Wi-Fi 8 Features: Deep Dive into 802.11bn PHY and MAC

Introduction : The evolution of Wi-Fi has reached a pivotal turning point with the transition from Wi-Fi 7 (IEEE 802.11be) to Wi-Fi 8 (IEEE 802.11bn). While previous wi-fi generations; specifically Wi-Fi 5, 6, and 7 focused almost entirely on “Extreme High Throughput” (speed), Wi-Fi 8 introduces a “Reliability First” architecture. Standardized as Ultra High Reliability (UHR), Wi-Fi 8 focuses on making the connection stable, predictable, and resilient even in crowded or long range environments.

Wi-Fi 8 Physical Layer (PHY) Evolution and features

The PHY layer in Wi-Fi 8 maintains the high speed foundations of Wi-Fi 7 (320 MHz bandwidth and 4096QAM) but adds tools to ensure these speeds are actually reachable in real world conditions.

Distributed-tone Resource Units (DRU) vs. Legacy RRU:

• Previous Versions: Used Regular Resource Units (RRU) where subcarriers were grouped in a single contiguous block.
• Wi-Fi 8 introduces DRUs, which scatter subcarriers across the frequency band.
• Benefit: This overcomes Power Spectral Density (PSD) limits in the 6 GHz band, allowing for a massive boost in uplink transmit power. It effectively doubles or triples the reliable range of the signal.

Enhanced Long Range (ELR) PPDU:

• Previous Versions: Range was often limited by the “Link Budget Imbalance” (the AP can talk to the phone, but the phone is too weak to talk back).
• In Wi-Fi 8, ELR uses data duplication and a restricted 20 MHz format to ensure the uplink remains connected even at extreme distances or through heavy interference.

Unequal Modulation (UEQM):

• Previous Versions: All spatial streams in a transmission typically used the same modulation (e.g., all 1024QAM).
• Wi-Fi 8 allows each stream to have its own modulation level based on specific channel quality.
• Benefit: Dramatically improves beamforming performance in complex environments.

Wi-Fi 8 MAC Layer Evolution and Features

Wi-Fi 8 introduces “Socially Aware” networking, where devices and Access Points (APs) coordinate instead of competing. The MAC layer determines “who gets to talk and when.”

Non-Primary Channel Access (NPCA):

• Previous Versions: If the “Primary” 20 MHz channel was busy, the entire 160 MHz or 320 MHz band was unusable.
• Wi-Fi 8 allows devices to dynamically switch to an alternative primary channel.
• Benefit: Ends the “Primary Channel Bottleneck,” leading to a much higher utilization of available spectrum.

Multi-AP Coordination (MAPC):

• Previous Versions: APs acted as “islands,” ignoring each other and causing interference.
• In Wi-Fi 8, APs now communicate to perform Coordinated Beamforming and Spatial Reuse.
• Techniques such as Coordinated TDMA (Co-TDMA) and Coordinated Restricted Target Wake Time (Co-RTWT) are used in MAPC framework.
• Benefit: APs can “null out” interference for each other’s clients, allowing multiple APs to transmit simultaneously on the same channel without noise.

Priority EDCA (P-EDCA):

• Previous Versions: Simple probability based prioritization (Voice > Video > Data).
• Wi-Fi 8 introduces a “Defer Signal” (DS-CTS) that clears the airwaves for ultra time sensitive traffic.
• Benefit: Guarantees sub-10ms latency for critical applications like AR/VR and industrial robotics.

Summary

By evolving the PHY layer with DRU and ELR, and the MAC layer with MAPC and NPCA, Wi-Fi 8 effectively solves the three biggest headaches of modern wireless networking i.e. the link budget imbalance, the primary channel bottleneck and inter-AP interference. For the end user, this translates to a Wi-Fi experience that finally feels as robust and reliable as a wired Ethernet connection.