In the Example illustrated in FIG. 5, the message sequence may be as follows: The incumbent 505 transmits “Request Spectrum” message 511 to the SAS controller 504 to indicate that spectrum is required by incumbent 505. The SAS controller 504 transmits “Request Vacating of Spectrum” message 512 to SAS SW stack 503 to indicate that spectrum is required by incumbent 505. In the SAS SW stack 503 groups of users affected by vacating of spectrum are created 513. Then, SAS SW stack 503 transmits “request creation of user groups” message 514 to RLAN 502 to request for creation of user groups. RLAN 502 answers with Acknowledgement 515. The SAS SW stack 503 then prepares for vacating action (e.g. sleep mode, blocking of MAC addresses, etc.) 516 and transmits message “issue vacating request to user groups” to RLAN 502 to inform RLAN 502 about vacating request to user groups. RLAN 502 transmits message “request users to vacate band” 518 to RLAN UE 501 to inform specific users about vacating request. RLAN UE 501 answers with Acknowledgement 519. Then, RLAN 502 transmits Acknowledgement 520 to SAS SW stack 503 which transmits Acknowledgement 521 to SAS controller 504 which transmits Acknowledgement 522 to Incumbent 505.
