IEEE 802.11ac is the standard for wireless computer networks and transmits exclusively in the 5 GHz band. With the right devices, it is therefore possible to achieve relatively high speeds.
What is 802.11ac?
Even if the term “802.11ac” means nothing to you, you certainly know its other name: Wi-Fi 5. IEEE 802.11ac is in fact the standard for Wi-Fi networks with data rates in the 5 GHz band. Like previous standards and its successor, 802.11ax, it was defined by the Institute of Electrical and Electronics Engineers (IEEE). Compared to its predecessors 802.11b, g, a and n, the 802.11ac standard, officially published at the end of 2013, generates significantly higher bandwidths and transmission rates in the gigabit range. Its maximum throughput is theoretically 6,933 megabits per second. However, this value is almost impossible to achieve in practice due to various restrictions.
The standards mentioned for Wi-Fi networks all belong to the IEEE 802.11 family. But there are still many other network standards, for example:
How does 802.11ac work?
The 802.11ac standard is therefore not completely new and is based on its various predecessors. Compared to the 802.11n standard, IEEE 802.11ac presents few new features. The significantly higher transmission rate is achieved through several adaptations and optimizations. Thus, the 802.11ac standard offers high bandwidth, which can be extended to 80 MHz or 160 MHz. In addition, up to eight MIMO (Multiple Input Multiple Output) channels can be used simultaneously. From four antennas it is also possible to implement multi-user MIMO (MU-MIMO), when the access point and client support it. Higher modulation schemes such as 256-QAM with 3/4 and 4/5 FEC are also used.
What are the advantages of the IEEE 802.11ac standard?
The 802.11ac standard therefore offers several interesting advantages compared to its predecessors. The technique is more efficient and even faster than many traditional Ethernet connections, at least in theory. The use of a 5 GHz band offers Significantly higher data rates and fewer bandwidth issues than with a 2 GHz band. However, the advantages are only really noticeable if all the devices used also support the new features of the 802.11ac standard, of which here are the main ones:
MIMO
By MIMO we mean wireless communication via multiple transmitting and receiving antennas. The 802.11ac standard allows this communication with up to eight antennas. This means that up to eight data streams can pass simultaneously and the transmission rate is thus significantly increased.
256 QAM
256-QAM (quadrature amplitude modulation) is a modern and efficient modulation process also used by the 802.11ac standard. The number 256 represents the 256 levels of the modulation procedure. 256 QAM is four times more efficient than the 64 QAM modulation used until now. With this method, 8 bits are transmitted per signal period.
Beamforming
Beamforming is the focusing of a wireless signal on a given client, which significantly improves the connection. In this case, multiple antennas send a signal to a specific receiver, which increases the transmission rate and allows a higher level of modulation. IEEE 802.11n already offered this possibility, at least in theory. In practice, however, the results were rather disappointing. With IEEE 802.11ac, beamforming is much more efficient. However, it is essential that the device in question supports beamforming.
802.11ac speed levels
The IEEE 802.11ac standard offers many different speed levels in principle. The transmission speed depends on various factors. In addition to the channel width, the number of antennas and the modulation method, the access point and client must also support all relevant performance characteristics. However, this is not always the case. Most devices only have limited performance specifications, which is why the theoretical maximum speed of 802.11ac is almost never achieved. This is 6,936 megabits per second. To support it, a maximum bandwidth of 160 MHz, eight-fold MIMO and 256 QAM would be required.
Support for DFS and TPC
As described previously, the 802.11ac standard transmits exclusively on the 5 GHz band. In Europe, this means that technology must support DFS and TPC, not least because the transmissions could otherwise disrupt important systems such as regional weather radars. DFS (Dynamic Frequency Selection) recognizes radio signals from other systems. In the event of overlap, DFS allows you to fall back on other channels. TPC (Transmit Power Control) offers dynamic control of access points or routers and allows, in the event of a good radio link, data to be transmitted with lower transmission power.
If routers or access points forgo DFS and TPC support, they can only transmit on channels 36 to 48 and occupy them entirely. Not only does the transmission rate decrease significantly, but access from another router is not excluded, which can lead to strong disruptions. Devices that do not support DFS and TPC are therefore not suitable for IEEE 802.11ac.
