Detailed explanation of WiFi related knowledge

wifi7 The protocol standards have been It has entered the implementation stage , A few days to see 11be Related agreements of Find a lot of Just have forgotten , So here's another review .

atim packets --> When you point to IBSS In the system , Because in ibss In the system No, ap To cache data frames , So when a data frame arrives, it will send a atim packets Tell the others Here comes the member data Be prepared to accept .

CF-Poll  packets --> No competition cycle confirmation frame , Report ap The cache frame can be transferred , It's also sta To confirm whether there is data to be transmitted .

PS-Poll packets --> sta from power save Mode wakes up Hair ps-poll Frame report ap You can send the cache .

NULL function  （no data)  --> After the data transmission is completed Transmit a There is no... In this bag MSDU 

Action  no ack  Used to trigger the measurement action To require the workstation to take the necessary actions （11k 11v 11r You can see this packets）

DTIM --> data Length of cache time ,

short GI --> Data transfer interval

MSDU --> Mac service Data unit  ,mac Layer data unit Maximum 3041

RTS/CTS and ACK  -->  Frame control and frame confirmation are the means of flow control , Flow control helps the receiver to make a too fast sender reduce the speed of sending frames , Frame confirmation ACK It helps the sender to know which frames are correctly received .802.11 Network support RTS/CTS, Flow control by slowing transmission . When RTS/CTS When enabled , A station sends a before sending a data frame RTS frame , When the receiver is willing to receive traffic , It will respond to a CTS frame , On receipt of CTS After the frame , Will open a time window （ stay CTS Frame identification ）, It is used to send data frames to the station that confirms the reception
 

dBm = 10 log(power/1mw)

1mw = 0dBm  10mw=1dBm  100mw=20dBm

Every drop 3dBm Reduce the power by half ,  A negative number indicates that the power is less than 1mw

 

802.11k -> The optimized neighbor list contains ap Address and channel information , It is thought that traditional customers need to leave their current channel regularly to scan other channels And provide information of other channels . Support 11k The terminal only needs to go to a specific channel for other tests Thought he already had Most used ap And the channel .

802.11v --》 solve client Adhesiveness of steer The right to decide lies in client . ap Take the initiative to send a message to client Let him go steer, Support 11v Of client You can also send it to ap To request steer

802.11r -》 Fast Authentication , He put the key The four steps of exchange Ahead of time auth and assoc In the process of . This can quickly switch