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Combating the channel time dispersion (avoiding EQs)

CP

Passing the channel h(n)

Y

i

(

t

)

Y

j

(

t

)

h

(

n

)

=

(

1

)

–

n

/

n

n

=

0

,

…

,

2

3

Y

j

(

t

)

Y

i

(

t

)

1

Y

i

(

t

)

Furthermore, it converts Lineal conv. = Cyclic conv.

(Method: overlap-save)

CP functions:

• It accommodates the decaying transient of the previous symbol (ISI)

• It avoids the initial transient reaches the current symbol (ICI)

Including the Cyclic Prefix

Symbol: 8 periods of fi

Symbol: 4 periods of fi

Initial transient

remains within

the CP

Final transient

remains within

the CP

The inclusion of a CP

maintains the orthogonality

Passing the channel h(n)

Initial transient

Decaying transient

Channel:

Symbol: 8 periods of fi

Symbol: 4 periods of fi

Without the Cyclic Prefix

Loss of orthogonality

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