A wireless transmit/receive unit, WTRU, comprising: a processor; and a memory comprising instructions that when executed by the processor cause the WTRU to: receive a plurality of demodulation reference signal, DM-RS, configurations, each DM-RS configuration corresponding to a respective carrier segment of a set of carrier segments, wherein each respective carrier segment is used for receiving a physical data shared channel, PDSCH, and wherein each respective DM-RS configuration indicates one or more DM-RS parameters that are used to determine a respective DM-RS structure for a respective carrier segment, and wherein the respective DM-RS structure for the respective carrier segment comprises a respective mapping of one or more DM-RSs, wherein the respective mapping of the one or more DM-RSs comprises a mapping of the one or more DM-RSs to a respective set of resource blocks, RBs, upon which a corresponding PDSCH is mapped; and receive a PDSCH transmission in at least one carrier segment of the set of carrier segments, wherein the received PDSCH transmission comprises the one or more DM-RSs that are in accordance with the respective DM-RS structure for the at least one carrier segment. a processor; and a memory comprising instructions that when executed by the processor cause the WTRU to: receive a plurality of demodulation reference signal, DM-RS, configurations, each DM-RS configuration corresponding to a respective carrier segment of a set of carrier segments, wherein each respective carrier segment is used for receiving a physical data shared channel, PDSCH, and wherein each respective DM-RS configuration indicates one or more DM-RS parameters that are used to determine a respective DM-RS structure for a respective carrier segment, and wherein the respective DM-RS structure for the respective carrier segment comprises a respective mapping of one or more DM-RSs, wherein the respective mapping of the one or more DM-RSs comprises a mapping of the one or more DM-RSs to a respective set of resource blocks, RBs, upon which a corresponding PDSCH is mapped; and receive a PDSCH transmission in at least one carrier segment of the set of carrier segments, wherein the received PDSCH transmission comprises the one or more DM-RSs that are in accordance with the respective DM-RS structure for the at least one carrier segment. receive a plurality of demodulation reference signal, DM-RS, configurations, each DM-RS configuration corresponding to a respective carrier segment of a set of carrier segments, wherein each respective carrier segment is used for receiving a physical data shared channel, PDSCH, and wherein each respective DM-RS configuration indicates one or more DM-RS parameters that are used to determine a respective DM-RS structure for a respective carrier segment, and wherein the respective DM-RS structure for the respective carrier segment comprises a respective mapping of one or more DM-RSs, wherein the respective mapping of the one or more DM-RSs comprises a mapping of the one or more DM-RSs to a respective set of resource blocks, RBs, upon which a corresponding PDSCH is mapped; and receive a PDSCH transmission in at least one carrier segment of the set of carrier segments, wherein the received PDSCH transmission comprises the one or more DM-RSs that are in accordance with the respective DM-RS structure for the at least one carrier segment.