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Wireless & Mobility · Advanced

Inter-Symbol Interference (ISI)

Corruption that occurs when delayed multipath copies of one symbol overlap the next symbol.

Definition

When the delay spread of multipath exceeds the guard interval, energy from one symbol bleeds into the next, causing decoding errors. OFDM mitigates ISI with long symbol times and a guard interval between symbols. Severe ISI increases retransmissions and lowers data rates.

Exam tip

Guard interval exists primarily to protect against ISI caused by delay spread.

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