A method, comprising: determining a multi-carrier structure of a flexible spectrum wireless cell based at least in part on at least one of detected individual carriers of the flexible spectrum wireless cell , synchronisation channels of the detected individual carriers of the flexible spectrum wireless cell and broadcast channels of the detected individual carriers of the flexible spectrum wireless cell , wherein the multi-carrier structure comprises carriers that are compatible with an earlier version of a communication standard, or carriers that are compatible with a later version of the communication standard, or carriers that are compatible with the earlier version of the communication standard and carriers that are compatible with the later version of the communication standard, wherein the determining comprises determining the multi-carrier structure of the flexible spectrum wireless cell based on at least one of: relative positions of the detected individual carriers in a spectrum band; relative timing alignments of the synchronisation channels; contents of the synchronisation channels; contents of the broadcast channels; and layer one cell-carrier identifiers, wherein each of the broadcast channels of the detected individual carriers comprises an explicit or implicit advertisement element indicating whether a respective carrier is compatible with either the earlier version or the later version of the communication standard; and using the advertisement element and the determined multi-carrier structure to select an intended carrier for at least one of initial access and cell reselection to the flexible spectrum wireless cell . determining a multi-carrier structure of a flexible spectrum wireless cell based at least in part on at least one of detected individual carriers of the flexible spectrum wireless cell , synchronisation channels of the detected individual carriers of the flexible spectrum wireless cell and broadcast channels of the detected individual carriers of the flexible spectrum wireless cell , wherein the multi-carrier structure comprises carriers that are compatible with an earlier version of a communication standard, or carriers that are compatible with a later version of the communication standard, or carriers that are compatible with the earlier version of the communication standard and carriers that are compatible with the later version of the communication standard, wherein the determining comprises determining the multi-carrier structure of the flexible spectrum wireless cell based on at least one of: relative positions of the detected individual carriers in a spectrum band; relative timing alignments of the synchronisation channels; contents of the synchronisation channels; contents of the broadcast channels; and layer one cell-carrier identifiers, wherein each of the broadcast channels of the detected individual carriers comprises an explicit or implicit advertisement element indicating whether a respective carrier is compatible with either the earlier version or the later version of the communication standard; and using the advertisement element and the determined multi-carrier structure to select an intended carrier for at least one of initial access and cell reselection to the flexible spectrum wireless cell . <EOS>