A network node (202, 1600) comprising: a wireless interface to communicate over a wireless link with a plurality of mobile devices, and at least one processor to: determine whether a cell on a backward compatible first carrier of a first type is to be used as a reference cell, wherein the first carrier and a second carrier of a second carrier type are synchronized and part of a carrier aggregation, and wherein the reference cell is at least one selected from among a pathloss reference cell and a timing reference cell; send, to a mobile device of the plurality of mobile devices, system information regarding the second carrier of the second carrier type, wherein carriers of the second carrier type do not carry primary synchronization signals, PSS, or secondary synchronization signals, SSS; send, to the mobile device, information indicating whether the cell on the first carrier of the first type is to be used as the reference cell; send, to the mobile device, configuration information regarding whether the mobile device is to monitor an enhanced control channel; determine a delay value associated with modification of the carrier aggregation, the delay value representing a time delay during which the mobile device is unable to receive signaling from the network node responsive to the modification of the carrier aggregation; and send, to the mobile device, the delay value. a wireless interface to communicate over a wireless link with a plurality of mobile devices, and at least one processor to: determine whether a cell on a backward compatible first carrier of a first type is to be used as a reference cell, wherein the first carrier and a second carrier of a second carrier type are synchronized and part of a carrier aggregation, and wherein the reference cell is at least one selected from among a pathloss reference cell and a timing reference cell; send, to a mobile device of the plurality of mobile devices, system information regarding the second carrier of the second carrier type, wherein carriers of the second carrier type do not carry primary synchronization signals, PSS, or secondary synchronization signals, SSS; send, to the mobile device, information indicating whether the cell on the first carrier of the first type is to be used as the reference cell; send, to the mobile device, configuration information regarding whether the mobile device is to monitor an enhanced control channel; determine a delay value associated with modification of the carrier aggregation, the delay value representing a time delay during which the mobile device is unable to receive signaling from the network node responsive to the modification of the carrier aggregation; and send, to the mobile device, the delay value. determine whether a cell on a backward compatible first carrier of a first type is to be used as a reference cell, wherein the first carrier and a second carrier of a second carrier type are synchronized and part of a carrier aggregation, and wherein the reference cell is at least one selected from among a pathloss reference cell and a timing reference cell; send, to a mobile device of the plurality of mobile devices, system information regarding the second carrier of the second carrier type, wherein carriers of the second carrier type do not carry primary synchronization signals, PSS, or secondary synchronization signals, SSS; send, to the mobile device, information indicating whether the cell on the first carrier of the first type is to be used as the reference cell; send, to the mobile device, configuration information regarding whether the mobile device is to monitor an enhanced control channel; determine a delay value associated with modification of the carrier aggregation, the delay value representing a time delay during which the mobile device is unable to receive signaling from the network node responsive to the modification of the carrier aggregation; and send, to the mobile device, the delay value.