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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


    Joni Tyagi


    5G Enhanced Mobile Broadband

    Joni Tyagi

    Enhanced mobile broadband (abbreviated as eMBB) is one of three primary use cases that the 3rd Generation Partnership Project (3GPP) telecommunications standards group initially defined for the new 5G New Radio (NR) standard.

    3GPP extensively used the eMBB use case with Machine Type Communication (mMTC) and Ultra-Reliable Low-Latency Communications (URLLC) to determine what type of functionality 5G NR is needed.

    As its name suggests, eMBB reflects the growth in mobile broadband use cases supported by the 4G Long Term Evolution (LTE) standard.

    eMBB use cases 
    – including improved automobile infotainment.
    – improved Wi-Fi services. 
    – mobile high-definition video streaming.
    – 3D multi-player games.
    – all enabled by 5G NR's faster data transmission speeds.
    – lower latency.
    – greater capacity and other performance improvements.
    – High data rate and high traffic volume.

    NR 5G RRC Overview

    Joni Tyagi

    NR 5G RRC Overview

    The Radio Resource Control (RRC) state machine for New Radio (NR) is shown in Fig.

    A UE starts from RRC Idle mode when it first camps on a 5G cell. for example. This can happen immediately after the device is switched on, or it can happen after inter-system cell reselection from LTE. A UE makes the transition from RRC idle to RRC Connected by completing the RRC setup process. An RRC connection is a logical connection between the UE and the base station.

    In RRC connected mode a UE is assigned one or two C-RNTI (Cell Radio Network Temporary Identifiers). C-RNTI is used for addressing UEs when it require resource allocation from cell. A single C-RNTI is allocated when the UE is connected to a single base station. Two C-RNTIs are allocated when UE is connected using Multi-RAT Dual Connectivity (MR-DC)

    In RRC connected mode a UE is configured with at least one Signaling Radio Bearer (SRB) and usually one or more Data Radio Bearers (DRB). SRBs can be used to transfer signaling messages between the UE and the base station. Signaling messages can be related to the RRC signaling protocol or the non-access striatum (NAS) signaling protocol. The base station uses the NG Application Protocol (NGAP) to transfer NAS messages to and from the AMF. The DRB can be used to transfer application data between the UE and the base station. Base station Uses a GTP-U tunnel to transfer data to and from the UPF.

    UE has to change to RRC connected mode to register with the network, i.e. to change from RM-deregistered to RM-registered. Once a UE is registered with the network the UE will normally remain RM-registered, regardless of the RRC state. The registration process allots the UE with a temporary identity known as 5G-S-TMSI. Use of temporary identification instead of permanent identity, e.g. IMSI helps to improve security.

    UE has to change to CM-IDLE to CM-connected, the UE must change to RRC connected mode. UE is returned to the CM-IDLE Whenever a RRC connection is released. The UE remains in CM-connected until change it state from RRC Connected to RRC idle.

    A UE change from RRC Connected to RRC Inactive using the RRC Release procedure. The RRC release message includes a 'suspendConfig' parameter structure that indicates that the UE is being moved to RRC inactive instead of RRC idle. The NG signaling connection between the base station and the AMF is maintained while the UE RRC is inactive. In addition, GTP-U tunnels are maintained between the base station and UPF (one GTP-U tunnel per PDU session). UE context is also maintained by both the network and the UE

    The RRC Idle state allows the UE to return to RRC Connected and begin transferring application data or signaling messages with minimal latency. For RRC-associated signaling load is reduced relative to inactive RRCs because the UE context is already established. The RRC idle state allows the UE to reduce the battery power consumption associated with the RRC. This can be achieved with longer DRX cycles and does not require channel quality reporting.

    The AMF can request the base station to provide notifications when the UE moves between RRC connected and RRC inactive. This request can be included in the ngap 'Initial context setup request' or 'UE context modification request' messages. The base station subsequently provides updates using the NGAP 'RRC inactive Transition Report'. The AMF can use this information to adjust its observation timer with respect to the RRC status of the UE. For example, if the AMF knows that the UE is connected to the RRC it can expect a rapid response to any downlink transaction and therefore it can implement a relatively short supervision timer. If the AMF knows that the UE RRC is inactive it can expect a less rapid response to any downlink transactions as those transactions must be paginated in the UE before forwarding to the UE. The amf can thus apply a long observation timer to the UE that is RRC inactive.

