<s>
SIMNET	B-General_Concept
was	O
a	O
wide	O
area	O
network	B-Architecture
with	O
vehicle	O
simulators	O
and	O
displays	O
for	O
real-time	O
distributed	O
combat	O
simulation	O
:	O
tanks	O
,	O
helicopters	O
and	O
airplanes	O
in	O
a	O
virtual	O
battlefield	O
.	O
</s>
<s>
SIMNET	B-General_Concept
was	O
developed	O
for	O
and	O
used	O
by	O
the	O
United	O
States	O
military	O
.	O
</s>
<s>
SIMNET	B-General_Concept
development	O
began	O
in	O
the	O
mid-1980s	O
,	O
was	O
fielded	O
starting	O
in	O
1987	O
,	O
and	O
was	O
used	O
for	O
training	O
until	O
successor	O
programs	O
came	O
online	O
well	O
into	O
the	O
1990s	O
.	O
</s>
<s>
SIMNET	B-General_Concept
was	O
perhaps	O
the	O
world	O
's	O
first	O
fully	O
operational	O
virtual	O
reality	O
system	O
 [ Sterling ] 	O
and	O
was	O
the	O
first	O
real	O
time	O
,	O
networked	O
simulator	O
.	O
</s>
<s>
In	O
the	O
early	O
1980s	O
,	O
DARPA	O
decided	O
to	O
create	O
a	O
prototype	B-Application
research	O
system	O
to	O
investigate	O
the	O
feasibility	O
of	O
creating	O
a	O
real-time	O
distributed	O
simulator	O
for	O
combat	O
simulation	O
.	O
</s>
<s>
SIMNET	B-General_Concept
,	O
the	O
resulting	O
application	O
,	O
was	O
to	O
prove	O
both	O
the	O
feasibility	O
and	O
effectiveness	O
of	O
such	O
a	O
project	O
(	O
Pimental	O
and	O
Blau	O
1994	O
)	O
.	O
</s>
<s>
Long-haul	O
networking	O
for	O
SIMNET	B-General_Concept
was	O
run	O
originally	O
across	O
multiple	O
56	O
kbit/s	O
dial-up	O
lines	O
,	O
using	O
parallel	O
processors	O
to	O
compress	O
packets	O
over	O
the	O
data	O
links	O
.	O
</s>
<s>
SIMNET	B-General_Concept
was	O
developed	O
by	O
three	O
companies	O
:	O
Delta	O
Graphics	O
,	O
Inc.	O
;	O
Perceptronics	O
,	O
Inc.	O
;	O
and	O
Bolt	O
,	O
Beranek	O
and	O
Newman	O
(	O
BBN	O
)	O
,	O
Inc	O
.	O
</s>
<s>
There	O
was	O
no	O
prime	O
contractor	O
on	O
SIMNET	B-General_Concept
;	O
independent	O
contracts	O
were	O
made	O
directly	O
with	O
each	O
of	O
these	O
three	O
companies	O
.	O
</s>
<s>
BBN	O
developed	O
the	O
vehicle	O
simulation	O
and	O
network	B-Architecture
software	I-Architecture
,	O
as	O
well	O
as	O
other	O
software	O
such	O
as	O
artillery	O
,	O
resupply	O
,	O
and	O
semi-automated	O
forces	O
often	O
used	O
for	O
opposing	O
forces	O
.	O
</s>
<s>
Perceptronics	O
,	O
based	O
in	O
Los	O
Angeles	O
,	O
was	O
responsible	O
for	O
the	O
actual	O
SIMNET	B-General_Concept
simulators	O
;	O
the	O
company	O
's	O
engineers	O
,	O
human	O
factors	O
personnel	O
and	O
manufacturing	O
team	O
designed	O
,	O
developed	O
and	O
built	O
over	O
300	O
full-crew	O
simulators	O
,	O
integrating	O
the	O
controls	O
,	O
sound	O
systems	O
and	O
visual	O
systems	O
