Method of Indoor Position

Techniques of Indoor Positioning OutlineIntroductionBasic TechniquesAdvanced TechniquesCommercial ProductsUsing the Indoor Map InformationIndoor Positioning Using Femtocell4G LTE-A Localization SystemIn-Location AllianceConclusionsIntroductionLocation-aware real-time servicesElderly nursingChild monitoringObject positioningGlobal Positioning System (GPS) is the most well-known positioning serviceThe restrictions of GPSRequiring a line of sight (LOS) with satellite systemsIntroduction (cont.)GPS signal is easily affected by buildingsErrors up to 10mNeed other techniques for indoor positioningBasic TechniquesEmploy some information between beacon nodes and the unknown node

Trilateration

Trilateration (cont.)Node As coordinate is (xa, ya) Node Bs coordinate is (xb, yb)Node Cs coordinate is (xc, yc)The unknown node Ds coordinate is (x, y)The distance between A (or B or C) and D is d1 (or d2 or d3)

Trilateration (cont.)

Triangulation (cont.)

Triangulation (cont.)The unknown node Ds coordinate is (x, y) Node As coordinate is (xa, ya) and the angle to the D is ADBNode Bs coordinate is (xb, yb) and the angle to the D is ADCNode Cs coordinate is (xc, yc) and the angle to the D is BDC

Triangulation (cont.)

Measuring Distance Three basic properties to measure the distance between a beacon node and a unknown nodeReceived signal strength indication (RSSI)Time of flight (TOF)Angle of arrival (AOA)

Received signal strength indicationTwo kinds of methods for RSSI locationDatabaseRadio propagation modelReceived signal strength indication (cont.)DatabaseMeasure the relation between distances and RSSI valuesSet up a databaseAccording the database, we can calculate the distance between two nodesReceived signal strength indication (cont.)Radio propagation modelIn the RADAR system, the Wall Attenuation Factor (WAF) model is:

where n indicates the rate at which path loss decreases with distance, P(d0) signal power at some reference d0, and d is the transmitter-receiver distance.

Received signal strength indication (cont.)Moreover, C is the maximum number of obstructions (walls), nW the number of obstructions between the transmitter and receiver, and WAF is the wall attenuation factor.Time of flight Calculate the distance between a transmitter and a receiver by the time of flightTime of arrival (TOA)Time difference of arrival (TDOA)Time of flight (cont.)TOAThe transmitter and receiver must synchronize their timeThe transmitter sends a signal to the receiverUpon receiving the signal, based on the propagation time, the receiver can calculate the distance between the transmitter and itTime of flight (cont.)

Time of flight (cont.)TDOABased on the difference of time between different signals from the transmitter arriving at the receiverThe transmitter sends two different signals with propagation speeds 1 , 2, respectivelyThe receiver receives two such signals at different times, say T1 and T2, respectivelyThe distance is

Time of flight (cont.)

Angle of arrivalBy the propagation direction of radio-frequency waves incident on an antenna array

ComparisonsRSSIAdvantage: simple hardwareDisadvantage: unstable, easily impacted by the environmentTOAAdvantage: good accuracyDisadvantage: time synchronization required, complex hardwareComparisons (cont.)TDOAAdvantage: no time synchronization, good accuracyDisadvantage: complex hardwareAOAAdvantage: nice accuracyDisadvantage: Directional antenna array requiredMaximum likelihood estimation

Maximum likelihood estimation (cont.)n reference nodes with coordinates

The unknown node in (x, y) The distances between reference nodes and the unknown node are , respectively, measured by RSSI values

Maximum likelihood estimation (cont.)Subtract the last equation from each equation

Maximum likelihood estimation (cont.)Use the matrix representation AX=b

The coordinate of the unknown node :

28Self-Calibrating Indoor Positioning System Based On ZigBee DevicesThis paper presents a positioning system based on the round-trip time-of-flight (RTT) measurementRTT can be modeled as:

System ArchitectureThe developed system is composed of three types of transponders:Mobile nodeCalibration nodeFixed node

System Architecture (cont.)Mobile nodeChipcon CC2431 : Zigbee chipTMS320C6713(DSP) : Timing and control functionsTDC-GP2 : Time interval measurement function, timing and control functions

System Architecture (cont.)Calibration nodeChipcon CC2431 : Zigbee chipTDC-GP2 : Time interval measurement function, timing and control functions

Fixed nodeChipcon CC2431 : Zigbee chip

Measuring procedureMeasuring procedureInitiated by a mobile nodeIt transmits a packet to a fixed nodeFixed node retransmits a packetThe master node receives the packet and its TDC determines the RTTCalibrating procedureInitiated by a mobile nodeIt transmits a packet to a calibration nodeThe calibration node initializes its TDC

