In the release 8.1 of Cisco Wireless LAN Controller, a new feature has been introduced called Dynamic Bandwidth Selection (DBS). This algorithm is aimed to improve the channel reuse pattern and overall help improve the performance of the Wireless network as a whole.
The 802.11ac standard introduced wider channel width like 80MHz, 160MHz and 80+80 MHz. In environments where 11ac and 11n (and legacy) networks exists simultaneously, the channel reuse can become an issue. Due to the static nature of the channel width (40MHz, 80MHz etc), there can be an overlap of 11ac APs on a particular 80MHz channel and 11n or legacy AP serving on a subset of that 80MHz channel. DBS allows 11ac APs operating on higher channel widths like 80MHz and 160MHz (future), to change the operating channel width lower / narrower bandwidths such as 20MHz or 40MHz. This is particularly useful for networks that have 11ac APs along with legacy APs and or clients, which only have the narrower bandwidths.