Will Wi-Fi 7 be a revolution?

A Google search for “famous members of Generation Z” turns up all sorts of names I’ve never heard of (I did recognize Greta Thunberg, though). But one name was conspicuously absent: IEEE 802.11, or what we commonly call Wi-Fi.

Wi-Fi was born in 1997 and has had a far greater impact on human life than any other Gen Z celebrity. Its steady growth and maturity have gradually freed network connections from the old regime of cables and connectors, to the point where wireless broadband Internet access—unthinkable in the dial-up era—is often taken for granted.

I'm old enough to remember the satisfying click of an RJ45 plug, signaling a successful connection to the rapidly expanding online multiverse. These days I rarely need RJ45s, and the tech-saturated teenagers I know probably don't even know they exist.

The general public's preference for Wi-Fi isn't surprising. Compared to the tremendous convenience of wireless, Ethernet cables seem almost barbaric. But as an engineer who only cares about data link performance, I still think Wi-Fi is inferior to wired connections. Will 802.11be bring Wi-Fi closer to completely replacing Ethernet?

Wi-Fi Standards Brief: Wi-Fi 6 and Wi-Fi 7

Wi-Fi 6 is the public name for IEEE 802.11ax. Fully ratified in early 2021, Wi-Fi 6 is a robust standard that doesn’t seem ripe for a quick replacement, thanks to more than two decades of cumulative improvements to the 802.11 protocol.

A Qualcomm blog post summarizes Wi-Fi 6 as “a collection of features and protocols designed to drive as much data as possible to as many devices as possible, simultaneously.” Wi-Fi 6 introduces a variety of advanced features to improve efficiency and increase throughput, including frequency domain reuse, uplink multi-user MIMO, and dynamic slicing of data packets.

Wi-Fi 6 uses OFDMA (Orthogonal Frequency Division Multiple Access) technology to improve spectrum efficiency in multi-user environments.

Image courtesy of Cisco

So why is the 802.11 working group already well on its way to developing a new standard? And why are we already seeing headlines about the first Wi-Fi 7 demos? Despite its collection of cutting-edge radio technologies, Wi-Fi 6 is considered, at least in some quarters, to be underwhelming in two important areas: data rates and latency.

By improving on the data rate and latency performance of Wi-Fi 6, the architects of Wi-Fi 7 hope to provide a fast, smooth, and reliable user experience that is easier to achieve than using Ethernet cables.

About Wi-Fi protocol data rate and latency

Wi-Fi 6 supports data rates approaching 10 Gbps. Whether this is “good enough” in an absolute sense is a highly subjective question. However, in a relative sense, Wi-Fi 6’s data rates are objectively lackluster: Wi-Fi 5 delivered a 1,000% data rate increase over its predecessor, while Wi-Fi 6 delivers less than a 50% data rate increase over Wi-Fi 5.

The theoretical streaming data rate is by no means a comprehensive means of quantifying the "speed" of a network connection, but it is important enough to warrant close attention by those responsible for the continued commercial success of Wi-Fi.

Comparison of the past three generations of Wi-Fi network protocols. Image courtesy of Intel

Latency as a general concept refers to the delay between input and response.

In the case of network connections, excessive latency can degrade the user experience even more than limited data rates—blazingly fast bit-rate transmissions won’t do you much good if you have to wait five seconds before a web page starts loading. Latency is especially important for real-time applications like video conferencing, virtual reality, gaming, and remote device control. Users have only so much patience for glitchy video, laggy games, and draggy machine interfaces.

Wi-Fi 7 data rates and latency

The project authorization report for IEEE 802.11be includes increasing data rates and reducing latency as explicit goals. Let’s take a closer look at these two upgrade paths.

Data Rate and Quadrature Amplitude Modulation

The architects of Wi-Fi 7 want to see a maximum throughput of at least 30 Gbps. We don't know what features and technologies will be included in the finalized 802.11be standard, but some of the most promising candidates for increased data rates are 320 MHz channel width, multi-link operation, and 4096-QAM modulation.

By accessing additional spectrum resources in the 6 GHz band, Wi-Fi can increase the maximum channel width to 320 MHz. Relative to Wi-Fi 6, the 320 MHz channel width increases the maximum bandwidth and theoretical peak data rate by two times.

In multi-link operation, multiple client stations with their own links function together as a "multi-link device" with one interface to the network's logical link control layer. Wi-Fi 7 will have access to three frequency bands (2.4 GHz, 5 GHz, and 6 GHz); a Wi-Fi 7 multi-link device can send and receive data on multiple bands simultaneously. Multi-link operation has the potential to significantly increase throughput, but it presents some significant implementation challenges.

In multilink operation, a multilink device has one MAC address even if it contains multiple STAs (which stands for station, meaning a communicating device such as a laptop or smartphone). Image courtesy of IEEE

QAM stands for Quadrature Amplitude Modulation. It is an I/Q modulation scheme where specific combinations of phase and amplitude correspond to different binary sequences. We can (theoretically) increase the number of bits transmitted per symbol by increasing the number of phase/amplitude points in the system's "constellation" (see figure below).

This is the constellation diagram for 16-QAM. Each circle on the complex plane represents a phase/amplitude combination corresponding to a predefined binary number. Image courtesy of IEEE

Wi-Fi 6 uses 1024-QAM, which supports 10 bits per symbol (because 2 10 = 1024). If 4096-QAM modulation is used, the system can transmit 12 bits per symbol, provided it can achieve enough SNR at the receiver for successful demodulation.

Latency characteristics: MAC layer and PHY layer

The threshold for reliable functionality of real-time applications is 5-10 milliseconds of worst-case latency; in some use cases, latency as low as 1 millisecond is beneficial. Achieving such low latency in a Wi-Fi environment is not trivial.

Functions operating at the MAC (media access control) layer and the physical layer (PHY) will help bring Wi-Fi 7 latency performance into the sub-10 millisecond realm. These include multi-access point coordinated beamforming, time-sensitive networking, and multi-link operation.

Key features of Wi-Fi 7. Image courtesy of IEEE

Recent research suggests that multi-link aggregation, included in the general title of multi-link operation, may help enable Wi-Fi 7 to meet the latency requirements of real-time applications.

Are you optimistic about the future of Wi-Fi 7?

We don’t know exactly what Wi-Fi 7 will look like yet, but it will undoubtedly include impressive new radio frequency and data processing techniques. Is all this research and development worth it? Will Wi-Fi 7 revolutionize wireless networking and completely eliminate the few remaining advantages of Ethernet cables? Feel free to share your thoughts in the comments section below.