How the Wi-Fi Industry Can Overcome Congestion on Unlicensed Spectrum

Unlicensed spectrum is the lifeblood of Wi-Fi. It is the medium by which data are transferred wirelessly, and the quantity and properties of the available spectrum determines Wi-Fi performance. An abundance of spectrum resources can deliver seamless, reliable connectivity and enable high-throughput, low-latency demanding applications. On the other hand, environments suffering from insufficient spectrum will face degraded user experiences, as multiple devices competing for the same finite resources causes interference, and a lack of bandwidth allows for only the most basic of applications. Throughout the history of Wi-Fi, the pendulum has swung between these two states. In the early years of Wi-Fi, when there were few Wi-Fi devices and performance demands were rudimentary, the 570 Megahertz (MHz) offered by the 2.4 Gigahertz (GHz) and 5 GHz bands was sufficient. Yet, by the late 2010s, an explosion in Wi-Fi devices and their requirements meant that this meager spectrum was quickly becoming inadequate. Many regulators responded by expanding unlicensed access to the 6 GHz spectrum, injecting fresh spectrum, which created an abundance of resources. Yet, this is only a temporary solution, and with the ceaseless increase in both the number and the demands of Wi-Fi devices showing no sign of abating, this supply of spectrum is likely to also one day run dry. There are two main ways in which the industry can overcome this future spectrum scarcity. The first is a further expansion of access to unlicensed spectrum, increasing the pool that Wi-Fi can draw upon, while the second is developing new technologies that can improve spectrum efficiency, helping to extract more value from existing resources. This ABI Insight examines these two approaches, assessing how the industry will look to employ them in the coming years. We will end with additional steps that the industry can take to address the challenge. 

The first solution to the challenge is to enlarge the pool of spectrum that Wi-Fi can harness. This is perhaps the most obvious response, and if enacted, it is guaranteed to produce a significant impact, as the gradual release of the 6 GHz spectrum for unlicensed use in many nations worldwide in recent years has shown. Yet, the story of 6 GHz also highlights how spectrum access is a highly contested domain, with both the Wi-Fi and the International Mobile Telecommunications (IMT) industries competing fiercely to secure as much of the band as possible for their respective technologies. While in the United States the Wi-Fi industry came out on top and was awarded the full 1200 MHz of the band, in Europe the band was split into two portions, with only the lower half being assigned for unlicensed use. In many other countries, including the world’s largest market for residential Wi-Fi Customer Premises Equipment (CPE)—Mainland China—none of the band has been assigned for unlicensed. The divergent approach toward spectrum allocations taken by regulators globally prevents expanded spectrum access from being a universal solution to the spectrum congestion challenge, and thus it alone cannot be the only method for overcoming the challenge of spectrum scarcity.

The second solution to spectrum scarcity is the development of technologies that enhance spectrum efficiency. Wi-Fi 7 did introduce several features that helped enhance efficiency, notably Multi-Link Operation (MLO), which enables the aggregation of separate unconnected links together to form wider channels. While this represented a major development in improving spectrum utilization for communications between an Access Point (AP) and a single client device, each AP within the network still acts in isolation, without knowledge of their counterparts. This lack of collaboration inhibits further optimization, and leaves unaddressed the interference caused by the simultaneous use of multiple APs competing for the same spectrum. With mesh nodes proliferating throughout consumer homes and enterprise environments facing an increasing densification of APs, this challenge must be addressed for further progress to occur.

The Wi-Fi industry’s answer to this issue is Multi-AP Coordination (MAPC), the most anticipated new feature of the next Wi-Fi standard, Wi-Fi 8. MAPC encompasses a range of features, which together are designed to maximize spectrum efficiency and improve performance by optimizing channel selection for all client/APs and balancing the load evenly and intelligently between APs in the network. Features include Coordinated Spatial Reuse (Co-SR), Coordinated Beamforming (Co-BF), Coordinated Orthogonal Frequency Division Multiple Access (Co-OFDMA), and Coordinated Time Division Multiple Access (Co-TDMA), Coordinated Uplink Multi-User Multiple Input, Multiple Output (Co-UL-MU-MIMO), and Joint Transmission (JT). To understand the impact of MPAC, let’s examine for a moment how the first of these features, Co-SR, will work in practice. Co-SR involves a new framework through which multiple APs can coordinate collectively and simultaneously to dynamically adjust their respective power levels. This feature will be performed in three steps. In the first step, the “Cross-BSS Measurement Phase,” all APs in the environment will be assembled into Co-SR groups, and they will share among themselves their measurements of Overlapping Basic Service Sets (OBSS) interference on their network. This will be followed by a “Multi-AP Coordination Phase,” during which one AP in the group will initiate a Co-SR Announce frame that details the transmission power limitations for each specific AP. In the final “Concurrent Transmission Phase,” each AP will transmit data simultaneously at their mandated power level.

