9.5.1 Average Slot Delay Analysis
In general, the performance of anticollision protocols is represented by average slot delay.
Average slot delay can be de?¬?ned as the expected number of slots consumed for identifying
m tags. In most existing protocols to date which are related with RFID tag, anticollision
aimed to minimize average slot delay or maximize average slot throughput. In similar
vein, we will present the performance of tag anticollision protocols in slot delay in analytic
manner, dividing them into binary tree protocol and adaptive framed slotted ALOHA.
TABLE 9.1
Notations
Symbol Description
F Frame size
Ntag Estimated number of tags
S Number of readable slots
C Number of collided slots
I Number of idle slots
SEXP(F,Ntag) Expected value of readable slot given frame size and the number of tags
CEXP(F,Ntag) Expected value of collided slot given frame size and the number of tags
IEXP(F,Ntag) Expected value of idle slot given frame size and the number of tags
Comparative Performance Analysis of Anticollision Protocols in RFID Networks 171
Theorem 9.1
The average slot delay of binary tree protocol approximates to 2.8853m.
Proof
The proof of this theorem follows an analysis presented in Ref. [20], which is based on a
research that investigated on tree-based multiple access channel [5]. The average slot delay
T
(m), which is the expected number of consumed slots until identifying m tags, in binary
tree protocol is as follows:
T
(m) ?? C
(m) ??I
(m) ?? m, (9:5)
where C
(m) and I
(m) denote the average number of collided slots and idle slots, respectively.
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