The IEEE 802.11r protocol, also known as Fast BSS Transition (FT), is designed to support real-time applications by enabling faster roaming between APs. This protocol reduces the number of packets exchanged during the reauthentication process when a client moves from one AP to another, thus ensuring a more seamless transition and maintaining the quality of service required by real-time applications such as voice and video conferencing. Reference: Designing Cisco Enterprise Wireless Networks (ENWLSD 300-425)

In a medical treatment environment where both data and voice services are required, continuous coverage of
-67 dBm from one access point is the minimum requirement. This ensures that there is sufficient signal strength for reliable voice communication, which is critical in medical settings. The -67 dBm threshold is commonly recommended for voice applications to ensure call quality and reliability.

So -67dBm covers both Data & Voice with a single AP

When a client roams between two access points (APs) that are registered to different controllers with interfaces in the same client subnet, the controllers will exchange mobility control messages over UDP port
16666. This is in accordance with the Designing Cisco Enterprise Wireless Networks (ENWLSD) guidelines.
The purpose of these messages is to ensure seamless roaming, where the client's session and authentication state are transferred from one controller to another without requiring re-authentication or re-association by the client. The mobility control messages facilitate the coordinated transfer of the client database entry from the original controller to the new one, maintaining a consistent experience for the user.