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A blind navigation system using RFID for indoor environments

Authors:

Abstract

A location and tracking system becomes very important to our future world of pervasive computing, where information is all around us. Location is one of the most needed information for emerging and future applications. Since the public use of GPS satellite is allowed, several state-of-the-art devices become part of our life, e.g. a car navigator and a mobile phone with a built-in GPS receiver. However, location information for indoor environments is still very limited. Several techniques are proposed to get location information in buildings such as using a radio signal triangulation, a radio signal (beacon) emitter, or signal fingerprinting. Using radio frequency identification (RFID) tags is a new way of giving location information to users. Due to its passive communication circuit, RFID tags can be embedded almost anywhere without an energy source. The tags stores location information and gives it to any reader that is within a proximity range which can be up to 10-15 meters for UHF RFID systems. We propose an RFID-based system for navigation in a building for blind people or visually impaired. The system relies on the location information on the tag, a userpsilas destination, and a routing server where the shortest route from the userpsilas current location to the destination. The navigation device communicates with the routing server using GPRS networks. We build a prototype based on our design and show some results. We found that there are some delay problems in the devices which are the communication delay due to the cold start cycle of a GPRS modem and the voice delay due to the file transfer delay from a MMC module.
A Blind Navigation System Using RFID for Indoor
Environments
Sakmongkon Chumkamon, Peranitti Tuvaphanthaphiphat, Phongsak Keeratiwintakorn*
Department of Electrical Engineering
King Mongkut’s University of Technology North Bangkok, Thailand
Email: impet14@hotmail.com
, hyde_cerberusy@hotmail.com, phongsakk@kmutnb.ac.th*
Abstract-A location and tracking system becomes very
important to our future world of pervasive computing, where
information is all around us. Location is one of the most needed
information for emerging and future applications. Since the
public use of GPS satellite is allowed, several state-of-the-art
devices become part of our life, e.g. a car navigator and a mobile
phone with a built-in GPS receiver. However, location
information for indoor environments is still very limited. Several
techniques are proposed to get location information in buildings
such as using a radio signal triangulation, a radio signal (beacon)
emitter, or signal fingerprinting. Using Radio Frequency
Identification (RFID) tags is a new way of giving location
information to users. Due to its passive communication circuit,
RFID tags can be embedded almost anywhere without an energy
source. The tags stores location information and gives it to any
reader that is within a proximity range which can be up to 10-15
meters for UHF RFID systems. We propose an RFID-based
system for navigation in a building for blind people or visually
impaired. The system relies on the location information on the
tag, a user’s destination, and a routing server where the shortest
route from the user’s current location to the destination. The
navigation device communicates with the routing server using
GPRS networks. We build a prototype based on our design and
show some results. We found that there are some delay problems
in the devices which are the communication delay due to the cold
start cycle of a GPRS modem and the voice delay due to the file
transfer delay from a MMC module.
I. INTRODUCTION
In a pervasive computing world, location information is
very precious. Several new emerging applications is based on
location information. For example, location information can
be used to help users find what they need and where it is from
the current location of the users. A tracking system can be
used to prevent lost kids in a shopping mall by attaching
location devices to them to locate their current location.
Similarly, a navigation system is used to guide users to a
certain location. For example, a car navigator is used to guide
a driver to a destination based on the current location of the
vehicle in real-time or turn-by-turn. The location given to the
navigator is typically calculated by Global Position System
(GPS) receiver that receives reference radio signals from GPS
satellites. Thus, the GPS-based navigation does not work for
indoor navigation. An indoor navigation is important for
some applications. For example, people can utilize an indoor
navigation system to locate devices throughout a building,
tourists can use it as a tour guide in a museum, or fire fighters
can use it to find an emergency exit in the smoky
environments where it is difficult to see the way.
Several techniques have been proposed for indoor
navigation system. For example, a fingerprinting technique is
used with Wireless Local Area Network (WLAN) to calculate
a current location of a device [1]. A radio signal emitter is
used to broadcast a beacon as a reference to calculate a
distance from the emitter to a device [2]. A Radio Frequency
Identification (RFID) tag is used to store its location as a
reference point to an RFID reader [3]. Some navigation
system has proposed a hybrid solution using both GPS and
RFID to retrieve location information for disabilities [4].
Similar work of RFID-based on-foot navigation for outdoor
and indoor environments with experiments is shown in [5] and
[6]. An active RFID-based navigation system is proposed to
use radio signal strength of the active RFID signal, and the
result shows little accuracy improvement [7].
