The Next Generation of Wi-Fi 6 Explained
Wi-Fi is set to get better and faster with its upcoming major update. While plenty of routers are already available with chips using draft specifications, 802.11ax Wi-Fi won’t be finalized until December 2019, ushering in a wave of updated devices touting new wireless capabilities that will contribute toward next-generation networks with more speed and less congestion.
802.11ax also known as ‘high-efficiency wireless’ will be commonly referred to as Wi-Fi 6.
This is a new naming standard set by the Wi-Fi Alliance, with previous generations now being known as Wi-Fi 5 (802.11ac) and Wi-Fi 4 (802.11n). This labeling convention is expected to appear on devices as shown below.
Technically, Wi-Fi 6 will have a single-user data rate that is 37% faster than 802.11ac, but what’s more significant is that the updated specification will offer four times the throughput per user in crowded environments, as well as better power efficiency which should translate to a boost in device battery life.
To achieve those improvements, 802.11ax implements a variety of changes including several multi-user technologies which have been borrowed from the cellular industry – namely MU-MIMO and OFDMA – techniques that greatly improve capacity and performance by enabling more simultaneous connections and a more thorough use of spectrum.
Home users who upgrade their hardware can look forward to some improvements from these technologies, especially over time as the number of devices per household increases – some estimates suggest there will be as many as 50 nodes per home by 2022.
However, as mentioned, Wi-Fi 6 is anticipated to have a more immediate impact in areas where networks are highly congested and will ultimately aid in laying a foundation for the number of nodes expected on upcoming smart infrastructure (e.g. Internet of Things devices). Along with addressing overlapping coverage from the sheer number of devices and network deployments emerging as IoT rolls out, Wi-Fi 6 will be equipped to handle the ever-increasing demand for faster multi-user data rates.
Overall, Wi-Fi 6 builds on 802.11ac with more than fifty updated features, though not all of them will necessarily be included in the finalized specification.
Here’s some of what Wi-Fi 6 is expected to accomplish:
- More overall bandwidth per user for ultra-HD and virtual reality streaming
- Support for more simultaneous streams of data with increased throughput
- More total spectrum (2.4GHz and 5GHz, eventually bands in 1GHz and 6GHz)
- Said spectrum split into more channels to enable more routes for communication
- Packets contain more data and networks can handle different data streams at once
- Improved performance (as much as 4x) at the maximum range of an access point
- Better performance/robustness in outdoor and multi-path (cluttered) environments
- Ability to offload wireless traffic from cellular networks where reception is poor
802.11n vs. 802.11ac vs. 802.11ax
|802.11n (Wi-Fi 4)||802.11ac Wave 2 (Wi-Fi 5)||802.11ax (Wi-Fi 6)|
|Bands||2.4GHz & 5GHz||5GHz||2.4GHz & 5GHz, spanning to 1GHz – 7GHz eventually|
|Channel Bandwidth||20MHz, 40MHz (40MHz optional)||20MHz, 40MHz, 80MHz, 80+80MHz & 160MHz (40MHz support made mandatory)||20MHz/40MHz @ 2.4GHz, 80MHz, 80+80MHz & 160MHz @ 5GHz|
|FFT Sizes||64, 128||64, 128, 256, 512||64, 128, 256, 512, 1024, 2048|
|Subcarrier Spacing||312.5kHz||312.5kHz||78.125 kHz|
|OFDM Symbol Duration||3.6ms (short guard interval) 4ms (long guard interval)||3.2ms (0.4/0.8ms cyclic prefix)||12.8ms (0.8/1.6/3.2ms cyclic prefix)|
|Data Rates||Ranging from 54Mb/s to 600Mb/s (max of 4 spatial streams)||433Mb/s (80MHz, 1 spatial stream) 6933Mb/s (160MHz, 8 spatial stream)||600Mb/s (80MHz, 1 spatial stream) 9607.8Mb/s (160MHz, 8 spatial stream)|
|SU/MU-MIMO-OFDM/A||SU-MIMO-OFDM||SU-MIMO-OFDM Wave 1, MU-MIMO-OFDM Wave 2||MU-MIMO-OFDMA|
Released in 2013, 802.11ac (now also known as Wi-Fi 5) was standardized in 2013 and while this specification is largely adequate for today’s typical home usage, it only uses bands in the 5GHz spectrum and lacks the level of multi-user technologies that will support a growing number of devices connected at once.
As a point of reference for the changes coming in Wi-Fi 6, here is what 802.11ac (Wi-Fi 5) expanded on 802.11n (Wi-Fi 4):
- Wider channels (80MHz or 160MHz versus a max of 40MHz in the 5GHz band)
- Eight spatial streams instead of four (spatial streams illustrated)
- 256-QAM versus 64-QAM modulation (transmits more bits per QAM symbol)
- Multi-User MIMO (MU-MIMO) on 802.11ac Wave 2, enabling four downlink connections at once instead of only one on Single-User MIMO (still 1×1 on uplink)
When Wi-Fi 6 is launched in full, the specification will be backward compatible with previous standards, incorporating both 2.4GHz and 5GHz along with eventually expanding that spectrum to include bands in 1GHz and 6GHz when they become available.
