<s>
Continuous	B-Device
phase	I-Device
modulation	I-Device
(	O
CPM	O
)	O
is	O
a	O
method	O
for	O
modulation	B-Application
of	O
data	O
commonly	O
used	O
in	O
wireless	B-Device
modems	I-Device
.	O
</s>
<s>
M-PSK	O
)	O
,	O
with	O
CPM	O
the	O
carrier	O
phase	O
is	O
modulated	O
in	O
a	O
continuous	O
manner	O
.	O
</s>
<s>
This	O
discontinuity	O
requires	O
a	O
relatively	O
large	O
percentage	O
of	O
the	O
power	O
to	O
occur	O
outside	O
of	O
the	O
intended	O
band	O
(	O
e.g.	O
,	O
high	O
fractional	O
out-of-band	O
power	O
)	O
,	O
leading	O
to	O
poor	O
spectral	B-Protocol
efficiency	I-Protocol
.	O
</s>
<s>
Therefore	O
,	O
CPM	O
is	O
attractive	O
because	O
the	O
phase	O
continuity	O
yields	O
high	O
spectral	B-Protocol
efficiency	I-Protocol
,	O
and	O
the	O
constant	O
envelope	O
yields	O
excellent	O
power	O
efficiency	O
.	O
</s>
<s>
The	O
modulation	B-Application
and	O
demodulation	B-Device
of	O
CPM	O
is	O
complicated	O
by	O
the	O
fact	O
that	O
the	O
initial	O
phase	O
of	O
each	O
symbol	O
is	O
determined	O
by	O
the	O
cumulative	O
total	O
phase	O
of	O
all	O
previous	O
transmitted	O
symbols	O
,	O
which	O
is	O
known	O
as	O
the	O
phase	O
memory	O
.	O
</s>
<s>
This	O
requires	O
a	O
maximum-likelihood	O
sequence	O
estimator	O
(	O
MLSE	O
)	O
,	O
which	O
is	O
efficiently	O
implemented	O
using	O
the	O
Viterbi	B-Algorithm
algorithm	I-Algorithm
.	O
</s>
<s>
Minimum-shift	B-Device
keying	I-Device
(	O
MSK	O
)	O
is	O
another	O
name	O
for	O
CPM	O
with	O
an	O
excess	O
bandwidth	O
of	O
1/2	O
and	O
a	O
linear	O
phase	O
trajectory	O
.	O
</s>
<s>
The	O
spectral	B-Protocol
efficiency	I-Protocol
of	O
CPM	O
can	O
be	O
further	O
improved	O
by	O
using	O
a	O
smooth	O
phase	O
trajectory	O
.	O
</s>
<s>
A	O
MLSE	O
must	O
be	O
used	O
to	O
optimally	O
demodulate	B-Device
any	O
signal	O
in	O
the	O
presence	O
of	O
ISI	O
.	O
</s>
<s>
Since	O
the	O
optimal	O
demodulation	B-Device
of	O
full-response	O
CPM	O
already	O
requires	O
MLSE	O
detection	O
,	O
using	O
partial-response	O
signaling	O
requires	O
little	O
additional	O
complexity	O
,	O
but	O
can	O
afford	O
a	O
comparatively	O
smoother	O
phase	O
trajectory	O
,	O
and	O
thus	O
,	O
even	O
greater	O
spectral	B-Protocol
efficiency	I-Protocol
.	O
</s>
<s>
It	O
is	O
also	O
used	O
in	O
802.11	O
FHSS	O
,	O
Bluetooth	B-Protocol
,	O
and	O
many	O
other	O
proprietary	O
wireless	B-Device
modems	I-Device
.	O
</s>
<s>
Continuous-phase	O
frequency-shift	O
keying	O
(	O
CPFSK	O
)	O
is	O
a	O
commonly	O
used	O
variation	O
of	O
frequency-shift	O
keying	O
(	O
FSK	O
)	O
,	O
which	O
is	O
itself	O
a	O
special	O
case	O
of	O
analog	B-Application
frequency	I-Application
modulation	I-Application
.	O
</s>
<s>
FSK	O
is	O
a	O
method	O
of	O
modulating	O
digital	B-General_Concept
data	I-General_Concept
onto	O
a	O
sinusoidal	O
carrier	O
wave	O
,	O
encoding	O
the	O
information	O
present	O
in	O
the	O
data	O
to	O
variations	O
in	O
the	O
carrier	O
's	O
instantaneous	O
frequency	O
between	O
one	O
of	O
two	O
frequencies	O
(	O
referred	O
to	O
as	O
the	O
space	O
frequency	O
and	O
mark	O
frequency	O
)	O
.	O
</s>
<s>
where	O
Ac	O
represents	O
the	O
amplitude	O
of	O
the	O
CPFSK	O
signal	O
,	O
fc	O
is	O
the	O
base	O
carrier	O
frequency	O
,	O
and	O
Df	O
is	O
a	O
parameter	O
that	O
controls	O
the	O
frequency	B-Device
deviation	I-Device
of	O
the	O
modulated	O
signal	O
.	O
</s>
<s>
Note	O
that	O
this	O
does	O
not	O
mean	O
that	O
m(t )	O
must	O
be	O
continuous	O
;	O
in	O
fact	O
,	O
most	O
ideal	O
digital	B-General_Concept
data	I-General_Concept
waveforms	O
contain	O
discontinuities	O
.	O
</s>
