New blog post: 5G NR PDCCH. In this post I show how to decode the Physical Downlink Control Channel, by using as example the PDCCH for the SIB1 in a srsRAN gNB recording. The PDCCH is used to transmit control information such as downlink scheduling and uplink grants.

Finally, I parse the fields of this DCI format 1_0 that contains the SIB1 PDSCH scheduling and show how the values match what we see in the waterfall.

Read more: destevez.net/2025/05/5g-n...

UE Power Saving Techniques in 5G Release 16/17 by Lothar Walther, Rohde & Schwarz - www.rohde-schwarz.taipei/data/activit...

#Free5Gtraining #3G4G5G #RohdeSchwarz #3GPP #5G #Release16 #Release17 #UEPowerSaving #cDRX #WUS #UAI #RedCap #SDT #PEI #SSSG #PDCCH

I had already shown how to demodulate the PDCCH and process its DM-RS (demodulation reference signal) in previous posts. I had also decoded the PBCH, which contains the MIB, that has some configuration parameters required to process the PDCCH.

New blog post: 5G NR PDSCH. In this post I show how to decode the 5G PDSCH (downlink data) by using the SIB1 from an srsRAN gNB recording as an example. I go into the details of how LDPC and the rest of rate matching and other encoding work.

I explain how all these parameters define which resource elements are occupied by the PDCCH, and why this PDCCH transmission is formed by two disjoint segments in frequency, due to the interleaved mapping of the CCEs to REG bundles.

New blog post: 5G NR downlink reference signals. I continue the analysis of a short recording of an srsRAN gNB. I show how to generate the pseudorandom sequences for the CSI-RS, the TRS, and the DM-RS for PDDCH and PDSCH.

youtu.be/Lj2cbB91PKE?...

The PDCCH is encoded using Polar coding, in the same way as the PBCH. However, one challenge is that the message size (the DCI size) is not fixed and is unknown in general, specially in a sniffing scenario where we only have access to the downlink signal.

Yue Xiu, Ning Wei, Zixian Song, Tianyu Liu: Mixture-of-Experts Deep Reinforcement Learning for Reliability-Constrained Energy-Efficient PDCCH Monitoring in Internet of Thing Device https://arxiv.org/abs/2607.06084 https://arxiv.org/pdf/2607.06084 https://arxiv.org/html/2607.06084

One step further is to retransmit a 3rd party signal (like a cellular PDCCH or even a jamming signal) with the encrypted distortions. The receiver correlates the clean 3rd party signal with the noisy version, and then equalizes and decrypts the baseband symbols.

First the PDSCH symbols are equalized using the appropriate transmission mode. We use the DCI information in the PDCCH to know whether transmit diversity (broadcast info) or close-loop spatial multiplexing (info for a single UE) was used.