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About "BB11ARxCarrierSense" RRS feed

  • Question

  • In sdr_phy_cs.c, the function "BB11ARxCarrierSense" is called in "PhyDot11ACs".There is a comment of "if carrier sense never reaches the radio RX stream end, CS in DPC_LEVEL". My question is what is the comment exact mean? if the Sora does not reaches the radio RX stream end, can it  CS and RX correctly? 

    Thank you for your attentions

    Sunday, June 10, 2012 2:06 PM

Answers

  • If you check the Section 4.3 in Sora Manual version 1.6, you will see below description.
    "The pbTouched flag is set when the returned signal block is the last block in the RX channel, ie. the most recently received signal block."

    The Sora hardware is pumping samples into the RX stream, and carrier sense on most recently received signal blocks will give correct judgement of the current status of the wireless channel, which is a must 802.11a/b MAC FSM.
    If carrier sense works on dated signal blocks, it will not be a big problem for decoding received frames. However, if another frame will be send after carrier sense, the wrong judgement of the channel status will bring channel confliction.
    • Proposed as answer by Qi LuoEditor Thursday, June 14, 2012 2:43 AM
    • Marked as answer by Qi LuoEditor Thursday, June 14, 2012 5:25 AM
    Thursday, June 14, 2012 2:43 AM
    Answerer

All replies

  • Hi,

    Sorry for the unclear comments. It means that after the carrier sense function is called, the return value may indicates the reading pointer in the RX stream does not reach the stream end, ie. it just process the dated samples in the RX stream. Then the priority should remain in the DISPATCH_LEVEL, and continue carrier sense until reaching RX stream end. Then CS and RX can work correctly on the most recent samples in the RX stream.

    You can refer KeRaiseIrqlToDpcLevel on MSDN to know about DISPATCH_LEVEL. Roughly it is a very high priority in kernel mode, higher than page fault interrupt. The code running in this level should be time-critical and non-pagable code.

    • Proposed as answer by Qi LuoEditor Tuesday, June 12, 2012 5:59 AM
    Tuesday, June 12, 2012 5:59 AM
    Answerer
  • Thank you very much.

    As we know, the flag "pTouched" denotes whether carrier sense reaches RX stream end. What is the role of this flag for CS? 

    Wednesday, June 13, 2012 8:16 AM
  • If you check the Section 4.3 in Sora Manual version 1.6, you will see below description.
    "The pbTouched flag is set when the returned signal block is the last block in the RX channel, ie. the most recently received signal block."

    The Sora hardware is pumping samples into the RX stream, and carrier sense on most recently received signal blocks will give correct judgement of the current status of the wireless channel, which is a must 802.11a/b MAC FSM.
    If carrier sense works on dated signal blocks, it will not be a big problem for decoding received frames. However, if another frame will be send after carrier sense, the wrong judgement of the channel status will bring channel confliction.
    • Proposed as answer by Qi LuoEditor Thursday, June 14, 2012 2:43 AM
    • Marked as answer by Qi LuoEditor Thursday, June 14, 2012 5:25 AM
    Thursday, June 14, 2012 2:43 AM
    Answerer
  • Thank you very much

    Thursday, June 14, 2012 3:28 AM
  • If you check the Section 4.3 in Sora Manual version 1.6, you will see below description.
    "The pbTouched flag is set when the returned signal block is the last block in the RX channel, ie. the most recently received signal block."

    The Sora hardware is pumping samples into the RX stream, and carrier sense on most recently received signal blocks will give correct judgement of the current status of the wireless channel, which is a must 802.11a/b MAC FSM.
    If carrier sense works on dated signal blocks, it will not be a big problem for decoding received frames. However, if another frame will be send after carrier sense, the wrong judgement of the channel status will bring channel confliction.

    Excuse me, does your Sora Manual 1.6 has Section 4.3?

    Unfortunately, our Manual 1.6 downloaded from this forums only has Section 4.1 and 4.2.

    Friday, June 15, 2012 7:14 AM
  • Sorry for the mistake. Please refer the Section 3.4 in Sora Manual version 1.6.

    Monday, June 18, 2012 6:22 AM
    Answerer