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• the tag has been read only by the first group. In this case the transition is not
complete and the database is not updated.
• The tag has already been read by the second group. In this case we have a full
transition but when the user moves back the tag is read again from the first
group and the database is updated again.
– The second application is the interface located on the PDA decoding and show-
ing the data kept inside the RFID bracelets regarding the health conditions of the
patient.
– The third application provides an HTML interface to interact directly with the sys-
tem. This application manages the search of the devices and the employees in the
structure and provides a grafic interface to read and write the RFID bracelets, de-
coding also the the electronic case history (Fig. 3).
– The last application interacts with the USB reader allowing the writing and the
reading of the RFID bracelets. This application doesn’t have an interface. It only
uses the APIs provided with the reader to send the data introduced with the HTML
interface to the tags and to download the information stored in the bracelets inside
the database everytime that the reading of a bracelet is performed.
5.3 The Case History
Standard RFID passive tags can usually store data for no more than 256 byte. If opti-
mized, the information kept on a single transponder can be notably extensive.
In our case we divided the information about the patients in two parts. The first part is
formed by the personal data like name, surname, date of birth and address. These data
are not strictly vital and can also be stored on a remote support.
The UID of the RFID bracelet is used to retrieve this information. In the case of the
PDA a Wi-Fi connection to the main server has to be set up in order to download these
data. So, if the PDA is located in a place without Wireless connection this kind of in-
formation will not be provided. In the case of the workstation there will be a direct
Ethernet connection ensuring the chance to get these personal information.
The second part represents vital information, like allergies or blood type. The doctors
or nurses must have the possibility to retrieve these data in every place and in every
situation. The best way to ensure this fact is to keep them directly on the tag.
The information will be organized on the tag creating an array of presence/absence
flags.
Once downloaded, the string retrieved from the tag will be decoded reading the number
1 as Presence of the specific allergy or feature, while the number 0 will mean Absence.
Other specific features like blood type will also be identified by a numeric code.
It’s important to understand that in a passive RFID system the data transfer rate is quite
low. It’s therefore evident that reducing the number of bytes saved on the tag will in-
crease the speed of the reading operations.
In our case we used a 32-byte string. Using the UID of the tag as the mean of identifi-
cation, we were able to use every byte to describe a single feature.
Another way to reduce the number of bytes could have been to use a binary coding of
the information, reducing eight informative flags into one single byte.
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