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IEEE 802.11be: Wi-Fi 7 Strikes Back
Adrian Garcia-Rodriguez, David Lopez-Perez, Lorenzo Galati-Giordano, Giovanni Geraci
TL;DR
Growing device demand and latency-sensitive uses motivate 802.11be, and the paper reviews its features while examining multi-AP coordinated beamforming. In standard-compliant simulations, coordination reduces 0.01%-worst-case latency by about ninefold relative to a PSR-capable system.
Problem
Growing Wi-Fi use and dense deployments increase demand for wireless services, including low-latency communication for time-sensitive applications.
Source: §I · p. 1Method
The article reviews 802.11be features and details a multi-AP coordinated beamforming implementation built on the spatial-reuse framework.
Source: §I · p. 1, B. Coordinated Beamforming in 802.11be · p. 5Results
≈9× reduction in 0.01%-worst-case latencies with multi-AP coordination compared with a PSR-capable system.
Source: §V · p. 6Takeaways & Limitations
The article presents multi-AP coordinated beamforming as a way to augment spatial reuse and curb latency while increasing reliability in 802.11be.
Source: §IV · p. 4, §VI · p. 7
Abstract
from arXiv · showhide
As hordes of data-hungry devices challenge its current capabilities, Wi-Fi strikes back with 802.11be, alias Wi-Fi 7. This brand-new amendment promises a (r)evolution of unlicensed wireless connectivity as we know it. With its standardisation process being consolidated, we provide an updated digest of 802.11be essential features, vouching for multi-AP coordination as a must-have for critical and latency-sensitive applications. We then get down to the nitty-gritty of one of its most enticing implementations-coordinated beamforming-, for which our standard-compliant simulations confirm near-tenfold reductions in worst-case delays.
I. INTRODUCTION
Growing Wi-Fi use and denser, more demanding deployments are increasing the call for reliable gigabit connectivity, while 802.11be is being developed as the next Wi-Fi generation. The article reviews Wi-Fi 7’s development and features, then examines multi-AP coordinated beamforming and its simulated latency gains.
I. INTRODUCTION
- 802.11be is driven by demand for reliable gigabit service in increasingly dense homes and enterprises, including low-latency factory-floor communication.The article also notes expanding data collection, live video, and remote-friendly conferencing as sources of demand.Source: §I · p. 1
- The FCC’s opening of 6 GHz and ongoing IEEE work on 802.11be mark concurrent developments toward expanded unlicensed Wi-Fi connectivity.The Wi-Fi Alliance was expected to provide interoperability certification for Wi-Fi 6 devices in the new band.Source: §I · p. 1
- The article reviews Wi-Fi 7’s status, technical-feature decisions, and timeline, then details coordinated beamforming and standard-compliant simulations of its latency gains.The simulation setup is a realistic digital enterprise scenario.Source: §I · p. 1
II. A CONCISE UPDATE ON WI-FI
- Wi-Fi 6 improves efficiency and battery consumption for crowded deployments, while Wi-Fi 6E and 802.11be are presented as two further steps beyond it.Wi-Fi 6E adds newly available unlicensed frequencies; 802.11be is the subsequent amendment, expected to be certified as Wi-Fi 7.Source: §II · p. 1
A. Wi-Fi 6E: Our Traffic Gets a New Lane
Wi-Fi 6E extends Wi-Fi into the 6 GHz band, while Wi-Fi 7 is framed as a broader upgrade targeting throughput, latency, and reliability. The standard’s two-phase development prioritizes features for earlier specification and implementation.