Each actor within the Wi-Fi industry has a role to play in ensuring that spectrum resources are both sufficient and utilized to their maximum extent. For national regulators, the gatekeepers of spectrum access, ABI Research recommends applying the following principles:

• Whenever Possible, Enable Spectrum Sharing: Coexistence technologies make it possible for multiple technologies to leverage the same spectrum resources without interfering with one another. For example, within the 5 GHz spectrum, this was achieved via Dynamic Frequency Selection (DFS), which first scans for radar signals in the 5250 MHz and 5730 MHz frequency range before authorizing Wi-Fi transmissions. Similarly, within the 6 GHz spectrum, new Automated Frequency Coordination (AFC) systems authorize Standard Power 36 Decibel-Milliwatts (dBm) 6 GHz transmissions following scanning for incumbents. National regulators can consider the same coexistence approach for other segments of spectrum to help maximize utilization.
• Periodically Reassess Spectrum Allocations: There is precedent for underutilized spectrum being reassigned for unlicensed Wi-Fi use. Recently, this includes the 5.9 GHz spectrum band in the United States, which spans 5850 MHz to 5925 MHz and is often referred to as U-NII-4. Originally reserved for Vehicle-to-Everything (V2X) back in 1999, the failure of these applications to emerge in the ensuing years led the Federal Communications Commission (FCC) to reallocate the lower 45 MHz portion of the band for unlicensed Wi-Fi use in November 2020. While the decision was protested by an association of U.S. transportation organizations, in August 2022, the DC Court of Appeals rejected the challenge and upheld the FCC’s decision. Regulators should emulate this approach to ensure that the maximum value is being extracted from the available spectrum.

Ecosystem vendors throughout the Wi-Fi industry also have a pivotal role to play, and ABI Research believes that the industry should collectively act to advance the following:

• Begin Strategizing for 7 GHz: Following the release of 6 GHz, key figures in the Wi-Fi industry have begun to advocate for the allocation of the 7 GHz spectrum band for unlicensed. For the Wi-Fi industry to be successful in reserving the 7 GHz band for Wi-Fi, it must make a watertight case for why additional spectrum resources should be allocated for the technology. Supporting arguments include that future expansion in the number and demands of Wi-Fi devices will inevitably result in growing strain on existing spectrum resources, that IMT does not currently, nor is it projected to have the need in the near future, and that Wi-Fi has a history of swiftly generating additional value from new spectrum resources (demonstrated by the rapid development of the 6 GHz Wi-Fi ecosystem). It is also recommended that the Wi-Fi industry be proactive in contesting the 7 GHz spectrum, instead of being reactive and only seeking the additional resources once congestion on the existing resources becomes an issue (as was the case for the industry’s approach to 6 GHz).
• Reevaluate the Potential of 60 GHz: Unlicensed 60 GHz ranges from 57.24 GHz to 70.20 GHz, although access to the spectrum varies somewhat between countries. The band holds significant, but for the most part underappreciated, potential to address spectrum sparsity for several reasons. First, and most obviously, it represents a large block of currently underutilized unlicensed spectrum, with high frequencies that make it ideal for high-throughput, low-latency applications. These high frequencies also imbue the band with very weak penetration abilities, meaning that Line of Sign (LoS) is necessary. While these propagation properties have often been considered a negative, they can actually be a positive toward spectrum efficiency, as they mitigate the chance of interference between 60 GHz signals in adjoining rooms. While 60 GHz Wi-Fi has been on the market for over a decade in the form of 802.11ad/ay, the Integrated Millimeter Wave (IMMW) Study Group within the IEEE plans to rejuvenate the technology by extending the existing mainstream 802.11 standards into 60 GHz.
• Scale Up Sub-1 GHz Wi-Fi: At the other end of the spectrum is the unlicensed 900 MHz band, which the nascent Wi-Fi HaLow (802.11ah) standard leverages to provide superior penetration abilities and strong throughputs across distances exceeding 1 kilometer (where speeds still reach 150 Kilobits per Second (Kbps)). Moreover, Wi-Fi HaLow is highly energy-efficient, and can connect over 8,000 client devices simultaneously. By shifting applications suitable for Wi-Fi HaLow over to the 900 MHz spectrum (such as Internet Protocol (IP) cameras), it is possible to alleviate congestion on the 2.4/5/6 GHz bands, helping to address the spectrum challenge. To make this possible, the industry must collaborate to develop the Wi-Fi HaLow ecosystem and to increase confidence in the technology. Steps to realize this include incorporating Wi-Fi HaLow capabilities into residential CPE and enterprise APs, and conducting further real-world Wi-Fi HaLow trials by industry associations.

• Leverage Spectrum Efficiency for Wi-Fi Reliability: With theoretical throughputs over 40 Gigabits per Second (Gbps), there is a general consensus that Wi-Fi 7 has already made possible data rates that are sufficient for the overwhelming majority of consumer and even enterprise applications. These speeds also exceed those possible with current mainstream fixed access technologies. Therefore, the industry is gradually shifting toward an emphasis on stability and consistency over simple maximum speed metrics. This is reflected in the mission statement of Wi-Fi 8, which in contrast to Wi-Fi 7’s focus on delivering an “Extremely High Throughput (EHT),” is orientated toward achieving “Ultra High Reliability (UHR).” Aside from the coming advancements of Wi-Fi 8, industry stakeholders should also invest in additional methods of improving reliability through spectrum efficiency. This could include research into the condensing of data transferred over Wi-Fi, to reduce bandwidth demands, or developing Artificial Intelligence (AI) capabilities to better manage and prioritize traffic.