Meaning
Signal distortion where adjacent symbols in a transmission sequence overlap and obscure each other degrades the reliability of digital communications. Modern wireless systems experience inter-symbol interference primarily due to multipath propagation, where delayed versions of a signal arrive at the receiver at different times. This distortion increases the bit error rate unless equalizers or guard intervals are deployed.
Multipath Origin
Signals reflect off buildings, terrain, and other obstacles, creating multiple paths of different lengths between the transmitter and the receiver. Because these paths have different propagation delays, the energy from a previously transmitted symbol arrives during the detection window of the current symbol. When the difference in arrival times exceeds the duration of a single symbol, the overlap becomes severe.
This condition renders high-speed transmissions impossible without active compensation.
Receiver Equalization
Advanced signal processing algorithms are implemented in receivers to reconstruct the distorted waveform. These structures estimate the channel’s impulse response and apply filtering to undo the temporal spreading. By subtracting the calculated interference of previous symbols from the current symbol, the receiver recovers the original data.
Mitigation Strategy
Protocols often use multi-carrier schemes like orthogonal frequency division multiplexing to increase the symbol duration, which reduces susceptibility to this distortion. Extending the symbol duration makes the multipath delay spread a smaller fraction of the total symbol time. Additionally, inserting a cyclic prefix provides a protective buffer that entirely eliminates the problem.
