In a
casewheremultiple readers try to read the sametag, the tag cannot select a particular reader to
respond to. Therefore, passive tags, in which the collision may take place, are not able to take
part in the collision resolution. Reader??“reader collision not only decreases throughput of tag
identi?¬?cation, but also increases the bandwidth usage.
5.1.3 Solution
The software-de?¬?ned RFID reader, from here on referred to as SDLR, was developed to
solve this interoperability problem. Traditional radios use hardware circuits, ?¬?xed at the
time of manufacture, to perform the high-speed signal-processing tasks that convert back
94 RFID Handbook: Applications, Technology, Security, and Privacy
and forth between user data and the radio waveform. SDLR exploits advances in components
such as digital signal processors (DSPs) and ?¬?eld-programmable gate arrays to
make the hardware generic, and move all of the waveform-speci?¬?c tasks into software.
One SDLR device can support a variety of communications standards, just as one PC can
run a variety of software applications. SDLR has a number of bene?¬?ts in addition to
improving interoperability.
SDLR has signi?¬?cant advantages over traditional RFID readers, that is why many Auto-
ID labs are supporting its development.
Desirable characteristics include:
1. Receive and transmit various modulation methods using a common set of hardware.
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