Research on the process of WiFi communication--(1) WiFi Basic Property Introduction

First, WiFi basic properties Introduction

(i), WLAN

WLAN is the abbreviation of wireless LAN (WLAN), IP-based communication, can provide a certain range of high-speed data connection, Generally use 2.4GHz or 5.8GHz Wireless band (ISM band) transmission, no cable restrictions, transmission distance of dozens of meters, the use of special technology can reach more than hundreds of meters.

The IEEE's work on WLAN only defines protocols below the two layer, and is currently focused on security, signaling between APS, and spectrum expansion.

(b), WiFi

WiFi is wireless Fidelity (wireless high fidelity) abbreviation, is essentially a commercial certification, Wi-Fi certified products comply with the IEEE 802.11 wireless network specification, it is currently the most widely used WLAN standard, using 2.4G and 5G two spectrum. WiFi is a technology in WLAN, but most of the time Wi-Fi is equated with WLAN understanding.

(iii), 802.11 series of agreements

802.11 series Standard, the IEEE developed a wireless LAN standard, mainly used to solve the LAN, the user and the user Terminal wireless access. A port-based network access control Protocol is defined, which is applicable to point-to-point connection between the access device and the access port, where the port can be either a physical port or a logical port. is for the user access authentication, authentication through the port for the user to open.

The 802.11 protocol defines the physical layer of wireless LAN and the standard of MAC layer, defines the transmission mode of physical layer data, and adopts the CSMA/CA protocol similar to the Wired Ethernet CSMA/CD protocol in MAC layer.

Figure 1 The relationship between the protocol and the transfer rate

The 802.11 protocol defines the protocol standard for the WLAN physical layer as well as the MAC layer, as shown in 2.

Figure 2 802.11 Protocol definition criteria

Figure 3 Relationship between 802.11 series protocols and sub-layers

(iv), physical layer and data link layer

The physical layer consists of three parts: the physical layer management layer, the Physical Layer Convergence Protocol (PLCP), and the physical media dependent sublayer (PMD).

The data link layer consists of two parts: The logical connection Control sub-layer (LLC), the media access control sublayer (MAC).

The 802.11MAC layer is responsible for communication between the client and the AP. Key features include: Scan, access, authentication, encryption, roaming, and synchronization.

(v), wireless transmission

Interference factors of wireless transmission-multipath interference, obstacle and electromagnetic interference

Real-world performance of WiFi devices-throughput rate, coverage distance

Research on the process of WiFi communication--(1) WiFi Basic Property Introduction