<s>
In	O
telecommunication	O
technology	O
,	O
a	O
Barker	B-Protocol
code	I-Protocol
,	O
or	O
Barker	B-Protocol
sequence	I-Protocol
,	O
is	O
a	O
finite	O
sequence	O
of	O
digital	O
values	O
with	O
the	O
ideal	O
autocorrelation	O
property	O
.	O
</s>
<s>
These	O
patterns	O
,	O
called	O
Barker	B-Protocol
Sequences	I-Protocol
are	O
better	O
known	O
as	O
Barker	B-Protocol
code	I-Protocol
after	O
the	O
inventor	O
Ronald	O
Hugh	O
Barker	O
.	O
</s>
<s>
for	O
radar	B-Application
,	O
missile	O
and	O
gun	O
fire	O
control	O
and	O
encryption	O
.	O
</s>
<s>
The	O
Barker	B-Protocol
sequence	I-Protocol
process	O
at	O
the	O
time	O
produced	O
great	O
interest	O
,	O
particularly	O
in	O
the	O
United	O
States	O
as	O
his	O
method	O
solved	O
the	O
problem	O
,	O
initiating	O
a	O
huge	O
leap	O
forward	O
in	O
telecommunications	O
.	O
</s>
<s>
The	O
process	O
has	O
remained	O
at	O
the	O
forefront	O
of	O
radar	B-Application
,	O
data	O
transmission	O
and	O
telemetry	O
and	O
is	O
now	O
a	O
very	O
well	O
known	O
industry	O
standard	O
,	O
still	O
being	O
researched	O
in	O
many	O
technology	O
fields	O
.	O
</s>
<s>
The	O
governing	O
code	O
pattern	O
,	O
he	O
insisted	O
,	O
could	O
be	O
unambiguously	O
recognized	O
by	O
the	O
detector	B-Application
.	O
</s>
<s>
A	O
Barker	B-Protocol
code	I-Protocol
or	O
Barker	B-Protocol
sequence	I-Protocol
is	O
a	O
finite	O
sequence	O
of	O
N	O
values	O
of	O
+1	O
and	O
1	O
,	O
</s>
<s>
Only	O
nine	O
Barker	B-Protocol
sequences	I-Protocol
are	O
known	O
,	O
all	O
of	O
length	O
N	O
at	O
most	O
13	O
.	O
</s>
<s>
Here	O
is	O
a	O
table	O
of	O
all	O
known	O
Barker	B-Protocol
codes	I-Protocol
,	O
where	O
negations	O
and	O
reversals	O
of	O
the	O
codes	O
have	O
been	O
omitted	O
.	O
</s>
<s>
A	O
Barker	B-Protocol
code	I-Protocol
has	O
a	O
maximum	O
autocorrelation	O
sequence	O
which	O
has	O
sidelobes	O
no	O
larger	O
than	O
1	O
.	O
</s>
<s>
Barker	B-Protocol
codes	I-Protocol
of	O
length	O
N	O
equal	O
to	O
11	O
and	O
13	O
are	O
used	O
in	O
direct-sequence	B-Device
spread	I-Device
spectrum	I-Device
and	O
pulse	B-Algorithm
compression	I-Algorithm
radar	I-Algorithm
systems	O
because	O
of	O
their	O
low	O
autocorrelation	O
properties	O
(	O
The	O
sidelobe	O
level	O
of	O
amplitude	O
of	O
the	O
Barker	B-Protocol
codes	I-Protocol
is	O
1/N	O
that	O
of	O
the	O
peak	O
signal	O
)	O
.	O
</s>
<s>
A	O
Barker	B-Protocol
code	I-Protocol
resembles	O
a	O
discrete	O
version	O
of	O
a	O
continuous	O
chirp	B-Application
,	O
another	O
low-autocorrelation	O
signal	O
used	O
in	O
other	O
pulse	B-Algorithm
compression	I-Algorithm
radars	B-Application
.	O
</s>
<s>
The	O
positive	O
and	O
negative	O
amplitudes	O
of	O
the	O
pulses	O
forming	O
the	O
Barker	B-Protocol
codes	I-Protocol
imply	O
the	O
use	O
of	O
biphase	B-General_Concept
modulation	I-General_Concept
or	O
binary	O
phase-shift	B-General_Concept
keying	I-General_Concept
;	O
that	O
is	O
,	O
the	O
change	O
of	O
phase	O
in	O
the	O
carrier	O
wave	O
is	O
180	O
degrees	O
.	O
</s>
<s>
Similar	O
to	O
the	O
Barker	B-Protocol
codes	I-Protocol
are	O
the	O
complementary	B-Algorithm
sequences	I-Algorithm
,	O
which	O
cancel	O
sidelobes	O
exactly	O
when	O
summed	O
;	O
the	O
even-length	O
Barker	B-Protocol
code	I-Protocol
pairs	O
are	O
also	O
complementary	O
pairs	O
.	O
</s>
<s>
There	O
is	O
a	O
simple	O
constructive	O
method	O
to	O
create	O
arbitrarily	O
long	O
complementary	B-Algorithm
sequences	I-Algorithm
.	O
</s>
<s>
In	O
the	O
802.11	O
standard	O
,	O
an	O
11-chip	O
Barker	B-Protocol
sequence	I-Protocol
is	O
used	O
for	O
the	O
1	O
and	O
2Mbit/sec	O
rates	O
.	O
</s>
<s>
The	O
value	O
of	O
the	O
autocorrelation	O
function	O
for	O
the	O
Barker	B-Protocol
sequence	I-Protocol
is	O
0	O
or	O
−1	O
at	O
all	O
offsets	O
except	O
zero	O
,	O
where	O
it	O
is	O
+11	O
.	O
</s>
