Wi-Fi 7Data Rates, and Latency Understanding the IEEE 802.11be Standard

Born in 1997, Wi-Fi has influenced human life far more than any other Gen Z celebrity. Its steady growth and maturation have gradually liberated network connectivity from the ancient regime of cables and connectors to the extent that wireless broadband Internet access—something unthinkable in the days of dial-up—is often taken for granted.

I’m old enough to remember the satisfying click by which an RJ45 plug signified a successful connection to the rapidly expanding online multiverse. Nowadays I have little need for RJ45s, and tech-saturated teenagers of my acquaintance might be unaware of their existence.

In the 60s and 70s, AT&T developed modular connector systems to replace bulky phone connectors. These systems later expanded to include the RJ45 for computer networking

The preference for Wi-Fi among the general populace is not at all surprising; Ethernet cables seem almost barbaric compared to the prodigious convenience of wireless. But as an engineer concerned simply with datalink performance, I still see Wi-Fi as inferior to a wired connection. Will 802.11be bring Wi-Fi a step—or maybe even a leap—closer to completely displacing Ethernet?

A Brief Introduction to Wi-Fi Standards: Wi-Fi 6 and Wi-Fi 7

Wi-Fi 6 is the publicized name for IEEE 802.11ax. Fully approved in early 2021, and benefiting from over twenty years of accumulated improvements in the 802.11 protocol, Wi-Fi 6 is a formidable standard that does not appear to be a candidate for rapid replacement.

A blog post from Qualcomm summarizes Wi-Fi 6 as “a collection of features and protocols aimed at driving as much data as possible to as many devices as possible simultaneously.” Wi-Fi 6 introduced various advanced capabilities that improve efficiency and increase throughput, including frequency-domain multiplexing, uplink multi-user MIMO, and dynamic fragmentation of data packets.

Wi-Fi 6 incorporates OFDMA (orthogonal frequency division multiple access) technology, which increases spectral efficiency in multi-user environments

Why, then, is the 802.11 working group already well on its way to developing a new standard? Why are we already seeing headlines about the first Wi-Fi 7 demo? Despite its collection of state-of-the-art radio technologies, Wi-Fi 6 is perceived, at least in some quarters, as underwhelming in two important respects: data rate and latency.

By improving upon the data rate and latency performance of Wi-Fi 6, the architects of Wi-Fi 7 hope to deliver the fast, smooth, reliable user experience that is still more easily achieved with Ethernet cables.

Data Rates vs. Latencies Concerning Wi-Fi Protocols

Wi-Fi 6 supports data transmission 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 data rates are objectively lackluster: Wi-Fi 5 achieved a one-thousand-percent increase in data rate compared to its predecessor, whereas Wi-Fi 6 increased data rate by less than fifty percent compared to Wi-Fi 5.

The theoretical stream data rate is definitely not a comprehensive means of quantifying the “speed” of a network connection, but it’s important enough to merit the close attention of those responsible for Wi-Fi’s ongoing commercial success.

Comparison of the past three generations of Wi-Fi network protocols

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

In the context of network connections, excessive latency can degrade user experience as much as (or even more than) limited data rate—blazing-fast bit-level transmission doesn’t help you much if you have to wait five seconds before a web page starts to load. Latency is particularly important for real-time applications such as video conferencing, virtual reality, gaming, and remote equipment control. Users only have so much patience for glitchy videos, laggy games, and dilatory machine interfaces.

Wi-Fi 7's Data Rate and Latency

The Project Authorization Report for IEEE 802.11be includes both increased data rate and reduced latency as explicit objectives. Let’s take a closer look at these two upgrade pathways.

Data Rate and Quadrature Amplitude Modulation

The architects of Wi-Fi 7 want to see maximum throughput of at least 30 Gbps. We don’t know which features and techniques will be incorporated into the finalized 802.11be standard, but some of the most promising candidates for increasing data rate are 320 MHz channel width, multi-link operation, and 4096-QAM modulation.

With access to additional spectrum resources from the 6 GHz band, Wi-Fi can feasibly increase the maximum channel width to 320 MHz. A channel width of 320 MHz increases maximum bandwidth and theoretical peak data rate by a factor of two relative to Wi-Fi 6.

In multi-link operation, multiple client stations with their own links function collectively as “multi-link devices” that have one interface to the network’s logical link control layer. Wi-Fi 7 will have access to three bands (2.4 GHz, 5 GHz, and 6 GHz); a Wi-Fi 7 multi-link device could send and receive data simultaneously in multiple bands. The multi-link operation has the potential for major throughput increases, but it entails some significant implementation challenges.

In multi-link operation, a multi-link device has one MAC address even though it includes more than one STA (which stands for station, meaning a communicating device such as a laptop or smartphone)

QAM stands for quadrature amplitude modulation. This is an I/Q modulation scheme in which specific combinations of phase and amplitude correspond to different binary sequences. We can (in theory) increase the number of bits transmitted per symbol by increasing the number of phase/amplitude points in the system’s “constellation” (see the diagram below).

This is a constellation diagram for 16-QAM. Each circle on the complex plane represents a phase/amplitude combination that corresponds to a predefined binary number

Wi-Fi 6 uses 1024-QAM, which supports 10 bits per symbol (because 2^10 = 1024). With 4096-QAM modulation, a system can transmit 12 bits per symbol—if it can achieve sufficient SNR at the receiver to enable successful demodulation.

Wi-Fi 7 Latency Features:

MAC Layer and PHY Layer
The threshold for reliable functionality of real-time applications is worst-case latency of 5–10 ms; latencies as low as 1 ms are beneficial in some usage scenarios. Achieving latencies this low in a Wi-Fi environment is not an easy task.

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

Key features of Wi-Fi 7

Recent research indicates that multi-link aggregation, which is included within the general heading of multi-link operation, may be instrumental in enabling Wi-Fi 7 to satisfy the latency requirements of real-time applications.

The Future of Wi-Fi 7?

We don’t yet know what exactly Wi-Fi 7 will look like, but it will undoubtedly comprise impressive new RF technologies and data-processing techniques. Will all the R&D be worth it? Will Wi-Fi 7 revolutionize wireless networking and definitively neutralize the few remaining advantages of Ethernet cables? Feel free to share your thoughts in the comments section below.

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