Background
The IEEE 802.11bn Ultra High Reliability study group was established in 2021 to address the need for more reliable wireless communications in increasingly dense and interference-prone environments. Unlike previous Wi-Fi generations that focused primarily on increasing peak data rates, Wi-Fi 8 represents a shift toward improving effective throughput and reducing latency in real-world conditions. [7] [6]
The development recognizes that while theoretical peak throughput of modern Wi-Fi often exceeds application requirements, users frequently experience intermittent connectivity issues due to environmental factors, interference, and protocol overhead in dense deployment scenarios. [8]
Technical specifications
802.11bn maintains the same frequency bands as Wi-Fi 7: 2.4 GHz, 5 GHz, and 6 GHz. The maximum channel bandwidth remains at 320 MHz, and it continues to support 4096-QAM modulation and up to 8 spatial streams. The theoretical maximum data rate is expected to remain at approximately 23 Gbps, the same as Wi-Fi 7. [9]
Wi-Fi 8 requirements
The 802.11bn standard (Wi-Fi 8) defines ultra-high reliability capability for both isolated Basic Service Sets (BSSs) and overlapping BSSs. Specifically, compared to Wi-Fi 7, Wi-Fi 8 targets to:
- increase throughput by 25% at a given signal-to-interference-and-noise ratio compared to Wi-Fi 7
- reduce latency by 25% for the 95th percentile of the latency distribution
- decrease MAC protocol data unit (MPDU) loss by 25%, especially for transitions between BSSs [10] [1]
Additionally, the 802.11bn standard aims to enhance power save for Access Points (including mobile ones) and improve Peer-to-peer operation. [1]
Key features
Multi-AP coordination
Wi-Fi 8 introduces enhanced coordination between multiple access points (i.e., BSSs). Many Multi-AP schemes have been discussed during the development of 802.11be but were postponed due to specification complexity, so 802.11bn continues this direction. In short, Multi-AP leverages the classical Wi-Fi mechanisms, e.g., Restricted Target Wake Time, Spatial Reuse, Beamforming, and others, by strengthening them thanks to enabling their cooperative work across multiple BSSs. Correspondingly, 802.11bn introduces multiple schemes, each varying with targets, efficiency, complexity, and overhead:
- Coordinated R-TWT (Co-RTWT)
- Coordinated Spatial Reuse (Co-SR)
- Coordinated Beamforming (Co-BF)
- Coordinated Time Division Multiple Access (Co-TDMA)
- Coordinated Channel Recommendation (Co-CR) [1]
These Multi-AP schemes allow access points to manage interference more effectively while sharing spectrum resources, enabling simultaneous transmissions that would otherwise conflict. [11]
Seamless Roaming
Wi-Fi 8 offers Seamless Roaming Domain (SMD) to address high latency and low reliability cases that are often experienced when devices move between Wi-Fi networks. SMD defines a single entity covering multiple AP MLDs, which may not be colocated within a physical device. Within an SMD, the context, i.e., the states of handshakes, sequence numbers, security keys, and capabilities, can be transferred between multiple AP MLDs, i.e., among Wi-Fi networks. Such coordination reduces the unavailability time and decreases the loss ratio when a client MLD device roams from one Wi-Fi network to another. An SMD also enables a step-by-step per-link transition of the client MLD between AP MLDs, which promises to enable seamless connectivity. [1]
Enhanced spectrum utilization
Dynamic Sub-channel Operation (DSO) and Non-Primary Channel Access (NPCA) optimize spectrum allocation to improve performance when devices have disparate channel bandwidth capabilities. These features address scenarios where high-bandwidth access points must reduce their transmission capability to accommodate lower-bandwidth clients.
Extended range capabilities
The Enhanced Long Range (ELR) protocol data unit format is designed to overcome link budget imbalances between uplink and downlink transmissions, improving spectrum efficiency for stations operating at greater distances from access points. ELR operates at 20 MHz bandwidth with support for BPSK and QPSK modulation. [10]
Distributed-tone resource units
Distributed-tone Resource Units (DRUs) use a separate OFDM tone plan with distributed OFDM subcarriers. Specifically, while a regular resource unit spans a continuous subset of subcarriers, each DRU spreads its tones across the entire available distribution bandwidth. [1] This feature helps to overcome regulatory power spectral density limitations, which are defined in terms of narrow bandwidth pieces, thus achieving higher transmission power across a wider bandwidth for multiple stations in uplink transmissions. This feature supports distribution bandwidths of 20 MHz, 40 MHz, and 80 MHz.
Additional MCS values
Wi-Fi 8 introduces four new Modulation and Coding Scheme values to provide finer granulation between existing MCS levels, improving link adaptation accuracy and transmission rates by 5–30% depending on channel conditions.
Quality of service enhancements
High Priority Enhanced Distributed Channel Access (HIP EDCA) and TXOP Preemption mechanisms are designed to reduce long-tail latency for time-sensitive applications such as gaming, video conferencing, and real-time communications.
In-Device Coexistence
In-Device Coexistence (IDC) mechanisms improve coordination between Wi-Fi and other wireless technologies such as Bluetooth, Zigbee, and Ultra-wideband within the same device, reducing interference and improving overall performance.
Industry adoption
Major networking equipment manufacturers and chipset vendors are actively participating in the 802.11bn development process. Companies including MediaTek, Qualcomm, Intel, and Broadcom are contributing to the specification and developing early implementations. [7]
The wireless industry anticipates Wi-Fi 8 will be particularly valuable in environments where reliability is more critical than peak performance, complementing rather than replacing 5G cellular networks for internet access.
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