Measuring procedure (cont.)The calibration node transmits a packet to a selected fixed nodeThe selected fixed node received and retransmits the packetThe calibration node receives the packet and its TDC determines the RTTThe calibration node repeats the foregoing procedure to a set of fixed nodes The results of RTT are sent to the mobile node for calibration

Measuring procedure (cont.)By using the calibration data, the mobile node DSP can determine the unknown position more accurately

Tested ResultThree fixed node, one calibration node

NTU Indoor LocalizationRSSI fingerprinting localizationTraining Collect RSSI values at every specific positionUse all collected RSSI values to build a databaseTrackingUpon receiving RSSI values, an end-device can compare them with those in the databaseThen calculate the position by KNN (K-Nearest-Neighbor)

NTU Indoor Localization (cont.)

Fingerprintlocation(B1,B2,B3,B4)(x1,y1,z1).........Beacon 1 Beacon 3 Beacon 2

Look up the tableNTU Indoor Localization (cont.)

NTU Indoor Localization (cont.)Example of KNN

AP2AP1AP312121110987654330m50mNTU Indoor Localization (cont.)STEP1The end-device receives the RSSI values and normalizes themSTEP2The normalized RSSI values are compared with those in the database, and find the minimum L differences Dn ST is the received RSSI valueSn is store at the databaseSTEP3For L nearest neighbors, the location estimate is

NTU Indoor Localization (cont.)STEP1PT = (-94dbm -96dbm -95dbm)PT = (0dbm -2dbm -1dbm)RL123456789101112x,y10,1020,1030,1040,1010,2020,2030,2040,2010,3020,3030,3040,30AP1-73-82-89-94-82-86-91-95-89-91-94-97AP2-82-86-91-95-73-82-89-94-66-80-87-93AP3-94-89-82-73-93-87-80-66-94-89-82-73AP1000000000000AP2-9-4-2-19421231174AP3-21-77-21-11-11129-521224NormalizeNTU Indoor Localization (cont.)STEP2

STEP3

RL123456789101112D218822156133025131626

AeroScout

AeroScout Tag

Tag using RFID 2.4Ghz WiFi transmission, MAX read range 200M, LF125k precise positioning 1~2M

AeroScout Location Receivers Location Receivers allow accurately positioning in outdoor or harsh environmentsThey execute sophisticated radio signal measuring and calculating methodsThen the results are sent to the AeroScout Engine for accurately positioning

46AeroScout TDOAUse TDOA for positioning

AeroScout System Architecture

48AeroScout Engine Processes information received from any vendor's wireless Access Points nearby Allow accurate and reliable positioning for assets equipped with AeroScout's Wi-Fi-based Active RFID Tags

49AeroScout MobileViewCustomers use MobileView to TRACK, MANAGE and INTEGRATE their assets from a single platform

50Ekahau

Ekahau System ArchitectureEkahau RTLS works on top of any standard 802.11 compliant networks, even with multi-vendor networksKey components of the system include:Wi-Fi tagsVarious physical formats, battery options and featuresEkahau RTLS Controller (ERC)Sends messages and remotely configure the tagsServer softwareCalculates the location using Wi-Fi signal strength readings52Ekahau System Architecture (cont.)Ekahau Site Survey (ESS)An easy-to-use utility for network verification and creating positioning models during system set-upEkahau VisionA web-based rules, work-flow and alerting engine Allows users to configure a variety of applications and alerts that take advantage of the precise location calculated by ERCConfigures various status, event and tag rules

53Ekahau System Architecture

Ekahau Tags

Using 2.4G WiFi (RSS)& IR transmission,MAX read range 100M, precise positioning 1MEkahau RTLS (ERC)Ekahau's patented algorithm adopts a probabilistic approach for interpreting the RF signalsCalled Multi-Hypotheses trackingThe algorithm is constantly calculating multiple possible locations for a tracked object and gives each possible location a scoreBased on all known factors outside: environment characteristics, differences between mobile devices, signal history and the movement modelsChooses the location with the highest score 56Ekahau Site SurveyA easy-to-useprofessional Wi-Fi Network planning,site survey,and management software tool

57Ekahau Site Survey (cont.)ESS enables users to quickly and easily create, improve and troubleshoot a Wi-Fi positioning system

Ekahau Vision

Help usersfind importantassets and people

59Ekahau APITag location, presence and status informationTag commissioning and managementTwo-way text messaging and commandsFloor plan images and zonesBusiness rules and event notificationsOpen architecture and XML-based web services

