802.11 is a set of specifications approved by the IEEE for Wi-Fi wireless networks. The first version of the standard was introduced in 1997, operating at 2.4 GHz and with a maximum transfer rate of 1.2 Mbps. Two years later, in September 1999, two 802.11a and 802.11b standards were released, the first in the 5 GHz band and the second in the 2.4 GHz band. The 802.11b data transfer rate with nearly ten times increase reached to 11 Mbps. On the other hand, the 802.11a transfer rate was equivalent to 54 Mbps, although the use of a higher bandwidth band made it more vulnerable to the obstacles and had a shorter range.
In 2003, the standard 802.11g was released, combining the best features of the two previous standards. Simply put, this standard worked in the 2.4 GHz frequency band and at 54 Mbps data rate. In this way, users were able to experience a truly usable wireless network for various uses.
Fast wireless networks
At that time, cable networks of 100 Mbps were considered as a standard for public applications, and wireless networks were following them with some distance. But Gigabit Ethernet networking and equipment were gradually entering the consumer market. While the Gigabit Ethernet ports were pre-installed on motherboards and many routers or switches provided such ports to users, the speed gap of wireless networks got quite obvious.
IEEE released the 802.11n standard in 2009, using both 5 and 2.4 GHz frequency bands. This standard supports the 150Mbps transfer rate, which puts it at a level higher than Ethernet 10/100. However, the standard also introduced a new feature called Multi-Input Multiple Output (MIMO), which allowed the use of multiple antennas to have virtually several input and output streams simultaneously. This feature allows the 802.11n standard to deliver a maximum transfer rate of up to 600 Mbps. Majority of wireless networks you use today are based on this standard.
Entering the gigabit range
The next Wi-Fi standard, the 802.11ac, was released in 2013. This standard was fully compatible with 802.11n and was actually released as an evolutionary version. The new standard operates in the 5 GHz frequency band, but routers that conform to this standard also support 2.4 GHz frequency band and thus cover all 802.11n-compliant devices. The 802.11ac has been able to bring the transmission rate of the networks to a gigabit level, although at the cost of lower range. This standard, in its evolution process, relying on three features, has greatly increased the speed of data transfer:
1 - More MIMO streams (8 instead of 4 in the previous standard)
2. Wider frequency channel (80 and 160 MHz instead of 40 MHz in the previous standard)
3 - Introduction of MU-MIMO (Multi-User MIMO) feature that allows delivering MIMO streams to multiple users.
By combining all these features, 802.11ac aggregate transfer rate reaches to about 7 Gbps (close to 1 gigabyte per second).
The first point to note about this standard is that it's not compatible with any of the previous standards since it essentially uses a different frequency spectrum in the range of millimeters, the 60 GHz range. Utilizing this frequency spectrum allows 802.11ad reach transmission rate of 7 Gbps but at a maximum range of 10 meters, which is practically limited to below 5 meters. In general, it can be said that this standard is designed to provide the highest possible wireless transfer speed in your personal space.
Of course, some manufacturers of networking equipment have provided products that support all three 2.4, 5, and 60 GHz frequency bands, but note that they are running in separate subnets. And you should not confuse this issue with 802.11ad compatibility with other standards.
Telecomm and Networking