Perhaps more noteworthy than the inclusion of this additional spectrum are the technologies that will put this bandwidth to use. With more spectrum available, Wi-Fi 6 can split the bandwidth into narrower (more) sub-channels, creating more avenues for clients and access points to communicate along with enabling support for additional devices on any given network.
While Wi-Fi 5 can serve four users on downstream at once courtesy of MU-MIMO – a considerable improvement over the single-user MIMO on Wi-Fi 4 – today’s AC wireless (Wi-Fi 5) can still only handle one user at a time on upstream. On paper, 802.11ax will increase that to eight users on both up and downlink, with the potential to deliver four simultaneous streams to a single client.
However, we’ve read that uplink MU-MIMO may not be supported on the first round of 802.11ax-certified hardware, and few if any current devices can benefit from four spatial streams, much less the eight supported on Wi-Fi 6, as most existing MU-MIMO-equipped smartphones and laptops only have 2×2:2 or 3×3:3 MIMO radios.
This number formatting (AxB:C) is used to demonstrate the maximum amount of transmit antennas (A), the maximum amount of receive antennas (B) and the maximum amount of spatial data streams (C) supported by a MIMO radio. While a Wi-Fi device must support MU-MIMO to directly benefit from that technology, hardware without MU-MIMO chips should indirectly benefit from the additional air time available on MU-MIMO-enabled access points.
Wi-Fi 6 also introduces support for up and downlink “Orthogonal Frequency Division Multiple Access” (OFDMA), a modulation scheme that is equated to a multi-user version of OFDM (the spec on 802.11ac/n), which will reduce latency, boost capacity and improve efficiency by allowing as many as 30 users at once to share a channel.
To help you visualize those technologies, instead of one clerk serving a single line of customers individually, the combination of MU-MIMO and OFDMA can be equated to having many clerks and many lines, with each clerk capable of serving multiple customers at once.
Further, 802.11ax informs clients more clearly when a router is available instead of having them contend for access, along with boosting the amount of data delivered in each payload courtesy of 1024-QAM encoding versus the 256-QAM modulation on Wi-Fi 5 and 64-QAM on Wi-Fi 4.
Although Wi-Fi 6’s overall data rates and channel widths are similar to Wi-Fi 5, dozens of technologies have been implemented to the updated specification that should significantly improve the efficiency and throughput of future Wi-Fi networks, which could potentially serve dozens of devices on a single channel with speeds of several gigs a second.
Here are some of the core technologies that Wi-Fi 6 will change from current Wi-Fi specifications:
MU-MIMO (Multi-User Multiple-Input Multiple-Output) – Wi-Fi 5 Wave 2 introduced Multi-User MIMO but only supports four simultaneous connections on downstream (one on upstream), while Wi-Fi 6 will be able to handle eight streams of data in either uplink or downlink, supporting more users at once and offering four times the maximum theoretical throughput of Wi-Fi 5.
MU-MIMO access points also handle more signal processing than SU-MIMO APs, offloading that burden from end point devices, and MU-MIMO traffic is considered to be secure until tools are developed for processing the signals, as only the intended recipient can read the data.
OFDMA (Orthogonal Frequency-Division Multiple Access) – Not a part of Wi-Fi 5, which has regular OFDM. Borrowed from 4G LTE networks. Allows for resource unit allocation in a given bandwidth. Incorporated on Wi-Fi 6 so more clients (as many as 30) can share the same channel instead of waiting, while also improving efficiency by combing different traffic types. OFDMA is compared as a multi-user version of OFDM.
1024-QAM (Quadrature Amplitude Modulation) – An increase from 256-QAM on Wi-Fi 5, though some routers from this generation have 1024-QAM as an experimental feature. This boosts throughput by cramming more data into each packet.
1024-QAM uses 10 bits per OFDM symbol versus 8 bits for 256 QAM, a 25% capacity boost that results in a theoretical single-stream data rate of 600Mb/s using an 80MHz channel (39% better than the theoretical 433Mb/s single-stream data rate of Wi-Fi 5).
Longer OFDM Symbols – Increases the duration that an OFDM symbol is transmitted from 3.2ms on Wi-Fi 5 to 12.8ms on Wi-Fi 6 and supports a longer cyclic prefix for each symbol.
A cyclic prefix (CP) adds a portion of the end of a OFDM symbol to the front of the payload to provide a guard interval against intersymbol interference and to improve robustness since this portion can be used if necessary. This figure can be adjusted depending on overhead requirements (a longer CP repeats more data and occupies more space in a symbol, resulting in a lower data rate).
Dynamic fragmentation – Whereas Wi-Fi 5 has static fragmentation, which requires all fragments of a data packet to be the same size (except for the last fragment), dynamic fragmentation allows these pieces to be of a varying size for better use of network resources.
Spatial frequency reuse/OBSS (BSS coloring) – If multiple access points are operating on the same channel(s), they can transmit data with a unique “color” identifier that allows them to communicate over the wireless medium at the same time without waiting as the colors enable them to differentiate between each other’s data.
