5G DL Channel: 5G Physical Downlink Control Channel(PDCCH)

[@hereisanan]

thank you! wonderful presentation!

[@mohamedeladawiashour]

Thank you

[@smakkapati31]

Thank you very much , Very Informative and great explanation

[@mohamedeladawiashour]

Thanks a lot, Rao

[@georgioskarouzos7418]

Hello Mohamed!! In 4G PDCCH OFDM symbols is informed to the UE by PCFICH. In 5G SA this is done via RRC specific signaling during RACH procedure. Is it correct ? thank you

[@mohamedeladawiashour]

Hi Geroge; yes you are right about 4G Part. Regarding 5G SA Part. i am not quite sure from the answer but based on 3GPP TS 38.213 and 5G NR in Bullets. gNB transmits core information element inside MIB message which is used as a pointer within 3GPP Specified tables to identify Frequency & Time domain Positions including the number of resources blocks and number of OFDM Symbols used for CORESET(PDCCH).

[@imadhasan3208]

Very well explained Mohammed. Can you also please share 5G EN-DC KPIs and counters to check each degradation in the KPIs and same for the SA please.

[@mohamedeladawiashour]

Thanks a lot, Imad, Sure, I will consider it and will add it to my plan.

[@vijayshinde9638]

Very Informative. One question From which point on wards UE will start monitoring ue specific search space? After RRC Setup?

[@mohamedeladawiashour]

Good question, yes as per my knowledge UE specific search space will be measured in the connected mode.

[@sambitroutray8297]

Hi Mohamed. I have 1 query: 1. CORSET & Search space contains the information related to frequency and time domain position of PDCCH. With these info UE will perform blind decoding on PDCCH candidates with different AL. >My question is where UE will get the information related to AL & PDCCH candidates on which UE will perform blind decoding of PDCCH which carries SIB1 ? > And what are AL used by UE for blind decoding SIB1 on Type-0 PDCCH CSS set??? Thanks

[@mohamedeladawiashour]

"Hello Sam, from what I recall, during the initial access (SSB acquisition), the UE receives and interprets MIB via PBCH. This MIB contains information about search space 0, which enables the UE to decode SIB1 and subsequently obtain additional information for other SIBs and SEARCH SPACE and regarding AL question for what the AL UE initially uses, I'm not entirely certain, but I believe it starts with the minimum allowed AL. The network then determines whether to adjust the AL based on PDCCH BLER. I need to revisit the details on PDCCH, as the last time I reviewed it was while preparing for this video. Please see the below information sent in the MIB Message RRC-MSG ..msg 0> 01 00000001 T ....struBCCH-BCH-Message ......struBCCH-BCH-Message ........bcchbchmessage 1> 5B 0------- * ..........mib -101101- ............systemFrameNumber:101101(2D) -------1 ............subCarrierSpacingCommon:scs30or120 (1) 2> 25 0010---- ............ssb-SubcarrierOffset:0x2 (2) ----0--- ............dmrs-TypeA-Position:pos2 (0) ............pdcch-ConfigSIB1 -----101 3> 25 0------- ..............controlResourceSetZero:0xa (10) -0100--- ..............searchSpaceZero:0x4 (4) -----1-- ............cellBarred:notBarred (1) ------0- ............intraFreqReselection:allowed (0) -------1 ............spare:1(01) Subsquent information received in SIB1 ..................pdcch-ConfigCommon ......................controlResourceSetZero:0xa (10) ......................searchSpaceZero:0x4 (4) ......................commonSearchSpaceList ........................SearchSpace ..........................searchSpaceId:0x1 (1) ..........................controlResourceSetId:0x0 (0) ..........................monitoringSlotPeriodicityAndOffset ..........................monitoringSymbolsWithinSlot:10000000000000(20 00) ..........................nrofCandidates ............................aggregationLevel1:n0 (0) ............................aggregationLevel2:n0 (0 ) ............................aggregationLevel4:n4 (4) ............................aggregationLevel8:n2 (2) ............................aggregationLevel16:n1 (1) ..........................searchSpaceType ............................common ..............................dci-Format0-0-AndFormat1-0 ........................SearchSpace ..........................searchSpaceId:0x8 (8) ..........................controlResourceSetId:0x0 (0) ..........................monitoringSlotPeriodicityAndOffset ............................sl40:0x15 (21) ..........................duration:0x2 (2) ..........................monitoringSymbolsWithinSlot:10000000000000(20 00) ..........................nrofCandidates ............................aggregationLevel1:n0 (0) ............................aggregationLevel2:n0 (0) ............................aggregationLevel4:n4 (4) ............................aggregationLevel8:n2 (2) ............................aggregationLevel16:n1 (1) ..........................searchSpaceType ............................common ..............................dci-Format0-0-AndFormat1-0 ......................searchSpaceSIB1:0x0 (0) ......................searchSpaceOtherSystemInformation:0x8 (8) ......................pagingSearchSpace:0x1 (1) ......................ra-SearchSpace:0x1 (1)

