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Web Posted on: August 4, 1998



An Orientation and Information System for Blind People based on RF-Speech-Beacons

Martin Kemmerling
Hans-Jürgen Schliepkorte
Fraunhofer-IMS-Duisburg

Finkenstr. 61, D-47057 Duisburg
Germany
tel: + 49 203 3783 241
fax: + 49 203 3783 266
email:
kemmer@ims.fhg.de

1. Summary

A very useful microelectronic system for the acoustic information and orientation of blind people has been developed by FhG-IMS by order of an industrial client (RTB GmbH, Bad Lippspringe, Germany). The system is based on mobile hand held units and fixed information posts. Acoustic orientation information is transferred to mobile parts using wireless transmission of digitally coded and compressed speech. The first prototype version of the so called "ORTI" system was successfully presented at the REHA fair at Düsseldorf, Germany, in October 1997. Further improvements are under development and will be finished in summer 1998.



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2. Introduction

Blind people have, especially in unknown environments like streets, buildings in cities abroad, a lot of serious and persistent problems. Mostly they are concerned with the task of orientation. Signposts for example have optical information, so they are useless for blind people. Although optical information cannot be adapted by blind persons, they normally have a well trained hearing. This leads to the idea to create a system based on "acoustic signposts".

Beyond the ability to announce acoustic information to the user, further technical features must be realized in order to achieve a successful product, which can be accepted by blind users and by those companies who install and run the system. These additional requirements are maintainability, portability, extremely low power consumption and very low costs for the system components and their installation.

The development of an orientation system based on these ideas is described here. A typical application of the system is shown in fig. 1:

Typical Application for the Communication between Beacon and HHU

Fig. 1: Typical Application

 



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3. Technical Solution

3.1 General System Information

Two kernel knowledge fields of the IMS department "Systems and Applications" are transponder systems and communication systems. Based on the knowledge of these fields the IMS developed a system consisting of two main components:

- a hand held unit (HHU) and

- a RF-beacon.

Additional, but less important system components are the battery charger for the HHU and a programming adapter for the configuration of beacons.

The HHU is the mobile part of the system, which is carried by the blind person, normally in a pocket of a shirt or a jacket. The beacons can be mounted in various positions, for example on the top of traffic lights, at the wall of a building, at the entrances of offices or shops. Many other applications are possible, even at the doors of buses or trains.

3.2 Photovoltaic Supplied Speech Beacon

The RF-beacon (see fig. 2) is supplied by a solar cell in combination with a rechargeable battery pack. Using this way of power supply the installation of beacons is very cheap and simple, because there is no expense to lay cables. The very low power consumption and the sizes of solar cell and built-in battery pack allow a secure function of the system even during several days with very poor solar power emission.

Internal Structure of the Photovoltaic Supplied Speech Beacon

Fig. 2: Photovoltaic Supplied Speech Beacon

A microprocessor and its software control all the actions and algorithms of the beacon. Especially the data transmission protocol is realized by software. In order to save energy special sleep and halt modes are used. A real time clock wakes up the processor periodically, so that it can check if there is a need to transmit speech information.

Compressed speech (according to recommendation G.723.1) is stored in a digital representation in a memory (ROM and/or RAM). In the situation illustrated in fig. 1 this speech information is the name of the street. Using a PC the speech information has off-line been recorded and compressed with a special speech compression algorithm. After this procedure the result is downloaded to the beacon. This can be done either using serial data communication by wire or using the wireless RF-transmission.

The stored speech information can be transmitted by the beacon via RF-transceiver and antenna. In the first version of the system the carrier frequency was 433 MHz.

Various speech information files can be stored in the beacon. Each speech file has additional qualification data that specify the type of speech information. There are flags for different languages and for different kinds of speech announcements (for example taxis and bus stops, public buildings and offices, streets and places, physicians and pharmacies, commercials,...). Using the special communication protocol and the additional specification data the hand held units can choose the kind of speech information that has to be transmitted. The user can program his hand held unit according to his special needs.