In this paper, we proposed an RFID based navigation
system for in-building navigation for blind people. Our
proposed system helps blind people to find a shortest path
from his current location to a destination. It also helps to them
when they get lost by automatically detecting the lost and
recalculate a new route to the same destination. Our proposed
system embeds RFID tags into a footpath that can be read by
an RFID reader with a cane antenna. Our proposed work can
also be used as a tourist guide system for a museum or a
navigation system for a rescue in hazardous environments
where it is difficult to find an emergency exit.
For the rest of this paper, we discuss some related work in
Section II, and discuss our proposed work in Section III. The
experiment and results are explained in Section IV. We
conclude our work and suggest for future work in Section V.
II. R
ELATED WORK
A group of researchers at National Institute of Standard and
Technology (NIST) has proposed an indoor navigation for
first responders or firefighters using RFID system [3]. Each
RFID tag is attached a location in a building as a location
information reference. The RFID reader is attached to a
firefighter and an inertial sensor system. When a firefighter
moves, the inertial sensor records the movement and estimates
the location of the firefighter. The location of the firefighter is
adjusted when he passes through the point of location
reference which is the location of RFID tags. The feasibility
study of such navigation system has shown that it is possible
to locate users in a building with the location error of 10% -
15% of the distance between waypoints.
Another RFID-based navigation system is proposed for a
user friendly guidance system for disabilities [4]. The system
utilizes several technologies for the guidance including a GPS
receiver attached to a Pocket PC to get location information,
an RFID reader to get information from embedded RFID
tracks, a Infrared sensor to get a traveling direction. The
improved prototype replaces the Pocket PC with a GPS-
enabled mobile phone. The system has been tested with 46
persons including visually impaired, blind, low vision, hearing
impaired, wheelchair users, physically impaired and elderly.
Our proposed system is similar to that proposed in [4]
except that our system is for indoor environment that utilizes
only RFID system for location information retrieval. In
addition, our proposed system adds a routing system that is
used to help users to navigate to a destination with a shortest
path. The routing system is also used to help lost users to find
a new route to the same destination.
Figure 1. The guidance system for a blind person [4]
III. B
LIND NAVIGATION SYSTEM
The proposed blind navigation system is composed of three
subsystems, the track infrastructure, the navigation device, and
the navigation server as shown in Figure 2. The track
infrastructure is composed of RFID tags. Each tag can be
embedded into a stone block and put it on a footpath. The
RFID stone block is also used by blind people for navigation.
Alternatively, each tag can be installed at sign posts along a
pathway. The type of RFID tags is selected upon the usage.
For the stone block, we select the LF RFID tags since the
radio signal penetrates the block better. The tags can be
installed along the footpath or at least at the junction of the
footpath. The tag stores the tag ID, and the tag location. To
reduce the massive amount of location information for users,
the location can be hierarchically divided; for example, each
tag location is identified by a location area, a path, a link, and
a node in term of latitude and longitude. The location area is
identified by a set of paths, the path is defined by a set of links,
and the link is defined by a set of nodes.
Secondly, the navigation device is an embedded system that
is equipped with a microprocessor unit (MCU), an RFID
reader, a communication module, a user interface module, a
memory module. The proposed device is shown in Figure 3.
The MCU is PIC18LF4620 with 3986 bytes of SRAM, 64
Kbytes of Flash memory, and 1024 bytes of EEROM. The
RFID reader is from IET operating at 134.2 kHz that is
compliant to ISO11784/5 standard. The reader is connected to
MCU via RS-232 Serial port. The reader retrieves the
information from a tag and transfers it to the MCU for further
processing. The communication module communicates with
the navigation server to send a request and to receive a
planned route from the server for navigation. We use the
GPRS module to convey information via cellular networks.
The connection to the server is only when the navigation starts
or when the user navigates out of the planned route to reduce
the communication cost.
Figure 2. The proposed blind navigation system
Figure 3. The proposed navigation device
RFID
Tag
MP3
SD/MMC
Speaker
Serial
RFID
Reader
GPRS
MCU
PIC
User
Input
Serial
Serial
RFID
Tag
RFID
Tag
RFID
Tag
Last, the navigation server receives tag information of the
current location and the destination location. Then, using the
shortest path algorithm the server calculates the shortest route
according to the distance. The whole route is returned to the
device for navigate. Users may navigate outside the
designated route or get lost; therefore, the device detects the
incident according to the location information from tags along
the route, and sends a new request back to the server to
calculate a new route to the same destination based on the new
current location information. Figure 4 shows the flowchart of
the navigation program that explains how the navigation
works.
Figure 4. The flowchart of the navigation program
IV. E
XPERIMENTS AND RESULTS
We have built a system prototype including a simulated
map of 16 tags to form a grid of 4x4 paths. Each tag contains
Tag ID and its location. All locations of the tags are used to
calculate the distance between tags used as the routing cost of
the shortest path algorithm. Figure 5 is the snapshot of the
Java-based navigation server program that shows the tag
locations on the left and the monitoring window on the right
of the figure. Between each tag is the cost of the routing in
term of distance.