    Switching between NR RRC CONNECTED <-> INACTIVE <-> IDLE State Change


    UE is in CM-CONNECTED state
    UE stores Access Stratum context
    UE reads System Information
    UE monitors the Paging by PDCCH DCI using the P-RNTI
    UE is addressed using C-RNTI allocated by gNodeb
    Connected Mode DRX can be configured
    Mobility is based upon handovers
    AMF maintains NG signalling connection with gNodeb
    UPF maintains GTP-U tunnels with gNodeb
    Radio Access Network is responsible for UE reachability
    Uplink and downlink data can be transferred
    UE reports Channel State Information (CSI)
    UE monitors Control Channels for Resource Allocations
    UEs supporting CA, use of one or more SCells, aggregated with the SpCell, for increased bandwidth
    UEs supporting DC, use of one SCG, aggregated with the MCG, for increased bandwidth


    switching between RRC CONNECTED and RRC INACTIVE state
    UE stores Access Stratum context
    UE reads System Information
    UE monitors the Paging by PDCCH DCI using the P-RNTI
    UE monitors the PCCH for CN paging using the 5G-S-TMSI and RAN paging using the I-RNTI
    UE applies DRX for paging
    Mobility is based upon Cell Reselection
    AMF maintains NG signalling connection with gNodeb
    UPF maintains GTP-U tunnels with gNodeb
    Radio Access Network is responsible for UE reachability
    UE Performs RNA updates
    gNodeb knows the UE location with a resolution of a RAN Notification Area (RNA)
    RRCRelease  with SuspendConfig
    <Table 1.>
    <Table 2.>
    <Table 3.>

    Signalling used to resume an RRC Connection at a Target eNodeb

    Figure 112. shows the signaling call flow used to resume the RRC connection at a Target gNodeb. UE initiates the process by sending either RRC Resume Request or RRC Resume Request 1. The contents of these messages are presented in Tables No. 2 or 3. The selection is based on the 'useFullResumeID' flag present in SIB1. Both messages contain I-RNTI, MAC-I and cause values. The MAC-I information element is used to authenticate the UE before the UE is re-enter to RRC Connected at source gNodeb.
    Signalling used to resume an RRC Connection at a Source eNodeb
    <Figure 112>


    UE is in CM-IDLE state
    UE reads System Information
    UE monitors the Paging by PDCCH DCI using the P-RNTI
    UE monitors the PCCH for CN paging using the 5G-S-TMSI
    UE applies DRX for paging
    Mobility is based upon Cell Reselection
    Core Network knows UE location with resolution of Registration Area (one or more Tracking Areas)
    UE performs Registration Area updates with Core Network

    NR RRC Interaction with LTE RRC

    NR RRC is involved not only in NR but also in other radio access technology. The interaction of NR RRC and LTE RRC can be represented as follows. Here are the things to note
    1. when UE in idle state it's NR RRC IDLE can reselect to EUTRA RRC IDLE and EUTRA RRC IDLE can reselct to NR RRC IDLE.
    2. But, when UE is in NR RRC INACTIVE state, it can select to EUTRA RRC IDLE state, but EUTRA RRC IDLE state cannot reselect to NR RRC INACTIVE state.
    NR_NGC Interaction with LTE_EPC

    5G QoS

    Joni Tyagi

    Quality of Service (QoS) with 5GC Quality

    A flow in this context is a QoS flow: all Packet Data Units (PDUs) that will receive the same QoS facility in the network, are used to classify PDUs into QoS flows. Filters can be provided with 5G policy control or can be pre-configured in 5G cores.

