<s>
Olivia	B-Device
MFSK	I-Device
is	O
an	O
amateur	O
radioteletype	O
protocol	O
,	O
using	O
multiple	B-Device
frequency-shift	I-Device
keying	I-Device
(	O
MFSK	B-Device
)	O
and	O
designed	O
to	O
work	O
in	O
difficult	O
(	O
low	O
signal-to-noise	O
ratio	O
plus	O
multipath	O
propagation	O
)	O
conditions	O
on	O
shortwave	B-Algorithm
bands	I-Algorithm
.	O
</s>
<s>
It	O
is	O
commonly	O
used	O
by	O
amateur	O
radio	O
operators	O
to	O
reliably	O
transmit	O
ASCII	B-Protocol
characters	I-Protocol
over	O
noisy	O
channels	O
using	O
the	O
high	B-Algorithm
frequency	I-Algorithm
(	O
3	O
–	O
30MHz	O
)	O
spectrum	O
.	O
</s>
<s>
The	O
effective	O
data	O
rate	O
of	O
the	O
Olivia	B-Device
MFSK	I-Device
protocol	O
is	O
150	O
characters/minute	O
.	O
</s>
<s>
Olivia	O
modes	O
are	O
commonly	O
referred	O
to	O
as	O
Olivia	O
X	O
/	O
Y	O
(	O
or	O
,	O
alternatively	O
,	O
Olivia	O
Y	O
/	O
X	O
)	O
,	O
where	O
X	O
refers	O
to	O
the	O
number	O
of	O
different	O
audio	O
tones	O
transmitted	O
and	O
Y	O
refers	O
to	O
the	O
bandwidth	B-Algorithm
in	O
hertz	O
over	O
which	O
these	O
signals	O
are	O
spread	O
.	O
</s>
<s>
The	O
first	O
on-the-air	O
tests	O
were	O
performed	O
by	O
two	O
radio	O
amateurs	O
,	O
Fred	O
OH/DK4ZC	O
and	O
Les	O
VK2DSG	O
,	O
on	O
the	O
Europe-Australia	O
path	O
in	O
the	O
20-meter	O
amateur	B-Algorithm
band	I-Algorithm
.	O
</s>
<s>
The	O
following	O
table	O
lists	O
the	O
common	O
center	O
frequencies	O
used	O
in	O
the	O
amateur	B-Algorithm
radio	I-Algorithm
bands	I-Algorithm
.	O
</s>
<s>
Following	O
the	O
introduction	O
of	O
new	O
amateur	O
radio	O
digital	O
modes	O
and	O
the	O
resulting	O
overlapping	O
with	O
the	O
Olivia	O
calling	O
frequencies	O
on	O
some	O
amateur	B-Algorithm
radio	I-Algorithm
bands	I-Algorithm
,	O
US	O
radio	O
amateur	O
Tomas	O
Hood	O
NW7US	O
consulted	O
the	O
members	O
subscribed	O
to	O
an	O
Olivia	B-Device
MFSK	I-Device
users	O
newsgroup	O
and	O
created	O
a	O
new	O
list	O
of	O
calling	O
frequencies	O
in	O
November	O
2017	O
.	O
</s>
<s>
Conversations	O
using	O
Olivia	O
are	O
by	O
convention	O
initiated	O
using	O
either	O
Olivia	O
16/500	O
(	O
16	O
tones	O
over	O
a	O
500Hz	O
bandwidth	B-Algorithm
)	O
or	O
Olivia	O
32/1000	O
(	O
32	O
tones	O
over	O
a	O
1000Hz	O
bandwidth	B-Algorithm
)	O
.	O
</s>
<s>
Available	O
bandwidths	B-Algorithm
for	O
Olivia	O
are	O
125Hz	O
,	O
256Hz	O
,	O
512Hz	O
,	O
500Hz	O
,	O
1000Hz	O
,	O
and	O
2000Hz	O
with	O
wider	O
bandwidths	B-Algorithm