A. Wi-Fi 6E: Our Traffic Gets a New Lane
- 6 GHz spans 5.925–7.125 GHz and nearly quadruples available bandwidth; its shorter propagation range may help isolate BSSs in dense environments.Unlicensed operation is subject to rules protecting incumbent services, including outdoor contention-based access and power limits.Source: A. Wi-Fi 6E: Our Traffic Gets a New Lane · p. 2
- Wi-Fi 6E devices were expected to receive a Wi-Fi Alliance certification, initially giving them access to a low-interference 6 GHz setting.The passage states that more than 300 million compliant devices were expected to come to market in 2021.Source: A. Wi-Fi 6E: Our Traffic Gets a New Lane · p. 2
B. Wi-Fi 7: (Not Just) Extremely High Throughput
- Wi-Fi 7 is projected to support at least 30 Gbps per AP while targeting lower latency and higher reliability for time-sensitive networking.The passage associates lower-than-5-ms delays with real-time applications and three or more ‘nines’ of reliability with potential replacement of some wired communications.Source: B. Wi-Fi 7: (Not Just) Extremely High… · p. 2
- 802.11be uses two development phases, with the first prioritizing features by gain-to-complexity ratio, standardization and implementation time, interest, and market needs.The standardization, certification, and commercialization timeline is illustrated in Fig. 1.Source: B. Wi-Fi 7: (Not Just) Extremely High… · p. 2, Figure 1 · p. 2
III. A PRIMER ON THE FUTURE WI-FI 7
The Specification Framework Document collects the functional operations from which 802.11be drafts will be derived. Release 1 includes multi-link operation, with provisions for link discovery, traffic mapping, channel access, and power saving.
III. A PRIMER ON THE FUTURE WI-FI 7
- The Specification Framework Document collects 802.11be’s basic functional operations and serves as the basis for successive standard drafts.The article digests the framework’s latest updates.Source: §III · p. 2
A. Release 1 Features
- Release 1 features were expected to mature in Draft 1.0 by May 2021, with further expansion and refinement possible through Draft 2.0 in March 2022.The timeline is indicated in Fig. 1.Source: A. Release 1 Features · p. 2
1) Multi-Link Operation:
- A multi-link device has multiple affiliated APs or STAs and one MAC service access point to the LLC layer, supporting operations across 2.4, 5, and 6 GHz bands.The stated aims include load balancing, multi-band aggregation, and simultaneous downlink/uplink transmission.Source: 1) Multi-Link Operation · p. 2
- Multi-link operation allows dynamic updates to simultaneous-frame-exchange capability and affiliated-link information, maps traffic identifiers across setup links, and uses one reordering buffer per TID.Each AP or STA accesses its links independently and maintains its own power state; an enabled link may carry buffered-data indications for other links.Source: 1) Multi-Link Operation · pp. 2–3
2) Low-Complexity AP Coordination:
802.11be’s low-complexity coordination includes coordinated spatial reuse, where a sharing AP can trigger simultaneous transmissions by other APs. The task group had also begun work on Release 2 features ahead of their formalization in later drafts.
2) Low-Complexity AP Coordination:
- Coordinated spatial reuse lets a sharing AP with a TXOP trigger shared APs to transmit simultaneously using power control and link adaptation, creating more reuse opportunities and fewer collisions than 802.11ax spatial reuse.APs advertise coordination capabilities in beacons or management frames; CSR was a possible Release 1 feature.Source: 2) Low-Complexity AP Coordination · p. 3
- 802.11be direct upgrades include 320 MHz transmissions, optional 4096-QAM with a −38 dB transmitter EVM requirement, and multiple resource units per STA.The 320 MHz bandwidth doubles 802.11ax’s 160 MHz; multiple resource units add flexibility for spectrum utilization.Source: 3) Direct Enhancements of 802.11ax · p. 3
B. Release 2 Features
- Release 2 features were slated for formalization in Drafts 3.0 and 4.0, due in November 2022 and November 2023, while task-group work and SFD progress were already underway.The passage describes this progress as notable.Source: B. Release 2 Features · p. 3
1) MIMO Enhancements:
802.11be expands MIMO capacity and examines HARQ and low-latency features while supporting three forms of multi-AP coordination. The section outlines their operation and relevant complexity, synchronization, and backhaul considerations.
