Wi-Fi by the numbers

This FAQ briefly reviews the generations of Wi-Fi and backward compatibilities, looks at the different frequency bands used by the latest Wi-Fi specifications, and reviews the bandwidths offered by various Wi-Fi implementations. The first five generations of Wi-Fi focused on evolutionary and incremental advancements and backward compatibility. Wi-Fi 6 changed that trajectory and is a disruptive implementation of Wi-Fi. The latest version provides 1.2 GHz of the spectrum and supports up to seven 160 MHz channels. What can be expected from Wi-Fi 7 extremely high throughput (EHT) technology when it’s introduced, probably in 2024? And will the combination of Wi-Fi 6 and Wi-Fi 7 compete with 5G telephony?

WiGig and HaLow

The Wi-Fi WiGig and HaLow extensions are designed to enable Wi-Fi to service high-speed and data-intensive connections and longer-range and lower-power connections, respectively (Figure 1). WiGig is designed to support virtual reality, augmented reality, multimedia streaming, gaming, and enterprise applications using the 60 GHz frequency band with wide channels to transmit data at multi-gigabit speeds. Often called ’60 GHz Wi-Fi,’ WiGig actually operates over the 2.4, 5, and 60 GHz bands. Since the 60 GHz millimeter waves cannot typically penetrate walls, the protocol automatically switches to the lower bands, resulting in slower transmission rates when the user roams outside the main room.

Figure 1: While most Wi-Fi embodiments use the 2.4 and 5 GHz bands, there are exceptions: WiGig operates at 60 GHz, and Wi-Fi HaLow operates in the sub-1 GHz band. (Image: Wi-Fi Alliance)

WiGig includes the IEEE 802.11ad standard and also the recently-approved IEEE 802.11ay-2021 standard. IEEE 802.11ay is called Enhanced Throughput for Operation in License-exempt Bands above 45 GHz, is an extension of the IEEE 802.11ad WiGig standard, which quadruples the bandwidth and adds MIMO up to 8 streams. 802.11ay WiGig can transmit at 20 to 40 Gbit/s over a distance up to 500 meters under optimal conditions.

While WiGig was developed to use high frequencies to support high data rates, IEEE 802.11ah, called ‘Wi-Fi HaLow’ (pronounced ‘HEY-Low’) uses the 900 MHz license-exempt bands between 750 MHz and 928 MHz to provide low-power extended-range Wi-Fi networks (Figure 1). HaLow is designed to support large networks of wireless sensors in the Internet of Things (IoT) applications and competes with Bluetooth, but with higher data rates, wider coverage areas, and only a relatively small increase in energy demands.

Wi-Fi 6 and 6E use Cellular Telephony Tech

Wi-Fi 6, IEEE 802.11ax, operates in the 2.4 GHz and 5 GHz bands, and Wi-Fi 6E in the 6 GHz band is also known as High-Efficiency Wi-Fi. Increased throughput in high-density deployments was a key goal of Wi-Fi 6 and 6E. A higher spectral efficiency makes it possible to quadruple overall throughput. The higher throughput is made possible by employing orthogonal frequency-division multiple access (OFDMA) cellular technology in 802.11ax (Figure 2).

Figure 2: With a traditional Wi-Fi network (top), devices may have to wait for the client to send or receive data on a crowded network. OFDMA (bottom) allows more devices to be served data in the same transmission window, resulting in more efficient communication with multiple devices simultaneously. (Image: Intel)

WI-FI 6 also supports eight-stream multi-user, multiple-input multiple-output (MU-MIMO) technology providing efficient transmission of high-bandwidth traffic. Wi-Fi 6 also enables 8×8 access points to use all eight streams to transmit data. And the higher-order 1020-QAM modulation increases the efficiency and speed of data transmission up to 25%. The 6 GHz band in Wi-Fi 6E has a shorter range than the 5 GHz band but supports up to fourteen 80MHz channels or seven 160MHz channels. Additional benefits include:

There is more available spectrum and less overlap between nearby networks in densely populated areas such as apartment complexes or offices and more capacity for applications like 8K video streaming, high-definition video conferencing, and VR gaming.
6 GHz does not require dynamic frequency selection (DFS). Devices in the 6 GHz band don’t share spectrum with other devices such as television stations or radars, unlike the 5 GHz bands, enabling the use of full 160 MHz channels.
6 GHz is a new spectrum for Wi-Fi, so there are no legacy devices to slow transmission speeds. Wi-Fi 6E devices can take full advantage of the bandwidth, spectrum, and speed improvements of 6 GHz without concern for slower legacy devices.
More security. Wi-Fi Protected Access (WPA) 3 is required for all Wi-Fi 6 devices operating in 6 GHz. WPA3 is the newest and most secure Wi-Fi authentication protocol, making 6 GHz networks harder to hack.