giving	O
faster	O
throughput	O
and	O
narrower	O
bandwidths	B-Algorithm
giving	O
slower	O
throughput	O
.	O
</s>
<s>
Being	O
a	O
digital	O
protocol	O
,	O
Olivia	O
transmits	O
a	O
stream	O
of	O
ASCII	B-Protocol
(	O
7-bit	O
)	O
characters	O
.	O
</s>
<s>
The	O
most	O
common	O
transmission	O
bandwidth	B-Algorithm
is	O
1000Hz	O
and	O
the	O
baud	O
rate	O
is	O
31.25	O
MFSK	B-Device
tones/second	O
.	O
</s>
<s>
To	O
accommodate	O
for	O
different	O
conditions	O
and	O
for	O
the	O
purpose	O
of	O
experimentation	O
the	O
bandwidth	B-Algorithm
and	O
the	O
baud	O
rate	O
can	O
be	O
changed	O
.	O
</s>
<s>
The	O
Olivia	O
transmission	O
system	O
is	O
constructed	O
of	O
two	O
layers	O
:	O
the	O
lower	O
,	O
modulation	O
and	O
forward	B-Error_Name
error	I-Error_Name
correcting	I-Error_Name
(	O
FEC	O
)	O
code	O
layer	O
is	O
a	O
classical	O
multiple	B-Device
frequency-shift	I-Device
keying	I-Device
(	O
MFSK	B-Device
)	O
while	O
the	O
higher	O
layer	O
is	O
a	O
forward	B-Error_Name
error	I-Error_Name
correcting	I-Error_Name
code	O
based	O
on	O
Walsh	O
functions	O
.	O
</s>
<s>
For	O
the	O
first	O
layer	O
the	O
orthogonal	B-Algorithm
functions	I-Algorithm
are	O
(	O
co	O
)	O
sine	O
functions	O
,	O
with	O
32	O
different	O
frequencies	O
(	O
tones	O
)	O
.	O
</s>
<s>
The	O
demodulator	O
measures	O
the	O
amplitudes	O
of	O
all	O
the	O
32	O
possible	O
tones	O
(	O
using	O
a	O
Fourier	B-Algorithm
transform	I-Algorithm
)	O
and	O
(	O
knowing	O
that	O
only	O
one	O
of	O
those	O
32	O
could	O
have	O
been	O
sent	O
)	O
picks	O
up	O
the	O
tone	O
with	O
the	O
highest	O
amplitude	O
.	O
</s>
<s>
For	O
the	O
second	O
FEC	O
layer	O
:	O
every	O
ASCII	B-Protocol
character	I-Protocol
is	O
encoded	O
as	O
one	O
of	O
64	O
possible	O
Walsh	O
functions	O
(	O
or	O
vectors	O
of	O
a	O
Hadamard	O
matrix	O
)	O
.	O
</s>
<s>
Thus	O
the	O
first	O
layer	O
demodulator	O
actually	O
produces	O
soft	O
decisions	O
for	O
each	O
of	O
the	O
5	O
bits	O
associated	O
to	O
an	O
MFSK	B-Device
tone	O
instead	O
of	O
simply	O
picking	O
up	O
the	O
highest	O
tone	O
to	O
produce	O
hard	O
decisions	O
for	O
those	O
5	O
bits	O
.	O
</s>
<s>
This	O
stage	O
simply	O
shifts	O
and	O
XORs	B-Application
bits	O
with	O
predefined	O
scrambling	O
vectors	O
and	O
so	O
it	O
does	O
not	O
improve	O
the	O
performance	O
where	O
the	O
white	O
(	O
uncorrelated	O
)	O
noise	O
is	O
concerned	O
,	O
but	O
the	O
resulting	O
pattern	O
gains	O
certain	O
distinct	O
characteristics	O
