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    when a new technology introduce, if you are not a part of the Mainstream, you are part of the road.

    some men see things as they are, and ask why?. I dream things that never were and ask why no?t

    some men see things as they are, and ask why?. I dream things that never were and ask why no?t

    Relationship with Wifi become strong when connected, weak when it locked in passwords.

    Relationship with Wifi become strong when connected, weak when it locked in passwords.

    The Engineer is not a person who gives the right answers, he is one who asks the right questions.

    The Engineer is not a person who gives the right answers, he is one who asks the right questions.

    Latest Posts

    5G Interview Questions Answers Part-2

    Joni Tyagi
    5G Interview Questions Answesrs

    Q26. What is AMF? What is the essential function of AMF in 5G NR?

    Q27. What is R(AN)? What is the essential function of R(AN) in 5G NR?

    Q28. What is SMF? What is the essential function of SMF in 5G NR?

    Q29. What is UPF? What is the essential function of UPF in 5G NR?

    Q30. What is PCF? What is the essential function of PCF in 5G NR?

    Q31. What is AF? What is the essential function of AF in 5G NR?

    Q32. What is UDM? What is the essential function of UDM in 5G NR?

    Q33. What is AUSF? What is the essential function of AUSF in 5G NR?

    Q34. What is NEF? What is the essential function of NEF in 5G NR?

    Q35. What is NRF? What is the essential function of NRF in 5G NR?

    Q36. What is Network Slicing? What is the essential function of NSSF in 5G NR?

    Q37. What is uRLLC? Why it’s use in 5G NR?

    Q38. What is mMTC? Why it’s use in 5G NR?

    Q39. What is eMBB? Why it’s use in 5G NR?

    Q40. Bandwidth range use in NR?

    Q41. What is MCG? What kind of functionality it play in 5G NR?

    Q42. What is SCG? And what kind of funtionality it play in 5G NR?

    Q43. What is Split Bearer in 5G NR? How’s it works?

    Q44. Explain the data call flow when UE use MCG, SCG and Split Bearer in 5G NR?

    Q45. What is Mn and Sn in 5G NR?

    5G Interview Questions Answers Part-1

    Joni Tyagi


    5G Interview Questions Answesrs

    Q01. What is 5G NR? Why it’s need if we have 4G?

    Q02. What are the limitations in 4G?

    Q03. Explain 5G NR High Level Architecture?

    Q04. Explain 5G NR Low Level Architecture?

    Q05. What is Dual Connectivity?

    Q06. What is MRDC?

    Q07. What is ENDC?

    Q08. What is NRDC?

    Q09. Explain the Interfaces uses in 5G NR Architecture?

    Q10. What is gNB? And what’s the use of gNB in 5G NR?

    Q11. What is en-gNB? And How’s it different from gNB?

    Q12. What is ng-eNB? And How’s it different from en-gnb?

    Q13. What is EPC and 5G NRC?

    Q14. What is NSA and SA? Name of the Deployment options available in NSA or SA as per 3gpp defined?

    Q15. Explain frequency range define in 5G NR?

    Q16. What is mmWave? Why it doesn’t it travels far from origin?

    Q17. What’s are the Deployment option’s of RAN’s implementation availble in 5G NR.

    Q18. What is CU, DU use in 5G NR?

    Q19. Name of Interface use between CU and DU?

    Q20. What is CU-CP and CU-UP?

    Q21. Name of Interface use in CU-CP and CU-UP?

    Q22. What do you mean by Class 1 and Class 2 messages?

    Q23. Please tell me the Class 1 and Class 2 messages that’s are use in F1AP protocol?

    Q24. Explain the protocol structure of 5G NR?

    Q25. Please tell me the name of protocol use between UE and R(AN) in 5G NR?


