<s>
Singulation	B-Device
is	O
a	O
method	O
by	O
which	O
an	O
RFID	B-Application
reader	O
identifies	O
a	O
tag	O
with	O
a	O
specific	O
serial	O
number	O
from	O
a	O
number	O
of	O
tags	O
in	O
its	O
field	O
.	O
</s>
<s>
When	O
all	O
the	O
tags	O
cooperate	O
with	O
the	O
tag	O
reader	O
and	O
follow	O
the	O
same	O
anti-collision	O
protocol	O
,	O
also	O
called	O
singulation	B-Device
protocol	O
,	O
</s>
<s>
In	O
RFID	B-Application
technology	O
,	O
various	O
strategies	O
have	O
been	O
developed	O
to	O
overcome	O
this	O
situation	O
.	O
</s>
<s>
There	O
are	O
different	O
methods	O
of	O
singulation	B-Device
,	O
but	O
the	O
most	O
common	O
is	O
tree	O
walking	O
,	O
which	O
involves	O
asking	O
all	O
tags	O
with	O
a	O
serial	O
number	O
that	O
starts	O
with	O
either	O
a	O
1	O
or	O
0	O
to	O
respond	O
.	O
</s>
<s>
Because	O
of	O
privacy	O
and	O
security	O
concerns	O
related	O
to	O
this	O
,	O
the	O
Auto-ID	B-Application
Labs	I-Application
have	O
developed	O
two	O
more	O
advanced	O
singulation	B-Device
protocols	O
,	O
called	O
Class	O
0	O
UHF	O
and	O
Class	O
1	O
UHF	O
,	O
which	O
are	O
intended	O
to	O
be	O
resistant	O
to	O
these	O
sorts	O
of	O
attacks	O
.	O
</s>
<s>
The	O
first	O
offered	O
singulation	B-Device
protocol	O
is	O
the	O
ALOHA	O
protocol	O
,	O
originally	O
used	O
decades	O
ago	O
in	O
ALOHAnet	O
and	O
very	O
similar	O
to	O
CSMA/CD	O
used	O
by	O
Ethernet	O
.	O
</s>
<s>
In	O
the	O
worst	O
case	O
,	O
an	O
ALOHA	O
protocol	O
network	O
can	O
reach	O
a	O
state	O
of	O
congestion	B-Protocol
collapse	I-Protocol
.	O
</s>
<s>
With	O
RFID	B-Application
it	O
is	O
applied	O
for	O
concurrence	O
of	O
readers	O
(	O
CSMA	O
)	O
as	O
well	O
as	O
with	O
concurrence	O
of	O
tags	O
.	O
</s>
