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  • 5G Interview Questions Answers 37-45

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

    Ans. URLLC stands for Ultra Reliable Low Lentancy Communication which a one of the effective technology introduced by 3GPP in Release-15.
    URLLC have new techniques that’s supporting new requirements from vertical industries such as autonomous driving for the automotive industry, remote surgery for eHealth and cloud robotics for Industry 4.0. All applications demand
    Improved guarantee latency to be 1ms or less
    Improved reliability
    Higher availability
    Higher security
    efficient control and data resource sharing

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

    Ans. mMTC stands for Massive machine type communications. The use of mMTC is to targets the cost-efficient and robust connection of billions of devices without overloading the network. Critical success factors include
    Coverage
    Cost efficiency
    Low power consumption
    Longtime availability

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

    Ans. Enhanced mobile broadband (eMBB) focuses on supporting the ever-increasing end user data rate and system capacity. To fulfill this demand, eMBB introduces two major technology enhancements:
    Shift of frequency spectrum to cmWave and mmWave range to achieve much higher bandwidth allocations
    Advanced antenna array that includes tens or even hundreds of TX/RX antenna elements to enable massive MIMO and beamforming

    Q40. Bandwidth range use in NR?

    Ans. 5G NR (New Radio) has been developed to operate in two distinct bands; radioWave sub-6 GHz , and mmWave 24GHz to 52GHz. Despite actually running into the 7 GHz band, FR1 continues to be commonly referred to as the "Sub-6 GHz" band.
    FR1: 410 to 7125 MHz
    FR2: 24250 to 52600 MHz
    Each band may operate in either FDD or TDD duplex mode.
    Reference:
    (3GPP 38.104-5.2.1 FR1), (3GPP 38.104-5.2.2 FR2)

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

    Ans. MCG stands for Master Cell Group, in ENDC architecture the MCG node (MN) is LTE and SCG node (SN) is NR.
    * Please note that “node” here simply refers to a base station. Both nodes have a direct interface with the existing core network (EPC).
    * only master node has the direct interface towards EPC in the control plane that carries the signaling traffic between the mobile device and the core network.
    * The LTE node is responsible for maintaining the connection state transitions, handling the connection setup/release, and initiating the first-time secondary node addition, that is, the EN-DC setup.
    * The bearer became hera called MCG bearer.

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

    Ans. SCG stands for Secondary Cell Group, in ENDC architecture the SCG node (SN) is NR and MCG node (MN) is LTE.
    * SCG is a radio bearer served by the gNB.
    In Control plane(SCG): SRB use is (SRB3): it is Direct SRB between the secondary node and the mobile device by which secondary node RRC messages are sent.
    In User plane SCG: DRBs – Direct DRBs: with only one lower layer configuration, either corresponding to LTE or NR lower layers.
    Bearers terminated at the SN and using only the secondary node lower layers.

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

    Ans. Split bearer is one of the finest technology which is introduced in 5g.
    * each node MN and SN have a additional bearer called Split bearer which is carry LTE as well as NR data and direct forward to relevant nodes.
    Now a question comes into mind how it’s happen so without any doubt let’s resolve this issue. Please refer below image.
    What-is-Split-Bearer-in-5G-NR
    In above picture if you seen option3 and 3A MN receive data from epc and have a split bearer also that’s have NR data which is directly forwarded to SN node via X2-U interface.
    In option 3x SN node (en-gNB) receive LTE data from epc and send it to LTE MN node (eNB) via X2-U interface.
    Now a another question here how layer works here: The answer is in below picture
    What-is-MCG-Split-Bearer-in-5G-NR
    The MCG split bearer PDCP carry’s the LTE and NR data. LTE data forward to LTE RLC and NR data forwarded to NR RLC layer.
    Same scenario follow in SCG split bearer, the SCG split bearer PDCP layer also carry’s LTE and NR data which is also forwarded to respected RLC.

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

    Ans Please refer the Q43 how data forward in MCG SCG and split bearer in 5g.

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

    Ans. MN stands for Master Node and SN stands for Secondary Node. In endc MN is LTE node (eNB) and SN is NR Node (en-gNB) both’s are connected to EPC.

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