into	O
the	O
special	O
simulator	O
shells	O
;	O
they	O
also	O
installed	O
the	O
simulators	O
in	O
a	O
number	O
of	O
facilities	O
in	O
the	O
US	O
and	O
Germany	O
,	O
trained	O
the	O
operators	O
and	O
supported	O
the	O
system	O
for	O
several	O
years	O
.	O
</s>
<s>
BBN	O
was	O
responsible	O
for	O
developing	O
the	O
dynamic	O
simulation	O
software	O
for	O
each	O
of	O
the	O
simulators	O
,	O
as	O
well	O
as	O
the	O
distributed	O
networking	O
communication	O
software	O
that	O
kept	O
each	O
simulator	O
informed	O
of	O
the	O
position	O
(	O
and	O
other	O
state	O
information	O
)	O
of	O
other	O
simulators	O
that	O
were	O
within	O
potential	O
line-of-sight	O
within	O
the	O
shared	O
virtual	B-General_Concept
environment	I-General_Concept
.	O
</s>
<s>
Each	O
simulator	O
maintained	O
its	O
own	O
copy	O
of	O
this	O
virtual	B-General_Concept
environment	I-General_Concept
,	O
and	O
broadcast	O
its	O
own	O
state	O
information	O
to	O
the	O
other	O
simulators	O
.	O
</s>
<s>
Since	O
this	O
was	O
a	O
networked	O
simulation	O
,	O
each	O
simulation	O
station	O
needed	O
its	O
own	O
display	O
of	O
the	O
shared	O
virtual	B-General_Concept
environment	I-General_Concept
.	O
</s>
<s>
The	O
network	B-Architecture
was	O
designed	O
to	O
support	O
up	O
to	O
several	O
hundred	O
users	O
at	O
once	O
.	O
</s>
<s>
SIMNET	B-General_Concept
used	O
the	O
concept	O
of	O
“	O
dead	O
reckoning	O
”	O
to	O
correlate	O
the	O
positions	O
of	O
the	O
objects	O
and	O
actors	O
within	O
the	O
simulated	O
environment	O
.	O
</s>
<s>
Duncan	O
(	O
Duke	O
)	O
Miller	O
,	O
the	O
BBN	O
SIMNET	B-General_Concept
program	O
manager	O
,	O
first	O
used	O
this	O
term	O
,	O
which	O
harks	O
back	O
to	O
the	O
earliest	O
days	O
of	O
ship	O
navigation	O
,	O
to	O
explain	O
how	O
simulators	O
were	O
able	O
to	O
communicate	O
state	O
change	O
information	O
to	O
each	O
other	O
while	O
minimizing	O
network	B-Architecture
traffic	O
.	O
</s>
<s>
The	O
SIMNET	B-General_Concept
protocols	O
provided	O
that	O
whenever	O
the	O
true	O
state	O
of	O
a	O
simulator	O
deviated	O
by	O
more	O
than	O
a	O
certain	O
threshold	O
from	O
its	O
state	O
as	O
computed	O
by	O
dead	O
reckoning	O
,	O
the	O
simulator	O
was	O
obligated	O
to	O
send	O
out	O
a	O
new	O
state	O
update	O
message	O
.	O
</s>
<s>
The	O
use	O
of	O
SIMNET	B-General_Concept
protocols	O
and	O
SIMNET-based	O
training	O
systems	O
in	O
the	O
First	O
Gulf	O
War	O
demonstrates	O
the	O
success	O
of	O
the	O
SIMNET	B-General_Concept
,	O
and	O
its	O
legacy	O
was	O
viewed	O
as	O
proof	O
that	O
realtime	O
interactive	O
networked	O
cooperative	O
virtual	O
simulation	O
is	O
possible	O
for	O
a	O