1) MIMO Enhancements:
- 802.11be doubles the maximum SU-MIMO and MU-MIMO spatial streams to 16, while limiting MU-MIMO to 8 spatially multiplexed STAs and 4 streams per STA.These limits help control precoder complexity and CSI acquisition overhead; implicit CSI sounding is being investigated as an optional way to curb that overhead.Source: 1) MIMO Enhancements · p. 3
2) Hybrid Automatic Repeat Request (HARQ):
- HARQ may be introduced in R2, but the SFD does not include HARQ procedures at the time of writing.The task group evaluated MPDU- and PHY-codeword-based HARQ units for performance and complexity trade-offs.Source: 2) Hybrid Automatic Repeat Request… · p. 3
3) Low-Latency Operations:
- For TSN, the SFD is to collect protocol enhancements aimed at reducing worst-case latency and improving reliability.Possible approaches include differentiated QoS across multiple links or AP coordination for more aggressive spectrum reuse and fewer harmful collisions.Source: 3) Low-Latency Operations · p. 3
4) Advanced AP Coordination:
- The task group agreed to support three multi-AP coordination schemes to reach coordination's full potential.Source: 4) Advanced AP Coordination · p. 3
- Coordinated OFDMA lets a TXOP-holding AP share frequency resources in 20 MHz multiples with neighboring APs, which may report their resource needs.Source: 4) Advanced AP Coordination · p. 3
- Joint multi-AP transmissions require bounded phase-synchronization errors and timing offsets, and can provide gains under reasonable impairments when adequate backhauling is available.The planned joint sounding scheme lets APs transmit sounding frames simultaneously and obtain CSI feedback pertaining to all APs.Source: 4) Advanced AP Coordination · p. 3
- Coordinated beamforming spatially multiplexes associated STAs while placing radiation nulls toward neighboring non-associated STAs.It can use joint or sequential sounding and avoids joint data processing, significantly reducing backhaul needs relative to joint transmissions.Source: 4) Advanced AP Coordination · p. 3
IV. AUGMENTING SPATIAL REUSE VIA MULTI-AP COORDINATED BEAMFORMING
The section presents 802.11ax parameterised spatial reuse (PSR) as a building block for multi-AP coordination in 802.11be. It explains how a donor AP offers an overlapping BSS a conditional reuse opportunity during its uplink reception.
IV. AUGMENTING SPATIAL REUSE VIA MULTI-AP COORDINATED BEAMFORMING
- 802.11ax parameterised spatial reuse (PSR) enables dynamic cooperation between devices in different BSSs.Source: §IV · p. 4
A. Parameterised Spatial Reuse in 802.11ax
- A donor AP can use a trigger frame to offer overlapping-BSS devices concurrent spectrum reuse during its uplink reception, subject to interference conditions.The trigger provides scheduling and synchronization for its own uplink STAs and advertises the reuse opportunity with a PSR field specifying tolerable interference and the donor AP's transmit power.Source: A. Parameterised Spatial Reuse in… · p. 4
- After measuring the trigger's received power, OBSS devices use the PSR field to decide whether and at what power they can contend.In the example, STA21 and STA22 can contend, but nearby STA23 cannot meet AP1's interference conditions; STA21 transmits first, and STA22 can re-contend if time allows.Source: A. Parameterised Spatial Reuse in… · p. 4
1) Benefits of PSR:
PSR improves spatial reuse by allowing more channel access, with throughput and latency benefits.
1) Benefits of PSR:
- PSR increases network throughput through more concurrent transmissions, increases STA file throughput by reducing contention time, and can reduce latency for time-sensitive short-file traffic.Such STAs may avoid waiting for broadband STAs to finish lengthy transmissions.Source: 1) Benefits of PSR · p. 4
2) Challenges of PSR:
The section identifies transmit-power constraints and receiver-side interference as challenges that limit PSR's effectiveness, particularly in dense or latency-sensitive settings.
2) Challenges of PSR:
- PSR users must lower transmit power to limit interference, which can reduce throughput or leave devices unable to access reuse when they cannot reach their receiver.Source: 2) Challenges of PSR · p. 4
- PSR users lack awareness and control of interference at their receivers, so nearby transmissions can make uplink reception fail, a concern in dense or latency-sensitive settings.Source: 2) Challenges of PSR · p. 5
B. Coordinated Beamforming in 802.11be
802.11be coordinated beamforming extends spatial reuse by using collaborative APs to suppress OBSS interference, with an illustrative implementation built on the PSR framework. The protocol coordinates APs, acquires relevant CSI, and then supports spatially multiplexed communication.
