New Wi-Fi standard extends MU-MIMO to 8×8 arrays

Article By : Kevin Krewell

802.11ax will address increasing congestion and will bring better bandwidth management.

Current state-of-the-art wireless routers are based on the 802.11ac Wave-2 standard with multi user (MU) MIMO and 4×4 antenna arrays. They enable spatial reuse to minimise channel sharing among multiple simultaneous users. The marketing for these systems is typically based on their peak data rates to clients, but their most important benefit is increased capacity and improved user experience in crowded networks.

The success of Wi-Fi leads to new problems in channel congestion and being able to fairly deliver bandwidth to all clients as the number of clients and their data demands rise. At CES 2017, we expect to hear about silicon support for 802.11ax and maybe see a few access points supporting it. 802.11ax will address increasing congestion and will bring better bandwidth management. While the 802.11ax standard may not be ratified until as late as 2019, we do expect to see early silicon in 2017.

The new standard extends MU-MIMO to 8×8 antenna arrays for both the 2.4GHz and 5GHz bands. The result is a potential for a 4x increase in capacity over 802.11ac which limits these techniques to the 5GHz band. With better antenna and other signaling improvements, the .11ax standard will also have better coverage than .11ac, especially outdoors.

The 802.11ax spec also supports better bandwidth allocation. Wi-Fi has used a listen-before-transmit approach to avoiding collisions that had its origins in wired Ethernet protocols. The .11ax standard borrows from more modern cellular LTE technology.

Specifically, the addition of the Orthogonal Frequency-Division Multiple Access (OFDMA) protocol brings scheduled resource allocation to Wi-Fi. In this model, each access point acts more like a small cell tower, controlling channel band allocation. It essentially splits channels into smaller bands for each user.

The .11ax OFDMA protocol supports both down and uplink channel management. This is extremely useful in efficiently serving devices with diverse needs. For example, bandwidth is appropriately allocated to devices running 4K streaming video versus short and bursty instant messaging or a data-sipping IoT application.

While OFDMA will help improve channel efficiency and quality of service, it needs support on both ends of the signal to work. So this benefit will emerge over time as the penetration of clients with OFDMA support increases.

In the meantime, the 8×8 MU MIMO antennas will be the primary method for improving capacity management. These arrays will benefit .11ac Wave-2 and other legacy devices, allowing users to enjoy the benefits of .11ax networks even during the ramp up of .11ax devices.

The new standard also lets clients schedule awake times to communicate. This reduces power and contention by allowing the client to keep the radio circuits asleep longer. In addition, it supports 1024 QAM encoding and support for long OFDM symbols for greater channel bandwidth. There’s also improved management for multiple access points.

Another benefit of 802.11ax is that it works in conjunction with other Wi-Fi standards such as 802.11ad (WiGig). The 60GHz .11ad standard provides maximum bandwidth for in-room links such as wireless HDMI for 4K video, VR headset connections and wireless docking stations.

The 802.11ax standard will have immediate benefits for overcrowded businesses, hot spots, apartment buildings and homes with many clients. It takes the best of Wi-Fi and adds technology from LTE, hence the mastery of both technologies will be key in developing best performing .11ax solutions.

For the consumer market, the challenge will be communicating these density advantages as opposed to theoretical peak data speeds. Ultimately what should matter to consumers is the best user experience, not the number on the box.

First published by EE Times.

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