LANDMARC : Indoor Location Sensing Using Active RFID Student :Yi-Shyuan WU Adviser : Kai-Wei Ke Date : 2006.3.14.

LANDMARC : Indoor Location Sensing Using Active RFIDStudent :Yi-Shyuan WUAdviser : Kai-Wei KeDate : 2006.3.14

Outline

Introduction of location-aware systems

RFID technologyLANDMARC approachLANDMARC systemSome effect and Influence in

LANDMARC systemConclusionReferences

location-aware application—three principal technique

Triangulation– uses the geometric properties of triangles to compute object

locations.Lateration : using distance measurements.Angulation : using primarily angle or bearing measurements

Scene analysis– uses features of a scene observed from a particular vantage

point to draw conclusions about the location of the observer or of objects in the scene

Proximity– A proximity location-sensing technique entails determining

when an object is “near” a known location.

location-aware system

Outdoor:GPS(Global Positioning System)

Indoor:Infrared used diffuse infrared technology802.11 RADAR is an RF based system, is not as optim

al as desired Ultrasonic Cricket Location Support System & Active Bat

location system, high effective and accurate, and cost is exorbitant

location-aware system

Indoor:RFID(SpotON use received radio SSI)802.15.3/Ultra-wideband802.15.4/Zigbee 的定位導覽系統

RFID technology

Radio Frequency IdentificationReader 、 Tag(Transponder) Host ( 主電腦應用系統 ) 、 antenna

RFID technology — Reader

RFID Reader 包含 :與主電腦相連接的介面 RS232 、 RS485 、 RS422 、 Bluetoot

h 、 802.11控制電路、收發模組與收發天線 控制電路包含 Microcontroller 用來控制 收發模組與收發天線發射 RF 無線電波對 Tag 進行讀取與寫入的動作

Transponder

RFID 系統

Active Tag

Passive Tag

感應器標籤Sensor Tag

其他主動式標籤

EAS 防竊系統

LF低頻系統

HF`高頻系統

UHF極高頻系統

Microwave微波系統

ISO 14443通訊協定

ISO 15693通訊協定

RFID technology — Tag

RFID technology — 操作原理

Reader: 當主電腦下辨識命令給 Reader 時 ,Reader 透過 Antenna 發射 RF 無線電波 , Tag 在偵測範圍內即透過 RF 機制傳回給 Reader, 再傳回給電腦進行辨識

Tag: 進入偵測範圍時 , 其內的 Antenna 感應到電磁能量後 , 其 RF 收發機制感應耦合出電流 , 再經過電容充電成可用電源 (Passive), 將資料傳回給 Reader

RFID technology — 國際標準之缺乏

在國際標準方面，因涉及各國之法令、利益及各大廠商之利害關係

RFID 系統中，須標準化的流程有 :Air Interface 與 Data Management 之標準

化。Reader 與 Host Computer 間之 Interface 。

目前 RFID 的國際標準及組織ISO 標準 :ISO 14443 大眾運輸票價卡、 ISO 1

5693 門禁卡 EPC :MIT Auto ID Center 提出的是一個電子

產品碼 Electronic Product Code (EPC )

LANDMARC approach

LANDMARC( Location Identification based on Dynamic Active RFID Calibration )

Idea of having extra fixed location reference tags to help location calibration

SSI( signal strength information ) & Power Level( 1-8 in LANDMARC

system)

LANDMARC approach

Advantage:

– No need for a large number of expensive RFID reader.

– Environmental dynamic can easily be accommodated.

– Location information is more accurate and reliable.

LANDMARC system

LANDMARC system includes RF Reader, Reference Tag and Tracking Tag.

– RF Reader : using IEEE 802.11b wireless network

– Reference Tag : Serve as reference points in the system

– Tracking Tag / Moving Tag

LANDMARC system

LANDMARC system setup

System setup—API software (1/2)

1. Device ( RF readers )setup : Configuring the IP address.

2. Range : Specify what range for tags is to be scanned.

3. Time/tag limit per log file : How long and how much tag events recorded, somewhat critical to the configuration in sense of its effect on efficiency.

