Published: October 2019
The new 802.11ax wireless standard, also known as Wi-Fi 6, is generating a lot of interest in the networking industry. For good reason, as Wi-Fi 6 brings several improvements that will help enterprise networks operate with greater efficiency and serve an ever-increasing number of wireless devices. Wi-Fi 6 also brings the potential of higher throughput under certain conditions. Though the primary focus and benefits will be achieved through lower latency, increased capacity and overall efficiency even in traditionally challenging high-density scenarios. New energy-saving mechanisms are also expected to improve battery life in Internet of Things (IoT) endpoints and other mobile devices that mutually support these new capabilities.
Cisco Catalyst 9100 Series Access Points and Cisco Meraki MR45/MR55 Series Access Points support Wi-Fi 6 today, as well as various client devices from the likes of Samsung, Intel, and Apple, just to name a few. With more Wi-Fi 6 capable devices expected throughout late 2019 and beyond as this shift continues.
Yet, as with any new industry standard, full adoption of Wi-Fi 6 in enterprise networks and the device ecosystem won’t happen overnight. This is true for Cisco’s internal networks, as we will roll out a Wi-Fi 6 solution in phases over a multi-year period. Given the scope of the undertaking, this will be a transition effort for the foreseeable future, and we expect to support a mix of Wi-Fi 6 and earlier-standard devices for some time.
Around the globe, the Cisco enterprise network connects nearly 13,000 access points across more than 400 wireless LAN controllers. For user devices, we serve about 135,000 Cisco-owned laptops today, none of which support the latest Wi-Fi 6 capabilities. However, the 802.11ax standard continues to allow for backwards compatibility with devices that operate under the earlier 802.11a/b/g/n/ac standards. This compatibility means we can migrate to laptops that are Wi-Fi 6 capable gradually and with relative ease, as part of our ongoing fleet refresh.
Mobile devices that connect to the Cisco network will have a less defined path for upgrade to Wi-Fi 6. The vast majority of the 68,000 smartphones and tablets authorized on the Cisco network on a daily basis are owned by employees, who will decide whether and when to upgrade to a Wi-Fi 6 device. We anticipate these employee upgrades will happen sooner and likely at a faster pace than our corporate laptop upgrades in some cases. As a result, we have begun extensive planning for how to best bring Wi-Fi 6 technology into our environment.
As a first step in planning for this shift, we must understand what benefits the 802.11ax standard can potentially bring to our wireless networks and connected devices. Then we will review the expected improvements to further help us prioritize and prepare the network for an effective deployment of this new technology.
An efficient wireless network is effective and powerful network. However, efficiency in an ever-changing and shared medium like RF has traditionally been difficult to attain. The stated goal of 802.11ax is to achieve precisely that, and from its inception the standard has been officially designated as High Efficiency Wireless (HEW). Much of these improvements will come from several unique features that help promote more efficient use of the wireless spectrum, and in turn help support more client devices in moderate to high-density environments.
Access. Perhaps the most important new capability introduced with Wi-Fi 6 is Orthogonal Frequency Division Multiple Access (OFDMA). This RF modulation technique allows multiple Wi-Fi 6 clients to simultaneously receive data during the same transmit opportunity. Allowing more information for multiple devices to be transmitted in parallel during a particular window of opportunity, all while reducing some of the traditional overhead of sending the same amount of information independently.
OFDMA divides a channel into further subcarriers compared to Orthogonal Frequency Division Multiplexing (OFDM). It also aggregates data to or from potentially several stations (STA) by dynamically allocating these same subcarriers into Resource Units (RU). Ultimately, each individual subcarrier can support data to or from multiple Wi-Fi 6 devices during a single transmit opportunity by slicing these subcarriers into multiple RUs as needed. The benefits for Wi-Fi 6 capable client devices will likely be measured in terms of increased aggregate throughput overall, as well as reduced latency and jitter for frames of various sizes and requirements.