Wi-Fi 7 EHT

Each successive Wi-Fi generation has delivered faster connectivity. IEEE 802.11be, Wi-Fi 7, will be no exception. Called extremely high throughput (EHT) or wireless fidelity, Wi-Fi 7 will not simply enhance Wi-Fi 6; it will introduce more new networking technologies to drive even faster connectivity (Figure 3). With Wi-Fi 7, latency will be more predictable and less variable.

Wi-Fi 7 will include tri-band operation, wider 320 MHz channels, 4096 QAM modulation, up to 16×16 MIMO, and multi-link operation (MLO).

Figure 3: Wi-Fi 7 will build on the foundation of earlier generations to support 8K video streaming plus real-time AR/VR games. (Image: Versa Technology)

The enhanced version of OFDMA added with Wi-Fi 7 will be more flexible and provide increased spectrum efficiency and reduce latency by supporting the assignment of punctured resource units (RUs) to a single station (STA) and also supporting direct link transmissions. Wi-Fi 7 will use puncturing to eliminate transmission in parts of the channel (up to 20 MHz) to accommodate spectrum restrictions that may prohibit the use of part of the band. Puncturing will also make it possible to use wide channels in environments with insufficient contiguous spectrum available. Wi-Fi 7 will increase the modulation rate to 4096 QAM, increasing throughput by 20% over Wi-Fi 6.

Wi-Fi 7 will double the maximum channel size to 320 MHz compared with 160 MHz supported by Wi-Fi 6, doubling the throughput. Wi-Fi 7 will also support 160+160MHz, 240+180MHZ, and 160+80MHz channels to combine non-contiguous spectrum blocks.

With multi-line operation (MLO) with separate PHY layers and a common MAC layer, Wi-Fi 7 client stations and access points will transmit and receive simultaneously on multiple links. For example, devices will transmit and receive on both the 5 GHz and 6 GHz bands simultaneously. This feature will support greater aggregate throughput and lower latency.

The Wi-Fi 7 standard doubles the number of spatial streams up to 16 and double throughput compared to Wi-Fi 6 with eight spatial streams. The addition of 16×16 MIMO support will improve spectral efficiency with MU-MIMO. Wi-Fi 7 is expected to support both downlink and uplink MU-MIMO, further enhancing performance.

Overall, Wi-Fi 7 is expected to improve wireless access point coordination, using several tools including various combinations of:

Orthogonal frequency division multiple access
Spatial reuse
Time-division multiple access
Beamforming
Joint processing

Wi-Fi 6 and Wi-Fi 7 vs. 5G

Wi-Fi 7 is expected to be a true wireline/Ethernet replacement for high bandwidth, low-latency applications when it rolls out. Wi-Fi 7 could be competitive with 3GPP 5G technology in smart factory and industrial IoT (IIoT) applications. They will be similar but not exact replacements for each other.

A significant difference is that 5G is not expected to be used with previous-generation 4G technologies. At the same time, Wi-Fi 6 and Wi-Fi 7 will not only be interoperable, but they will also be complimentary. Wi-Fi 6 is expected to be most useful in high-density areas like a warehouse or other enterprise environments. Wi-Fi 7 will improve support for applications that require deterministic latency, high reliability, and quality of service (QoS) such as wireless time sensitive networking) (WTSN). It will be possible to combine Wi-Fi 6 and Wi-Fi 7 in a single device to gain the base of both standards.

5G includes the Ultra-Reliable Low-Latency Communication (URLLC) specification that meets industrial automation’s strict latency and reliability demands and is important when implementing WTSN. The new Sidelink device-to-device specification in 5G will also blur the lines between 5G and Wi-Fi.

Sidelink is another protocol in addition to uplink and downlink. The network controls resource allocation and link adaptation with uplinks and downlinks (Figure 4). With Sidelink, a device performs both functions autonomously. Sidelink enables device-to-device communication link to one hop, significantly reducing device-to-device communication latency, which is one key to enabling WTSN applications. In the future, Wi-Fi 6, Wi-Fi 7, and 5G are expected to be used together in industrial wireless networks to support edge computing, distributed and cloud architectures, virtualization, and WTSN.

Figure 4: 5G Sidelink device to device is expected to significantly reduce device-to-device communication latency, helping to enable WTSNs and enabling 5G to compete more directly with Wi-Fi. (Image: Springer Link)

Summary

Wi-Fi is a well-established wireless networking protocol. It has evolved significantly over the years, with the latest version, Wi-Fi 6, accelerating technological advancements. Wi-Fi 6 and Wi-Fi 6E offer a preview of what’s to come with the introduction of Wi-Fi 7 in a few years. Once Wi-Fi 7 has arrived, Wi-Fi will become a competitor and partner with 5G wireless services and help provide WTSN and other advanced networking capabilities to wireless networks in industrial and commercial settings.

References
What is the difference between Wi-Fi 6 and Wi-Fi 6E?, Netgear
What is Wi-Fi 6? Intel
Wi-Fi 7, Litepoint
Wi-Fi 7: The Next Generation, Versa Technology
Wi-Fi CERTIFIED HaLow, Wi-Fi Alliance