<s>
CDMA	B-Protocol
spectral	I-Protocol
efficiency	I-Protocol
refers	O
to	O
the	O
system	O
spectral	B-Protocol
efficiency	I-Protocol
in	O
bit/s/Hz/site	O
or	O
Erlang/MHz/site	O
that	O
can	O
be	O
achieved	O
in	O
a	O
certain	O
CDMA	B-Protocol
based	O
wireless	O
communication	O
system	O
.	O
</s>
<s>
CDMA	B-Protocol
techniques	O
(	O
also	O
known	O
as	O
spread	B-Architecture
spectrum	I-Architecture
)	O
are	O
characterized	O
by	O
a	O
very	O
low	O
link	B-Protocol
spectral	I-Protocol
efficiency	I-Protocol
in	O
(	O
bit/s	O
)	O
/Hz	O
as	O
compared	O
to	O
non-spread	O
spectrum	O
systems	O
,	O
but	O
a	O
comparable	O
system	O
spectral	B-Protocol
efficiency	I-Protocol
.	O
</s>
<s>
The	O
system	O
spectral	B-Protocol
efficiency	I-Protocol
can	O
be	O
improved	O
by	O
radio	B-Protocol
resource	I-Protocol
management	I-Protocol
techniques	O
,	O
resulting	O
in	O
that	O
a	O
higher	O
number	O
of	O
simultaneous	O
calls	O
and	O
higher	O
data	O
rates	O
can	O
be	O
achieved	O
without	O
adding	O
more	O
radio	O
spectrum	O
or	O
more	O
base	O
station	O
sites	O
.	O
</s>
<s>
This	O
article	O
is	O
about	O
radio	B-Protocol
resource	I-Protocol
management	I-Protocol
specifically	O
for	O
direct-sequence	B-Device
spread	I-Device
spectrum	I-Device
(	O
DS-CDMA	O
)	O
based	O
cellular	O
systems	O
.	O
</s>
<s>
Examples	O
of	O
DS-CDMA	O
based	O
cellular	O
systems	O
are	O
:	O
</s>
<s>
the	O
3GPP/UMTS	O
3G	B-Architecture
radio	O
interfaces	O
WCDMA	O
,	O
HSDPA	O
and	O
HSUPA	O
used	O
globally	O
.	O
</s>
<s>
CDMA	B-Protocol
is	O
not	O
expected	O
to	O
be	O
used	O
in	O
4G	B-Architecture
systems	O
,	O
and	O
is	O
not	O
used	O
in	O
pre-4G	O
systems	O
such	O
as	O
LTE	O
and	O
WiMAX	O
,	O
but	O
is	O
about	O
to	O
be	O
supplemented	O
by	O
more	O
spectral	O
efficient	O
frequency-domain	O
equalization	O
(	O
FDE	O
)	O
techniques	O
such	O
as	O
OFDMA	O
.	O
</s>
<s>
The	O
aim	O
of	O
improving	O
system	O
spectral	B-Protocol
efficiency	I-Protocol
is	O
to	O
use	O
limited	O
radio	O
spectrum	O
resources	O
and	O
radio	O
network	O
infrastructure	O
as	O
efficiently	O
as	O
possible	O
.	O
</s>
<s>
The	O
objective	O
of	O
radio-resource	B-Protocol
management	I-Protocol
is	O
typically	O
to	O
maximize	O
the	O
system	O
spectral	B-Protocol
efficiency	I-Protocol
under	O
constraint	O
that	O
the	O
grade	O
of	O
service	O
should	O
be	O
above	O
a	O
certain	O
level	O
.	O
</s>
<s>
The	O
grade	O
of	O
service	O
is	O
also	O
affected	O
by	O
blocking	O
due	O
to	O
admission	O
control	O
,	O
scheduling	B-Operating_System
starvation	I-Operating_System
or	O
inability	O
to	O
guarantee	O
quality	B-General_Concept
of	I-General_Concept
service	I-General_Concept
that	O
is	O
requested	O
by	O
the	O
users	O
.	O
</s>
<s>
There	O
are	O
many	O
ways	O
of	O
increasing	O
system	O
spectral	B-Protocol
efficiency	I-Protocol
.	O
</s>
<s>
It	O
is	O
hence	O
important	O
to	O
initialize	O
interference	B-Protocol
cancellation	I-Protocol
techniques	O
such	O
as	O
pilot	O
interference	B-Protocol
cancellation	I-Protocol
(	O
PIC	O
)	O
and	O
forward	O
link	O
interference	B-Protocol
cancellation	I-Protocol
(	O
FLIC	O
)	O
together	O
in	O
the	O
network	O
.	O
</s>
<s>
Quasi-linear	O
interference	B-Protocol
cancellation	I-Protocol
(	O
QLIC	O
)	O
is	O
a	O
technique	O
used	O