    Jitendra Kumar
    ANR (Automatic Neighbour Relation)

    Actually before understand about ANR we have to clear little bit concept on neighbour cell scenario. What happened is every eNB attached the neighbour cell list inside SIBs. This is operator work to configure these details in system Info So There are two ways that network operator put this details inside the various cells.
    1.    Manually configuration: Its done manually by the Operator but here are some issue with it:
    a.    First operator need to provide special person to investigate it which is cost effective and also neighbour cells are changes time to time by shifting cells on demand
    2.    Automatic configuration : This is technique the eNB are used  for automatic configuration of neighbour cell which is known as Automatic neighbour request. Its a easier way of configuration. Procedure is as follows:
    a.    First N/W will send Measurement control Req to UE  for performing the measurement of cell around its geographical area and provide list to N/W that has sent Measurement control Req earlier.
    b.    N/W will decode the measurement report and update the neighbouring list according to the received report from UE.

    TAU(Tracking Area Update)

    TAU is a kind of report which sent by UE to MME at a certain time, whenever the TAC(Tracking Area Code) is changed than TAU is needed not only that time there is some more condition when its needed.
    First the question is How UE get to know that TAC is changed? So our answer is this information is present in a SIB1.
    Now second question is when TAU report has to send?
    Actually we have something called TAI list which is already has provided by MME to UE at the time of registration. For more information Refer TAI.

           Below I have attached the flow of  TAU procedure:

    TAU Procedure flow Diagram

    TAU trigger conditions:
    1.    Normal TAU is due to mobility i.e when UE enters in Tracking Area which is not included within the list of tracking areas with which the UE has registered.
    2.    Periodic TAU after T3412 timer Expires.
    3.    Reregistering the EPS after CSFB connection has been completed.
    4.    MME load balancing. 

    Note 1: It is triggered in both in IDLE and Connected mode, but Suppose UE in connected mode and try to to move to new location, In this UE known to the network and easily handed over to new cell but if UE found that its TAC isn’t part of TAI list now than it will triggered TAU procedure to the MME.


    Note 2: It doesn’t means UE always be in Connected mode but it can be come again in IDLE mode.Than Suppose if N/W want to send some information to the UE than in this case MME need to know the exact location of UE because might be UE was is moving state in IDLE and doing its cell selection and reselection than here also only extreme procedure which we have is TAU procedure. But as in the above flow diagram we have seen that TAU is piggybacked on rrcconnectionsetupcomplete msg so its a connected mode msg so how this stuff work. So The perfect answer is UE can begin the TAU procedure in IDLE mode but UE must be in RRC Connected mode to actually complete the procedure.


    5G PUCCH and 5G PUSCH

    Joni Tyagi

    5G PUCCH and 5G PUSCH

    PUCCH is used to carry Uplink Control Information (UCI), and following types of UCI are supported in NR:
    ·         Hybrid automatic repeat request acknowledgement (HARQ-ACK): information to report whether the DL transmission of a TB is successful or not
    ·         Scheduling request (SR): signal to request UL grant to gNB
    ·         Channel state information (CSI): information represents channel condition between gNB and UE
    The UCI can be carried by PUCCH or PUSCH. The channel coding schemes for different UCI sizes are shown in Table.

    Channel coding for uplink control information (UCI)

