H35-481 exam questions

1. Question 1

   Single answer

   A rural NR cell uses long-format PRACH preambles with a root sequence length of 839, and each cell must offer 64 preambles. From the planned cell radius, the operator has set the cyclic shift size (Ncs) to 46.

   How many consecutive logical root sequences must be reserved for this cell?

   • A

     3 root sequences

   • B

     4 root sequences

   • C

     18 root sequences

   • D

     2 root sequences

   Reveal answer

   Correct answer

   • B

     4 root sequences

2. Question 2

   Single answer

   An operator's TDD NR sites near a border area begin showing raised uplink interference in the same week that another network starts service on an adjacent carrier in the same band. Observations:

   - The interference is present throughout the day and is highest when the other network's traffic peaks.

   - Only the sites closest to the other network's cells are affected, and the effect falls off quickly with distance.

   - It is concentrated in uplink symbols that coincide with the other network's downlink transmission.

   - There is no night-time peak and no dependence on the operator's own traffic.

   What is the root cause?

   • A

     An external narrowband transmitter operating in the border area

   • B

     Passive intermodulation triggered by the operator's own downlink load

   • C

     Atmospheric ducting from the other network's distant base stations

   • D

     Misaligned TDD frame structures between the two operators' networks

   Reveal answer

   Correct answer

   • D

     Misaligned TDD frame structures between the two operators' networks

3. Question 3

   Single answer

   One sector of an FDD NR site shows its uplink noise floor raised by several dB across the whole uplink band during the day, returning to normal at night. Other sectors of the site and the neighboring sites are clean. At 03:00, with no UEs on the cell, the engineer enables simulated full downlink load on this sector: the uplink noise floor rises by the same amount, and disabling the load restores the quiet level.

   What is the most likely cause?

   • A

     Passive intermodulation in this sector's feeder or antenna path

   • B

     An external transmitter occupying a fixed block of PRBs in the uplink band

   • C

     Uplink interference from UEs served in the neighboring cells during busy hours

   • D

     Remote interference from distant base stations carried by atmospheric ducting

   Reveal answer

   Correct answer

   • A

     Passive intermodulation in this sector's feeder or antenna path

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5. Question 4

   Single answer

   A cell is planned with PCI 401. During a drive test, the engineer checks which identity the UE obtains from each synchronization signal to reconstruct that PCI.

   Which decomposition is correct?

   • A

     N_ID(2) = 1 from the PSS and N_ID(1) = 133 from the SSS

   • B

     N_ID(1) = 2 from the PSS and N_ID(2) = 133 from the SSS

   • C

     N_ID(2) = 2 from the PSS and N_ID(1) = 133 from the SSS

   • D

     N_ID(2) = 2 from the SSS and N_ID(1) = 133 from the PBCH

   Reveal answer

   Correct answer

   • C

     N_ID(2) = 2 from the PSS and N_ID(1) = 133 from the SSS

6. Question 5

   Single answer

   An operator is dimensioning fronthaul for 64T64R massive MIMO AAUs on 100 MHz carriers. A consultant notes that a classic CPRI design would need far more fiber capacity than the eCPRI design the vendor proposes for the same AAUs.

   What explains the difference?

   • A

     eCPRI compresses the NG-U user-plane traffic before it enters the fronthaul, while CPRI does not

   • B

     CPRI carries IQ per antenna path; eCPRI, with part of the PHY in the AAU, carries layers

   • C

     CPRI must carry each carrier on its own fiber, whereas eCPRI can multiplex carriers on one

   • D

     eCPRI removes the fronthaul time-synchronization overhead that CPRI must carry

   Reveal answer

   Correct answer

   • B

     CPRI carries IQ per antenna path; eCPRI, with part of the PHY in the AAU, carries layers

7. Question 6

   Single answer

   Mobility statistics for the relation cell A to cell B, both on the same NR carrier, show a rising drop count. Call traces for the drops show the UE sending an A3 measurement report only moments before losing the link, radio link failure in cell A, and RRC re-establishment in cell B. A drive test confirms that cell B has been several dB stronger than cell A for a few seconds along that road before each drop. Cell A's other neighbor relations perform normally.

