doi:10.1109/ACCESS.2026.3654254engSalazar-Riaño, J.-L.Fernández-Navajas, J.Hernández-Solana, A.Ruíz-Mas, J.Azuara-Guillén, G.Cajal-Pérez, R.Legacy-Compatible Multi-User Wi-Fi Aggregation for Enhanced Downlink Efficiency and SecurityART-2026-147619This work introduces a novel Wi-Fi frame aggregation mechanism that enables efficient multiuser downlink transmissions in IEEE 802.11 networks (including earlier standards). We focus on exploring feasible and practical approaches to enable or approximate multi-user aggregation by leveraging existing features, while ensuring the compatibility with legacy standards. The proposed approach, implemented and evaluated on a real-world testbed, allows the Access Point (AP) to aggregate MAC Service Data Units (MSDUs) destined for multiple users/stations, using a scheme based on Multichannel Broadcast Encryption of Short Messages. It is particularly effective in scenarios involving a high volume of small data packets to multiple users/stations and where communication reliability is critical to maintaining high-quality service. This innovative solution not only extends and improves the efficiency of standard aggregation schemes in such scenarios but also enables efficient multi-user downlink transmissions and enhances security by strengthening the protection of transmitted data.2026http://zaguan.unizar.es/record/16803210.1109/ACCESS.2026.3654254http://zaguan.unizar.es/record/168032oai:zaguan.unizar.es:168032info:eu-repo/grantAgreement/ES/DGA/T31-23Rinfo:eu-repo/grantAgreement/ES/MCINN/PID2022-136476OB-I00IEEE Access (2026), 19 pp.byhttps://creativecommons.org/licenses/by/4.0/deed.esinfo:eu-repo/semantics/openAccess