A protocol that allows an IEEE 802.11a wireless LAN (WLAN) to actively shift frequency channels.As 802.11a competes for spectrum with HiperLAN, the standard developed and promoted by the European Telecommunications Standards Institute (ETSI), 802.11a implementations in Europe must use DFS and transmission power control (TPC), which reduces the power level to no more than needed. In combination, these protocols serve to eliminate interference issues with incumbent signals. See also 802.11a, ETSI, frequency, IEEE, HiperLAN/1, HiperLAN2, interference, protocol, and WLAN.