You have designed your wireless network for data coverage. However, as 5 GHz device a client's increase over legacy 2.4 GHz devices, you observe roaming issues and instability of wireless…

While a voice design has more stringent requirements, the fundamental physical issue causing roaming problems for 5 GHz devices in a data design is more specific than simply needing a different design type, pointing instead to coverage planning.

Band Select (or Band Steering) typically attempts to encourage dual-band clients to connect to the 5 GHz band over the 2.4 GHz band, not the other way around, to utilize the less congested 5 GHz spectrum.

Radio Resource Management (RRM) optimizes channel and power settings for both bands to improve overall network performance and capacity, not to inherently favor 2.4 GHz legacy devices to the detriment of 5 GHz client roaming.

5 GHz radio waves experience greater attenuation and thus have a shorter effective range compared to 2.4 GHz radio waves at the same transmit power. If a wireless network is designed primarily for 2.4 GHz coverage, the resulting 5 GHz cell sizes will be significantly smaller, leading to insufficient overlap between access points and causing roaming instability and communication issues for 5 GHz clients as they move.