A control signaling method for use in a wireless communication system , the wireless communication system including: an Evolved NodeB, eNB; and at least one user equipment , UE, wherein the wireless communication system is capable of carrier aggregation, CA, with up to 32 downlink, DL, component carriers, CCs, or cells, but only a single uplink, UL, CC, and control signaling between the eNB and a UE is operable in the following CA modes: a self-scheduling mode wherein the control signaling method comprises performing control signaling between the eNB and the UE , and sending by the eNB to the UE a CA configuration message that disables cross-carrier scheduling; a cross-carrier scheduling mode wherein the control signaling method comprises performing control signaling between the eNB and the UE , and sending by the eNB to the UE a CA configuration message that enables cross-carrier scheduling; and a hybrid CA mode wherein the control signaling method comprises performing control signaling between the eNB and the UE , wherein performing control signaling between the eNB and the UE includes transmitting a 5-bit Radio Resource Control, RRC, parameter for identifying a servicing-cell or CC, wherein the 5-bit RRC parameter is divided into 4 first servicing-cell-index groups and each servicing-cell-index group has at most 8 CCs and is identified with a service-cell-index, and wherein in the hybrid CA mode, the method further comprises sending by the eNB to the UE , via a RRC connection, a CA configuration message that: enables cross-carrier scheduling and self-scheduling; configures serving cell index groups, scheduling cells and associated scheduled cells, and self-scheduling cells; configures a set of 4 or more PUCCH resource indexes; configures UE Specific Search Space, USS, on the configured scheduling cells with the restriction that USSs for DL CCs within the cross-scheduling group should not overlap with USSs for DL CCs in other cross-scheduled groups; and configures USS on the configured self-scheduling cells. an Evolved NodeB, eNB; and at least one user equipment , UE, a self-scheduling mode wherein the control signaling method comprises performing control signaling between the eNB and the UE , and sending by the eNB to the UE a CA configuration message that disables cross-carrier scheduling; a cross-carrier scheduling mode wherein the control signaling method comprises performing control signaling between the eNB and the UE , and sending by the eNB to the UE a CA configuration message that enables cross-carrier scheduling; and a hybrid CA mode wherein the control signaling method comprises performing control signaling between the eNB and the UE , enables cross-carrier scheduling and self-scheduling; configures serving cell index groups, scheduling cells and associated scheduled cells, and self-scheduling cells; configures a set of 4 or more PUCCH resource indexes; configures UE Specific Search Space, USS, on the configured scheduling cells with the restriction that USSs for DL CCs within the cross-scheduling group should not overlap with USSs for DL CCs in other cross-scheduled groups; and configures USS on the configured self-scheduling cells. <EOS>