60Identec

Identec System Architecture

Tags62

Identec Tags

Active RFID UHF & LF UHF label

916.5MHz, MAX read range 500Mi-SAT 300 RTLS

i-MARK 2i-PORT M350 RTLS

i-CARD CF 350i-Q350 RTLS Identec SensorSMART Platform

Identec Software (i-SHARE, Watcher, CTAS)i-SHARE

65Identec Software (i-SHARE, Watcher, CTAS)CTAS

66Identec Software (i-SHARE, Watcher, CTAS)Watcher

67ComparisonsAeoScoutEkahauIdentecZigbee& LFRFID2.4G WiFi & LF2.4G WiFi(RSS) & IRRFIDUHF & LFTag 2.4GHz2.4GHz2.4GHz920Mhz0.5~6M20cm~6MNA0~3.5M1~543~54/ 120sec/3.755min/315min/42sec/80M200M100M500M3M1~2M1M1MGsensorOKN/AN/ALCDN/AN/AN/ATag(NTD)1200~60003000~6000N/AN/AComparisons (cont.)Wi-Fi(RSS)ITRI, Ekahau, Skyhook, Intel Research15m2040mWiFi APWi-Fi(TDOA)AeroScout, Hitachi AirLocation15mA Real-Time Indoor Positioning System Using the Indoor Map InformationBackgroundWireless sensor networks(WSN) requirements

71National Chung Hsing University System and Network Laboratory71Background (cont.)Low communication speedLow power consumptionLow cost IEEE802.15.4802.15.1802.11bZigBeeBluetoothWi-Fi868MHz/915MHz/2.4GHz2.4GHz2.4GHzO-QPSK,BPSKGFSKCCK,PBCC30m~100m10m100m20Kbps40Kbps250Kbps1Mbps11Mbps65536732YearsDaysHours///72WiFiZigbeeZigBee72Knowledge of Map MatchingUsing digital map and road network to enhance the positioning accuracy

73National Chung Hsing University System and Network Laboratory73Knowledge of Map Matching(cont.)Vertex-based Map MatchingSegment-based Map Matching

74National Chung Hsing University System and Network Laboratory74Knowledge of Map Matching(cont.)Vertex-based Map MatchingSegment-based Map Matching

75National Chung Hsing University System and Network Laboratory75Knowledge of Map Matching(cont.)Map Matching TechniqueDistance of point-to-pointDistance of curve-to-curveAngle of curve-to-curve

76National Chung Hsing University System and Network Laboratory76Knowledge of Map Matching(cont.)Distance of point-to-point

77National Chung Hsing University System and Network Laboratory

Knowledge of Map Matching(cont.)78National Chung Hsing University System and Network LaboratoryKnowledge of Map Matching(cont.)

79National Chung Hsing University System and Network LaboratorySystem ImplementationUser (End Device)RouterCoordinatorServer (laptop)80National Chung Hsing University System and Network Laboratory

System Implementation (cont.)Hardware: CC2530ZDK

81National Chung Hsing University System and Network LaboratorySystem Implementation (cont.)Software: IAR Embedded Workbench IDEFor ZigBee network

Visual C#2010For positioning algorithm

82National Chung Hsing University System and Network LaboratorySystem Implementation(cont.)

83System Implementation (cont.)RSSI data collect84System Implementation (cont.)Positioning AlgorithmTwo-intersected-circles algorithm

Indoor-map-matching algorithm85National Chung Hsing University System and Network LaboratorySystem Implementation (cont.)Two-intersected-circles algorithm

86National Chung Hsing University System and Network LaboratorySystem Implementation (cont.)

87National Chung Hsing University System and Network LaboratorySystem Implementation (cont.)

88National Chung Hsing University System and Network LaboratoryFlow Chart89

System Implementation (cont.)Indoor-map-matching algorithmPath databaseMatching algorithm

90National Chung Hsing University System and Network LaboratoryPath DatabaseUse vertices and segments to denote paths

91National Chung Hsing University System and Network LaboratoryPath Database (cont.)VertexIDXYSegmentIDIDIDabc92National Chung Hsing University System and Network Laboratory92Matching AlgorithmIf there is no reference node, use distance of point-to-pointIf there is a reference node, use distance of curve-to-curve

93National Chung Hsing University System and Network LaboratoryMatching Algorithm (cont.)Planning paths and set up the database in the serverIf no reference node, find the closest vertex to the unknown nodeFind all the segments that are connected to the closest vertex, and determine the closest segmentIf there is a reference node, find the closest segment like step1~394National Chung Hsing University System and Network LaboratoryMatching Algorithm(cont.)If the segment is connected with previous segment, this segment is the right segment If it is not connected, calculate the distances between the two nodes and the two segmentsCompare the sum of distances. The smaller one is the right segment95National Chung Hsing University System and Network LaboratoryFlow Chart96