    QoS Model General Overview

    The 5G QoS model supports the QoS flow-based framework. The 5G QoS model supports both QoS flows that require guaranteed flow bit rates and QoS flows that do not require guaranteed flow bit rates. The 5G QoS model also supports reflective QoS.
    QoS architecture in NR and NGCN

    EPC vs NGCN – Bearers vs Flows
    QoS flow is the best granularity of QoS resolution in a PDU session.
    QoS flow is the best granularity of QoS resolution in a PDU session. QoS Flow ID (QFI) is used to identify QoS flows in a 5G system. User plane traffic with the same QFI within the PDU session receives the same traffic forwarding treatment (eg scheduling, admission threshold). The QFI is carried in an encapsulation header on N3 (and N9), ie without making any changes to the e2e packet header. It can be applied to various types of payloads, ie IP packets, non-IP PDUs, and PDUs with Ethernet frames. The QFI will be unique within the PDU session.

    Note: Policing of user plane traffic (eg MFBR enforcement) is not considered QoS differentiation and is carried out by the UPF at SDF level granularity.

    Each QoS flow (GBR and non-GBR) is associated with the following QoS parameters:
    • 5G QoS Indicator (5QI),
    • Allocation and Retention Priority (ARP).
    Each GBR QoS flow is associated with the following QoS parameters:
    • Guaranteed Flow Bit Rate (GFBR) - UL and DL;
    • Maximum flow bit rate (MFBR) - UL and DL;
    • Notification control.
    Two methods of controlling QoS flow are supported:
    1) For non-GBR QoS flows with standardized 5QI, the standardized 5QI value is used as QFI and the default ARP is used. In this case no additional N2 signaling is required at the time of traffic when the corresponding QoS flow starts, or;

    2) For GBR and non-GBR QoS flows, all the required QoS parameters related to QFI are sent as a QoS profile to the (R) AN in the PDU session establishment or QoS flow establishment / modification

    The QoS parameters of a QoS flow are provided to the (R)AN as a QoS profile over N2 at PDU Session or at QoS flow establishment and when 5G-RAN is used at every time the User Plane is activated. QoS parameters can be pre-configured in (R) AN for non-GBR QoS flows (ie without the need to signal over N2).

    The UE classifies and marks the UL user plane traffic based on QoS rules, that is, the linking of uplink traffic to the QoS flow. These rules can be explicitly signalled over N1 (on PDU session establishment or QoS flow establishment), preconfigured in UE or implicitly derived by UE from reflective QoS. The QoS rule consists of a QoS rule identifier, the QFI of the QoS flow, and a QoS flow template (ie the set of packet filters and the associated precedence values ​​associated with the QoS flow).

    A default QoS rule is required for every PDU session. The default QoS rule shall be the only QoS rule of a PDU session which is allowed not to have a QoS flow template. If the default QoS rule does not contain a QoS flow template, the default QoS rule defines the treatment of packets that do not match a QoS flow template of a QoS rule in a PDU session.

    The SMF allocates the QFI for each QoS flow and derives its QoS parameters from the information provided by the PCF. When applicable, the SMF provides the QFI with a QoS profile containing the QoS parameters of a QoS flow to the (R)AN. The SMF provides the SDF template (i.e. the set of packet filters associated with the SDF derived from the PCF) with the SDF preference and the corresponding QFI to the UPF enabling the classification and marking of user plane traffic. When applicable, SMF generates QoS rule (s) for QoS flows by allocating QoS rule identifiers, adding QFIs to QoS flows, and setting the QoS flow template using one or more SDF templates. QoS rules are then provided to the UE to enable classification and marking of UL user plane traffic.

    For DL traffic AN can detect which flow a received packet belongs to by looking in the encapsulation tunnel header, where the UPF has marked the packet with the QoS Flow Indicator (QFI). Information about the treatment of each flow is sent from 5GCN to AN over N2.

    UE for UL traffic marks traffic with the correct QFI based on the information received from the SMF over N1 interface. The solution will also be available for Reflective QoS where the UE marks the UL traffic based on which QFI is the DL traffic corresponding to the same flow. AN informs the UE how to send PDUs over the air (which radio bearer to use).

