<s>
In	O
digital	O
modulation	O
,	O
minimum-shift	B-Device
keying	I-Device
(	O
MSK	O
)	O
is	O
a	O
type	O
of	O
continuous-phase	B-Device
frequency-shift	O
keying	O
that	O
was	O
developed	O
in	O
the	O
late	O
1950s	O
by	O
Collins	O
Radio	O
employees	O
Melvin	O
L	O
.	O
Doelz	O
and	O
Earl	O
T	O
.	O
Heald	O
.	O
</s>
<s>
Similar	O
to	O
OQPSK	O
,	O
MSK	O
is	O
encoded	O
with	O
bits	O
alternating	O
between	O
quadrature	B-Algorithm
components	I-Algorithm
,	O
with	O
the	O
Q	O
component	O
delayed	O
by	O
half	O
the	O
symbol	O
period	O
.	O
</s>
<s>
In	O
addition	O
to	O
being	O
viewed	O
as	O
related	O
to	O
OQPSK	O
,	O
MSK	O
can	O
also	O
be	O
viewed	O
as	O
a	O
continuous-phase	B-Device
frequency-shift	O
keyed	O
(	O
CPFSK	O
)	O
signal	O
with	O
a	O
frequency	O
separation	O
of	O
one-half	O
the	O
bit	O
rate	O
.	O
</s>
<s>
A	O
variant	O
of	O
MSK	O
called	O
Gaussian	O
minimum-shift	B-Device
keying	I-Device
(	O
GMSK	O
)	O
is	O
used	O
in	O
the	O
GSM	O
mobile	O
phone	O
standard	O
.	O
</s>
<s>
Gaussian	O
minimum-shift	B-Device
keying	I-Device
,	O
or	O
GMSK	O
,	O
is	O
similar	O
to	O
standard	O
minimum-shift	B-Device
keying	I-Device
(	O
MSK	O
)	O
;	O
however	O
,	O
the	O
digital	O
data	O
stream	O
is	O
first	O
shaped	O
with	O
a	O
Gaussian	O
filter	O
before	O
being	O
applied	O
to	O
a	O
frequency	O
modulator	O
,	O
and	O
typically	O
has	O
much	O
narrower	O
phase	O
shift	O
angles	O
than	O
most	O
MSK	O
modulation	O
systems	O
.	O
</s>
<s>
GMSK	O
has	O
high	O
spectral	B-Protocol
efficiency	I-Protocol
,	O
but	O
it	O
needs	O
a	O
higher	O
power	O
level	O
than	O
QPSK	O
,	O
for	O
instance	O
,	O
in	O
order	O
to	O
reliably	O
transmit	O
the	O
same	O
amount	O
of	O
data	O
.	O
</s>
<s>
GMSK	O
is	O
most	O
notably	O
used	O
in	O
the	O
Global	O
System	O
for	O
Mobile	O
Communications	O
(	O
GSM	O
)	O
,	O
in	O
Bluetooth	B-Protocol
,	O
in	O
satellite	O
communications	O
,	O
and	O
Automatic	O
Identification	O
System	O
(	O
AIS	O
)	O
for	O
maritime	O
navigation	O
.	O
</s>
