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    Showing posts with label RF Interview Questions. Show all posts

    LTE ISI (INTER SYMBOL INTERFERENCE)

    Jitendra Kumar

    LTE INTER SYMBOL INTERFERENCE


    When Interference occurs between two symbols because of straight path and reflected path it’s called ISI.
    LTE-INTER-SYMBOL-INTERFERENCE

    ISI STRAIGHT VS REFLECTED WAVE:


    ISI-STRAIGHT-VS-REFLECTED-WAVE
    ISI SOLUTIONS:
    ** ISI OLD SOLUTIONS:

    (1) Rake Receiver:

    It’s a Multi Finger antenna which is capable for receiving and separating multi directional waves.
    Advantages:
    ·         No ISI any more.
    ·         Due to Multipath reception diversity increases the signal decoding success rate.
    Disadvantage:
    ·         Expensive due to use of Rake receiver
    ·         High Power consumption required for multi signal processing.

    (2) ISI FACTORS

    ·         Delay Time: If delay time increase than ISI will increase and vice versa.
    ·         Bandwidth: If Bandwidth increase than ISI will increase and vice versa.

    ** ISI NEW SOLUTIONS:

    (1) Sub Carrier Techniques:

    In this techniques each sub-carrier size should be 15 kHz Bandwidth because if lower the bandwidth so ISI also less.
    LTE Sub-carrier: Scalable Bandwidth in below table:
    lte-Subcarrier-Techniques
     LTE Cyclic Prefix Method:
    Add a waste piece at a start of a symbol so that it can absorb the shock of the impact.
    ·         Short CP: 14000 symbols per second per sub carrier and remaining 1000 symbols are used as a cyclic prefix.
    ·         Long CP: 12000 Symbols per second per sub-carrier.

    RF Interview Questions Part 2

    Joni Tyagi
    LTE-RF-Interview-Questions 

    Q01. What is LTE and Full-form of LTE and it’s functionality?
    Q02. LTE Architecture?
    Q03. What is the meaning of Interface? What is the interface name between UE to EnodeB?
    Q04. Need to remember UE to PDN all interfaces names?
    Q05. When a UE perform cell re-selection in signalling (idle) then X2 which interface is using?
    Q06. When a UE perform handover in connected state, then X2 which interface is using?
    Q07. What is name of Application Protocol & Transport Protocol in S1-MME interface?
    Q08. What is the name of Application Protocol & Transport Protocol in S1-U interface?
    Q09. Which protocol is using between MME to S-GW interface? Name of transport protocol of same interface?
    Q10. Which protocol is using in MME to EIR or HSS and why?
    Q11. Name of the interface present in MME to MME, and protocol name?
    Q12. What is the name of Protocol using in P-GW to OCS and OFCS?
    Q13. How many famous LTE technique? And how many types of badwidth use in LTE?
    Q14. What is Resource Block (RB)?
    Q15. How many events are in LTE ?
    Q16. How many System Information Blocks (SIBs) are present in LTE?
    Q17. What kind of information SIBs carry?
    Q18. What is MIB? Is MIB also a part of System Information? If yes then what kind or information it carrying?
    Q19. What is OFDM symbol? How many symbol present in a subframe in Normal & Extended?
    Q20. How many Channels are used in LTE system?

    RF Interview Questions Part 1

    Joni Tyagi
    RF-Interview-Questions 

    Q00. Define RF? And use of RF in Wireless Technology?
    Q01. Why we need 4G if 3G working well?
    Q02. What is the Limitation of 3G?
    Q03. What are the changes occurred (architecture) in LTE from 3G?
    Q04. Difference between Bandwidth and Frequency?
    Q05. Difference between band and bandwidth?
    Q06. if 900 band have 5Mhz or 20Mhz bandwidth and 2300 band also have 5Mhz or 20Mhz bandwidth then what is effect on coverage would be happen?
    Q07. What is Throughput? How Throughput calculate in LTE?
    Q08. What are the Conditions of Handover in LTE?
    Q09. What is ANR?
    Q10.Whatis interference and how it will overcome?
    Q11. What is CINR?
    Q12. What is Rank Indicator in MIMO?
    Q13. How many Types of Towers have in Radio Networks?
    Q14. What is PCI? How to calculate PCI in LTE? Total PCI present in LTE?
    Q15. What is PCI Collision?
    Q16. What do mean by RSRP, RSRQ and RSSI in LTE? And what kind of information they carry?
    Q17. What is SWAP? And how many type of SWAP’s are in LTE?
    Q18. How many types of Antenna’s are using in network?
    Q19. What is Front loop and Back loop Coverage of Antenna’s?
    Q20.Whatis Antenna Gain? How it affect on Coverage?
    Q21. How many types of TILT present in Antenna and their jobs in network coverage?
    Q22. How many Testing Tools are used for network testing?
    Q23. How many different-2 types of testing doing for network testing?
    Q24. What is call initiation (connect) duration of CSFB and Volte?
    Q25. What is Microwave? Why it is used in network?
    Q26. How to check microwave visibility? And what is hop-to-hop?
    Q27. How to reduce interference in LTE?
    Q28. What is difference between db power and dbm power?
    Q29. What is ping? And Latency required in LTE?
    Q30.Whatis KPI?
    Q31. How many types of KPI used in LTE?
    Q32. What is Counter? And how many types of counter in LTE?
    Q33. What is LAC, RAC and TAC in network? Where these required?
    Q34. What is difference between Soft reset and Hard reset?
    Q35. What is reserve mode and why it use?
    Q36. Which Access Class SIM is required to latch on reserved network?
    Q37. In FDD and TDD? Which technique has more Interference?
    Q38. In FDD and TDD? Which technique gives more throughputs?
    Q39. What is Alarm? And what kind of information they provide to RNO?
    Q40.Name of some famous Alarm monitoring Tools?