    Each PDU session in a session establishment is associated with a default QoS profile (a set of QoS parameters).
    • The default QoS profile is usually configured in UDM and can be authorized by PCF
    • The QoS profile indicates the treatment of all PDUs transferred within the PDU session and for which the network has not indicated PDU specific treatment.
    • The PCF can modify the default QoS profile for a PDU session at any time during the session

    QoS parameters per QoS flow:

    • 5G QoS indicator (5QI)
    • Allocation and Retention Priority (ARP)
    • Maximum Flow Bit Rate
    • Guaranteed Flow Bit Rate
    • Notification control. Controls whether notification should be made if the QoS targets are no longer fulfilled for a QoS flow

    QoS parameters per PDU session

    • Aggregated session maximum bitrate (UL and DL) for all QoS flows of a PDU session that do not require a guaranteed flow bit rate.
    • Aggregated UE maximum bitrate (UL and DL) for all QoS flows and sessions of the UE that do not require a guaranteed flow bit rate.
      Evolved QoS
    • Multiplexing flow within a PDU (PDN) session tunnel
    • Flow identities indicates on the QoS profile
    • The DRB is mapped to the PDU session tunnel
    • Multiple DRBs possible per PDU session tunnel
    • The PDCP header on UL carries the Flow Id to map to DSCP on UL
    • Each packet have the DL Flow ID

    Definitions & Assumptions NextGen Core network

    Services are mapped to the Service Data Flow (SDF)

    SDF, which consists of the following, assigned QoS profile:
    • SDF priority
    • Maximum bitrate per SDF:
    • Bitrate required per SDF
    • Delivery characteristic per SDF
    • Network behavior per service data flow
    The SDF is mapped to a QoS flow and the packet is marked with a QoS flow Id
    QoS Mapping IP packets

    QoS flow, which contains the following parameters, a QoS profile is assigned:

    • QoS flow priority
    • Maximum bitrate per QoS flow
    • Bitrate required per QoS flow
    • Delivery characteristic per QoS flow
    • Network behavior per QoS flow

    The SDF of the same IP-CAN session can be considered as the SDF Aggregate

    • All SDFs should have the same QCI / ARP
    • GBR / MBR is summarized in GBF SDFs when multiplexing GBR SDFs

    SDF Aggregates are mapped to UL/DL Packet Filters/EPS Bearers

    • 1:1 relation – an SDF Aggregate uniquely defines the EPS Bearer
    • Bearer QoS profile (QCI, ARP, GBR, MBR), per-UE parameter AMBR and subscription parameter RFSP signaled over S1

    QoS Flow Id is mapped to Radio Bearers

    • N: 1 relation

    Based on pre-configured nodes, via OSS-RC

    • Standardized QCI Characteristics
    • Resource Type
    • GBR / Non-GBR
    • Packet Delay Budget (PDB)
    • Packet Loss Rate (PLR)
    • Priority
    • Priority between bearers when target PDB cannot be met (by bearers
    • competing for the same resource)
    • Other parameters set in OSS, by operator in MOM

    Marquis Interview Question Answer

    Joni Tyagi
    Q01. How you do log analysis on your day to day activity?
    Q02. How you configure ue for testing?
    Q03. What type of bugs you have find out?
    Q04. While doing analysis a bug report what analysis you get to the development team?
    Q05. What kind of analysis you have done for ex: rach, attach, re-configuration failure what kind of analysis you’re doing?
    Q06. What is ca and it’s functionality in ue conformance testing?
    Q07. Which message ue send capability report to network?
    Q08. What are the information elements present in ue capability report?
    Q09. Do you have idea about srvcc and csfb?
    Q10. What is the conditions of re-establishment?
    Q11. What is the rrc re-establishment time?
    Q12. If you send a wrong configuration than how will you know it’s a network issue or something?
    Q13. How do you find network issue?
    Q14. What is network forwarding?
    Q15. Define lab setup?
    Q16. How would you report bug to the development team?
    Q17. Define handover redirection?
    Q18. Why handover required?
    Q19. What is the irat event?
    Q20. Define c.a?
    Q21. What is the release version you currently worked on?
    Q22. Why you want to join?
    Q23. What is lte events?
    Q24. Which system simulator you are currently working?
    Q25. What you do on anite-9000?
    Q26. What is your role in your company?
    Q27. Do you have any question for me?

