Wi-Fi接入和交互流程，以及帧间间隔（IFS: interframe space）

帧间间隔（IFS: interframe space）

1.广播帧 beacon frame 发送

The AP is periodically transmitting (broadcasting) a special signal called Beacon signal saying "I am here.. I am here .. I am capable of this and that .. etc)". Basically this Beacon is like MIB/SIB + Physical Layer Sync channel in mobile communication (e.g, WCDMA/LTE etc). AP broadcast this Beacon several times per seconds. Beacon transmission interval is contained in one of Beacon information fields. (See Beacon data field)

2.解码广播帧beacon 建立无线信号同步无线认证和连接，接收注册流程

the device first detect and decode this beacon signal and establish physical synchronization.

After the physical Sync get established, the device and WLAN network goes through the authentication process and then association process which is similar concept to the registration process in mobile phone communication

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数据发送和接收流程

Data Transmission in Detail

More detailed process of this data tranmission in terms of timing can be illustrated as shown below.

i) Source transmit the short RTS burst which carries source, destination and duration of following transaction.

ii) All other devices around the source may receive the RTS burst. They are all checking if the RTS is for itself or not.

iii) If it is for itself and the medium is free, the destination device transmit the CTS which also carries the duration of following transaction.

iv) Now all the other device (the neighbouring device other than 'Destination' device) also knows that the medium will be occupied for a certain time from now, they would set their NAV(Network Allocation Vector) accordingly so that it would not try sensing and try to transmit anything during that period.