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  • LTE MAC Layer Interview Questions and Answers

    1. What is Full Form of Mac Layer?, Out of 3 Layer [L1,L2,L3], where it lies?
    2. What is the Main function of MAC Layer in LTE?
    3. How do you know that how many RAPIDs are there and length of the RAR?
    4. How UE Mac know that the received message is RAR?
    5. How many times UE1 tries to re-transmit Preamble if its preamble information is not present in received RAR Msg?
    6. What is the timer value of receiving RAR Message?
    7. What is name of RNTI's in which preamble sent and RAR Received?
    8. What is contention resolution identity?What UE get information after receiving CRI?
    9. What is the difference between Mac Transport Block and Physical Layer generated Codeword?
    10. How to determine Transport Block size?
    11. Define Mac Protocol Design?
    12. If Mac Pulling Data from 4 Logical Channel and make a Transport Block [TB], then How many Sub-Header we have?
    13. Why Timing Advance not dealing by Physical layer in Transmission?
    14. What is delta Value? Why delta value use in Mac Layer?
    15. What is Truncated BSR?
    16. UE in connected state, Now UE Required Uplink Resource to transmit data after a long time [Long DRX], So UE will do?
    17. In Connected State does UE send MSG3 [RRC Connection Request]? if yes Which RNTI's against?
    18. What is DRX and DRX active period? What channels does it monitor in active period?
    19. What is MAC-ContentionResolutionTimer – What is the start and end activity?
    20. In Logical Channel Prioritization, what is PBR, GBR and BSD?
    21. What is HARQ RTT Timer?
    22. What is msg3 buffer?
    23. What is PRACH Resource Index?
    24. What is ra-PRACH-MaskIndex?
    25. What are the Logical Channels carried through HARQ?
    26. What are the Logical Channels NOT carried through HARQ?
    27. What are the Physical Channels Terminate at MAC/Physical boundary and are irrelevant to the upper layers?
    28. What are the Logical channels through which PBCH is carried through?
    29. What are the Logical Channels Carried by UL-SCH and DL-SCH?
    30. What Logical channels are carried by PDCCH and PUCCH Physical Channels?
    31. Which entities and situations and when do they initiate MAC RA Procedure? List them.
    32. When is your Temporary C-RNTI gets converted to C-RNTI? How many bits is it?
    33. How many RA Preambles are there? Why some of them are reserved by eNB?
    34. What is the RA-Preamble-Group A and B? What is the difference?
    35. While UE trying RA, if paging & Reserved-preamble comes from eNB, will UE abandon the current RA and restart?
    36. RA-RNTI = 1+t_id+10*f_id. Explain what is t_id and f_id and their possible value range?
    37. What are the types of RAR?
    38. How do you know how many RAPIDs are there and length of the RAR?
    39. What is Backoff indicator? What is the UE action on receiving this?
    40. What is RAR window?
    41. If UE receives the RAR but not contention resolution message, within what time/mechanism it will retransmit?
    42. What are the parameters/info you get from eNB in the RAR?
    43. What is relationship between HARQ Entity and HARQ Process. What is the maximum entity and processes allowed in each UE?
    44. Why there is a dedicated MAC process for BCH?
    45. What is the maximum time a UE will backoff, before retransmitting the RA?
    46. What is TTI bundling? How many TTI’s can be bundled together?
    47. How much is Bj incremented each TTI and what is its maximum value in MAC?
    48. Rewrite the channels/data in the priority order which MAC considers – CCCH, any other LoCH, BSR, PHR,BSR with padding.
    49. What is SPS? Explain SPS?
    50. In what are the scenario RACH is triggered?
    51. What is RACH Procedure?
    52. What is SR? What is the use of SR? 

    Joni Tyagi

    Author & Editor


    1. after 2 year i have seen now very very useful doc , thanks a lots sir


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