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Difference between DL and UL in LTE

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what is main Difference between DL and UL in LTE ?

OFDMA

  • Advantages
  • Robust against narrow-band co-channel interference
  • Robust against Intersymbol interference (ISI) and fading
  • High spectral efficiency
  • Efficient implementation using FFT
  • Drawbacks
  • High Peak-to-Average Power Ratio

The power limitation is more problematic in UL than in DL Signal with high PAPR will limit the Tx power in UL and reduce coverage.

LTE uses in UL a modified form of OFDMA process, called SC-FDMA

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SC-FDMA = Single Carrier – Frequency Division Multiple Access

SC-FDMA improves the peak-to-average power ratio (PAPR) compared to

OFDM

Reduced power amplifier cost for mobile

Reduced power amplifier back-off -> improved coverage

In DL, use OFDM together with some PAPR reduction techniques (“clipping and filtering”, “tones reservation”, etc…)
In UL, find an alternative to OFDM combining some of OFDM’s advantages, but with a PAPR equivalent to single carrier’s one: DFT-Spread OFDM (DFT-SOFDM), also known as Single-Carrier FDMA (SC-FDMA).

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