ieee 802.11 ac

The IEEE 802.11 WLAN represents the IEEE designation for wireless networking. IEEE 802.11 standard defines how RF in the unlicensed ISM frequency bands is used for the physical layer and the MAC sub-layer of wireless links. Several implementations of the IEEE 802.11 standard has defined by IEEE over the years. All the standards use the Ethernet protocol and the CSMA/CA access method. The highlights of these standards are:

• 802.11– 802.11 was released in 1997. This is the original WLAN standard. The operating frequency of that standard is 2.4 GHz band. The speeds of this standard are up to 2 Mbps. This standard is now obsolete. When 802.11 standards were providing 2 Mbps speed, at the same time wired LANs was operating at 10 Mbps speed.
• IEEE 802.11a– 802.11a was released in 1999. The speed of this standard is 54 Mbps and the operating frequency is 5GHz. It is incompatible with the 802.11b and 802.11g wireless standards. Due to high frequency, the coverage area of this standard is smaller and the devices contain one antenna for transmission and reception of signals.
• IEEE 802.11b– The standard was released in 1999. Operating frequency of this standard is 2.4 GHz and offering speed is up to 11 11Mbps. The range of devices with 802.11b standard is long-range than 802.11a because the operating frequency is lower than 802.11a. The devices can better penetrate building structures than devices based on 802.11a standard. Wireless devices contain a single antenna to transmit and receive signals.
• IEEE 802.11g– 802.11is a popular wireless standard today is the successor of 802.11b. It was released in 2003. The operating frequency is 2.4 GHz band; the standard offers speeds of up to 54 Mbps. The frequency band is the same as 802.11b but with better speed than 802.11b. The devices have one antenna to transmit and receive wireless signals. It is also compatible with 802.11b. The speed of the device is reduced when supporting an 802.11b client.
• IEEE 802.11n– This is the first standard specify MIMO, was released in 2009. The standard allows operating with two frequencies – 2.4 GHz and 5 GHz and is referred to as a dual-band device. The data rates range is between 150 Mbps to 600 Mbps covering the distance range of up to 70 m. APs and wireless client using 802.11g required multiple antennas for multiple-in multiple-out (MIMO) technology. MIMO required multiple antennas for both the transmitter and receiver. Up to four antennas can be used with 802.11n devices. The standard is also is backwards compatible with 802.11a/b/g devices.
• IEEE 802.11ac– Current home wireless routers are likely  802.1ac-compliant, and operate in the 5 GHz frequency space was released in 2013, providing data rates ranging from 450 Mbps to 1.3 1300 Mbps. It also uses MIMO technology to get better communication performance. The standard can support up to eight antennas. The standard is backwards compatible with 802.11a/n devices but it limits the expected data rates.
• IEEE 802.11ad – The standard is expected to be approved in November 2019. It is also known as “WiGig”, uses tri-band: 2.4 GHz, 5 GHz, and 60 GHz, and offers theoretical speeds of up to 7 Gbps. However, this speed can achieve only if the client device is situated within 3.3 meters or 11 feet of the access point. Because 7 Gbps speed is possible on 60 GHz which required line-of-site, therefore, it cannot penetrate through walls. It switches to 2.4 GHz and 5 GHz bands for backward compatibility with existing Wi-Fi devices. The compatibility environment limits the expected data rates.
• The table below illustrates the comparison between all IEEE 802.11 standards including the backwards compatibility.