What is MU-MIMO wireless technology?

Did you know that wireless technology dates back to the 19th century? Through the years, great inventors like Michael Faraday, Thomas Edison and Nicola Tesla helped mold the concepts and theories behind electromagnetic radio frequency (RF).

It wasn’t until 1997, however, that the first 802.11 technology was introduced, which is known as the 802.11 legacy standard today. Since then, each new standard either introduced new technology or significantly improved over an older one.

The same holds true for 802.11ac technology. 802.11ac Wave 1 offered a significant enhancement over its predecessor, 802.11n. 802.11ac Wave 1 provided higher channel bandwidth and a new modulation scheme, significantly increasing the max data rates.

The Wave 2 wireless standard

Technology is always replaced and improved upon. Here, 802.11ac Wave 1 technology was replaced by today’s 802.11ac Wave 2 technology. With technologies like the Multi-User Multiple Input Multiple Output (MU-MIMO), increased channel width and more spatial streams (SS) than ever before to make Wave 2 technology a game-changer. Even though the theoretical maximum data rate as per the Wave 2 standard is 6.9 Gbps (8SS AP), the theoretical maximum with a 4SS access point (AP) is 3.5 Gbps.

Compare the evolution of wireless capabilities from 802.11n to today’s Wave 2 standard.

What is MU-MIMO and how is it different from SU-MIMO?

MU-MIMO is a Wave 2 technology. With Single User Multiple Input Multiple Output (SU-MIMO), the AP is able to talk to only one client at a time. However, with MU-MIMO technology the AP can now transmit up to four devices at a time in the downstream direction.

Talking to more devices in a single transmission decreases airtime, increases efficiency and delivers a better user experience. For MU-MIMO to work, both the AP and the client must support the technology. Since the 11ac Wave 2 technology is backwards-compatible, if the Wave 2 AP has to transmit to a Wave 1 device it will fall back to the Wave 1 technology and use SU-MIMO to transmit.

MU-MIMO improves wireless speed, performance

Faster data transmission with MU-MIMO improves efficiency and ensures more airtime for all clients.  802.11ac Wave 2 enhancements lead to faster data rates, providing higher throughputs, better performance and user experience.

With a 4SS AP, operating on 160MHz channel, sending data to a 3SS client device, the maximum data rate that can be achieved is 2.6 Gbps. However, this is the maximum theoretical data rate. For reference, the latest Apple MacBook Pro is a 3SS 802.11ac Wave 1 device. The MacBook Air is a 2SS 802.11ac Wave 1 device and the Galaxy S3 is a 1SS 802.11ac Wave 1 device.

Overall, MU-MIMO increases network capacity and throughput. This allows the wireless network to meet the rising demand for data-hungry applications. Since the wireless access point can talk to multiple devices at the same time, the number of devices in the queue decreases, resulting in reduced wait time and latency. Increase in the overall network capacity and reduced latency benefits not just the Wave 1 and Wave 2 devices, but also the legacy clients. More than one client is needed to take advantage of MU-MIMO.

Wave 2 access point data rates in Mbps with different client types.

What happens during MU-MIMO transmission?

A MU-MIMO-capable AP sends a sounding signal to the client devices in the network. Each of the clients sends back a Channel State Information (CSI) based on the information it receives from the sounding signal. The AP calculates the phase and signal strength based on the CSI it receives from each client and selects the MU-MIMO-capable devices that can be grouped in one transmission.

Does MU-MIMO rely on any external factors?

Yes, MU-MIMO relies heavily on multipath and beamforming. Multipath is the process of two or more signals reaching the client at the same time or within nanoseconds of each other. Multipath happens due to RF barriers like walls, metal surfaces and concrete that cause the signals to reflect, refract, etc. Beamforming, however, directs the signal in the direction of the client.

Is it the right time to buy 802.11ac Wave 2 or should I wait for 802.11ax?

According to multiple analyst sources, the Wi-Fi market is not slowing down. For instance, IHS forecasts 11ac Wave 2 technology to increase 12 percent annually for the next three years. There are a number of Wave 2-capable devices in the market today and this will increase in the near future.

Should you wait for 802.11ax? The answer is simple: no. You are looking at a couple of years for the full-fledged adoption of 11ax products. The standard in itself is expected to be ratified in late 2019 after which it needs to pass interoperability testing by Wi-Fi Alliance.

Once manufacturers release 11ax-capable APs that are certified by the Wi-Fi Alliance, mainstream adoption will occur, which is expected to be around 2020. At the same time, 11ax-capable client devices are required to reap the full benefits of the 11ax network. For the next couple of years, 11ac Wave 2 technology will remain the next-gen wireless connectivity standard.

Where can I buy Wave 2 wireless access points?

SonicWall SonicWave Wave 2 access points (432i/432e/432o 802.11ac) provide all the benefits of Wave 2 technology. You can expect superior performance and reliability with these access points. MU-MIMO technology enables SonicWave 400 series access points to transmit up to four devices at the same time.

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Srudi Dineshan

Product Marketing Manager | SonicWall

As the product marketing manager for the SonicWall secure wireless access product line, Srudi is responsible for marketing strategies, content creation and product launches. Prior to her role at SonicWall, she served as a competitive technical marketing engineer with Aruba Networks. During this time, she worked on multiple competitor solutions and gained over four years of wireless expertise. Srudi holds an M.S. in Telecommunication and Network Management from Syracuse University and various certifications such as CWNA, CCNA, SPM and PMC.