Wi-Fi 6 Fundamentals: Basic Service Set Coloring (BSS Coloring)

By Dennis Huang, Ruckus Networks.

Introduction

According to IDC, 802.11ax (Wi-Fi 6) deployment is projected to ramp significantly in 2019 and become the dominant enterprise Wi-Fi standard by 2021. This is because Wi-Fi 6 will deliver faster network performance and connect more devices simultaneously. Additionally, it will transition Wi-Fi from a ‘best-effort’ endeavor to a deterministic wireless technology that is now the de-facto medium for internet connectivity.

With a four-fold capacity increase over its 802.11ac (Wi-Fi 5) predecessor, Wi-Fi 6 deployed in dense device environments will support higher service-level agreements (SLAs) to more concurrently connected users and devices with more diverse usage profiles. This is made possible by a range of technologies that optimize spectral efficiency, increase throughput and reduce power consumption. These include BSS Coloring, Target Wake Time (TWT), Orthogonal Frequency-Division Multiple Access (OFDMA), 1024-QAM and MU-MIMO.

In this article, we’ll be taking a closer look at BSS Coloring and how Wi-Fi 6 wireless access points (APs) can utilize this mechanism to maximize network performance by decreasing co-channel interference and optimizing spectral efficiency in congested venues. These include high-density environments such as stadiums, convention centers, transportation hubs, and auditoriums.

BSS Coloring and Wi-Fi 6

Legacy high-density Wi-Fi deployments typically saw multiple access points assigned to the same transmission channels due to a limited amount of spectrum – an inefficient paradigm that contributed to network congestion and slowdowns. Moreover, legacy IEEE 802.11 devices were unable to effectively communicate and negotiate with each other to maximize channel resources. In contrast, Wi-Fi 6 access points are designed to optimize the efficient reuse of spectrum in dense deployment scenarios using a range of techniques, including BSS Coloring.

This mechanism intelligently ‘color-codes’ – or marks – shared frequencies with a number that is included within the PHY header that is passed between the device and the network. In real-world terms, these color codes allow access points to decide if the simultaneous use of spectrum is permissible because the channel is only busy and unavailable to use when the same color is detected. This helps mitigate overlapping Basic Service Sets (OBSS). In turn, this enables a network to more effectively – and concurrently – transmit data to multiple devices in congested areas. This is achieved by identifying OBSS, negotiating medium contention and determining the most appropriate interference management techniques. Coloring also allows Wi-Fi 6 access points to precisely adjust Clear Channel Assessment (CCA) parameters, including energy (adaptive power) and signal detection (sensitivity thresholds) levels.

Conclusion

Designed for high-density connectivity, Wi-Fi 6 offers up to a four-fold capacity increase over its Wi-Fi 5 predecessor. With Wi-Fi 6, multiple APs deployed in dense device environments can collectively deliver required quality-of-service (QoS) to more clients with more diverse usage profiles. This is made possible by a range of technologies – such as BSS Coloring – which maximizes network performance by working even within heavily congested, co-channel interference environments. From our perspective, BSS Coloring will play a critical role in helping Wi-Fi evolve into a collision-free, deterministic wireless technology as the IEEE looks to integrate future iterations of the mechanism into new wireless standards to support the future of Wi-Fi and beyond.