<s>
In	O
computer	B-Architecture
networking	I-Architecture
,	O
a	O
heterogeneous	B-Protocol
network	I-Protocol
is	O
a	O
network	O
connecting	O
computers	O
and	O
other	O
devices	O
where	O
the	O
operating	B-General_Concept
systems	I-General_Concept
and	O
protocols	O
have	O
significant	O
differences	O
.	O
</s>
<s>
For	O
example	O
,	O
local	B-General_Concept
area	I-General_Concept
networks	I-General_Concept
(	O
LANs	B-General_Concept
)	O
that	O
connect	O
Microsoft	B-Application
Windows	I-Application
and	O
Linux	B-Application
based	O
personal	B-Device
computers	I-Device
with	O
Apple	O
Macintosh	B-Device
computers	O
are	O
heterogeneous	O
.	O
</s>
<s>
Heterogeneous	B-Protocol
network	I-Protocol
also	O
describes	O
wireless	B-General_Concept
networks	I-General_Concept
using	O
different	O
access	O
technologies	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
wireless	B-General_Concept
network	I-General_Concept
that	O
provides	O
a	O
service	O
through	O
a	O
wireless	B-Architecture
LAN	I-Architecture
and	O
is	O
able	O
to	O
maintain	O
the	O
service	O
when	O
switching	O
to	O
a	O
cellular	O
network	O
is	O
called	O
a	O
wireless	O
heterogeneous	B-Protocol
network	I-Protocol
.	O
</s>
<s>
Reference	O
to	O
a	O
HetNet	B-Protocol
often	O
indicates	O
the	O
use	O
of	O
multiple	O
types	O
of	O
access	O
nodes	O
in	O
a	O
wireless	B-General_Concept
network	I-General_Concept
.	O
</s>
<s>
Mobile	O
experts	O
define	O
a	O
HetNet	B-Protocol
as	O
a	O
network	O
with	O
complex	O
interoperation	O
between	O
macrocell	O
,	O
small	O
cell	O
,	O
and	O
in	O
some	O
cases	O
WiFi	O
network	O
elements	O
used	O
together	O
to	O
provide	O
a	O
mosaic	O
of	O
coverage	O
,	O
with	O
handoff	B-Protocol
capability	O
between	O
network	O
elements	O
.	O
</s>
<s>
A	O
study	O
from	O
ARCchart	O
estimates	O
that	O
HetNets	B-Protocol
will	O
help	O
drive	O
the	O
mobile	O
infrastructure	O
market	O
to	O
account	O
for	O
nearly	O
US$57	O
billion	O
in	O
spending	O
globally	O
by	O
2017	O
.	O
</s>
<s>
Small	O
Cell	O
Forum	O
defines	O
the	O
HetNet	B-Protocol
as	O
‘	O
multi-x	O
environment	O
–	O
multi-technology	O
,	O
multi-domain	O
,	O
multi-spectrum	O
,	O
multi-operator	O
and	O
multi-vendor	O
.	O
</s>
<s>
From	O
an	O
architectural	O
perspective	O
,	O
the	O
HetNet	B-Protocol
can	O
be	O
viewed	O
as	O
encompassing	O
conventional	O
macro	O
radio	O
access	O
network	O
(	O
RAN	O
)	O
functions	O
,	O
RAN	O
transport	O
capability	O
,	O
small	O
cells	O
,	O
and	O
Wi-Fi	O
functionality	O
,	O
which	O
are	O
increasingly	O
being	O
virtualized	O
and	O
delivered	O
in	O
an	O
operational	O
environment	O
where	O
span	O
of	O
control	O
includes	O
data	O
center	O
resources	O
associated	O
with	O
compute	O
,	O
networking	O
,	O
and	O
storage	O
.	O
</s>
<s>
Importantly	O
,	O
functions	O
associated	O
with	O
HetNet	B-Protocol
