How RFID Technology can Assist the Visually Impaired:

The Sesamonet System

Marcello Barboni, Francesco Rizzo, Graziano Azzalin and Marco Sironi

Joint Research Centre of the European Commission

Institute for the Protection and Security of the Citizen

Via E. Fermi 2749, 21020 Ispra (Va), Italy

Abstract. The Project’s objective is the development of an integrated system to

increase mobility of people with disabilities and their personal safety and secu-

rity, by identifying a secure path to walk through selected areas, particularly for

people with visual disability. This is done through the use of mature and proven

technologies (RFID, antennas, bluetooth, etc.) which only have to be integrated

for this speciﬁc application.The system is based on 3 main components: a path

made of transponders, a custom- designed walking cane and a smart phone. Each

RFID tag is associated to a message or a small beep. The system describes the en-

vironment and warns the user if there is a potential danger such as a road crossing

or a step.

1 Introduction

According to the World Health Organisation, in 2002 the number of people with sight

impairments worldwide was over 161 million, about 37 million of whom were blind.

Such impairments mostly affect the population older than 50 years of age. This issue is

of particular relevance for Europe because of its ageing population. The limited reality

perception of visually impaired people givesrise to an impressive limitation in their mo-

bility. Their movement capabilities in both outdoor and indoor unknown locations are

limited and dangerous and frequently become impossible without external assistance.

Therefore, the creation of an electronic navigation system for visually impaired people

represents an issue of relevant social importance. Recent improvementsin computer sci-

ence and new technologies have opened new perspectives with respect to the possibility

of helping people with sight disabilities. In particular, in the last years many different

navigation solutions have been investigated and proposed by the scientiﬁc community.

A large class of such systems envisage the use of the Global Positioning System

(GPS) to enable outdoor navigation [1], [2], [3], [4], [5], [6]. Although the use of satel-

lite position determination for usual navigation purposes is quite thorough, in this do-

main the error of one meter or more might be limiting in some situations (i.e. in prox-

imity of a crosswalk); moreover, the difﬁculty in receiving satellite signals indoors with

low-cost GPS receivers makes GPS based navigation systems not viable as a stand-

alone solutions for this domain, whereas they could be successfully used in conjunction

with other systems such as Sesamonet.

Barboni M., Rizzo F., Azzalin G. and Sironi M. (2008).

How RFID Technology can Assist the Visually Impaired: The Sesamonet System.

In Proceedings of the 2nd International Workshop on RFID Technology - Concepts, Applications, Challenges, pages 142-148

DOI: 10.5220/0001733301420148

 SciTePress

Other navigation systems for visually impaired people rely on the presence of var-

ious electromagnetic sources in the navigation environment, such as infrared emitting

diodes, which emit a beam carrying location information. A navigation unit collects and

elaborates such information. The main limitations are the need of constant direct line

of sight between emitters and receiving unit and the necessity of a power supply for the

external emitters.

Finally, recent studies address the integration of different technologies such as GPS,

dead-reckoning sensor positioning and active Radio Frequency Identiﬁcation (RFID),

in order to obtain better navigation systems with a high accuracy in determining the

user’s position [7], [8]. Altough these systems offer a solution to the absence of indoors

GPS signal availability, they still have some essential lacks in the positioning require-

ments needed for an application for blind users. In particular, the error in the position

determination is about 1 meter or greater. Moreover, these systems are often complex

to use and have a cumbersome and uncomfortable sensors equipment.

Starting from these preliminary remarks, the Joint Research Centre, which repre-

sents the scientiﬁcal reference centre for the European Commission supporting the Eu-

ropean legislation, has proposed an innovative system for guiding visually impaired

people. In the continuation of this paper we discuss in detail the hardware infrastructure

of the prototype in section 2 and the software application and the navigation logic in

section 3. Finally, in section 4 we discuss results and possible future developments.

2 System Description

Starting from the state-of-art described in the introduction, we designed an innovative

and affordable navigation system for blind persons, based on the use of passive low

frequency RFID technology, called Sesamonet (Patent Pending). The project’s name is

the acronym of Secure and Safe Mobility Network.

Usually, visually impaired persons feel the environment by means of a greatly de-

veloped sensibility of auditory and tactile channels. In addition, they utilize useful tools,

such as the guide dog or the walking cane, to recognize surroundings and avoid obsta-

cles: our goal is to leverage as much as possible the blind person’s familiarity with

these tools by integrating the well-known walking cane with a navigation system based

on passive RFID technology. The main idea consists in recycling the RFID passive

transponders from animal tagging and installing them into the ground to create a secure

path: the blind person’s walking cane, ﬁtted with an antenna and a reading system, de-

tects and reads the RFID micro-chips and sends a signal, through a bluetooth channel,

to a Smart Phone. The Smart Phone, equipped with a database containing information

on the location, elaborates this signal and communicates to the user, through a bluetooth

headset, information regarding the path. Figure 1 illustrates the logical operation of the

Sesamonet system.