for	O
both	O
FLIC	O
and	O
PIC	O
.	O
</s>
<s>
Along	O
with	O
the	O
forward	O
link	O
,	O
reverse	O
link	O
interference	B-Protocol
cancellation	I-Protocol
is	O
also	O
important	O
.	O
</s>
<s>
The	O
1/8	O
rate	O
gating	O
on	O
the	O
reverse	O
fundamental	O
channel	O
(	O
R-FCH	O
)	O
is	O
the	O
method	O
used	O
for	O
gated	O
transmission	O
in	O
a	O
CDMA	B-Protocol
communication	O
system	O
.	O
</s>
<s>
A	O
mobile	O
station	O
(	O
mobile	O
phone	O
)	O
in	O
the	O
CDMA	B-Protocol
communication	O
system	O
transmits	O
a	O
reverse	O
pilot	O
signal	O
at	O
a	O
reverse	O
gating	O
rate	O
which	O
is	O
different	O
from	O
a	O
forward	O
gating	O
rate	O
in	O
a	O
gated	O
mode	O
,	O
and	O
a	O
base	O
station	O
transmits	O
a	O
forward	O
pilot	O
signal	O
at	O
the	O
forward	O
gating	O
rate	O
different	O
from	O
the	O
forward	O
gating	O
rate	O
in	O
a	O
gated	O
mode	O
.	O
</s>
<s>
This	O
behavior	O
is	O
not	O
present	O
in	O
any	O
other	O
CDMA	B-Protocol
modes	O
.	O
</s>
<s>
Another	O
CDMA	B-Protocol
invention	O
to	O
provide	O
a	O
device	O
and	O
technique	O
for	O
improving	O
a	O
downlink	O
phone	O
capacity	O
and	O
receiving	O
performance	O
by	O
gating	O
an	O
uplink	O
DPCCH	O
signal	O
in	O
a	O
partial	O
period	O
of	O
the	O
power	O
control	O
group	O
in	O
a	O
mobile	O
communication	O
system	O
.	O
</s>
<s>
The	O
CDMA	B-Protocol
radio	O
configuration	O
is	O
defined	O
as	O
a	O
combination	O
of	O
forward	O
and	O
reverse	O
traffic	O
channel	O
transmission	O
formats	O
that	O
are	O
characterized	O
by	O
physical	O
layer	O
parameters	O
such	O
as	O
data	O
rates	O
,	O
error-correction	O
codes	O
,	O
modulation	B-Application
characteristics	O
,	O
and	O
spreading	O
factors	O
.	O
</s>
<s>
The	O
forward	O
link	O
of	O
a	O
3G	B-Architecture
code-division	B-Protocol
multiple-access	O
(	O
CDMA	B-Protocol
)	O
system	O
may	O
become	O
a	O
limiting	O
factor	O
when	O
the	O
number	O
of	O
users	O
increases	O
maximal	O
capacity	O
.	O
</s>
<s>
The	O
conventional	O
channelization	O
code	O
,	O
Walsh	B-Error_Name
code	I-Error_Name
does	O
not	O
have	O
enough	O
available	O
bits	O
to	O
cope	O
with	O
maximal	O
use	O
.	O
</s>
<s>
Therefore	O
,	O
the	O
quasi-orthogonal	O
function	O
(	O
QOF	O
)	O
,	O
which	O
can	O
process	O
optimal	O
cross-correlation	O
with	O
Walsh	B-Error_Name
code	I-Error_Name
has	O
been	O
used	O
as	O
a	O
method	O
to	O
get	O
around	O
the	O
limitations	O
of	O
the	O
Walsh	B-Error_Name
Codes	I-Error_Name
.	O
</s>
<s>
To	O
enhance	O
the	O
overall	O
capacity	O
in	O
such	O
scenarios	O
,	O
alternative	O
sets	O
of	O
orthogonal	O
functions	O
called	O
the	O
quasi-orthogonal	O
functions	O
(	O
QOF	O
)	O
,	O
which	O
possess	O
optimal	O
minimax	B-Algorithm
cross	O
correlation	O
with	O
Walsh	B-Error_Name
code	I-Error_Name
sets	O
of	O
variable	O
length	O
,	O
have	O
been	O
incorporated	O
in	O
IS-2000	O
.	O
</s>
<s>
This	O
method	O
is	O
compared	O
with	O
the	O
alternative	O
method	O
for	O
enhancing	O
the	O
maximum	O
throughput	O
using	O
aggregation	O
of	O
a	O
smaller	O
number	O
of	O
Walsh	O
functions	O
,	O
but	O
with	O
a	O
higher	O
constellation	O
alphabet	O
size	O
(	O
multi-level	O
modulation	B-Application
)	O
.	O
</s>
<s>
There	O
have	O
been	O
many	O
industrial	O
and	O
academic	O
discussions	O
on	O
the	O