The reception and transmission range of the beacon signal is a circle with a radius from 2 meters to about 10 meters around the beacon. It is controlled by software and can be configured by the owner of the beacon.

Special service counters and registers are established within the software of the beacons. They count the numbers of data transfer events to hand held units, the number of transmission errors and the codes of the different hand held units they ever had contact with. Reading these counters and registers allows the owner or the operator to check the beacons,their individual use and their technical and commercial performance.

3.3 Portable Hand Held Unit

The hand held unit (see fig. 3) is small and handsome. It is supplied by a rechargeable battery pack. The RF-transceiver as a part of the HHU receives the RF-carrier with the digitized and compressed speech information (base band signal) modulated on the 433 MHz RF-carrier from the beacon. There is a special communication protocol to ensure an error-free data exchange between beacon and hand held unit.

Internal Structure of the Portable Hand Held Unit (HHU)

Fig. 3: Portable Hand Held Unit (HHU)

After demodulation and decompression of the received information the received speech information is stored in memory. The successful reception of speech information is announced by a short beep. After pressing a button at the user interface a decoder converts the digitized speech into an analogue signal which is applied to a small built-in loudspeaker using a standard audio amplifier.

Via two user interface buttons the blind person can control all settings of the HHU. The user can select the type of information he wants to receive; he can check the charging state of the battery pack; he can start the repetition of the last received information. All information for the user interface is realized in the manner of an acoustic selection menu, which is output by the HHU in form of speech (for example "volume" or "battery state"). The language for this user interface can be configured by the manufacturer of the HHU or by users who buy special programming units for their equipment.

In the beacon and in the HHU microprocessors control all actions in the devices by software. This software is developed for real-time-requirements, and all hardware is designed for the extreme low-power requirements. New software releases can be transferred into the units without opening the case and without changing any devices within the unit; this can be done using serial data transmission between a PC and the HHU.



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4. Conclusion and Future Developments

Using the "ORTI" system blind people will get acoustic information for their orientation. The main benefits of the system developed are:

- a very concrete orientation environment in an acoustic form (not only buzzer signals) resulting in higher safety for the blind people, especially in outdoor areas;

- the option of having actual information in the beacon prevents from orientation and information errors;

- because of programmability of the speech memory in the beacon the system can be used in all countries;

- the solar cell of the beacon makes the beacon autonomous and service free for a long period of usage.

The actual phase of the development concentrates on the increased quality of the data transmission channel. The first prototypes, which were created for the REHA fair in 1997, had sometimes difficulties with distortions because of the intensive use of the 433 MHz ISM frequency band by other systems and applications. The new prototypes, which will be ready in may 1998, will use a transmission frequency in the 867 MHz range. Furthermore the sharpness of the RF field borders will be increased by special antenna forms in order to achieve a closer relationship between the location of the beacon and the speech output of the HHU.

The pre-series production of beacons and hand held units will start in June 1998. The first application will be a field test in a suburb of Berlin starting in summer 1998. During this field test special attention will be paid to the quality of the wireless data transfer between beacon and hand held unit, to the quality of the photovoltaic power supply of the beacons and to the judgement of blind people who use the system for their individual needs. During the field test the service counters in the beacons will be periodically read out, so that the statistical evaluation of the use and the technical function of each individual beacon will be possible.

Further possible application fields are opened by the connection of the beacons to a data communication network, for example field busses, ISDN, DECT or GSM. This gives the potential for a large variety of applications where changing information has to be announced. This also opens application fields for normal seeing people in museums, exhibitions, production lines, public buildings of all kind or intelligent homes. Special beacons for the application in public traffic systems (bus or train) will be the next step to complete the ORTI system. These beacons will get a direct connection to the internal information system in the vehicle, so that the route number, the direction and the next station can be announced.



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