The Institute of Electrical and Electronics Engineers (IEEE) has ratified five major iterations of the 802.11 Wi-Fi protocol, culminating with Wi-Fi 5 (802.11ac) in 2013. However, despite a significant increase in speed, many organizations still find themselves limited by the Wi-Fi 5 standard, particularly in high-density venues such as stadiums, convention centers, transportation hubs
Indeed, Wi-Fi 6 (802.11ax) deployed in dense device environments supports higher service-level agreements (SLAs) with more concurrently connected users and devices and more diverse usage profiles. This is made possible by a range of technologies that optimize spectral efficiency, increase throughput and reduce power consumption. These include Multi-User Multiple Input Multiple Output (MU-MIMO), Target Wake Time (TWT), Orthogonal Frequency-Division Multiple Access (OFDMA), BSS Coloring and 1024-QAM
MU-MIMO describes a set of multiple-input and multiple-output (MIMO) technologies for wireless communication. MU-MIMO was first introduced to the wireless world in 2015 as part of the Wi-Fi 5 (802.11ac) standard, with the Wi-Fi 6 (802.11ax) protocol adding MU-MIMO support for uplink. MU-MIMO can be used in networks where a single access point (AP) must communicate with multiple clients simultaneously to improve overall efficiency.
MU-MIMO (Wi-Fi 5/802.11ac)
MU-MIMO allows an access point to communicate with multiple devices simultaneously. It is part of the Wi-Fi 5 (802.11ac) Wave 2 standard. With MU-MIMO, an access point or a wireless router can communicate with multiple network clients at the same time – thus increasing the speed of the data transfer without congestion. A significant advantage of MU-MIMO is its support for transmitting data from an AP to devices in a downlink connection. In addition, MU-MIMO reduces the delay for each end-device receiving the data and enhances the device connectivity between multiple end users.
However, MU-MIMO also has certain limitations. Its functionality works only within the 5GHz band, as Wi-Fi 5 (802.11ac) is defined only in this band. In addition, MU-MIMO works only when transmitting data from an AP to a client in downlink transmissions – and does not operate in reverse. Moreover, MU-MIMO supports only a limited number of simultaneous data streams.
MU-MIMO (Wi-Fi 6 / 802.11ax)
Wi-Fi 6 (802.11ax) leverages the multi-user version of OFDMA and MU-MIMO for better efficiency of uplink and downlink transmissions. OFDMA allows the transmission of big chunks of data over a single noisy channel. This technique works by splitting a single signal into multiple smaller signals that are transmitted. The combination of OFDMA and MU-MIMO allows Wi-Fi 6 (802.11ax) to achieve increased capacity, improved coverage and performance in ultra-high-density environments.
UL MU-MIMO is a new key feature introduced with Wi-Fi 6 (802.11ax). By leveraging UL MU-MIMO, multiple clients connected to the access point will be able to send acknowledgement responses (ack) simultaneously, thus saving airtime. This ultimately improves network throughput and efficiency.
Another important Wi-Fi 6 (802.11ax) feature is its support for 20MHz-only clients. This is particularly beneficial for low-cost IoT devices that require low power and pack very small batteries. In contrast, Wi-Fi 5 (802.11ac) mandates 80MHz clients. The Wi-Fi 6 (802.11ax) protocol enables simultaneous upstream and downstream MU-MIMO data transmissions on the same frequency. This results in higher Wi-Fi performance, especially in higher-density environments such as stadiums, convention centers, transportation hubs
It should be noted that MU-MIMO and OFDMA provide complementary techniques to concurrently serve multiple users. More specifically, MU-MIMO is most effective at close to mid-range, whereas OFDMA is effective at all ranges, close, medium and far. Moreover, MU-MIMO best serves multiple
Christian Kim, Senior Analyst IoT, Connectivity and Telecom
Electronics at IHS Markit, estimates that total Wi-Fi 6 (802.11ax) device shipments will increase
to 58 million units in 2021. Meanwhile, IDC
sees Wi-Fi 6 (802.11ax)
deployments ramping significantly in 2019 and becoming the
dominant enterprise Wi-Fi standard by 2021. This is because the new Wi-Fi 6 (802.11ax)
standard offers up to a four-fold capacity increase over its Wi-Fi 5 (802.11ac)
Wave 2 predecessor.
With Wi-Fi 6 (802.11ax), multiple APs deployed in dense device environments can collectively deliver required quality-of-service (QoS) to more clients with more diverse usage profiles. This is made possible by a range of technologies, such as the Wi-Fi 6 (802.11ax) iteration of MU-MIMO, which enables simultaneous MU-MIMO data transmissions on the same frequency. From our perspective, Wi-Fi 6 (802.11ax) is playing a critical role in helping Wi-Fi evolve in to a collision-free, deterministic wireless technology that dramatically increases aggregate network throughput to address high-density venues and beyond. Last, but certainly not least, Wi-Fi 6 (802.11ax) access points are also expected to enhance the overall Wi-Fi experience by providing tangible performance benefits for legacy wireless devices.