<s>
The	O
last	B-Protocol
mile	I-Protocol
or	O
last	O
kilometer	O
is	O
a	O
phrase	O
widely	O
used	O
in	O
the	O
telecommunications	O
,	O
cable	O
television	O
and	O
internet	O
industries	O
to	O
refer	O
to	O
the	O
final	O
leg	O
of	O
the	O
telecommunications	O
networks	O
that	O
deliver	O
telecommunication	O
services	O
to	O
retail	O
end-users	O
(	O
customers	O
)	O
.	O
</s>
<s>
More	O
specifically	O
,	O
the	O
last	B-Protocol
mile	I-Protocol
describes	O
the	O
portion	O
of	O
the	O
telecommunications	O
network	O
chain	O
that	O
physically	O
reaches	O
the	O
end-user	O
'	O
s	O
premises	O
.	O
</s>
<s>
Examples	O
are	O
the	O
copper	O
wire	O
subscriber	B-Architecture
lines	I-Architecture
connecting	O
landline	B-Application
telephones	I-Application
to	O
the	O
local	O
telephone	O
exchange	O
;	O
coaxial	O
cable	O
service	O
drops	O
carrying	O
cable	O
television	O
signals	O
from	O
utility	O
poles	O
to	O
subscribers	O
 '	O
homes	O
,	O
and	O
cell	O
towers	O
linking	O
local	O
cell	O
phones	O
to	O
the	O
cellular	O
network	O
.	O
</s>
<s>
The	O
word	O
"	O
mile	O
"	O
is	O
used	O
metaphorically	O
;	O
the	O
length	O
of	O
the	O
last	B-Protocol
mile	I-Protocol
link	O
may	O
be	O
more	O
or	O
less	O
than	O
a	O
mile	O
.	O
</s>
<s>
Because	O
the	O
last	B-Protocol
mile	I-Protocol
of	O
a	O
network	O
to	O
the	O
user	O
is	O
conversely	O
the	O
first	O
mile	O
from	O
the	O
user	O
's	O
premises	O
to	O
the	O
outside	O
world	O
when	O
the	O
user	O
is	O
sending	O
data	O
,	O
the	O
term	O
first	O
mile	O
is	O
also	O
alternatively	O
used	O
.	O
</s>
<s>
The	O
last	B-Protocol
mile	I-Protocol
is	O
typically	O
the	O
speed	O
bottleneck	O
in	O
communication	O
networks	O
;	O
its	O
bandwidth	B-Algorithm
effectively	O
limits	O
the	O
amount	O
of	O
data	O
that	O
can	O
be	O
delivered	O
to	O
the	O
customer	O
.	O
</s>
<s>
This	O
is	O
because	O
retail	O
telecommunication	O
networks	O
have	O
the	O
topology	O
of	O
"	O
trees	B-Data_Structure
"	O
,	O
with	O
relatively	O
few	O
high	O
capacity	O
"	O
trunk	O
"	O
communication	O
channels	O
branching	O
out	O
to	O
feed	O
many	O
final	O
mile	O
"	O
twigs	O
"	O
.	O
</s>
<s>
For	O
example	O
,	O
telephone	O
trunklines	O
that	O
carry	O
phone	O
calls	O
between	O
switching	O
centers	O
are	O
made	O
of	O
modern	O
optical	B-Architecture
fiber	I-Architecture
,	O
but	O
the	O
last	B-Protocol
mile	I-Protocol
is	O
typically	O
twisted	O
pair	O
wires	O
,	O
a	O
technology	O
which	O
has	O
essentially	O
remained	O
unchanged	O
for	O
over	O
a	O
century	O
since	O
the	O
original	O
laying	O
of	O
copper	O
phone	O
cables	O
.	O
</s>
<s>
In	O
recent	O
years	O
,	O
usage	O
of	O
the	O
term	O
"	O
last	B-Protocol
mile	I-Protocol
"	O
has	O
expanded	O
outside	O
the	O
communications	O
industries	O
,	O
to	O
include	O
other	O
distribution	O
networks	O
that	O
deliver	O
goods	O