trade-offs	O
with	O
respect	O
to	O
better	O
methods	O
for	O
increasing	O
capacity	O
in	O
IS-2000/3G	O
systems	O
.	O
</s>
<s>
There	O
are	O
some	O
places	O
where	O
the	O
utilization	O
of	O
the	O
site	O
is	O
very	O
high	O
and	O
excess	O
softer	B-Protocol
handoffs	I-Protocol
occur	O
.	O
</s>
<s>
soft	B-Protocol
handover	I-Protocol
,	O
see	O
below	O
)	O
,	O
is	O
any	O
one	O
of	O
several	O
wireless	O
diversity	O
schemes	O
that	O
use	O
two	O
or	O
more	O
antennas	O
to	O
improve	O
the	O
quality	O
and	O
reliability	O
of	O
a	O
wireless	O
link	O
.	O
</s>
<s>
Qualcomm	O
’s	O
fourth	O
generation	O
vocoder	O
(	O
4GV	O
)	O
is	O
a	O
suite	O
of	O
voice	O
speech	O
codecs	O
expected	O
to	O
be	O
used	O
in	O
future	O
4G	B-Architecture
networks	O
as	O
well	O
CDMA	B-Protocol
networks	O
,	O
that	O
allows	O
the	O
network	O
operators	O
to	O
dynamically	O
prioritize	O
voice	O
quality	O
to	O
increase	O
network	O
capacity	O
while	O
maintaining	O
voice	O
quality	O
.	O
</s>
<s>
Currently	O
,	O
the	O
4GV	O
suite	O
offers	O
EVRC-B	B-Algorithm
and	O
EVRC-WB	O
.	O
</s>
<s>
Enhanced	B-Algorithm
Variable	I-Algorithm
Rate	I-Algorithm
Codec	I-Algorithm
B	I-Algorithm
(	O
EVRC-B	B-Algorithm
)	O
is	O
a	O
speech	O
codec	O
used	O
by	O
CDMA	B-Protocol
networks	O
.	O
</s>
<s>
EVRC-B	B-Algorithm
is	O
an	O
enhancement	O
to	O
EVRC	B-Algorithm
and	O
compresses	O
each	O
20	O
milliseconds	O
of	O
8000Hz	O
,	O
16-bit	O
sampled	O
speech	O
input	O
into	O
output	O
frames	O
of	O
one	O
of	O
the	O
four	O
different	O
sizes	O
:	O
Rate	O
1	O
-	O
171	O
bits	O
,	O
Rate	O
1/2	O
-	O
80	O
bits	O
,	O
Rate	O
1/4	O
-	O
40	O
bits	O
,	O
Rate	O
1/8	O
-	O
16	O
bits	O
.	O
</s>
<s>
In	O
addition	O
,	O
there	O
are	O
two	O
zero	O
bit	O
codec	O
frame	O
types	O
:	O
null	O
frames	O
and	O
erasure	O
frames	O
,	O
similar	O
to	O
EVRC	B-Algorithm
.	O
</s>
<s>
One	O
significant	O
enhancement	O
in	O
EVRC-B	B-Algorithm
is	O
the	O
use	O
of	O
1/4	O
rate	O
frames	O
that	O
were	O
not	O
used	O
in	O
EVRC	B-Algorithm
.	O
</s>
<s>
This	O
provides	O
lower	O
average	O
data	O
rates	O
(	O
ADRs	O
)	O
compared	O
to	O
EVRC	B-Algorithm
,	O
for	O
a	O
given	O
voice	O
quality	O
.	O
</s>
<s>
The	O
new	O
4GV	O
Codecs	O
used	O
in	O
CDMA2000	O
are	O
based	O
on	O
EVRC-B	B-Algorithm
.	O
</s>
<s>
The	O
Enhanced	B-Algorithm
Variable	I-Algorithm
Rate	I-Algorithm
Codec	I-Algorithm
(	O
EVRC	B-Algorithm
)	O
is	O
a	O
speech	O
codec	O
used	O
for	O
cellular	O
telephony	O
in	O
cdma2000	O
systems	O
.	O
</s>
<s>
EVRC	B-Algorithm
provides	O
excellent	O
speech	O
quality	O
using	O
variable	O
rate	O
coding	O
with	O
3	O
possible	O
rates	O
,	O
8.55	O
,	O
4.0	O
and	O
0.8	O
kbit/s	O
.	O
</s>
<s>
However	O
,	O
the	O
Quality	B-General_Concept
of	I-General_Concept
Service	I-General_Concept
(	O
QoS	O
)	O
in	O
cdma2000	O
systems	O
can	O
significantly	O
benefit	O
from	O
a	O
codec	O
which	O
allows	O
tradeoffs	O
between	O
voice	O
quality	O
and	O
network	O
capacity	O
,	O
which	O
cannot	O
be	O
achieved	O
efficiently	O
with	O
the	O
EVRC	B-Algorithm
.	O
</s>
<s>
There	O
are	O
some	O
areas	O
with	O
more	O
soft	B-Protocol
handoff	I-Protocol
than	O
necessary	O
.	O
</s>
<s>
The	O
handoff	B-Protocol
parameters	O
has	O
to	O
be	O
reduced	O
to	O
save	O
the	O
base	O
station	O
power	O
.	O
</s>