operations	O
and	O
management	O
take	O
earlier	O
SON	O
capability	O
that	O
may	O
have	O
only	O
been	O
targeted	O
at	O
a	O
single	O
domain	O
or	O
technology	O
,	O
and	O
expand	O
it	O
to	O
deliver	O
automated	O
service	O
quality	O
management	O
across	O
the	O
entire	O
HetNet	B-Protocol
.	O
</s>
<s>
A	O
Heterogeneous	O
wireless	B-General_Concept
network	I-General_Concept
(	O
HWN	O
)	O
is	O
a	O
special	O
case	O
of	O
a	O
HetNet	B-Protocol
.	O
</s>
<s>
Whereas	O
a	O
HetNet	B-Protocol
may	O
consist	O
of	O
a	O
network	O
of	O
computers	O
or	O
devices	O
with	O
different	O
capabilities	O
in	O
terms	O
of	O
operating	B-General_Concept
systems	I-General_Concept
,	O
hardware	O
,	O
protocols	O
,	O
etc.	O
,	O
a	O
HWN	O
is	O
a	O
wireless	B-General_Concept
network	I-General_Concept
that	O
consists	O
of	O
devices	O
using	O
different	O
underlying	O
radio	B-Protocol
access	I-Protocol
technology	I-Protocol
(	O
RAT	O
)	O
.	O
</s>
<s>
Several	O
problems	O
still	O
need	O
to	O
be	O
solved	O
in	O
heterogeneous	O
wireless	B-General_Concept
networks	I-General_Concept
such	O
as	O
:	O
</s>
<s>
An	O
HWN	O
has	O
several	O
benefits	O
when	O
compared	O
with	O
a	O
traditional	O
homogeneous	O
wireless	B-General_Concept
network	I-General_Concept
,	O
including	O
increased	O
reliability	O
,	O
improved	O
spectrum	B-Protocol
efficiency	I-Protocol
,	O
and	O
increased	O
coverage	O
.	O
</s>
<s>
Spectrum	B-Protocol
efficiency	I-Protocol
is	O
improved	O
by	O
making	O
use	O
of	O
RATs	O
,	O
which	O
may	O
have	O
few	O
users	O
through	O
the	O
use	O
of	O
load	B-Application
balancing	I-Application
across	O
RATs	O
and	O
coverage	O
may	O
be	O
improved	O
because	O
different	O
RATs	O
may	O
fill	O
holes	O
in	O
coverage	O
that	O
any	O
one	O
of	O
the	O
single	O
networks	O
alone	O
would	O
not	O
be	O
able	O
to	O
fill	O
.	O
</s>
<s>
From	O
a	O
semantic	O
point	O
of	O
view	O
,	O
it	O
is	O
very	O
important	O
to	O
note	O
that	O
the	O
heterogeneous	B-Protocol
network	I-Protocol
terminology	O
can	O
have	O
different	O
connotations	O
in	O
wireless	O
telecommunications	O
.	O
</s>
<s>
For	O
instance	O
,	O
it	O
could	O
refer	O
to	O
the	O
paradigm	O
of	O
seamless	O
and	O
ubiquitous	O
interoperability	O
between	O
various	O
multi-coverage	O
protocols	O
(	O
aka	O
,	O
HetNet	B-Protocol
)	O
.	O
</s>
<s>
Therefore	O
,	O
using	O
the	O
term	O
"	O
heterogeneous	B-Protocol
network	I-Protocol
"	O
without	O
putting	O
it	O
into	O
context	O
can	O
result	O
in	O
a	O
source	O
of	O
confusion	O
in	O
scientific	O
literature	O
and	O
during	O
the	O
peer-review	O
cycle	O
.	O
</s>
<s>
In	O
fact	O
,	O
the	O
confusion	O
may	O
further	O
be	O
aggravated	O
,	O
especially	O
in	O
light	O
of	O
the	O
fact	O
that	O
the	O
HetNet	B-Protocol
paradigm	O
is	O
often	O
also	O
researched	O
from	O
a	O
geometrical	O
angle	O
.	O
</s>