to	O
customers	O
,	O
such	O
as	O
the	O
pipes	O
that	O
deliver	O
water	O
and	O
natural	O
gas	O
to	O
customer	O
premises	O
,	O
and	O
the	O
final	O
legs	O
of	O
mail	O
and	O
package	O
delivery	O
services	O
.	O
</s>
<s>
To	O
date	O
,	O
although	O
a	O
number	O
of	O
approaches	O
have	O
been	O
tried	O
,	O
no	O
single	O
clear	O
solution	O
to	O
the	O
'	O
last	B-Protocol
mile	I-Protocol
problem	O
 '	O
has	O
emerged	O
.	O
</s>
<s>
As	O
expressed	O
by	O
Shannon	O
's	O
equation	O
for	O
channel	O
information	O
capacity	O
,	O
the	O
omnipresence	O
of	O
noise	O
in	O
information	O
systems	O
sets	O
a	O
minimum	O
signal-to-noise	O
ratio	O
(	O
shortened	O
as	O
S/N	O
)	O
requirement	O
in	O
a	O
channel	O
,	O
even	O
when	O
adequate	O
spectral	B-Algorithm
bandwidth	I-Algorithm
is	O
available	O
.	O
</s>
<s>
These	O
grew	O
into	O
clusters	O
of	O
small	O
local	B-General_Concept
area	I-General_Concept
networks	I-General_Concept
(	O
LAN	B-General_Concept
)	O
.	O
</s>
<s>
The	O
TCP/IP	B-Protocol
suite	I-Protocol
of	O
protocols	B-Protocol
was	O
born	O
out	O
of	O
the	O
need	O
to	O
connect	O
several	O
of	O
these	O
LANs	B-General_Concept
together	O
,	O
particularly	O
as	O
related	O
to	O
common	O
projects	O
among	O
the	O
United	O
States	O
Department	O
of	O
Defense	O
,	O
industry	O
and	O
some	O
academic	O
institutions	O
.	O
</s>
<s>
In	O
addition	O
to	O
providing	O
a	O
way	O
for	O
multiple	O
computers	O
and	O
users	O
to	O
share	O
a	O
common	O
inter-LAN	O
connection	O
,	O
the	O
TCP/IP	B-Protocol
protocols	I-Protocol
provided	O
a	O
standardized	O
way	O
for	O
dissimilar	O
computers	O
and	O
operating	O
systems	O
to	O
exchange	O
information	O
over	O
this	O
inter-network	O
.	O
</s>
<s>
The	O
funding	O
and	O
support	O
for	O
the	O
connections	O
among	O
LANs	B-General_Concept
could	O
be	O
spread	O
over	O
one	O
or	O
even	O
several	O
LANs	B-General_Concept
.	O
</s>
<s>
As	O
each	O
new	O
LAN	B-General_Concept
,	O
or	O
subnet	O
,	O
was	O
added	O
,	O
the	O
new	O
subnet	O
's	O
constituents	O
enjoyed	O
access	O
to	O
the	O
greater	O
network	O
.	O
</s>
<s>
In	O
recent	O
years	O
,	O
the	O
capacity	O
of	O
fiber-optic	B-Application
communication	I-Application
,	O
aided	O
by	O
a	O
supporting	O
industry	O
,	O
has	O
resulted	O
in	O
an	O
expansion	O
of	O
raw	O
capacity	O
,	O
so	O
much	O
so	O
that	O
in	O
the	O
United	O
States	O
a	O
large	O
amount	O
of	O
installed	O
fiber	B-Architecture
infrastructure	I-Architecture
is	O
not	O
being	O
used	O
because	O
it	O
is	O
currently	O
excess	O
capacity	O
"	O
dark	B-Protocol
fiber	I-Protocol
"	O
.	O
</s>
<s>
Initially	O
,	O
only	O
the	O
inter-LAN	O
connections	O
were	O
high	O
speed	O
.	O
</s>
<s>
As	O
the	O
Shannon	O
–	O
Hartley	O
theorem	O
shows	O
,	O
it	O
is	O
the	O
combination	O
of	O
bandwidth	B-Algorithm
and	O
signal-to-noise	O