The system is designed to be as similar as possible to existing mobility-aiding tools,

while enhancing their capabilities and usefulness, and bringing them up to date with

modern technological developments. This does not mean, however, that Sesamonet is a

drop-in replacement for existing tools: the users should foresee a training period before

being able to exploit its full potential. Training should be carried out by qualiﬁed train-

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ing associations such as the Italian ”Association for orientation-mobility and personal

autonomy instructors”.

It is worthwhile noting that a large-scale deployment of the Sesamonet system

would create a need for consultants, instructors and other personnel; this would open

many opportunities of employment for the visually impaired, who would be the most

qualiﬁed to ﬁll this particular market’s demand.

The possibility to send information through the bluetooth channel makes it possible

to activate any electro-mechanical device which can be linked to a serial port, such as a

trafﬁc light. Similarly, if the system is deployed on a modern smartphone, there is also

the option of using WiFi to activate electro-mechanical devices.

The technology on which Sesamonet is based is low frequency (LF) RFID, at 134.2

KHz. The choice of LF transponders over other frequenciessuch as high frequency(HF)

or ultra-high frequency (UHF) was made primarily because of the former’s greater ro-

bustness to external interference factors, such as the proximity with liquids or metals.

The choice of passive technology was made because there usually is no ﬁxed power

source available in outdoor environments, and battery power is too expensive and lim-

ited for this application. In passive RFID the antenna irradiates the transponders with

its electromagnetic energy, and the transponders use this energy to reply to the reader.

Thus the tag doesnt need a battery to function, and this makes its lifespan theoretically

inﬁnite.

Fig.1. Sesamonet overview.

A navigation system similar to our Sesamonet project has been recently proposed in

Japan [9], [10]. Some important differences between these navigation systems could be

highlighted. The japanese Free Mobility Assistance project is based on the use of pas-

sive LF RFID tags working at the frequency of 125 KHz. In this system the RFID tags

are embedded into the concrete blocks guiding visually impaired people. Moreover, in

order to obtain an acceptable reading distance, the tag’s antenna have to be extended

over the entire guide block surface. Therefore, a large scale installation of such naviga-

tion paths should become difﬁcult from the economic and architectural points of view.

In addition, the portable information terminal used to elaborate the tags information

is a speciﬁc device (Ubiquitous Communicator) while in our solution any commercial

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Smart Phone, equipped with a minimun processor of 200MHz and a Bluetooth version

1.2 (or greater), should be used.

2.1 The Secure Path

Once the tag is irradiated by the reader, it responds by giving its UID (Unique IDen-

tiﬁer). This is a 12-digit code unique to the single tag. The secure path is made of a

sequence of tags embedded into the pavement, usually at a distance of 60cm one from

the other. In some conﬁgurations there is a single line of tags running parallel to a

natural landmark (e.g. a building, a sidewalk, etc), in others there can be a double or

triple line to help keep the user centered inside the path. The ﬁnal scheme of the secure

path is to be decided with representatives of the blind associations, and in general after

extensive testing of the system by visually impaired users.

The passive RFID transponders are embedded directly into the ground; as a conse-

quence, these components must have a high resistance to physical stress (i.e. vibrations,

humidity, temperature range etc.).

Fig. 2 shows the elements which constitue the system: a generic PDA with a blue-

tooth earphone, LF RFID transponders and the visually impaired stick with the suitable

electronic.

Fig.2. The Sesamonet components: PDA/Smartphone with a earphone, RFID transponders recy-

cled from animal tagging and the RFID-enabled walking cane.

We adopt passive RFID transponders recycled from animal tagging. Livestock iden-

tiﬁcation through RFID chip tagging, in compliance with ISO standard 11784/85, will

become compulsory in a near future for European Member States with an animal pop-

ulation exceeding 600000 units. The already large number of passive RFID tags avail-

able after the use in the livestock market will therefore see an increase. In Europe each

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year about 50 million tags used for the tagging of live animals are destroyed because,

for hygenical reasons, they cannot be reused on animals. Therefore, their re-use in the

Sesamonet project saves the cost of their disposal and, at the same time, reduces Sesa-

monet’s cost. Moreover, passive transponders do not require an external power source

because they are powered by the incoming radio frequency signal, thus decreasing the

overall system’s maintenance costs. Being designed for animal tagging, these transpon-

ders have a very high environmental resistance.

