Many who develop with microcontrollers have access to compatible Wi-Fi modules. Do you need to be concerned about updating to the latest version 802.11ax when it comes out? The answer depends on whether your MCU will reside in an area where the Wi-Fi access point is typically congested. If so, 802.11ax can help. In short, 802.11ax will help with areas that experience congested traffic or intermittent interference, power efficiency for Wi-Fi clients, and overall lower latency. The 802.11ax wireless standard’s focus is on more reliable service in a crowded space so wireless will seem faster for all clients (users).
Although the standards for the new 802.11ax version of Wi-Fi will not be finalized until 2019, chipsets and routers have already been manufactured. (A firmware update will bring the devices into compliance later.) D-Link’s AX11000 Ultra Wi-Fi router is rumored to be available soon; however, few devices will be able to support it. Eventually, 802.11ax will replace the 802.11ac standard in wide use today with higher throughput, improving the performance we experience in crowded places.
A saturated network, like Wi-Fi in a crowded airport, seems just to creep along. The Wi-Fi isn’t necessarily bad, it’s just over-loaded, now that nearly everyone has a smartphone. 802.11ax promises to run more efficiently, and while it cannot perform miracles, the “size of the pipe” with 802.11ax should see significant improvement. 802.11ax should provide a four-fold increase in throughput for the average user.
Recall that 802.11n was released in 2009, and 802.11ac was released in 2013. The 802.11ax specification is several months away from becoming final, and even though some 802.11ax chipsets and routers have been manufactured, lots of testing between devices that support 802.11ax will need to be performed before units will be sold and wide-spread adoption takes place, so plan to see 802.11ax in your local Starbucks, perhaps optimistically, at least 2 years from now. The good news is that 802.11ax is backward compatible with devices running with 802.11ac or 802.11n.
How does 802.11ax accomplish this new efficiency and throughput?
802.11ax operates in both the 2.4 and 5 GHz frequency bands. 802.11ax also adds more channels per Wi-Fi access point, as well as sub-channels, making it capable of handling up to eight simultaneous streams. This is why the D-Link AX11000 Ultra Wi-Fi router has eight antennas (see Figure 1). The new Wi-Fi standard also changes how Wi-Fi access points interact and even borrows some tricks on multiplexing from LTE cellular networking technology. Issues with our current Wi-Fi that the new standard aims to solve are related to overlapping Wi-Fi coverage areas, too many users sharing one Wi-Fi access point, and users traveling between Wi-Fi access points. Existing Wi-Fi uses Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA), a protocol borrowed from Ethernet, to send wireless signals over a channel (e.g., a 2.4 GHz or 5 GHz channel.) CSMA/CA is less efficient than it could be for how it’s being used in Wi-Fi in that the access point waits for an “all-clear” signal before attempting to transmit. CSMA/CA’s solution when encountering interference or congestion is to back-off and wait for the all-clear signal again. In a place crowded with Wi-Fi users, performance is severely affected. The new Wi-Fi standard does away with CSMA/CA and borrows some technology from cellular.
The technology that Wi-Fi has borrowed from cellular is Multi-Input, Multiple Output (MIMO), which exploits multipath propagation by multiplying radio link capacity with multiple transmit and receive antennas. It starts to get complicated quickly as advanced radio frequency (RF) technology is involved, but MIMO has proved essential in many wireless communication standards and is found in 3G, LTE 4G, 802.11n, and 802.11ac. There are two releases of the 802.11ac standard, called Wave 1 and Wave 2. Wave 2 of 802.11ac began using Multi-User MIMO (MU-MIMO). We have come a long way since older Wi-Fi standards permitted only one transmission at a time per access point. 802.11ax utilizes explicit transmit beamforming technology, an advanced signal-processing technique, to more accurately aim streams at a receiver’s antenna. The access point (e.g., router) uses information about the communication link it has established with wireless clients to optimize signal transmission to each one, aiming its signal at the receiving client. Aiming the signal is especially useful for communicating over 5 GHz because 5 GHz has less range than 2.4 GHz. Thus beamforming is used to boost 5 GHz performance. Beamforming is already available in 802.1ac access points, as 802.11ac only uses 5 GHz. 802.11n uses both 2.4 GHz and 5 GHz but does not use beamforming.
To further increase the efficiency of spectrum use, 802.11ax also uses an LTE cellular technology called Orthogonal Frequency Division Multiple Access (OFDMA). OFDMA creates four sub-channels out of each MU-MIMO communication stream into what the standard officially refers to as “resource units.” OFDMA effectively quadruples the bandwidth per stream, making it the most valuable update to Wi-Fi in this new standard.
Power savings for users
802.11ax also provides some power efficiency to users by using a sleep/wake technology called Target Wake Time (TWT). TWT negotiates with user devices to set up a schedules wake time to send or receive data. TWT is a mechanism for increasing device sleep duration, which should improve battery life. TWT was borrowed from 802.11ah and modified for 802.11ax. This battery-saving feature will be especially helpful for wearables, IoT devices, sensors, and other devices that do not require high-bandwidth throughput.
How fast is 802.11ax?
The main improvement that 802.11ax brings is the more efficient use of the spectrum. 80211.ax was developed with more of a focus on delivering enough bandwidth to many, versus a blazing fast wireless experience for one user. However, 802.11ax should be able to provide a single stream at 3.5 Gbps and up to four simultaneous streams to a single user or device. However, theoretically, the total bandwidth of an 802.11ax access point is 14 Gbps. The 802.11ax standard achieves improved spectrum efficiency in part by first establishing wider channels than older Wi-Fi standards and then dividing them into smaller sub-channels. Eight channels are then available for communication and devices to have a better chance of finding an opening to communicate with a Wi-Fi access point.
The smarter 802.11ax-based Wi-Fi will relieve the congestion we all experience in crowded venues, improving access over what we currently experience. Congestion relief comes from how 802.11ax more efficiently uses assigned frequency spectrums, reduces latency (the time it takes to respond) at a fundamental level, and increases overall efficiency in both communication and power savings for clients. 802.11ax will become the default standard as it matures, so expect anywhere from a year to two years before it starts to gain traction. You can only experience the full benefits of 802.11ax if your devices are either manufactured with 802.11ax or perhaps obtain some portion of benefit through a firmware update. You will not need to rush out and get a new device, however, since 802.11ax is backward compatible with older devices that still use 2009-era 802.11n or 2013-era 802.11ac Wi-Fi. Older devices will not experience the ability to receive up to 4 streams at once that 802.11ax devices will see. The general takeaway is that Wi-Fi on new devices built to support 802.11ax will seem faster and more reliable, but only if the 802.11ax access point has sufficient speed, or bandwidth, from the Internet Service Provider (ISP) that’s feeding the access point at the outset.