Dynamically switching carrier frequencies to make better use of the spectrum. It is somewhat related to software-defined radio, in that SDR's are typically used

Dynamically switching carrier frequencies to make better use of the spectrum. It is somewhat related to software-defined radio, in that SDR's are typically used to prototype cognitive radio. It hasn't really got mindshare though in the sense players like Qualcomm have all but ignored it and would rather work on proprietary comms schemes.