B. Coordinated Beamforming in 802.11be
- A four-antenna AP serving one STA has experimentally suppressed up to 10 dB of interference toward a neighbouring link, motivating CBF’s spatial suppression of OBSS interference [11].CBF builds on the PSR framework and does not require joint data processing, since each STA communicates with a single AP.Source: B. Coordinated Beamforming in 802.11be · p. 5
1) Multi-AP Coordination:
- Collaborative APs establish a coordination set containing participating AP and STA IDs, retain relevant OBSS frames, and may update the set semi-statically after tens or hundreds of TXOPs.The set supports communication with OBSS STAs and acquisition of CSI needed to place radiation nulls.Source: 1) Multi-AP Coordination · p. 5
- After the donor AP obtains a TXOP, it coordinates with the set to choose which STAs will take part in CSI acquisition and data communication.In the example, AP2 identifies STA21 and STA22 as candidates for a safe spatial reuse opportunity because they typically generate latency-sensitive traffic.Source: 1) Multi-AP Coordination · p. 5
2) CSI Acquisition:
- AP1 and AP2 acquire CSI only from relevant intra-BSS and OBSS devices to design filters for spatial multiplexing and bidirectional interference suppression in the subsequent communication phase.OBSS devices become aware that an OBSS AP will offer them a spatial reuse opportunity with more favourable channel access. The 802.11ax trigger frame can trigger data communications, allowing legacy STAs to keep using the legacy PSR framework seamlessly.Source: 2) CSI Acquisition · p. 5
3) Data communication:
The proposed CBF scheme reduces worst-case augmented-reality latency in the simulated enterprise deployment, while maintaining approximately the same broadband-STA throughput. The data-communication phases relax spatial-reuse conditions and suppress incoming interference, addressing limitations of PSR in the dense scenario.
3) Data communication:
- CBF makes STA21, STA22, and STA23 more likely to find spatial-reuse opportunities and succeed on time by relaxing access conditions and suppressing interference at AP2.AP1’s spatial suppression permits relaxed conditions, while AP2 suppresses interference from STA11 and STA12 during uplink reception.Source: 3) Data communication · pp. 5–6
V. PERFORMANCE OF 802.11BE COORDINATED BEAMFORMING
- The simulations model two ceiling-mounted eight-antenna APs and 24 uniformly distributed STAs in a 35 m × 20 m × 3 m enterprise space, including eight augmented-reality STAs.The other 16 STAs generate uplink broadband traffic.Source: §V · p. 6
- ≈9× lower 0.01%-worst-case latency than PSR-capable 802.11ax; 802.11be CBF also substantially reduces worst-case latency versus both evaluated 802.11ax systems.Broadband-STA throughput is approximately maintained across the three systems.Source: Figure 4 · p. 6, §V · p. 6
- 802.11ax without spatial reuse stays below 3 ms around 50% of the time but exceeds 200 ms in the 0.01%-worst cases, with random access and collisions contributing to the tail.Collisions lead to retransmissions.Source: §V · p. 6
- PSR-capable 802.11ax does not substantially reduce worst-case delays because nearby augmented-reality STAs cannot meet the dense scenario’s stringent channel-access interference conditions.Source: §V · p. 6
VI. CONCLUSION
The article reviews 802.11be’s development and technical agreements, and presents coordinated beamforming as a way to illustrate multi-AP spatial reuse benefits. It identifies integration with time-sensitive networking protocols as further research.
VI. CONCLUSION
- The article details IEEE 802.11be’s development steps, latest technical-feature agreements, and updated timeline.Source: §VI · p. 7
- Standard-compliant simulations illustrate benefits of multi-AP coordinated beamforming as a spatial-reuse technique.Source: §VI · p. 7
- Further research is needed to integrate these techniques into time-sensitive networking protocols.Source: §VI · p. 7