[@mohamedeladawiashour]

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[@sambitroutray8297]

@@mohamedeladawiashour Thank you very much for such a detailed explanation for my query. Regarding the below query, I am writing the ans which I read. Please correct me on this. Q: What are AL used by UE for blind decoding SIB1 on Type-0 PDCCH CSS set??? Ans : Common Search Space (CSS) PDCCH blind decoding procedure (Common RNTI's are mandated to use AL4, AL8,AL16) PDCCH blind decoding is performed based on following sequence, 4 CCEs (perform Blind decoding for 4 PDCCH Candidates), Then 8 CCEs(perform blind decoding for 2 PDCCH candidates) and Then, Finally 16 CCEs(perform Blind decoding for 1 PDCCH candidate). >If RNTI does not match with any of the 4 candidates in AL4, then CCE Aggregation Level8 is considered,. >If RNTI does not match with any of the 2 candidates in AL8, Then finally CCE Aggregation Level16 is considered, Channel estimation and PDCCH decoding is performed on the 16CCE’s and finally if RNTI match the DCI CRC scrambled RNTI then UE will get to know that DCI is allocated for that UE and it will drive the DCI Info to get the DL/UL scheduling information.. I referred from link : www.linkedin.com/pulse/5g-nr-pdcch-cce-aggregation-search-space-naveen-chelikani/

[@mohamedeladawiashour]

@sambitroutray8297 perfect; i think this answer make more sense; let ne go through the article as well. Thanks for sharing this

[@sambitroutray8297]

Hello Mohamed ....One of the best video with detailed info, how will decode pdcch. If possible could you please add 1 video on FDRA & TDRA. Thanks

[@mohamedeladawiashour]

Hello, thanks for your feedback; you need video for FDRA and TDRA for which channel?

[@sambitroutray8297]

@@mohamedeladawiashour thanks for your response. FDRA & FDRA for PBCH & PDSCH data

[@mohamedeladawiashour]

@sambitroutray8297 I have a plan to prepare a video to explain the details about this part for PDSCH. I will keep you posted. Thanks

[@sambitroutray8297]

@@mohamedeladawiashour thanks.... Really appreciate your effort.

[@georgioskarouzos7418]

Very helpful Mohamed! Ue specific search space identifies the time domain positions of Ue specific Pdcch.Is Ue specific Control resource set also necessary for frequency domain position of Pdcch? Thank you

[@mohamedeladawiashour]

Thanks a lot, As per my understanding, UE Specific Search Space is dedicated to each UE in connected mode and is used to identify both Freq/Time domains for PDSCH used for Data. UE is informed in the dedicated mode for UE Specific search space "After RRC Setup". While Common Search Space is the specific search space that every UE needs to search (Example PDCCH for SIB) or signaling message. For example, during the RACH process, UE must detect PDCCH for SIB1 reception or various DCI (PDCCH). Please confirm if it is clear, as I think you are might be confused between UE Specific Search Space and Common Search Space, and I apologize for the late response.

[@mohamedeladawiashour]

Please confirm if you got it as i am worry you are confused between ue specific search space and common searh space

[@georgioskarouzos7418]

Thank you again Mohamed for your response.Given that ControlResourceSet0 and Searchspace0 are necessary for a ue to identify pdcch sib1 freq/time domain position, i assume that besides ue-specific searchspace(time domain position of pdcch) also ue-specific controlresourceset is necessary for a ue to identify the freq. position of its pdcch.

[@mohamedeladawiashour]

Yes, you are absolutely right and this is part of common search space

[@georgioskarouzos7418]

Hello Mohamed! I would like some clarifications regarding search space for other SIBs that SIB1 carries : The abovementioned search space for other SIBs, that SIB1 carries, is part of the contents of PDSCH(SIB1). Is it correct ? Thank you

[@mohamedeladawiashour]

Hi Georgie;as per my knowledge, SIB1 will cover all the information needed for other SIBs

[@sambitroutray8297]

@@mohamedeladawiashour Please correct me if any: SIB1 can be used to provide an RRC configured look up table within the "pdcch-configcommon" parameter. In that case UE uses the RRC configured look up table when receiving PDSCH resource allocation for other SIBs. # If UE is not provided with an RRC configured look up table within "pdcch-configcommon" parameter, then UE uses the standardized table for reception of OSI.

[@sambitroutray8297]

Hi Mohamed. The search space will tell the starting symbol and slot where UE will monitor PDCCH whose CRC bit is scrambled with SI-Rnti within type 0 pdcch css set. So how and when the resources in time and frequency domain allocation happens. Thanks

[@mohamedeladawiashour]

Hi Sam; can you explain more please which parr exactly is not clear to you for time and frequency allocation in this video? I will definitely check and get back to you

[@hannamo979]

👏🏻👏🏻👏🏻

[@mohamedeladawiashour]

Thank you