Beamforming – Exists on Wi-Fi 5, though that standard supports four antennas and Wi-Fi 6 increases this to eight. Beamforming improves data rates and extends range by directing signals toward specific clients instead of in every direction at once. This aids MU-MIMO, which doesn’t work well with rapidly moving devices. Beamforming was optionally available on Wi-Fi 4 devices but became necessary with the implementation of MU-MIMO on Wi-Fi 5 Wave 2.
TWT (Target Wake Time) – Wake-time scheduling instead of contention-based access. A router can tell a client when to sleep and when to wake, which is expected to make a considerable difference in battery life since a device will know when to listen on a channel.
Uplink resource scheduler – Similarly, instead of users competing to upload data as on today’s wireless networks, Wi-Fi 6 schedules uplinks to minimize conflicts, resulting in better resource management.
Trigger-based Random Access – Also reduces data collisions/conflicts by specifying the length of an uplink window among other attributes that improve resource allocation and boost efficiency.
Two NAVs (Network Allocation Vector) – When a wireless station is transmitting, it advertises the duration it will take to complete so other stations can set their NAV to avoid conflicts when accessing the wireless medium. Wi-Fi 6 introduces two NAVs: One for the network that the station belongs to and one for neighboring networks. This should also reduce energy consumption by minimizing the need for carrier sensing.
Improved outdoor operation – Several of these features will result in better outdoor performance, including a new packet format, longer guard intervals and modes for improved redundancy and error recovery.
Expanding Wi-Fi 6 to Include 6GHz
Industry leaders such as Qualcomm have determined that adequate quality of service on future networks will require more spectrum than either 2.4GHz or 5GHz can provide. The 2.4GHz band has long been saturated by common electronics while 5GHz has insufficient spectrum for wider bandwidth channels (such as 80MHz or 160MHz) and portions of 5GHz are subject to restrictions that limit its use.
Qualcomm has suggested that regulators should expect to allocate around 1280MHz of unlicensed spectrum somewhere in the 5GHz band for unlicensed technologies.
In response to the FCC’s call for public comments in July 2017 regarding the expansion of mid-band spectrum between 3.7GHz and 24GHz, more than 30 technology companies including Qualcomm submitted a proposal insisting that the 5925-7125MHz band (the “6GHz band”) is “essential to meeting demand for the next generation of wireless broadband services.”
To fulfill this upcoming demand for Wi-Fi, the companies proposed that 6GHz be opened to unlicensed technologies and split into four sub-bands with different technical rules and interference protections.
Given that Wi-Fi 6 is currently being developed and that the US among other countries are opening the 6GHz band, the IEEE 802.11ax Task Group has decided to implement support for this spectrum on next-generation Wi-Fi 6.
Allocating the 6GHz band as unlicensed space is appealing to companies because they can use this frequency without filing for access with the FCC, which is expected to propel innovation and investment as the so-called fourth industrial revolution unfolds.
“By opening this entire band to unlicensed radio local access network operations, the Commission will allow us to bring consumers faster service, lower latency, and more pervasive coverage, and allow the nation to reap the economic and public safety benefits that are associated with unlicensed technologies,” the companies wrote in their proposal to the FCC.
Wi-Fi 6 or 802.11ax is only one of many upcoming wireless standards being developed to service the variety of network demands that will be made by different types of devices.
Standards span from 802.11aj/ay which can deliver tens of gigabits a second over 60GHz mmWave frequencies, to sub-1GHz specifications such as 802.11ah which offers lower bandwidth/better range for IoT sensors — all of which (and more) will be part of the licensed and unlicensed spectrum that comprise 5G.
Wrap Up: A Sky-Level View of Wi-Fi 6
Meant to replace both 802.11n and 802.11ac as the next WLAN standard, 802.11ax or Wi-Fi 6 is being developed to deliver considerable increases in network efficiency and capacity for dense population centers, with moderate improvements to peak data rates, which will be sustained better across more devices at once.
Or as Qualcomm likes to put it, “the problem isn’t how fast Wi-Fi can go, but if the Wi-Fi network has enough capacity to handle the growing demand for many different connected devices and services.”
Because Wi-Fi 6 will have an immediate impact on the performance of networks in crowded places such as stadiums or apartment buildings, the standard is expected to be adopted faster than previous Wi-Fi iterations and it will eventually be a necessity for home users as 100Mb/s to 1Gb/s broadband connections become more available, and as the roll-out of IoT leads to ‘everything’ being online.
Contemplating Wi-Fi 6 more broadly, the boost in multi-user support and particularly the increase in simultaneous upstream connections will arrive alongside an accelerating demand for user data, which will be gathered from IoT devices and used for purposes such as machine learning, fueling artificial intelligence, the future of technology as a whole and a growing digital economy.
As mentioned in the introduction of this article, routers are already available based on draft 802.11ax specifications, with final ratification of the standard due in December 2019. And again, the first round of official devices might not support the full capabilities of Wi-Fi 6, which could potentially be expanded with a second wave of hardware enabling further support for features such as higher order MU-MIMO and 6GHz spectrum.