   Which adjustment addresses this pattern?

   • A

     Raise the cell individual offset of cell B in cell A's neighbor relation

   • B

     Raise the hysteresis on the A3 event in cell A for handover toward every neighbor

   • C

     Lengthen the time-to-trigger of the A3 event used for handover from cell A to cell B

   • D

     Lower the individual offset of cell B in cell A's neighbor relation

   Reveal answer

   Correct answer

   • A

     Raise the cell individual offset of cell B in cell A's neighbor relation

8. Question 7

   Single answer

   A new sector is being added on an NR carrier where uplink reference-signal sequence groups follow PCI mod 30 (no group hopping and no separately configured sequence identity). Three existing cells overlap its planned footprint:

   - PCI 120: strong overlap across most of the sector

   - PCI 187: strong overlap across most of the sector

   - PCI 263: weak overlap at the far cell edge only

   The three neighbors already use all three mod-3 values, so one mod-3 sharing is unavoidable. None of the candidates is used in the neighbor-of-neighbor set.

   Which PCI is the best choice for the new sector?

   • A

     PCI 353

   • B

     PCI 452

   • C

     PCI 391

   • D

     PCI 405

   Reveal answer

   Correct answer

   • B

     PCI 452

9. Question 8

   Single answer

   An FR2 cell transmits eight SSBs per burst, each on a different beam. An idle UE at the cell edge detects SSB index 5 as its strongest beam and begins random access. The gNB must know which beam to use for the random access response before the UE has any RRC connection.

   How does the gNB learn the UE's best beam at this stage?

   • A

     The UE reports SSB index 5 in a CSI report on the PUCCH before random access

   • B

     The gNB measures an SRS that the idle UE transmits on each of the eight beams

   • C

     The UE sends its preamble in a PRACH occasion associated with SSB index 5

   • D

     The UE reports SSB index 5 in its Msg3 and the gNB then selects that beam

   Reveal answer

   Correct answer

   • C

     The UE sends its preamble in a PRACH occasion associated with SSB index 5

10. Question 9

    Single answer

    Each site in a town has co-sited NR cells on a 3.5 GHz carrier and a 2.1 GHz carrier with nearly identical footprints. The draft plan gives every 3.5 GHz cell TAC 4101 and every 2.1 GHz cell TAC 4102, each as a separate tracking area. Idle UEs routinely reselect between the two layers as indoor coverage varies. The core assigns each UE a registration area containing only the TAC of the cell where it last registered.

    What is the main problem with this TAC plan?

    • A

      Paging reaches only one layer, so a UE camped on the other layer misses it

    • B

      Separate TACs stop the two layers being configured as each other's neighbors

    • C

      Co-sited layers need TACs that differ in mod 3 to keep their PSS apart

    • D

      Every layer reselection on the same spot crosses a TA border and triggers a registration update

    Reveal answer

    Correct answer

    • D

      Every layer reselection on the same spot crosses a TA border and triggers a registration update

11. Question 10

    Single answer

    A UE was moved to RRC_INACTIVE by its serving gNB, which kept the UE context and the UE-associated NG connection. The UE then reselected to a cell of a different gNB inside the same RAN notification area and sent no signaling. Downlink data for the UE now arrives at the UPF.

    What happens next in normal operation?

    • A

      The anchor gNB receives the data and triggers RAN paging across the RAN notification area

    • B

      The new gNB receives the data directly, because the UE registered there when it reselected

    • C

      The AMF pages the UE across its tracking area list, because the core treats the UE as idle

    • D

      The UPF discards the data until the UE completes a new registration and PDU session setup

    Reveal answer

    Correct answer

    • A

      The anchor gNB receives the data and triggers RAN paging across the RAN notification area

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