utilizing physical layer information to improve rfid tag

CHAPTER 1
INTRODUCTION
Radio-Frequency Identification (RFID) technology is an automatic identifica-
tion technology (Auto-ID) which uses radio waves for the communication and retrieval
of identification data. Bar code identification is the most widely adopted Auto-ID
technology and is used is almost all walks of life. An RFID system consists of an
interrogator (reader) communicating with a tag which is affixed to the object to be
identified. Use of electromagnetic waves for identification gives RFID many advan-
tages over bar codes. RFID allows identification of multiple items at a very high
speed whereas bar codes can only identify a single item at a time. RFID systems also
offer higher memory capacity and a longer read range.
RFID systems operate over a wide range of frequencies from 100KHz to well
over 5GHz. They can be classified as either active or passive systems depending
upon the type of tags used. This thesis will focus on the UHF passive RFID system
operating over the 902-928MHz ISM band.
1.1 Background
Reliability and speed are the two major driving factors for ongoing RFID re-
search. Multiple tag identification capability of RFID systems allow them to be fast.
However an RFID tag has very limited resources and hence limited functionality
so all the tags within a reader’s field attempt to communicate with the reader as
soon as they get energized. This causes a communication collision and disrupts the
identification process. To overcome this problem, algorithms called anti-collision al-
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