    UCI size including CRC, if present
    Channel code
    Repetition code
    Simplex code
    Reed Muller code
    Polar code
    1. For HARQ-ACK feedback of PDSCH with corresponding DCI, PUCCH resource set(s) containing one or more PUCCH resources are configured.
    2. One PUCCH resource is determined based on the UCI payload size and the PUCCH resource indicator field in the DL assignment. For HARQ-ACK feedback of PDSCH without corresponding DCI, SR, and CSI report, a PUCCH resource is configured for each.
    3. When multiple PUCCHs are overlapped fully or partially in time, the UCIs are multiplexed in a PUCCH.
    4. When a PUCCH is overlapped with a PUSCH fully or partially in time, the UCI is multiplexed (i.e. piggybacked) on the PUSCH.
    5. Each PUCCH resource is configured with a PUCCH format. Various PUCCH formats are specified as in Figure.
    6. Each PUCCH format supports either durations of 1 to 2 symbols, or durations of 4 to 14 symbols.
    7. PUCCH formats 0/2 are called as short-PUCCH, which can deliver UCI by 1 or 2 symbols. PUCCH formats 0/2 are beneficial to reduce latency.
    8. PUCCH formats 1/3/4 are called as long-PUCCH, which can deliver UCI with any of 4 to 14 symbols. PUCCH formats 1/3/4 are adopted to improve coverage.
    9. The frequency/time-domain resources for PUCCH transmissions in NR are flexibly configurable.
    10. In PUCCH format 0/1/4, multiple PUCCH resources can be CDMed on the same time/frequency resource.
    11. A short-PUCCH can be TDMed with a long-PUCCH or a short PUCCH within a slot.
    pusch 5g pusch lte pusch pdcch 5g pdcch jamar pusch picea abies pusch pdcch in lte jamar pusch onlyfans jamar pusch twitter steph pusch pdcch lte lte pdcch pdcch 5g pusch peak pusch peak family dental lte dci format 5g nr pdcch hans pusch werner pusch pusch pucch pusch 5g pdcch format dennis pusch pusch commey pdcch in 5g physical uplink shared channel pdsch and pdcch picea pusch kurt pusch pusch channel gretchen pusch arthur pusch charlotte pusch ramona pusch ramona von pusch stephanie pusch p0 nominal pusch lte almira pusch kira pusch franz pusch 5g nr dci format pusch peak dental justin pusch rick von pusch picea abies pusch for sale kristin pusch picea abies acrocona pusch julie pusch jayden pusch 5g pusch dmrs 5g nr pusch dmrs pusch app madeleine pusch greg pusch mindy pusch acrocona pusch

    NR PUCCH formats

    PUSCH is used to transmit one TB. A DCI in a PDCCH can schedule a PUSCH transmission with DM-RS (and other RS if any). The PUSCH is transmitted based on the information in the PDCCH, for example, time/frequency-domain resource including frequency-hopping, modulation, and layer. The number of layers for PDSCH transmissions is 4. HARQ re-transmission is supported for PUSCH transmissions as mentioned in Section


    Joni Tyagi

    5G PDCCH and 5G PDSCH

    5G PDCCH is used to carry Downlink Control Information (DCI), and following types of DCI are supported in NR.
    *  PDSCH assignments to convey TB(s) to a certain UE, including time/frequency-domain resource information
    *  PUSCH grants for a certain UE to transmit a TB, including time/frequency-domain resource information
    *  Slot format indication, where how each of symbols within a slot is indicated
    *  Pre-emption indication, which is used to inform UEs that there is no DL transmission on the informed time/frequency-domain resources
    *  UL transmit power control (TPC)
    *  Each device monitors a number of PDCCHs, typically once per slot although it is possible to configure more frequent monitoring to support traffic requiring very low latency. Upon detection of a valid PDCCH, the device follows downlink control information contained in the PDCCH, e.g., the scheduling decision so that the device receives PDSCH (or transmits PUSCH) accordingly.
    *  The PDCCHs are transmitted in one or more control resource sets (CORESETs). A CORESET spans overdone, two or three OFDM symbol(s) in time domain and over a configurable bandwidth in the frequency domain. This is needed in order to handle devices with different bandwidth capabilities and also beneficial from a forward-compatibility perspective. One control channel element (CCE) is defined as 6 resource element groups (REGs), where 1 REG is composed of 12 resource elements (REs). In a CORESET, a PDCCH with DM-RS can be mapped on one or more CCEs as shown in Figure. Different number of CCEs (aggregation level) provides different coding rate for the control channels.
    There are different formats for DCI transmitted on a PDCCH as shown in DCI Table. A UE monitors one or more PDCCH candidates for DCI with CRC scrambled by a certain RNTI in PDCCH common search space (CSS) set and/or UE-specific search space (USS) set. DCI format is distinguished by the PDCCH payload size and the RNTI scrambling the CRC.
    pdcch 5g pdcch pdsch 5g pdsch lte pdcch lte pdsch dci formats dci 0 pdcch in lte pdsch in lte pdcch lte dci formats in lte pdsch lte pdsch 5g pdcch 5g lte dci format 5g nr pdcch pdcch format physical downlink shared channel pdcch in 5g pdcch order in lte pdsch and pdcch 5g nr pdsch 5g nr dci format lte dci format 0
    General description of NR PDCCH