The outdoor test paths we deployed so far did not suffer any loss of functionality

due to environmental factors. The oldest on, at JRC premises, is over two years old.

A possible critical situation for the system can occur when in the path are present

obstacles not already recorded in the database. In order to avoid such situation, it is

possible to mark the secure path borders with colourful signs which signal to sighted

persons the presence of the path.

2.2 The RFID-Enabled Walking Cane

The RFID-enabled walking cane has been designed to closely resemble a normal walk-

ing cane, the main difference being that this cane has an antenna with a ferrite core

located in correspondence of its tip as showed in Fig. 2, an electronic circuit that gov-

erns the transmission to and from the tag, a bluetooth module and a battery pack in the

handle. We decided for a bluetooth module Class 2, which has an operating range of 10

meters and a power consumption of 2.5 mW, as a comprise between power saving and

connection reliability. The result is a cane that weights a bit more than a normal cane,

but is well-balanced and usable. The walking cane is designed to detect and read a tag

within a 20 cm radius; a greater reading distance would be technically possible but it

would be counterproductive, as it would lower the precision of the system and raise the

uncertainty on which tag is actually being read.

2.3 The Smartphone

The brain of the system is the smartphone, where data are stored and elaborated. A

smartphone substantially is any PDA (Personal Digital Assistant) or any last (or second-

last) generation cellular phone. For example, any cell phone that supports the installa-

tion of applications such as a GPS navigator is capable of running Sesamonet. The

smartphone is associated by means of to a bluetooth communication to the walking

cane and to an earphone. An important hardware requirement for the smartphone is

that its bluetooth radio is a 1.2 (or greater) version device, in order to manage two or

more connections at the same time. Sesamonet has been developed and tested on PDAs

running Windows Mobile and Symbian operating systems.

The smartphone runs a software that seeks in its internal database the UID received

from the walking cane and retrieves the association between the UID and the voice

message that describes it. It then sends the message to the earphone.

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3 The Navigation System

The electronic path formed by the RFID tags embedded into the pavement can be

walked in both directions, and entered at any point. The path can fork into different

paths, can merge and can cross another path. These are common situations that have to

be managed by the navigation software. The software must have a way of knowing, at

all times, the position of the user within the path and the direction he/she is moving in.

To do this the path must be divided into logical segments and the tags must be

numbered sequentially within each segment. Each segment can have an arbitrary length.

We associate two numbers to each tag, one indicating the segment number and one

indicating the single tag position within the segment. This way a single ”seek” operation

will yield univocally all data associated to a tag.

The system stores in an internal buffer the last 5 tags read; it can thus recognize a

change in direction and adapt the choice of messages to relay to the user. For example a

”turn right” instruction becomes ”turn left” when navigating in the opposite direction.

If a user enters a path at a random point the system waits for the reading of the second

tag to decide the direction he is walking in. This second tag doesn’t necessarily need to

be consecutive.

3.1 Field Tests

After a ﬁrst test electronic path deployed at JRC premises, a full scale demonstration

of the system’s capabilities has been done on the 19th of October 2007 in the city of

Laveno (Varese, Italy). Sesamonet’s launch in Laveno gave the opportunity to show all

the features of the system by testing it with a visually impaired user. In particular, the

system’s possibility to guide the user along the electronic path automatically inverting

the navigation logic when the user changes direction, the possibility to enter the path

at any generic position and the capability of activating a trafﬁc light by simply reading

a designated transponder have been given. A second installation has been carried out

in December 2007 in the Prealpi Giulie Park (Udine, Italy). In both cases the system

is now installed and working. Visually impaired users who tried the system expressed

very positive feedbacks regarding its guidance features and its usability.

4 Summary and Future Developments

From a technical standpoint, the basic functionalities are in place and can serve as a

solid foundation for the addition of new features, including:

– addition of navigating functionalities so that the system can guide a person to des-

tination instead of only giving warnings and describing the environment,

– future generation smartphones will have an integrated GPS receiver: the system

will use the GPS data when available,

– addition of speciﬁc modules for different environments: for example in railway sta-

tions there could be a blind-friendly booking facility, express check-in in airports,

etc.

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Finally, the system can rely on a robust and widespread infrastructure such as the

GSM/GPRS network, it can update its database in real time and offer a great number of

additional services.

Our prototypes and test paths been tested in different environments in collaboration

with the Italian Blind Association and constitute a solid proof of principle. Being that

the JRC is a research institute, the next step (industrialization) has to be carried out by

parties interested in the exploitation of this technology. The system is patent pending.

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