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#1 2018-Dec-07 13:48:07
- Yan Wang
- Member
- Registered: 2018-Oct-25
- Posts: 21
802.11 Reference Design
Hello,
I have a question about the Entry Type RX_OFDM 's address as shown below. If AP send frames to STA, and STA received the frames and then send the corresponding ACK to AP. Thus, I want to know what is the addr1, addr2, addr3 indicated for the frames received in STA? 
And the ACK only has the addr1 indicating the receiver address, but in when I analysed the data in MATLAB extracted from two AP node, I found that the addr2 still has the value as can be seen in the figure. 
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#2 2018-Dec-08 14:13:54
- murphpo
- Administrator
- From: Mango Communications
- Registered: 2006-Jul-03
- Posts: 5159
Re: 802.11 Reference Design
You can refer to the 802.11 spec for the meaning of fields in the MAC headers of various packet types. In general, headers with 3 addresses use addr1 as the Receiver Address and addr2 as the Transmitter Address. In headers with one address filed, addr1 is typically the Receiver Address.
The wlan_exp log tools calculate the addr1/addr2/addr3 fields by slicing bytes from the underlying mac_payload filed. In ACK/CTS the mac_payload field only has 1 address field. In this case the addr2/addr3 values calculated by wlan_exp should be ignored. The tools still calculate addr2/addr3 values (it's much faster to calculate these fields for all packets than to calculate them conditionally based on the mac_payload length), but the underlying mac_payload bytes for those fields are not valid.
One request - please choose more descriptive topics when posting new forum threads. Posting new questions in new threads is fine (preferred, even), but using '802.11 Reference Design' as the topic makes it harder for other users to find relevant topics.
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