The Development History of WiFi Technology
Wi-Fi has become a ubiquitous technology in the world today, providing connections for billions of devices. It is also the preferred way for more and more users to access the Internet, and it has a tendency to gradually replace wired access. In order to adapt to new business applications and reduce the gap with wired network bandwidth, each generation of 802.11 standards has greatly increased its rate.
In 1997, the IEEE formulated the first wireless LAN standard 802.11, with a data transmission rate of only 2Mbps, but the birth of this standard changed the way users access and freed people from the shackles of cables.
As people's requirements for network transmission rates continue to increase, the IEEE issued the 802.11b standard in 1999. The 802.11b runs in the 2.4 GHz frequency band with a transmission rate of 11 Mbit/s, which is 5 times the original standard. In the same year, the IEEE supplemented and released the 802.11a standard, which adopted the same core protocol as the original standard. The operating frequency is 5GHz and the maximum original data transmission rate is 54Mbit/s, which meets the requirements of real network medium throughput (20Mbit/s). Since the 2.4GHz frequency band has been used everywhere, the use of the 5GHz frequency band gives 802.11a the advantage of fewer conflicts.
In 2003, the OFDM technology as the 802.11a standard was also adapted to operate in the 2.4 GHz frequency band, resulting in 802.11g. The carrier frequency is 2.4 GHz (same as 802.11b), and the original transmission speed is 54 Mbit/s. The net transmission speed is about 24.7Mbit/s (same as 802.11a).
The more important standard for Wi-Fi is 802.11n, which was released in 2009. This standard has made significant improvements to Wi-Fi transmission and access, introducing new concepts such as MIMO, security encryption, and some advanced functions based on MIMO. (Such as beamforming, spatial multiplexing...), the transmission speed reaches 600Mbit/s. In addition, 802.11n is also the first Wi-Fi technology to work in both 2.4 GHz and 5 GHz frequency bands.
However, the rapid development of mobile services and high-density access have placed higher requirements on the bandwidth of Wi-Fi networks. The 802.11ac standard released in 2013 introduced a wider radio frequency bandwidth (up to 160MHz) and advanced modulation technology (256-QAM), the transmission speed is up to 1.73Gbps, which further improves Wi-Fi network throughput. In addition, the 802.11ac wave2 standard was released in 2015, which pushed beam forming and MU-MIMO to the mainstream and increased the system access capacity. Unfortunately, 802.11ac only supports terminals in the 5GHz frequency band, which weakens the user experience in the 2.4GHz frequency band.
With more and more business applications such as video conferencing, wireless interactive VR and mobile teaching, there are Wi-Fi access terminals increasingly, and the development of IoT has brought even more mobile terminals access to wireless networks. Even home Wi-Fi networks that used to have fewer access terminals will become crowded with a rising number of smart home devices. Therefore, the Wi-Fi network still needs to continuously improve its speed, and it is also necessary to consider whether it can access more terminals to adapt to the ever-expanding number of client devices and the user experience requirements of different applications.
The next generation of Wi-Fi needs to solve the problem of reducing the efficiency of the entire Wi-Fi network due to the access of more terminals. As early as 2014, the IEEE 802.11 working group has begun to deal with this challenge. The 802.11ax standard, officially launched in 2019, introduces uplink MU-MIMO, OFDMA frequency division multiplexing, 1024-QAM high-order coding and other technologies, which will solve the problem of network capacity and transmission efficiency from the aspects of spectrum resource utilization and multi-user access. The goal is to increase the average user throughput by at least 4 times compared to today’s Wi-Fi 5 in a dense user environment, and the number of concurrent users to increase by more than 3 times. Therefore, Wi-Fi 6 (802.11ax) is also known as high-efficiency wireless (HEW).