A comparison of wi-fi and wimax with case studies - Florida State ...
A comparison of wi-fi and wimax with case studies - Florida State ...
A comparison of wi-fi and wimax with case studies - Florida State ...
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Whhere<br />
y = H. .X + n<br />
Figuree<br />
4-2 A Spaatial<br />
Multipllexing<br />
MIMMO<br />
System<br />
4.3.1.11.1.<br />
Fouur<br />
transmmission<br />
mode:<br />
SC, SCa, OFDDM<br />
<strong>and</strong> OOFDMA<br />
In IIEEE<br />
802.16-2004<br />
PHYY-layer,<br />
SCC<br />
(Signal Laayer)<br />
is respponsible<br />
forr<br />
the 10 – 666<br />
GHz b<strong>and</strong> d<br />
<strong>and</strong> SCCa<br />
is used ffor<br />
the 2 – 11GHz ba<strong>and</strong>.<br />
The coore<br />
<strong>of</strong> this st<strong>and</strong>ard iss<br />
the OFDM M/OFDMAA<br />
modulaation<br />
<strong>and</strong> ussed<br />
in the 2 – 10 GHz b<strong>and</strong>. Thiss<br />
method haas<br />
many advvantages<br />
annd<br />
has beenn<br />
<strong>wi</strong>dely used for maany<br />
<strong>wi</strong>relesss<br />
technologies.<br />
[50]<br />
4.3.1.11.2.<br />
AMMC<br />
(Adapptive<br />
Mod dulation a<strong>and</strong><br />
Codinng)<br />
Wi ith AMC, WWiMax<br />
can support va arious kindss<br />
<strong>of</strong> modulaation<br />
<strong>and</strong> foorward<br />
error r correctionn<br />
(FEC) ccoding.<br />
This<br />
method allows<br />
modu ulation scheemes<br />
to be cchanged<br />
forr<br />
each persoon<br />
based onn<br />
channell<br />
conditionss.<br />
AMC is very effecttive<br />
on opttimizing<br />
ovverall<br />
channnel<br />
capacity y in a time-<br />
varyingg<br />
channel. TTherefore<br />
uusers<br />
can bee<br />
provided <strong>wi</strong>th the poossible<br />
highhest<br />
data raate<br />
which iss<br />
allowedd<br />
by the ISPP<br />
<strong>and</strong> link conditions.<br />
The T theory iis<br />
that whenn<br />
the channeel<br />
condition ns are good; ;<br />
then it transmits aas<br />
high dataa<br />
rate as poossible.<br />
Whhen<br />
the cha annel condiitions<br />
are poor,<br />
then itt<br />
transmiits<br />
at a lowwer<br />
data ratee<br />
to avoid eexcessive<br />
ppackets<br />
beco oming lost. Lower dat te rates <strong>and</strong> d<br />
higher date rates ccan<br />
be achi ieved by ussing<br />
differeent<br />
modulattion,<br />
such aas<br />
QPSK an nd low-ratee<br />
error-coorrection<br />
coodes<br />
for loww<br />
speed, a<strong>and</strong><br />
64-QAMM<br />
<strong>and</strong> lesss<br />
robust errror-correctioon<br />
for highh<br />
speed. [ [50]<br />
In both IEEE 802.16-20006<br />
<strong>and</strong> IEEEE<br />
802.16ee-2005<br />
PHYY,<br />
the RS- CC (Reed Solomon –<br />
Convoluution<br />
Code) ) is the requuired<br />
codingg<br />
mode <strong>and</strong>d<br />
block turbo<br />
codes (BTTC),<br />
convol lution turboo<br />
44
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