LANDMARC system setup

System setup—API software (2/2)

4. Mode( Exception vs. Continuous ) : Exception mode : The reader will report

the tag when it is inside the detected range while it will not report again until the reader realizes the tag has gone out of range.

Continuous mode : The reader will continuously report the tag ID as long as it was in the configured range.

LANDMARC system Methodology

Methodology Suppose : n RF readers m reference tags u tracking tags Readers configured with continuous

mode and detection-rang of 1-8

LANDMARC system Methodology

Define : Signal Strength Vector of tracking tags Signal Strength Vector of reference tags

, denotes the tracking tag, reference tag received on reader i, whereiS

),...,,( 21 nSSSS

i

),1( ni

),...,,( 21 n

LANDMARC system Methodology

Define : Euclidean distance in signal strength

between a tracking tag and a reference tag j

When there are m reference tags, a tracking tag has its E vector as

n

i iij SE1

2)( ),1( mj

),...,,( 21 mEEEE

LANDMARC system Methodology

The process of locating the unknown tracking tags have three key issues:

1.The placement of the reference tags 2.To determine the number of reference

tags in a reference cell k-nearest neighbor algorithm

( =1/k ?)

3.To determine the weights assigned to different neighbors

k

i iii yxwyx1

),(),(

k

ii

ij

E

Ew

1 2

2

1

1

iw

LANDMARC system

Experimental results and performance evaluation

Define the location estimation error e:

real coordinates, computed coordinates

20

20 )()( yyxxe

),( 00 yx

),( yx

LANDMARC system

Effect of the number of nearest neighbors

k=2~5 k=4 works the best set k=4 as the value of k

LANDMARC system

Cumulative percentile of error distance for k from 2 to 5.

LANDMARC system

Influence of the environmental factors Time:

10 groups of data from midnight to early morning

10 groups of data from 10:00 Am to 3:00 PM

Tracking Tag placement: Two placement

LANDMARC system

Cumulative percentile of error distance in the daytime an

d at night.

LANDMARC system

Cumulative percentile of error distance between two trac

king tag placement configurations

LANDMARC system

Effect of the number of readers More RF readers to deal with non-line of

sight (NLOS) which create the multi-path problem.

With more RF readers, more data can be gathered by having extra readers to do the sensing

LANDMARC system

Cumulative percentile of error distance for 3 and 4 RF readers.

LANDMARC system

Effect of placement of reference tagsPartition

( or sometimes a person standing) Placement more reference tags

Higher reference tag density

lower reference tag density

LANDMARC system

LANDMARC system

LANDMARC system

LANDMARC system

Higher reference tag density

LANDMARC system

Cumulative percentile of error distance with a higher r

eference tag density

LANDMARC system

lower reference tag density

LANDMARC system

Cumulative percentile of error distance with a lower reference tag density

Conclusion

Although active RFID is not designed for accurate indoor location sensing, LANDMARC approach does show that active RFID is a viable cost-effective candidate for indoor location sensing.

Three problem :SSI & Power levelLong latencyVariation of the behavior of tags

References

Lionel M. Ni, "LANDMAC ： Indoor Location Sensing Using Active RFID," IEEE International Conference in Pervasive Computing and Communications 2003 (IEEE PerCom 2003) ， Dallas ，TX ， USA ， March 2003

P. Bahl and V. N. Padmanabhan., "RADAR ： An In-Building RF-based User Location and Tracking System," In Proc. of Joint Conference of the IEEE Computer and Communications Societies (INFOCOM), 2000.

J. Hightower and G. Borriello, A survey and taxonomy of location sensing systems for ubiquitous computing, CSE 01-08-03, University of Washington, Department of Computer Science and Engineering, Seattle, WA (August 2001), http://www.cs.washington.edu/homes/jeffro/pubs/hightower2001survey/hightower2001survey.pdf

RFID 系統入門 - 無線射頻辨識系統 陳宏宇 / 著 . 松崗