurements by two
z At least two TDOA measurements by two unambiguous positioning.
z Each base station have an accurate timin
z Time synchronisation between the ba
− Remote positioning the signal transmitted from the mobile
transmitted from the mobile device is received by several base stations and there must be a known time relationship between the receiver clocks.
of Arrival (TDOA) of Arrival (TDOA)
o base stations are required for o base stations are required for
ng source or common source for time ase stations is required
Enhanced Observed Ti Enhanced-Observed-Ti
Mobiles monitor synchronization bursts of serv
z Mobiles monitor synchronization bursts of serv same as in TDOA but the measurement is don
z Measurement Units (LMU) each have an accu
z The E-OTD technique offers an accuracy leve
z Mobile records burst arrival times
z Position is triangulated from:g
− Coordinates of BTSs
− Arrival time of burst from each BTS Timing differences between BTSs
− Timing differences between BTSs
me Difference (E OTD) me-Difference (E-OTD)
ving and all neighbor cells The method is the ving and all neighbor cells. The method is the ne by the mobile.
urate timing source
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el from 50 to 125m.
Cell of Orig Cell of Orig
COO is the most straightforward solution
z COO is the most straightforward solution (Cell ID) within the mobile network to iden
z Technique is often not very useful becau
z Position is known only in Cell level
gin (COO) gin (COO)
and uses the cell identification information and uses the cell identification information ntify the approximate location of the node se of the low positioning accuracy
Location Pattern Location Pattern
In this technique network system analyze
z In this technique network system analyze a database of standard signal characteris
z These characteristics include signal reflec
"anomalies "anomalies.
z When a computerized match is made, the
z The technique is effective in urban enviro obstructions, where other techniques mig
Matching (LPM) Matching (LPM)
es the radio signal and then compares it to es the radio signal, and then compares it to
stics
ctions (multipath), echoes and other signal e location of the caller can be determined
onments that include tall buildings and other ght not succeed.