Multi-User Multiple Input Multiple Output (MU-MIMO), as the name implies, is another unique mechanism to allow multiple clients to receive data in the same relative transmit opportunity. MU-MIMO support is a required feature for 802.11ax device certification. As a simple explanation, MU-MIMO creatively splits the available spatial streams amongst multiple client devices. MU-MIMO was introduced with 802.11ac wave 2, but only in the downlink direction from the access point to the client. In the 802.11ax standard MU-MIMO can also be supported in the uplink direction to the access point as well as from the clients. The lack of client adoption of MU-MIMO today, along with the overhead that comes with coordinating MU-MIMO sessions, and other factors such as distance required between participating clients all present real-world challenges to achieving the full potential of MU-MIMO. However, when MU-MIMO mechanisms in Wi-Fi 6 are also paired with OFDMA as we previously covered, it becomes a potentially interesting combo to watch in certain environments as the next few years of device adoption plays out.
Spatial reuse. The Basic Service Set (BSS) Coloring feature, first introduced in 802.11ah, is a mechanism that has great potential to improve spatial reuse and efficiency. Primarily by introducing a novel approach to help address many long-standing challenges with overlapping BSS, which is regularly observed in enterprise and high-density environments. A BSS Color is a unique identifier announced for a collection of disparate basic service sets among various APs. Which gives Wi-Fi 6 receivers in range a new mechanism to intuitively give preference to frames sent from one AP over the other, for example, if operating on the same channel. This is possible as participating radios can now dynamically increase or decrease corresponding Clear Channel Assessment (CCA) thresholds accordingly, based on the BSS Color announced in the 802.11ax frames. However, in order to fully realize this benefit, both the wireless infrastructure and the client device of course need to fully support the BSS Coloring feature.
Higher throughput. The 802.11ax standard also delivers throughput improvements with several enhancements in both the physical (PHY) and media access control (MAC) layers. Together these enhancements will aid with potentially delivering higher data rates compared to the 802.11ac standard and others before it. Though only in the most optimal of conditions required to achieve 1024-QAM and higher modulation and coding schemes (MCS) now introduced with 802.11ax.
Power savings for client devices. Client devices that support Wi-Fi 6 will enjoy more efficient use of radio power with the Target Wake Time (TWT) feature, among other factors. This feature will be particularly useful for IoT endpoints because it allows the device radio to sleep until a specified time that was negotiated among the access point and connected clients. The TWT feature will translate to longer battery life per charge, as clients can keep their radios in a power-saving sleep state for far longer as compared to traditional power-save mechanisms. Additionally, the access point can have clients awaken at different intervals to help reduce possible contention within a radio cell. Thus, the new TWT feature has great potential for IoT sensors or similar devices that infrequently transmit and receive information, or otherwise need to conserve as much power and battery life as possible.
The Cisco IT plan for Wi-Fi 6 looks at several fundamental aspects as we prepare to upgrade our wireless network.
First is a thorough evaluation of the RF design at each location. The access point footprint at some sites likely won’t change significantly once upgraded to Wi-Fi 6. Nevertheless, we recognize that this is a good time to conduct a proper assessment, as both user densities and application demands may have changed since the last site survey. As a result, we are reviewing the existing coverage, capacity and placement of all access points. This is to ensure that any new Wi-Fi 6 AP deployments are adequate for all use cases, applications, and services that depend on wireless access at the site. Not only for today, but for what we anticipate over the next several years to come.
We will then consider how Wi-Fi 6 capable access points will potentially allow for a higher ratio of clients per access point as compared to previous-generation access point models. This is particularly important in higher density environments such as dedicated conference centers or even cafeterias that are used for ad-hoc events. Performance in these spaces can be significantly impacted when a large number of users simultaneously engage using interactive video or other demanding applications across multiple devices. Though this will need to be balanced with the expected mix of both 802.11ax and non-802.11ax capable devices that will be in use for quite some time.
Finally, we understand that the fundamentals of wireless network design won’t radically change even in a Wi-Fi 6 enabled world. We also still need to answer this basic question: How will this new wireless infrastructure and RF design serve both our existing and upcoming business needs? New technology and its associated benefits are exciting and certainly welcome, as we’ve outlined thus far. However, an adherence to solid wireless design and the fundamentals thereof will remain a crucial foundation to any successful rollout of Wi-Fi 6 or similar.
Learn more about Cisco solutions for Wi-Fi 6.
For more technical information on Wi-Fi 6.
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