Figure 5. A simulated map formed by a grid of 4x4 paths
The prototype of the navigation device is shown in Figure 6.
The actual size of the prototype is about 12 x 18 x 6 cm in
dimension and about 0.5 kg by weight, not including the tag
reader. The tag reader is about 22 x 12 x 5 cm in dimension
and about 0.4 kg by weight. The device is portable equipped
with a headphone for blind navigation where only voice is
used to guide the users to navigate. The device is operated by
a rechargeable 9V battery that can last about 6 hours. The
device is attached to a user as shown in Figure 7 with a
navigation cane for blind people.
Figure 6. The prototype of the navigation device with a headphone
Start
Speak the menu
Wait for Input
Enter a
destination
p
oin
t
Read a starting
point
Send data to Server
by GPRS
Server finds a
shortest route
Server finds a new
shortest route
Is current position
in the route?
Restart
Is current position
the destination?
Reading the point
along the route
Yes
No
No
Yes
We have tested our system by a simulation of the navigation.
First, a user is at Point A to start the navigation and to go to
Point P as his destination. The server finds a route according
to the user request, and the result is shown in Figure 8. We
then test if the routing cost or the distance between points is
changed; a new route from Point A to Point P is returned. The
new route given to the user is shown in Figure 9.
Figure 7. The navigation device attached to a user with a headphone and the
RFID antenna built-in cane
Figure 8. The shortest route from Point A to Point P
Figure 9. The new route is given after the user gets lost
V. C
ONCLUSION AND FUTURE WORK
We have proposed an RFID system for blind navigation
which can be used by blind people, by tourists, or by fire
fighters for a rescue in a building with smoke. A system
prototype which includes RFID tags embedded in a footpath
block, the embedded system as a navigation device, and a
navigation server which is remotely connected to the device
via the Internet. The system prototype has shown the
promising result although its size is still large. We also found
some communication delay in the device to connect to our
server for the first time. This is due to the cold start cycle of
the GPRS module. There is also some delay in the voice
playback where the voice file is read from MMC module. In
our future work, we will reduce the cycle delay by using a pre-
start cycle. Additionally, we will improve the voice playback
module by storing some frequently-used words in the ROM
and pre-load some words in the RAM module for faster
speech transfer or using a speech synthesizer to generate voice.
A
CKNOWLEDGMENT
This project is supported by National Electronics and
Computer Technology Center (NECTEC)
(http://www.nectec.or.th
) and IE Technology Co., Ltd.
(http://www.iet.co.th
). We would like to thank IE Technology
staff to help us build the RFID reader cane.
R
EFERENCES
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GanuA System for LEASE: Location Estimation Assisted by Stationary
Emitters for Indoor RF Wireless Networks, IEEE INFOCOM 2004,
March 7-11, 2004, Hong Kong.
[3] Leonard E. Miller, “Indoor Navigation for First Responders: A
Feasibility Study,” Technical Report, National Institute of Standards and
Technology, February 2006.
[4] Hirohiko Ohkubo, Seiji Kitakaze, Yo Fujishima, Naoto Watanabe,
Minoru Kamata, “Integrated Way Finding/Guidance system using
GPS/IR/RFID with mobile device, Technology & Persons with
Disabilities Conference, March 14-19, 2005, Los Angeles, CA
[5] S. Willis, S. Helal, “RFID information grid for blind navigation and
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[6] Jongwhoa Na, The Blind Interactive Guide System Using RFID-Based
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[7] Sergio Polito and et.al., Performance Evaluation of Active RFID
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Integrated Way Finding/Guidance system using GPS/IR/RFID with mobile device
  • Hirohiko Ohkubo
  • Seiji Kitakaze
  • Yo Fujishima
  • Naoto Watanabe
  • Minoru Kamata
Hirohiko Ohkubo, Seiji Kitakaze, Yo Fujishima, Naoto Watanabe, Minoru Kamata, "Integrated Way Finding/Guidance system using GPS/IR/RFID with mobile device, Technology & Persons with Disabilities Conference, March 14-19, 2005, Los Angeles, CA
Sachin GanuA System for LEASE: Location Estimation Assisted by Stationary Emitters for Indoor RF Wireless Networks
  • P Krishnan
  • A S Krishnakumar
  • Wen-Hua Ju
  • Colin Mallows
P. Krishnan, A. S. Krishnakumar, Wen-Hua Ju, Colin Mallows, Sachin GanuA System for LEASE: Location Estimation Assisted by Stationary Emitters for Indoor RF Wireless Networks, IEEE INFOCOM 2004, March 7-11, 2004, Hong Kong.