which	O
are	O
of	O
great	O
help	O
to	O
the	O
synchronizer	O
.	O
</s>
<s>
The	O
default	O
mode	O
sends	O
32	O
tones	O
within	O
the	O
1000Hz	O
audio	O
bandwidth	B-Algorithm
and	O
the	O
tones	O
are	O
spaced	O
by	O
1000Hz/32	O
=	O
31.25Hz	O
.	O
</s>
<s>
The	O
tones	O
are	O
shaped	B-Language
to	O
minimize	O
the	O
amount	O
of	O
energy	O
sent	O
outside	O
the	O
nominal	O
bandwidth	B-Algorithm
.	O
</s>
<s>
Because	O
the	O
symbols	O
are	O
smoothly	O
shaped	B-Language
there	O
is	O
no	O
need	O
to	O
keep	O
the	O
phase	O
constant	O
,	O
which	O
normally	O
is	O
the	O
case	O
when	O
no	O
(	O
e.g.	O
,	O
square	O
)	O
shaping	O
is	O
used	O
.	O
</s>
<s>
The	O
modulator	O
uses	O
the	O
Gray	B-Device
code	I-Device
to	O
encode	O
5-bit	O
symbols	O
into	O
the	O
tone	O
numbers	O
.	O
</s>
<s>
To	O
adapt	O
the	O
system	O
to	O
different	O
propagation	O
conditions	O
,	O
the	O
number	O
of	O
tones	O
and	O
the	O
bandwidth	B-Algorithm
can	O
be	O
changed	O
and	O
the	O
time	O
and	O
frequency	O
parameters	O
are	O
proportionally	O
scaled	O
.	O
</s>
<s>
The	O
bandwidth	B-Algorithm
can	O
be	O
125	O
,	O
250	O
,	O
500	O
,	O
1000	O
or	O
2000Hz	O
.	O
</s>
<s>
Every	O
64-bit	O
vector	O
represents	O
a	O
7-bit	B-Protocol
ASCII	I-Protocol
character	O
,	O
thus	O
each	O
block	O
represents	O
5	O
ASCII	B-Protocol
characters	I-Protocol
.	O
</s>
<s>
The	O
two	O
layers	O
(	O
MFSK+Walsh	O
function	O
)	O
of	O
the	O
FEC	O
code	O
can	O
be	O
treated	O
as	O
a	O
two	O
dimensional	O
code	O
:	O
the	O
first	O
dimension	O
is	O
formed	O
along	O
the	O
frequency	O
axis	O
by	O
the	O
MFSK	B-Device
itself	O
while	O
the	O
second	O
dimension	O
is	O
formed	O
along	O
the	O
time	O
axis	O
by	O
the	O
Walsh	O
functions	O
.	O
</s>
<s>
The	O
formats	O
have	O
a	O
variation	O
in	O
bandwidth	B-Algorithm
(	O
125	O
,	O
250	O
,	O
500	O
,	O
1000	O
,	O
and	O
2000Hz	O
)	O
and	O
number	O
of	O
tones	O
used	O
(	O
2	O
,	O
4	O
,	O
8	O
,	O
16	O
,	O
32	O
,	O
64	O
,	O
128	O
,	O
or	O
256	O
)	O
.	O
</s>
<s>
The	O
standard	O
Contestia	O
formats	O
(	O
bandwidth/tones	O
)	O
are	O
125/4	O
,	O
250/8	O
,	O
500/16	O
,	O
1000/32	O
,	O
and	O
2000/64	O
.	O
</s>
<s>
The	O
increased	O
speed	O
of	O
Contestia	O
is	O
achieved	O
by	O
using	O
a	O
smaller	O
symbol	O
block	O
size	O
of	O
(	O
32	O
)	O
rather	O
than	O
Olivia	O
(	O
64	O
)	O
and	O
by	O
using	O
a	O
6-bit	O
decimal	O
character	O
set	O
rather	O
than	O
7-bit	B-Protocol
ASCII	I-Protocol
set	O
which	O
Olivia	O
uses	O
.	O
</s>
