utilizing physical layer information to improve rfid tag

CHAPTER 8
CONCLUSIONS AND FUTURE WORK
In this chapter we summarize the results of the research performed. This re-
search focusses on improving the identification rate of present RFID systems. Physical
layer collision signals were used for the same and changes in present algorithms are
suggested.
8.1 Conclusions
Section 6.1 described the results of detecting the number of tags invloved in a
collision using I-Q plot. Experimental results point out that in the 3 tag case, 71%
accuracy was possible while for the 4 tag case 73% accuracy was possible .
Section 6.2 presented a simulation to find the theoretical performance increase
using three different algorithms. The results are presented in table 8.1. Collision re-
covery by extracting the individual RN16s of the two tags involved in a collision can
be used to convert a collided slot to a read slot. We do not know the expected RN16
values of the tags since they are randomly generated for each session. Our algorithm
is used to recover the RN16s from the colliding signals. The only way to detect if the
RN16 was correct is to send an ACK to the tags with the decoded RN16 and check if
the tag responds. The EPC Class 1 Gen. 2 protocol allows only single ACK command
to be sent. Even if we correctly decode both RN16s, we can acknowledge only one
of the tags as the other tag will also receive this ACK and discard it as incorrect.
This could be solved by adding a STACK command to the protocol which instructs
tags involved in a collision to wait till the ACK command formed using their RN16 is
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