Interview questions on WLAN/WIFI/802.11

Below are typical questions which are faced in interviews, if applied for a position related to wlan development in companies such as Qualcomm, Broadcom, securify, moschip, Global Edge, Aricents, Mirafa, Graphene, Mojo Networks, Lantronix, Adtran, Votary Softech.

  1. What is WiFi?
  2. What are major differnces between 802.11 a/b/g/n?
  3. What are layers  in OSI model and where all WiFi related layers sit?
  4. What are the major differnces between Ethernet and wlan ?
  5. Data rates, modulation, throughout, range, channels supported, for each 802.11 a/b/g/n?
  6. What is the major function of LLC layer ?
  7. What all does MAC layer do in wlan point of view?
  8. What is major functional difference between PLCP & PMP?
  9. what are the services which 802.11 provide?
  10. What is CCA?
  11. Explain procedure followed while sending a packet in air using wlan ?
  12. What is CSMA-CA?
  13. What are major enhancements in 802.11n?
  14. What is MIMO ? What are benefits?
  15. Difference between short preamble and long preamble? When is each of it used?
  16. What is length of PLCP header? What fields it had?
  17. What is MPDU? What’s it format and header length?
  18. Explain fields in MAC header
  19. What are 4 address fields in MAC header convey? How are they interpreted?
  20. Significanceof each field in MAC header?
  21. What are MPDU, PPDU, PSDU, MSDU, AMSDU, AMPDU, SDU, PDU ?
  22. What is QOS ? When is it introduced in wlan ? How is it achieved ?
  23. What all are the fields of QOS control field of Mac header?
  24. What are different frames in Wlan ?
  25. Differences between Data frames, Management frames, Control frames ?
  26. What are action frames and their significance? Types?
  27. What is diff between Beacon frame and Probe response?
  28. What all a beacon frame say ? It’s significance?
  29. What is BSS ?
  30. What is authentication in Wlan ?
  31. How association process happens in Wlan ?
  32. What can be the reason for Deauthentocate a station by an AP?
  33. Major diff between AP and Station?
  34. What is BAR and who initiates it and when?
  35. What is scanning, types in it?
  36. What is NAV and how is it used in CSMA-CA?
  37. What is backoff and why is it used?
  38. How many times typically a packet is retransmitted in Wlan ?
  39. Do all packets expect an Ack  packet ?
  40. What is Cts and Rts ? Why and when are this frames used?
  41. What is self Cts mechanism?
  42. Advantages and disadvantages using Cts and Rts mechanisms?
  43. What is hidden node problem? How can it be solved?
  44. What is power save mechanism available in Wlan ? Mention and brief each of them ?
  45. What is Tim and Dtim ?
  46. What is significance of atim frame?
  47. What is diff between authentication and association?
  48. What are dfs channels, purpose?
  49. Format of Ack frame ?
  50. What is Block Ack and its usage?
  51. What is Physical carrier sense and Virtual carrier Sense?
  52. What is the purpose and usage of PS-poll frame?
  53. What is green field mode ?
  54. What are different interframe spaces and what is each value and significance?
  55. How will typically connection establish in Wlan ?
  56. What is the difference between Wpa and Wpa2
  57. What is wpa-eap ? How is it achieved?
  58. What is four way handshake, explain each frame?
  59. Diff between open authentication and shared authentication?
  60. What is pmk and psk ? Diff between them?
  61. What is Aggregation ? Types ?
  62. What all frames generally flow in sequence in process of station connecting to a AP?
  63. What is null data frame? Significance?
  64. How is data rate selected in Wlan?
  65. What are the criteria which initiate Cts/Rts usage in Wlan
  66. Why does a station send a unicast Probe request before initiating join?
  67. What is Hidden mode in AP ?
  68. What is roaming, how is it achieved? What triggers Roaming?
  69. Will add more……

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