Want to know why the wireless network transmission speed is fast or slow? Want to know how to choose a router with fast Internet access? Then let's first understand the 802.11 protocol.
| 【Introduction to 802.11 protocol family】 |
★802.11a★
802.11a: In 1999, the formulation of the IEEE 802.11a standard was completed, which stipulates that the wireless local area network operates in a frequency band of 5GHz, the data transmission rate reaches 54Mbps, and the transmission distance is controlled within 10-100 meters. 802.11a adopts the unique spread spectrum technology of Orthogonal Frequency Division Multiplexing (OFDM); it can provide 25Mbps wireless ATM interface and 10Mbps Ethernet wireless frame structure interface, as well as TDD/TDMA air interface; support voice, data and image services ; A sector can access multiple users, and each user can bring multiple user terminals.
★802.11b★
802.11b: In September 1999, IEEE 802.11b was officially approved. The standard stipulates that the wireless local area network works in the 2.4GHz frequency band, and the data transmission rate reaches 11Mbps. This standard is a supplement to IEEE 802.11. It adopts two operating modes: point-to-point mode and basic mode. In terms of data transmission rate, it can automatically switch between different rates of 11Mbps, 5.5Mbps, 2Mbps, and 1Mbps according to the actual situation. 802.11b and working The 802.11a standard on the 5GHz frequency is not compatible. Due to its low price, 802.11b products have been widely marketed and operated in many practical workplaces.
★802.11g★
The IEEE's 802.11g standard is a speed-up (up from 11Mb/s in 802.11b to 54Mb/s) over the popular 802.11b, the Wi-Fi standard. 802.11g access points support 802.11b and 802.11g client devices. Likewise, laptops with 802.11g network cards can access existing 802.11b access points as well as new 802.11g access points. However, products based on the 802.11g standard are still rare. If you need high speed, the 802.11a products that have been introduced can provide a maximum speed of 54Mb/s.
★802.11n ★
A wireless transmission standard protocol behind 802.11a/b/g by the Wi-Fi Alliance, 802.11N (TGn) came into being in order to realize high-bandwidth, high-quality WLAN service and make the wireless local area network reach the performance level of Ethernet. The 802.11n standard was not officially approved by the IEEE until 2009, using MIMO OFDM modulation technology, and has been widely used in PCs and notebook computers.
◇Comparison of 802.11a/b/g/n◇
★802.11ac★
The core technology of 802.11ac is mainly based on 802.11a
, which continues to work in the 5.0GHz frequency band to ensure backward compatibility, but the data transmission channel will be greatly expanded, increasing to 40MHz or 80MHz on the basis of the current 20MHz, and may even reach 160MHz. Coupled with about a 10% improvement in actual frequency modulation efficiency, the theoretical transmission speed of the new standard is expected to reach a maximum of 1Gbps, more than three times that of 802.11n 300Mbps.
802.11ac is the first standard that promises to increase wireless data rates beyond 1Gbps, but also includes many advanced features to improve the user experience. 802.11ac uses more multi-stream space transmission technology, adopts 8x8 (MIMO) multiple input and output, provides wider data transmission channel bandwidth (up to 80MHz), and can even use channel aggregation technology to increase the total data channel bandwidth to 160MHz . Furthermore, the key to 802.11ac's success is that it is an evolutionary technology: achieving its goals, surpassing several important paradigms, and building on the existing 802.11n foundation. This is a huge advantage because 802.11ac can be relatively easy to transition from existing wireless networks and applications (using 802.11n or earlier wireless protocols) for manufacturers and consumers who will be using 802.11ac.
◇Comparison of 802.11n and 802.11ac◇
| [Key technologies adopted by 802.11n] |
The key technologies adopted in the 802.11n physical layer include MIMO, MIMO-OFDM, 40MHz channel, Short GI, FEC, MRC, etc.
The key technologies adopted by the 802.11n MAC layer include block acknowledgment and frame aggregation.
●MIMO technology ●
802.11n brings WLANs to the full multi-antenna era. MIMO (Multiple Input Multiple Output) technology refers to the use of multiple transmit and receive antennas at the transmitter and receiver, respectively, and the signals pass through the transmitter and receiver, thereby improving the quality of service (bit error rate or data rate) for each user. .
In the traditional WLAN system, the AP and wireless users usually only use one antenna each, and use the 802.11a/b/g protocol for transmission. The transmission rate of the signal is up to 54Mb/s, and it is difficult to increase the rate. With the popularization and wide application of WLAN technology, the desire of users to greatly increase the wireless communication rate is becoming stronger and stronger. The 802.11n protocol adopts MIMO (Multiple Input Multiple Output) multi-antenna technology. The signal transmission of WLAN can easily break through the rate bottleneck caused by a single antenna and meet the user's requirements for bandwidth and signal quality.
●802.11n key technology - OFDM (Orthogonal Frequency Division Multiplexing) technology ●
●802.11n key technology - MIMO-OFDM ●
| 【Wireless encryption technology】 |
☆WEP (Wired Equivalent Encryption) of wireless network encryption technology☆
Although the name appears to be a security option for wired networks, it's not. The WEP standard was created in the early days of wireless networking with the goal of becoming a necessary security layer for wireless local area networks (WLANs), but the performance of WEP is undoubtedly very disappointing. Its roots lie in a flawed design. In systems using WEP, data transmitted over the wireless network is encrypted using a randomly generated key. However, the method used by WEP to generate these keys was quickly found to be predictable, making it easy for a potential intruder to intercept and crack the keys. Even a moderately skilled wireless hacker can quickly crack WEP encryption in two to three minutes.
☆WPA of wireless network encryption technology☆
WPA uses the WEP algorithm function RC4, but adds some features to eliminate some of the problems in the way WEP uses passwords: 1. Stricter authentication: An 802.1x server, such as a Radius server, can be used solely for user authentication. 2. Longer keys: WPA increases the length of the Initialization Vector (IV) to 48 bits and the length of the master key to 128 bits. 3. Temporal Key Integrity Protocol (TKIP) generates a different key for each client and uses a different key for each subsequent packet.
☆WPA2 of wireless network encryption technology☆
After the promulgation of 802.11i, the Wi-Fi Alliance introduced WPA2, which supports AES (Advanced Encryption Algorithm), so it needs new hardware support, and it uses CCMP (Counter Mode Cipher Block Chain Message Complete Code Protocol). In WPA/WPA2, the generation of PTK depends on PMK, and PMK can be obtained in two ways. One is the form of PSK, which is the pre-shared key. In this way, PMK=PSK, and in the other way, authentication is required. The server and the site negotiate to generate the PMK.
summary:
Currently the fastest transport protocol is 802.11ac. If you want to experience high-speed Internet access, you must pay attention when choosing electronic products to check whether the electronic products support the 802.11ac protocol. Especially mobile phones, computers, routers. Now that the gigabit network has become popular, if the electronic equipment does not support the 802.11ac protocol, it is impossible to enjoy the gigabit network.