    NR DCI formats

    DCI format
    DCI format 0_0
    Monitored on CSS or USS
    Scheduling PUSCH
    DCI format 0_1
    Monitored in USS
    Scheduling PUSCH
    DCI format 1_0
    Monitored in CSS or USS
    Scheduling PDSCH
    DCI format 1_1
    Monitored in USS
    Scheduling PDSCH
    DCI format 2_0
    Monitored in CSS
    Indicating slot format for slot(s)
    DCI format 2_1
    Monitored in CSS
    Indicating pre-emption of DL resource
    DCI format 2_2
    Monitored in CSS
    Group-TPC command for PUSCH/PUCCH
    DCI format 2_3
    Monitored in CSS
    Group-command for SRS

    PDSCH is used to transmit one or two transport blocks (TBs). A DCI in a PDCCH can assign a PDSCH transmission with DM-RS (and other RS if any). The PDSCH is decoded based on the information in the PDCCH, for example, time/frequency-domain resource, modulation, and layer. PDSCH transmissions are processed with durations from 2 to 14 symbols. The number of layers for PDSCH transmissions is 8. HARQ feedback/retransmission is supported for PDSCH transmissions as mentioned in HARQ Post.


    Jitendra Kumar

    RAP(Random Access Procedure)
    Random Access procedure is essential part of for LTE protocol communication and used for getting the grant of Uplink resources for sending RRC message first time so that UE will attached to Network. So Here I tried to provide you RAP step wise step.
    lte random access procedure, random access procedure, lte random access, random access, 5g random access, 5g random access procedure
    RA Procedure Messages with Timers

    1.     UE MAC(refer Ans 1) select a preamble out of the available 64 preamble randomly(0-64) either contention based or Non contention Based.
    2.     UE MAC gives this preamble to UE physical for dispatch.
    3.     UE MAC tells UE physical about which PRACH resource(refer Ans 23) should be used for preamble sending.
    4.     UE Phy transmit the preamble on the selected PRACH resources.
    5.     Before Transmission UE physical calculate RA-RNTI (refer Ans 36).
    6.     eNB physical received preamble on PRACH resource and calculate RA-RNTI first.
    7.     eNB phy forward the preamble to eNB MAC.
    8.     eNB MAC allocate UL resource for the UE and this information forwarded to UE.
    9.     eNB MAC prepares a message called RAR(Random Access Response) with the following detail:
    a.     Preamble ID
    b.     PUSCH PRB
    c.     T-C-RNTI
    d.     Timing Advance
    lte random access procedure, random access procedure, lte random access, random access, 5g random access, 5g random access procedure

    10.  This RAR must be sent to UE on PDSCH channel by reserving PRB.
    11.  eNB MAC allocate a PRB for the UE on PDSCH and gives these details [RAR+PDSCH PRB] to eNB physical.
    12.  First eNB phy have to send the PDSCH PRB reservation detail to UE on the PDCCH channel against RA-RNTI.
    13.   eNB PHY pack RAR info on PDSCH PRB and transmit it.
    14.  UE PHY always listening to PDCCH to get to know that there is any PRB allocates against his RA-RNTI on PDSCH.
    15.  UE PHY download the specified PRB and decode the info and send it to UE MAC.
    16.  UE MAC received RAR which contain many detail .
    17.  UE MAC verify the preamble id if matched than UE MAC decided to send “msg3”.
    18.  “msg3” is nothing but a RRC connection request message.
    19.  UE MAC send msg3 to UE PHY along with PUSCH PRB used for transmit.
    20.  Also MAC tells physical layer about how much timing advance must be applied before Tx.
    21.  UE PHY Tx “msg3” by coding into PUSCH PRB indicated.
    22.  eNB PHY received this and send to eNB MAC.
    23.  eNB MAC will perform the below task:
    a.     Send ACK in the name of CRI(refer Ans 19) to UE that I have received msg3.
    b.     Send msg3 to higher layer.
    24.  eNB reserve a PRB for the UE on the PDSCH against T-C-RNTI to send CRI and send it.
    25.  UE MAC compare the CRI received with Tx msg3, if equal than RAP is successful otherwise failed.

