5G DL Reference Signal: Demodulation Reference Signal - DMRS

Hi All,

This Video will clarify all the basic understanding regarding 5G DL DMRS for PDSCH different configurations, PBCH & PDCCH, and it will also explain most of the use cases of PDSCH-DMRS-related parameters.

The below is covered in this video.


  1. DMRS for PDSCH Configurations and main parameters
  2. DMRS for PBCH
  3. DMRS for PDCCH

YouTube: :point_right: https://www.youtube.com/watch?v=ydQlAsxef-U

Studying Source:

  • 5G NR in Bullets
  • 3GPP Reference TS 38.211~38.214 & TS 38.331

This Article will cover most of the related aspects and details about the 5G Downlink Demodulation Reference Signal (DL DMRS)

The article will go through all DL DMRS Types, which is summarized in the below picture.


Now, Let`s go through DL DMRS in more detail: :point_down:



Lets know whats PDSCH DMRS:

Certainly! In 5G, the Physical Downlink Shared Channel (PDSCH) is responsible for carrying user data from the base station (eNB/gNB) to the user equipment (UE). To facilitate accurate demodulation of the PDSCH, Demodulation Reference Signals (DMRS) are employed.

Here’s a more detailed breakdown:

  1. Purpose of PDSCH DMRS:

    • The primary function of PDSCH DMRS is to provide a reference signal that helps the UE accurately estimate the channel conditions on the PDSCH.
    • This reference signal aids in demodulating the received signal by the UE, compensating for channel impairments such as fading and interference.
  2. DMRS Positioning:

    • PDSCH DMRS symbols are specifically positioned within the PDSCH resource elements (REs). The DMRS positions are known to both the transmitter (base station) and the receiver (UE).
    • The DMRS positions may vary depending on the specific 5G numerology and configuration.
  3. DMRS Configuration:

    • 5G allows for different DMRS configurations, including the number of DMRS symbols, the type of DMRS (single or multiple), and the mapping of DMRS to resource elements.
    • Different configurations are defined to adapt to various channel conditions and system requirements.
  4. DMRS for Channel Estimation:

    • The UE utilizes the received PDSCH DMRS to estimate the channel characteristics between the base station and itself.
    • This channel estimation is crucial for the subsequent demodulation and decoding of the PDSCH payload.
  5. Adaptive Beamforming:

    • The information obtained from DMRS assists in adaptive beamforming, allowing the base station to optimize the transmission in the direction of the UE for improved signal quality.
  6. DMRS Symbols Structure:

    • The structure of DMRS symbols includes both time and frequency components. The time-domain structure allows for accurate timing alignment, while the frequency-domain structure aids in frequency-selective channel estimation.

In summary, PDSCH DMRS in 5G serves as a critical reference signal to enable precise demodulation of the downlink shared channel, ensuring reliable communication between the base station and the user equipment in varying radio channel conditions.

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