Experiment and Result

97Experiment and Result (cont.)Database 1

98National Chung Hsing University System and Network LaboratoryExperiment and Result (cont.)99National Chung Hsing University System and Network LaboratoryExperiment and Result (cont.)100National Chung Hsing University System and Network LaboratoryExperiment and Result (cont.)Database 2

101National Chung Hsing University System and Network LaboratoryExperiment and Result (cont.)102National Chung Hsing University System and Network LaboratoryExperiment and Result (cont.)103National Chung Hsing University System and Network LaboratoryExperiment and Result (cont.)Database 3

104

National Chung Hsing University System and Network LaboratoryExperiment and Result (cont.)105National Chung Hsing University System and Network LaboratoryExperiment and Result (cont.)106National Chung Hsing University System and Network LaboratoryIndoor Positioning Using Femtocell

Publication Year: 2011IEEE CONFERENCE PUBLICATIONS107Femtocell OverviewFemtocell coverage is smallerMainly used to compensate for the region the other base stations can not coverEnhances the data transfer rateTypically used for residential or small business environment.

Femtocell

108Femtocell Based Positioning MethodsTo locate a mobile device in a network of femtocells, we need to determine its position relative to at least three femtocells to achieve successful triangulationFemtocells locations are known

femtocell mobile femtocell

109Femtocell Based Positioning Methods (cont.)The distance between the mobile and a femtocell is estimated by:Calculating the signal propagation loss (pathloss) between themOr the time taken by the signal to propagate from one point to the other.

MobileFemtocells

110Femtocell Based Positioning Methods (cont.)Signal Strength Triangulation based methods:Generate a database of pathloss at all locations via ray-tracing simulation of detailed building interiorsUsing WinProp software toolBeing matched against the database to estimate the position

winProp

111Femtocell Based Positioning Methods (cont.)Time based methods :The signal propagation delay between femtocells and mobileThough useful in calculating distance, this is ineffective for indoor positioning

112Position Based On Downlink Signal StrengthThe position of a mobile can be estimated by measuring the strength of the received downlink signals at the mobile from a group of femtocellsThe pathloss to each visible femtocell can then be calculated using the femtocell transmit powersMobileFemtocellpilot cdma2000 1x and UMTS.113Position Based On Downlink Signal Strength (cont.)The serving femtocell requests the mobile to send a Measurement Report Message (MRM) Containing Ecp/Io and Ecp informationEcp is the received signal strength of the serving femtocell pilotIo is the total received energy on the serving femtocell frequency (as measured by the mobile)femtocellmobileMRMEcp/Io114Position Based On Downlink Signal Strength (cont.)The fingerprint is matched against the databaseContaining pathloss values from all points in the networks coverage region to all femtocellsThe methods used to create time orthogonalization of signalsTo avoid persistent interferences

femtocellmobileMRMEcp/Io115Position Based On Downlink Signal Strength (cont.)Inter-frequency Beacon TransmissionEach femtocell may transmit its beacon pilot on different frequency channelsIn a time division multiplexed manner (TDMA)As measurements are made by the mobiles on the channels at multiple instances, the mobile will now be able to detect signals from different femtocells as all other interferers are removed

femtocell fingerprint116Position Based On Downlink Signal Strength (cont.)Co-ordinated Silence TechniquesTechniques also help create time orthogonalization of signals to avoid the problem of strong interference from the serving femtocellSuch as HDP and OTDOA-IPDLFemtocells need to also support alternative solutions for mobiles that are not equipped with these features

F fingerprint 117Position Based On Uplink Signal StrengthThe position of a mobile can also be estimated by measuring the strength of the mobile uplink pilotReceived at a group of femtocellsSince the transmit power of the mobile is unknown and dynamic, the pathloss cannot be estimated from this measurementThe difference of the measured strength at two femtocells is equal to the pathloss difference from the mobiles location to these femtocells

downlikmobilefemtocell uplink pilot 118Position Based On Uplink Signal Strength (cont.)The difference in the pathloss values can be used as a fingerprint.Those femtocells that can sense the mobile send the measured Ecp/Nt and Nt values to the positioning serverThe server calculates the pathloss difference to a number of pairs of femtocells and matches this against the database to predict the mobiles position

fingerprintfemtocell mobile Ecp/NtNt 119Simulation Model

Simulation Model (cont.)

