Industrial Communication Systems

2-16 Industrial Communication Systems

needs to be equalized by the receiver that requires estimation of the channel. If the channel

response

has

multiple

zeros

in

the

frequency

domain,

it

might

happen

that

equalization

is

not

possible

an

y

lo

nger,

re

sulting

in a hi

gh

BE

R.

e

OFDM

approach

is

dierent

to

that:

the

single,

high

bit

rate

carrier

is

split

into

multiple

lower

bit

rate

carriers

(multicarrier

modulation).

is

has

some

benets:

the

sub-channels

have

low

bandwidth

and

at

fading

can

be

assumed

for

each

sub-channel

(even

if

the

entire

band-

width

across

all

sub-channels

shows

frequency

selective

fading).

Hence,

now

channel

estimation/

equalization

is

necessary.

Furthermore,

if

the

channel’s

frequency

response

has

nulls

on

some

sub- ...