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Unformatted text preview: o ﬁlter the received signal
to cancel the ISI introduced by the channel impulse response. This approach is generally known as
equalization. 4.1 Intersymbol Interference
To understand what ISI is, let us consider the transmission of a sequence of symbols with the basic
waveform Ù´Øµ. To send the Òth symbol Ò , we send Ò Ù´Ø ÒÌ µ, where Ì is the symbol interval. Therefore, the transmitted signal is
Ò Ù´Ø Ò ÒÌ µ (4.2) Based on the dispersive channel model, the received signal is given by Ö´Øµ
where Ú ´Øµ Ò Ú ´Ø Ò ÒÌ µ · Ò´Øµ (4.3) Ù £ ´Øµ is the received waveform for a symbol. If a single symbol, say the symbol ¼ , is transmitted, the optimal demodulator is the one that employs the matched ﬁlter, i.e., we can pass the
received signal through the matched ﬁlter Ú ´Øµ
time Ø Ú ´ Øµ and then sample the matched ﬁlter output at ¼ to obtain the decision statistic. When a sequence of symbols are transmitted, we can still employ this matched ﬁlter to perform demodulation. A reasonable strategy is to sample the matched
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This note was uploaded on 12/13/2012 for the course EEL 6535 taught by Professor Shea during the Spring '08 term at University of Florida.
- Spring '08