large	O
user	O
population	O
.	O
</s>
<s>
Later	O
,	O
the	O
Terrestrial	O
Wideband	O
Network	B-Architecture
(	O
a	O
high	O
speed	O
descendant	O
of	O
the	O
ARPANET	O
that	O
ran	O
at	O
T1	B-Protocol
speeds	O
)	O
was	O
used	O
to	O
carry	O
traffic	O
.	O
</s>
<s>
This	O
network	B-Architecture
remained	O
under	O
DARPA	O
after	O
the	O
rest	O
of	O
ARPANET	O
was	O
merged	O
with	O
NSFNet	O
and	O
the	O
ARPANET	O
was	O
decommissioned	O
(	O
Rheingold	O
1992	O
)	O
.	O
</s>
<s>
In	O
addition	O
to	O
the	O
network	B-Architecture
,	O
the	O
second	O
fundamental	O
challenge	O
at	O
the	O
time	O
SIMNET	B-General_Concept
was	O
conceived	O
was	O
the	O
inability	O
of	O
graphics	O
systems	O
to	O
handle	O
large	O
numbers	O
of	O
moving	O
models	O
.	O
</s>
<s>
In	O
contrast	O
,	O
Z-buffer	O
techniques	O
do	O
not	O
depend	O
on	O
pre-computed	O
depth	O
coherence	O
and	O
were	O
therefore	O
a	O
key	O
enabling	O
technology	O
for	O
SIMNET	B-General_Concept
's	O
on-ground	O
point	O
of	O
view	O
and	O
large	O
numbers	O
of	O
moving	O
vehicles	O
.	O
</s>
<s>
They	O
also	O
created	O
the	O
simulator	O
engine	O
and	O
networking	B-Architecture
software	I-Architecture
.	O
</s>
<s>
SIMNET	B-General_Concept
used	O
Z-buffer	O
displays	O
developed	O
by	O
Delta	O
Graphics	O
.	O
</s>
<s>
The	O
graphics	O
processor	O
,	O
the	O
GDP	O
,	O
custom	O
developed	O
for	O
SIMNET	B-General_Concept
by	O
Gary	O
Wilson	O
(	O
Sr	O
HW	O
Engineer	O
)	O
,	O
won	O
out	O
over	O
existing	O
Silicon	O
Graphics	O
HW	O
because	O
of	O
its	O
low	O
cost	O
and	O
because	O
its	O
architecture	O
.	O
</s>
<s>
SIMNET	B-General_Concept
was	O
actively	O
used	O
by	O
the	O
U.S.	O
Army	O
for	O
training	O
primarily	O
at	O
Fort	O
Benning	O
,	O
Fort	O
Rucker	O
,	O
and	O
Fort	O
Knox	O
.	O
</s>
<s>
The	O
follow-on	O
protocols	O
to	O
SIMNET	B-General_Concept
were	O
called	O
Distributed	B-Operating_System
Interactive	I-Operating_System
Simulation	I-Operating_System
;	O
the	O
primary	O
U.S.	O
Army	O
follow-on	O
program	O
was	O
the	O
Close	O
Combat	O
Tactical	O
Trainer	O
(	O
CCTT	O
)	O
.	O
</s>
<s>
The	O
SIMNET-D	O
(	O
Developmental	O
)	O
program	O
used	O
simulation	O
systems	O
developed	O
in	O
the	O
SIMNET	B-General_Concept
program	O
to	O
perform	O
experiments	O
in	O
weapon	O
systems	O
,	O
concepts	O
,	O
and	O
tactics	O
.	O
</s>
<s>
Additional	O
research	O
programs	O
after	O
the	O
end	O
of	O
SIMNET	B-General_Concept
included	O
work	O
in	O
weather	O
and	O
real-time	O
terrain	O
modifications	O
.	O
</s>
<s>
His	O
first	O
startup	O
,	O
RTIME	O
,	O
was	O
acquired	O
by	O
Sony	O
to	O
form	O
the	O
core	O
of	O
the	O
PlayStation	O
Network	B-Architecture
.	O
</s>
