Specifications

5.2. SELECTION OF THE RFID SYSTEM

5.2 Selection of the RFID system

When selecting the RFID system for the island, it is important to consider the

cost of replacing the existing system. The choice to use an active or passive

system ultimately requires the integrator to decide what the lifespans of the

tags are expected to be: how many read/write cycles and over what period.

This lifespan along with lower tag prices, is traded oﬀ against reduced read-

range, reduced tag memory, increased reader power requirements and slower

read speeds. The frequency is also important — high frequency devices’

signals attenuate signiﬁcantly through water and ﬂesh mediums.

The existing RFID system on the island is based on Texas Instruments’s

Series 2000 low frequency passive system. It is speciﬁcally designed to meet

the ISO 11784/85 speciﬁcations for animal tagging as well as automotive

applications. In order to remain backwards-compatible with this system

(and take advantage of the already-tagged birds), the replacement system

will also use low frequency passive technologies.

Transponder Selection The choice of tag ultimately depends on the

application. ISO standards exist for passive RFID tags designed for the

purposes of animal or agricultural equipment identiﬁcation. These are deﬁned

in ISO 11784 and ISO 11785 which were originally publishe d in 1996 [8].

The documents deﬁne the code structure and an operating frequency of

134.2kHz using FSK. Not speciﬁed is the minimum transponder performance,

half- or f ull-duplex operation and ID codes of these devices. This prevents

inter-operability of devices from various manufacturers and, more worryingly,

makes it possible for duplicate ID codes to exist. The standards have since

been revised, however, many of the problems with the original standard are

still unresolved.

For our purposes, we require an unobtrusive tag that will not interfere

with the birds’ daily lives. Originally, this was in the form of a non-electronic

external tags with engraved ID numbers which were clamped to animals’

ﬂippers. More recently, however, these have been replaced by modern glass-

encased, bio-safe capsules which are injected under the birds’ skin. This

system will form part of a study to determine whether thes e older ﬂipper