Inter-Symbol Interference in LTE
- Definition: ISI is a phenomenon in LTE where symbols transmitted over a communication channel overlap, causing distortion in the received signal.
- Causes:
- Multipath Propagation: Signals take multiple paths with different delays, leading to overlapping symbols.
- Time Dispersion: Variation in signal arrival times at the receiver contributes to ISI.
- Impact on LTE:
- Degrades Signal Quality: ISI results in difficulty in correctly interpreting symbols, leading to errors in data transmission.
- Reduces Data Rate: Impairs the ability to transmit data at higher rates due to increased likelihood of errors.
- Mitigation Techniques:
- Equalization: Techniques such as linear equalization are employed to mitigate ISI by compensating for channel distortions.
- Guard Intervals: Including guard intervals between symbols helps in reducing the impact of ISI.
In LTE, addressing ISI is crucial to ensure reliable and high-quality data transmission in wireless communication systems.
What is the multipath?
- Due to the signal propagation phenomena, like reflection or diffraction, a receiver can receive several delayed versions of the same signal.
- This creates Inter-Symbol Interference (ISI).
The modulation is based on the amplitude and on the phase, so in case of overlapping there are 2 different
The receiver is not able to decode the state of the symbol.
- The guard time is called the Cyclic Prefix (CP). It permits to facilitate demodulation.
- The cyclic prefix transforms the classical channel convolution into a cyclic convolution which permits easy demodulation after FFT.