3GPP TR 38.901 TDL Channel Profile & Coherence Bandwidth Calculator
Scaled RMS Delay Spread ($\sigma_\tau$):
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50% Coherence Bandwidth ($B_{c, 50\%} \approx \frac{1}{5\sigma_\tau}$):
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90% Coherence Bandwidth ($B_{c, 90\%} \approx \frac{1}{50\sigma_\tau}$):
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Maximum Tap Delay ($\tau_{\max}$):
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Frequency Correlation at $B_s$:
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Channel Regime: Flat Fading
No Equalizer Needed
Understanding 3GPP TR 38.901 TDL Channel Models & Selectivity
The 3GPP TR 38.901 specification defines standardized Tapped Delay Line (TDL) channel models to evaluate 5G NR physical layer (PHY) performance in link-level and system-level simulations.
TDL Profiles Overview
- TDL-A, TDL-B, TDL-C: Model Non-Line-of-Sight (NLOS) radio propagation environments with varying delay spreads.
- TDL-D & TDL-E: Model Line-of-Sight (LOS) conditions featuring a strong direct Ricean K-factor component ($K = 13.3\ \text{dB}$ and $K = 22.0\ \text{dB}$, respectively).
Coherence Bandwidth & Channel Selectivity Regimes
Coherence bandwidth ($B_c$) measures the frequency range over which the channel’s complex gain remains strongly correlated. It is inversely proportional to the RMS delay spread ($\sigma_\tau$):
- $$\text{50\% Frequency Correlation Bound: } B_{c, 50\%} \approx \frac{1}{5\sigma_\tau}$$
- $$\text{90\% Frequency Correlation Bound: } B_{c, 90\%} \approx \frac{1}{50\sigma_\tau}$$
When the signal bandwidth ($B_s$) exceeds $B_{c, 50\%}$, spectral components fade independently, leading to Frequency-Selective Fading and requiring equalization or OFDM multicarrier modulation. When $B_s \ll B_c$, the channel experiences Flat Fading across all subcarriers.