    5GC Architecture

    Joni Tyagi

    The 5G SA Core architecture is describe in the following figure.

    5G Core Architecture, 5g core, 5g core network, 5g core network architecture
    The SA Architecture
    * The SA architecture can be seen as the "full 5G deployment", not needing any part of a 4G network to operate.
    * The NR base station (logical node "gNB") connects with each other via the Xn interface, and the Access Network (called the "NG-RAN for SA architecture") connects to the 5GC network using the NG interface.
    * The continuation of this section refers to the SA architecture, the NSA being addressed in a subsequent, dedicated, section.

    Overview of the Core Network

    * In the SA deployment option, the 5G System (5GS) is composed of the User Equipment, the Access Network (including the "New Radio" or NR) and the Core Network (5GC or 5GCN).
    * The service requirements, as presented in the previous clause, were used as a basis to define the architecture. The architecture specification (also called, Stage 2) started with a preliminary study in TR 23.799, also called "NextGen TR", before being fully specified in TS 23.501, TS 23.502 and TS 23.503.
    * The 5GC architecture relies on a so-called "Service-Based Architecture" (SBA) framework, where the architecture elements are defined in terms of "Network Functions" (NFs) rather than by "traditional" Network Entities. Via interfaces of a common framework, any given NF offers its services to all the other authorized NFs and/or to any "consumers" that are permitted to make use of these provided services. Such an SBA approach offers modularity and reusability.
    * The basic (SA, non-roaming) 5G System architecture is shown below (figure introduced by the editor):
    5G Core Architecture, 5g core, 5g core network, 5g core network architecture
    Overview of the 5G System architecture
    At this stage, only the following essential Network Functions and elements are highlighted here:

    -    The User Equipment (UE);

    -    The (Radio) Access Network [(R)AN];

    -    The User Plane Function (UPF), handling the user data;

    -    The (external) Data Network (DN);

    -    Some remarkable Network Functions (NFs):

    -    The Application Function (AF), handling the application(s);

    -    The Access and Mobility management Function (AMF), that accesses the UE and the (R)AN;

    -    The Session Management Function (SMF) that accesses the UPF.

    The other NFs are introduced later.

    * The SBA (Service Based Architecture) approach enables a virtualized deployment. Indeed, a Network Function instance can be deployed as fully distributed, fully redundant, stateless and/or fully scalable. Several Network Function instances can be present within a same NF set. Conversely, the services can be provided from several locations.
    * In other words, when the services of a specific NF are invoked, this virtualization enables to route the UE's messages to any capable entity (within a pre-defined set of equivalent NFs).
    * This provides resiliency: any specific instance of the NF can e.g. be turned off for planned maintenance, and there will be auto-recovery without any service disruption.

    Overview of the Access Network

    As a first approach, the architecture of the 5G AN is extremely simple since it consists in one single entity, the gNB, which connects to the 5G CN via the NG interface. It may also connect to another gNB via the Xn interface and/or to the 4G's eNB via the X2 interface, as shown below in the editor-proposed picture inspired from TS 38.401 and TS 38.420. It also connects to the UE via the NR interface, not shown on the figure. Note that this AN architecture is rather similar in its principle to what was developed for LTE with the eNB, as can be seen in TS 36.401.
    Overview of the AN interfaces

    References for 5GS

    The main specifications for the 5G System are:
    [1]     TS 23.501, "System Architecture for the 5G System"
    [2]     TS 23.502, "Procedures for the 5G System"
    [3]     TS 23.503, "Policy and Charging Control Framework for the 5G System"
    [4]     TR 23.799 "Study on Architecture for Next Generation System"
    [5]     TS 38.401 " NG-RAN; Architecture description"
    [6]     TS 38.420 " NG-RAN; Xn general aspects and principles"
    [7]     TS 36.401 "Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Architecture description"


    Our Team

  • Joni TyagiMaster / Computer Science
  • Jitendra KumarMaster / Wireless Network
  • Priya TyagiMaster / Web GUI Designer