    HSC Interview Question Answer

    Joni Tyagi
    Q1. How a ue can search (provide) plmn list at that area where network is not available?
    Q2. Is all plmn list should be visible for all the UE’s present in a network?
    Q3. If physical layer provide all the plmn list in a geographical area then what NAS layer will do?
    Q4. If i purchase a sim card from delhi and i switch on my device into mumbai than what will be happen?
    Q5. How many PLMN id’s in a list?
    Q6. When you power on your UE and physical layer search all plmn and create a list, then how our sim verify that this is my PLMN?
    Q7. Your physical layer have own plmn list then why need to provide (plmn list) to higher layer?
    Q8. What information UE get from PSS and apart from that?
    Q9. How UE get the TS0 - - - TS19 of ofdm boundary there are 6 OFDM symbol and 7 OFDM symbol in a slot?
    Q10. What is the importance of MIB?
    Q11. We have 1024 SFN means 210 = 10bit SFN, but in MIB SFN is 8bit what is the reason?
    Q12. In physical layer how many bits are align to MIB?
    Q13. What kind of Information UE got into the RAR?
    Q14. What is the purpose to Timing Advanced?
    Q15. How enodeb calculate Timing Advanced?
    Q16. What is Contention Resolution?
    Q17. How network know that which preamble is using by which ue? How network differentite?
    Q18. What are the Attach Req ie’s?
    Q19. How many types of codec are there in LTE?
    Q20. Codec name of VOLTE and CS Domain?
    Q21. Handover happen before measurement gap or after measurement gap?
    Q22. What do you understande by MAC CE?
    Q23. Network send some update information to UE regarding update system information, so how ue know about update in SIB?
    Q24. Suppose if i have 2 device 1st is DUT and 2nd is Reference device and my both device are far 200m from enodeb then is my DUT get only 1 mbps DL speed and Reference device get 40 mbps DL speed what is wrong in my DUT?
    Q25. During handover performing what kind of Scheduling is happen? SPS or Dynamic?

    Qualcomm Interview Questions Answers

    Joni Tyagi
    Q1. Define resource allocation types in LTE?
    Q2. Why SFN mod==4 use for MIB?
    Q3. What is HARQ?
    Q4. What is Scheduling Request (SR)?
    Q5. Define BSR?
    Q6. What do you understand by MIB and SIB?
    Q7. Why PHICH comes in MIB?
    Q8. What is difference between RRCConnectionReconfiguration and RRCre-establishment?
    Q9. What is Measurement gap, and measurement object and what kind of information they will carry?
    Q10. Which DCI format use for RAR?
    Q11. Define Handover procedure?
    Q12. Define DRX information before power on?
    Q13. Define Cell Camping?
    Q14. Define LTE Events?
    Q15. How ue choose 1 Frequency out of many Frequencies broadcast by network?
    Q16. How many PHICH group in System Bandwidth?
    Q17. Why HARQ use 8 arm process?
    Q18. Define Attach Failure Causes?
    Q19. What is Fading? Type of Fading?
    Q20. How would you calculate PathLoss?
    Q21. Define Physical Layer data processing steps?
    Q22. What is PUCCH and UCI or it’s Formats?
    Q23. Define Transmission Mode? How many Transmission modes are present in LTE?
    Q24. What is sidelink? Define Sidelink mapping?
    Q25. How much experience do you have in TDD? Define TDD frame structure?
    Q26. What is DCI? How many DCI formats are present in LTE?
    Q27. What is Type0, Type1, and Type2 resource allocation in DCI?
    Q28. What is the latest Bug you have found?
    Q29. How would you report a Bug to developers? What is Bug Reporting format?
    Q30. What is DTCH message name?
    Q31. RRC send which message to NAS to get PLMN list?
    Q32. Which layer activate CA?

    Our Team

  • Joni TyagiMaster / Computer Science
  • Jitendra KumarMaster / Wireless Network