ratio	O
which	O
determines	O
the	O
maximum	O
information	O
rate	O
of	O
a	O
channel	O
.	O
</s>
<s>
Support	O
wide	O
transmission	O
bandwidth	B-Algorithm
.	O
</s>
<s>
Dielectric	O
optical	B-Architecture
fiber	I-Architecture
systems	I-Architecture
support	O
heavier	O
flow	O
at	O
higher	O
cost	O
.	O
</s>
<s>
Traditional	O
wired	O
local	B-General_Concept
area	I-General_Concept
networking	I-General_Concept
systems	O
require	O
copper	O
coaxial	O
cable	O
or	O
a	O
twisted	O
pair	O
to	O
be	O
run	O
between	O
or	O
among	O
two	O
or	O
more	O
of	O
the	O
nodes	O
in	O
the	O
network	O
.	O
</s>
<s>
The	O
decrease	O
in	O
information	O
capacity	O
made	O
available	O
to	O
an	O
individual	O
user	O
is	O
roughly	O
proportional	O
to	O
the	O
number	O
of	O
users	O
sharing	O
a	O
LAN	B-General_Concept
.	O
</s>
<s>
With	O
support	O
for	O
higher	O
transmission	O
bandwidth	B-Algorithm
and	O
improved	O
modulation	O
,	O
these	O
digital	O
subscriber	B-Architecture
line	I-Architecture
schemes	O
have	O
increased	O
capability	O
20-50	O
times	O
as	O
compared	O
to	O
the	O
previous	O
voiceband	O
systems	O
.	O
</s>
<s>
In	O
many	O
countries	O
the	O
last	B-Protocol
mile	I-Protocol
link	O
which	O
connects	O
landline	B-Application
business	O
telephone	O
customers	O
to	O
the	O
local	O
telephone	O
exchange	O
is	O
often	O
an	O
ISDN30	B-Protocol
which	O
can	O
carry	O
30	O
simultaneous	O
telephone	O
calls	O
.	O
</s>
<s>
Fiber	O
offers	O
high	O
information	O
capacity	O
and	O
after	O
the	O
turn	O
of	O
the	O
21st	O
century	O
became	O
the	O
deployed	O
medium	O
of	O
choice	O
(	O
"	O
Fiber	B-Architecture
to	I-Architecture
the	I-Architecture
x	I-Architecture
"	O
)	O
given	O
its	O
scalability	O
in	O
the	O
face	O
of	O
the	O
increasing	O
bandwidth	B-Algorithm
requirements	O
of	O
modern	O
applications	O
.	O
</s>
<s>
In	O
2004	O
,	O
according	O
to	O
Richard	O
Lynch	O
,	O
Executive	O
Vice	O
President	O
and	O
Chief	O
Technology	O
Officer	O
of	O
the	O
telecom	O
giant	O
Verizon	B-Application
,	O
the	O
company	O
saw	O
the	O
world	O
moving	O
toward	O
vastly	O
higher	O
bandwidth	B-Algorithm
applications	O
as	O
consumers	O
loved	O
everything	O
broadband	O
had	O
to	O
offer	O
and	O
eagerly	O
devoured	O
as	O
much	O
as	O
they	O
could	O
get	O
,	O
including	O
two-way	O
,	O
user-generated	O
content	O
.	O
</s>
<s>
Copper	O
and	O
coaxial	O
networks	O
would	O
not	O
–	O
in	O
fact	O
,	O
could	O
not	O
–	O
satisfy	O
these	O
demands	O
,	O
which	O
precipitated	O
Verizon	B-Application
's	O
aggressive	O
move	O
into	O
fiber-to-the-home	B-Architecture
via	O
FiOS	B-Protocol
.	O
</s>
<s>
Fiber	O
is	O
a	O
future-proof	O
technology	O
that	O
meets	O
the	O
needs	O
of	O
today	O
's	O
users	O
,	O
but	O
unlike	O
other	O
copper-based	O
and	O
wireless	O
last-mile	O
mediums	O
,	O
also	O
has	O
the	O
capacity	O
