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xieyaxiongfly / Atheros-CSI-Tool

Tool for extracting CSI from off-the-shelf Commercial Atheros WiFi NIC
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How CSI is calculated at Rx from HT-LTF preamble field #21

Open sayaz opened 6 years ago

sayaz commented 6 years ago

Hi, What I have understood from the 802.11n standard is that the Tx is sending NDP (HT sounding) to the Rx (explicit case). The preamble portion of HT sounding frame has a field (HT-LTF) that contains OFDM training symbols (+/-1) which are actually calculated at the Rx side to estimate CSI.

Can you please explain in brief, how this is being actually calculated at the Rx end to create the feedback matrix? Or any link/book you have that can help me to understand this?

xieyaxiongfly commented 6 years ago

1, The content of HT-LTF is known to both sides.

2, We assume the transmitted LTF is the same as the theoretical one.

3, The LTF received by receiver is different from the theoretical one.

4, The difference between the LTF sent out by sender (or theoretical one) and the LTF received by receiver is the CSI.

I think the HT-LTF of the preamble is not “calculated” at the RX side. It is received by the RX side.

From: Ayaz Mahmud [mailto:notifications@github.com] Sent: Tuesday, 20 February, 2018 8:40 AM To: xieyaxiongfly/Atheros-CSI-Tool Atheros-CSI-Tool@noreply.github.com Cc: Subscribed subscribed@noreply.github.com Subject: [xieyaxiongfly/Atheros-CSI-Tool] How CSI is calculated at Rx from HT-LTF preamble field (#21)

Hi, What I have understood from the 802.11n standard is that the Tx is sending NDP (HT sounding) to the Rx (explicit case). The preamble portion of HT sounding frame has a field (HT-LTF) that contains OFDM training symbols (+/-1) which are actually calculated at the Rx side to estimate CSI.

Can you please explain in brief, how this is being actually calculated at the Rx end to create the feedback matrix? Or any link/book you have that can help me to understand this?

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sayaz commented 6 years ago

Hi,

Do you know if I can have access the HT-LTF symbols with your tool? Or where is this HT-LTF defined?