IEEE 802.1X authentication using EAP-TLS enables clients to connect to a wireless network using smart cards. EAP-TLS (Extensible Authentication Protocol-Transport Layer Security) is a secure authentication protocol that uses digital certificates on smart cards to authenticate clients. By using this mechanism, clients can securely connect to the wireless network by presenting their smart card, which contains the necessary credentials and certificates for authentication. This ensures that only authorized clients with valid smart cards can access the network, providing an extra layer of security.