SIDEBAR: SUPPORTING WI-FI 5 OVER EXISTING CATEGORY 5E AND CATEGORY 6 CABLING PLANTS When Wi-Fi 5 (802.11ac) was introduced, its initial phase (Wave 1) required gigabit connectivity, easily supported by existing Category 5e and Category 6 cabling infrastructure. However, the subsequent Wave 2 phase doubled the speeds, demanding higher bandwidth. To accommodate Wave 2 Wi-Fi over existing cabling, the IEEE developed standards for 2.5GBASE-T and 5GBASE-T applications (IEEE 802.3bz) that fall within the frequencies for Category 5e/Class D and Category 6/Class F cabling, respectively. While most enterprises with certified Category 5e/Class D or Category 6/Class F infrastructure should be able to support 2.5 and 5GBASE-T, alien crosstalk can be a limiting factor. Since these cable categories do not have specific alien crosstalk specifications, industry standards bodies introduced guidelines using a parameter called Alien Limited Signal-to-Noise Ratio (ALSNR). ALSNR combines insertion loss, PSANEXT, and PSAACR-F calculations. Qualification testing is essential to determine if the existing cabling is suitable for 2.5/5GBASE-T. If testing reveals limitations, you can use several mitigation strategies. Unbundling cables, especially patch cables, can reduce alien crosstalk. Replacing patch cords with Category 6A/Class FA or shielded components, limiting 2.5/5GBASE-T applications to shorter cabling runs, and and selecting non-adjacent patch panel ports can also help. Figure 5 shows qualification testing that indicates support for a maximum speed of 2.5 Gb/s (2.5GBASE-T).
FIGURE 5: Qualification testing is essential to determine if the existing cabling is suitable for 2.5GBASE-T or 5GBASE-T to support Wi-Fi 5. These results indicate support for a maximum of 2.5 Gb/s. (Source: Fluke Corporation)
AUTHOR BIOGRAPHY: Mark Mullins is one of the founding members of Fluke Networks, which launched in 1993, and has been involved in all key areas of the business. He is currently the Product Marketing Manager for cable, network, and fiber optic products, from testing and troubleshooting to certification. His goal is to keep current and prospective customers around the world up to date on the latest Fluke Networks technologies and solutions. As a member of the Ethernet Alliance Marketing Committee, he is responsible for promoting the Gen 2 Power over Ethernet Certification program. Mark holds a BS in computer science and an MBA from the University of Washington.
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January/February/March 2025
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