for	O
years	O
to	O
come	O
,	O
by	O
upgrading	O
the	O
end-point	O
optics	O
and	O
electronics	O
without	O
changing	O
the	O
fiber	B-Architecture
infrastructure	I-Architecture
.	O
</s>
<s>
Fixed	B-Application
copper	I-Application
lines	I-Application
have	O
been	O
subject	O
to	O
theft	O
due	O
to	O
the	O
value	O
of	O
copper	O
,	O
but	O
optical	B-Architecture
fibers	I-Architecture
make	O
unattractive	O
targets	O
.	O
</s>
<s>
Optical	B-Architecture
fibers	I-Architecture
cannot	O
be	O
converted	O
into	O
anything	O
else	O
,	O
whereas	O
copper	O
can	O
be	O
recycled	O
without	O
loss	O
.	O
</s>
<s>
Mobile	O
CDN	O
coined	O
the	O
term	O
the	O
'	O
mobile	O
mile	O
 '	O
to	O
categorize	O
the	O
last	B-Protocol
mile	I-Protocol
connection	O
when	O
a	O
wireless	O
system	O
is	O
used	O
to	O
reach	O
the	O
customer	O
.	O
</s>
<s>
Wireless	O
systems	O
have	O
an	O
advantage	O
over	O
wired	O
systems	O
in	O
last	B-Protocol
mile	I-Protocol
applications	O
in	O
not	O
requiring	O
lines	O
to	O
be	O
installed	O
.	O
</s>
<s>
However	O
,	O
in	O
practical	O
last	B-Protocol
mile	I-Protocol
environments	O
,	O
obstructions	O
and	O
de-steering	O
of	O
these	O
beams	O
,	O
and	O
absorption	O
by	O
elements	O
of	O
the	O
atmosphere	O
including	O
fog	O
and	O
rain	O
,	O
particularly	O
over	O
longer	O
paths	O
,	O
can	O
greatly	O
restrict	O
their	O
use	O
for	O
last-mile	O
wireless	O
communications	O
.	O
</s>
<s>
On	O
the	O
other	O
hand	O
,	O
the	O
lower	O
carrier	O
frequencies	O
are	O
not	O
able	O
to	O
support	O
the	O
high	O
information	O
bandwidths	B-Algorithm
,	O
which	O
are	O
required	O
by	O
Shannon	O
's	O
equation	O
when	O
the	O
practical	O
limits	O
of	O
S/N	O
have	O
been	O
reached	O
.	O
</s>
<s>
For	O
high-information	O
capacity	O
,	O
highly-directive	O
point-to-point	B-Architecture
over	O
short	O
ranges	O
,	O
wireless	O
light-wave	O
systems	O
are	O
the	O
most	O
useful	O
.	O
</s>
<s>
Terrestrial	O
television	O
has	O
generally	O
been	O
limited	O
to	O
the	O
region	O
above	O
50MHz	O
where	O
sufficient	O
information	O
bandwidth	B-Algorithm
is	O
available	O
,	O
and	O
below	O
1,000	O
MHz	O
,	O
due	O
to	O
problems	O
associated	O
with	O
increased	O
path	O
loss	O
,	O
as	O
mentioned	O
above	O
.	O
</s>
<s>
For	O
terrestrial	O
and	O
satellite	O
systems	O
,	O
economical	O
,	O
high-capacity	O
,	O
last-mile	O
communications	O
requires	O
point-to-point	B-Architecture
transmission	O
systems	O
.	O
</s>
<s>
Aggregation	B-Architecture
is	O
a	O
method	O
of	O
bonding	B-Architecture
multiple	O
lines	O
to	O
achieve	O
a	O
faster	O
,	O
more	O
reliable	O
connection	O
.	O
</s>
<s>
Some	O
companies	O
believe	O
that	O
ADSL	O
aggregation	B-Architecture
(	O
or	O
"	O
bonding	B-Architecture
"	O
)	O
is	O
the	O
solution	O
to	O
the	O
UK	O
's	O
last	B-Protocol
mile	I-Protocol
problem	O
.	O
</s>
