VSDB

VSDB was mentioned in Broadcom Accelerates Wi-Fi Adoption with Next Generation Combo Chip and Wi-Fi Display Dongle on PR Newswire for the Broadcom BCM43242:

"Advanced Virtual Simultaneous Dual Band (VSDB) functionality enables peer-to-peer and access point connectivity at the same time."

It was also mentioned in a patch for brcmfmac: Add RSDB support.

"Broadcom devices with a single 802.11 core can work on two band concurrently using VSDB feature, ie. Virtual Simultaneous Dual-Band. For devices that are fitted with two 802.11 cores and RF paths the driver should support a firmware feature called RSDB, which stands for Real Simultaneous Dual-Band."