Beamforming basicsBeamforming uses multiple antennasControl the direction of a wavefront by appropriately weighting the magnitude and phase of ndividual antenna signals (transmit beamforming).This makes it possible to provide better coverage to specific areasBecause every single antenna in the array makes a contribution to the steered signal, an array gain (also called beamforming gain) is achieved

122Beamforming basics (cont.)Beamforming makes it possible to determine the direction that the wavefront will arriveDirection of Arrival, or DoAAdaptive beamforming refers to the technique of continually applying beamforming to a moving receiver. This requires rapid signal processing and powerful algorithms.

(Adaptive Beamforming)123Beamforming basics (cont.)

Antenna array with a distance d between the individual antennas. The additional path that a wavefront must traverse between two antennas is d * sin .

ddsin124Beamforming basics (cont.)The antenna diagram is affected by the distance d between the antennas.

(Two-element Array)(Side Lobe)dd1030501/2

125OTDOAOTDOAObserved Time Difference of Arrival

OTDOAObserved Time Difference of Arrival ()1264G LTE-A Localization127

Marcocell BS

UEFemtocell BS2Femtocell BS3Femtocell BS1

UEDownlinkOTDOA+DOAFemtocell BSFemtocell BS

UE

UEUEFemtocellUEBeam Steering UE DOAOTDOA

BSTX beamforming UEBS(Layers) GPSMarcocellFemtocellDOA estimation in UEBeamforming techniqueGPS+ MarcocellGPSLOSFemtocell BSPositioning system QoS

128UEDOADownlink Positioning Reference signals/pilots are arranged across time and frequency domain (OFDMA modulation)

Collect those pilots to form a virtual arrayBS129

Founded by 22 companies across industriesNokia, Samsung Electronics, Sony Mobile Communications, Qualcomm, Broadcom and CSR, etc.To drive innovation and market adoption of high accuracy indoor positioning and relatedThe primary solutions will be based on enhanced Bluetooth 4.0 low-energy technology and Wi-Fi (802.11.ac) standards In-Location Alliance :(Nokia)(Samsung Electronics)(Sony Mobile Communications)(Qualcomm)BroadcomCSR22

Wi-FiRFID(LBS)

130IEEE 802.11ac spec.802.11ac802.11nBand5GHz Band2.4GHz/5GHz(opt)Channel Bandwidth20,40,80,160 MHz20,40MHzMax Data rate6933Mbps~600MbpsSpatial StreamsUp to 8 spatial streams4 spatial streamsModulation256-QAM64-QAMMIMOMulti-User MIMOSingle-User MIMOBackward compatibility802.11n(on 5GHz)802.11a802.11 b/gBandOperating on 5GHz bandLess interference than on 2.4GHzMore non-overlapping channel avaliable. (25 to 3 on 2.4GHz) 7Mandatory support 20/40/80MHz, 160MHz optional.

Bandwidth

Table of Data rate: Higher Order Modulation

Increase 33% PHY rate relied on 256-QAMQAM is Quadrature Amplitude Modulation.6 bits coded information to 8bits coded information.Improved MIMOUp to 8 spatial streams4 spatial streams with 11n

Multi-Users MIMOSingle-Users MIMO

Beneficial for handset or tabletMultiple antennas are not necessaryDynamic Bandwidth ManagementImproved handshake mechanism.RTS/CTS

Interference detection threshold improved-62dBm down to -72dBm

Beamforming focuses the APs transmit energy of spatial stream toward Clients

Limitation of TxBeamforming on 5GHz bandSingle Closed Loop-Method Transmit BeamformingAPSTAsSpecial Sounding SignalReport their Beamformaing matricesBackward CompatibilityRequired to be fully compatible with 802.11n(Operating on 5GHz)and 802.11a802.11b/g not supportNOKIA Bluetooth 4.0 The High Accuracy Indoor Positioning (HAIP) technologyNokia is looking to employ it based on Bluetooth 4.0Even in its current form it will have accuracy of one meterThats certainly good enough for general positioning insideIt gets much more interesting when it can get down to 20cm with modificationIndustry application for stock controlHAIP4.0

20139

NOKIA Bluetooth 4.0 (cont.)Using a single antenna and fixed mobile height, mobile can resolve its 2D location 140

NOKIA Bluetooth 4.0 (cont.)Using multiple positioning beacons, mobile can resolve its 3D location or increasing the position reliability and accuracy 141Conclusions(NLOS propagation)GSM900WCDMAHSDPA(Multipath Interference)(power issue)142GSM900WCDMAHSDPAUHF RFID()3~4ICUHF RFID142Thanks for your attention!

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