802.11 basic knowledge

802.11 the basic specification covers the 802.11 mac and two physical layers (physical layer): one is the frequency hopping spread spectrum (frequenccy-hopping Spread-spectrum, referred to as FHSS) physical layer, The other is the direct sequence spread spectrum (Direct-sequence Spread-spectrum, referred to as DSSS) physical layer.

802.11 further divides PHY into two general components: one is the physical layer aggregation process (physical layer Convergence Procedure, referred to as PLCP), which is responsible for mapping Mac frames to the transmission medium; Physical media related (phisical Medium Dependent, referred to as PMD), is responsible for transmitting these frames.

The 802.11 network consists of four main physical components:

1) Workstation: Refers to a computing device equipped with a wireless network interface.

2) Access point: A device with a wireless-to-wired (wireless-to-wired) bridging capability is called an access point, referred to as an AP.

3) Wireless Media (Wireless Medium): 802.11 standard transmits frames between workstations in wireless media.

4) Distributed Systems (distribution System): logical components belonging to 802.11 that are responsible for forwarding frames to the destination. A distributed system is a backbone network that forwards frames between access points, so it is often referred to as a backbone (backbone network).

The RTS frame itself has two purposes: to reserve the right to use the wireless link and to remain silent on other workstations that require this frame to be received. Once the RTS frame is received, the receiving end is answered in CTS frames. Like RTS frames, CTS frames also keep nearby workstations silent. Wait until Rts/cts completes the exchange process. Workstations and APs that have already booked the link can transmit other frames. No need to worry about other hidden node interference.

If the driver for the 802.11 NIC is supported, the user can control the rts/cts exchange process by adjusting the RTS threshold (threshold). As long as the frame is larger than this threshold, the Rts/cts interchange process occurs, and the frame is transferred directly below this threshold.

Carrier monitoring (carrier sensing) is primarily used to determine whether the media is in a usable state. The 802.11 has two kinds of carrier monitoring functions: physical carrier monitoring (physical carrier-sensing) and virtual carrier monitoring (Vritual carrier-sensing).

802.11 basic knowledge