WIFI 802.11 a/b/g/n/ac

802.11 a/b/g/n/ac

FHSS: Frequency-hopping spread spectrum (FHSS) is a method of transmitting radio signals by rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver.

DSSS: Direct Sequence Spread Spectrum (DSSS) is a spread spectrum technique whereby the original data signal is multiplied with a pseudo random noise spreading code. This spreading code has a higher chip rate (this the bitrate of the code), which results in a wideband time continiuous scrambled signal

OFDM: Orthogonal frequency-division multiplexing

AP（Access point的简称，即访问点，接入点）

Station（工作站）：表示连接到无线网络中的设备，这些设备通过AP，可以和内部其它设备或者无线网络外部通信。

Assosiate：连接。如果一个Station想要加入到无线网络中，需要和这个无线网络中的AP关联（即Assosiate）。

SSID：Service Set ID 用来标识一个无线网络，每个无线网络都有它自己的SSID。

BSSID：用来标识一个BSS，其格式和MAC地址一样，是48位的地址格式,BSSID类似MAC地址

BSS（Basic Service Set）：由一组相互通信的工作站组成，是802.11无线网络的基本组件。

Channel Width（信道宽度）有”20M HZ“、”40M HZ“等

Channel（信道）:将5G或者2.4G的频段范围再划分为几个小的频段，每个频段称作一个Channel

Wireless Security（无线网络的安全性）:WEP、WPA、WPA2和RC4、TKIP、AES。

MLME Stands for Media Access Control (MAC) Sublayer Management Entity.

开发有两种方式，按模组比如Ti CC3100, CC3200，这种开发比较简单，一般就是UART， SPI。

另一种是直接对芯片，那么你就要自己写协议。在Linux提供丰富的成熟的开发接口。

in linux, there are FullMAC and softwareMAC two modes. 

Full MAC Devices: Implemented in device hardware

Soft MAC Devices: Implemented in device software

The responsibilities of MLME includes

MLME may assist in reaching:

• Authenticate
• Deauthenticate
• Associate
• Disassociate
• Reassociate
• Beacon
• Probe
• Timing Synchronization Function (TSF)

The core modules are cfg80211 and MAC80211.

Both Full MAC & Soft MAC works with CFG80211.MAC80211 driver API only supports Soft MAC Devices.

The important struct socket buffer