Uplink spectrum efficiency
Methods and systems are disclosed for reducing control signaling in uplink transmissions. A device, such as a wireless transmit/receive unit, may determine to use a demodulation reference signal (DM-RS) transmission schedule out of a plurality of DM-RS transmission schedules. The DM-RS transmission schedule may be characterized by a DM-RS transmission being mapped to a single orthogonal frequency-division multiplexing (OFDM) symbol per subframe of a data stream. The DM-RS transmission schedule may be characterized by a DM-RS transmission being mapped to a first subset of subcarriers of an OFDM symbol of a subframe of a data stream and Physical Uplink Shared Channel (PUSCH) transmission or Physical Uplink Control Channel (PUCCH) control information being mapped to a second set of subcarriers of the OFDM symbol. The first set of subcarriers may be different than the second set of subcarriers. The data stream may be transmitted according to the DM-RS transmission schedule.
1. A method implemented in a wireless transmit receive unit (WTRU), the method comprising:
receiving a radio resource control (RRC) configuration indicating a plurality of potential demodulation reference signal (DM-RS) transmission schedules associated with a Physical Uplink Shared Channel (PUSCH);
receiving downlink control information (DCI) associated with a PUSCH transmission, the PUSCH transmission to be performed over a plurality of Orthogonal Frequency-Division Multiplexing (OFDM) symbols;
determining, based at least on the DCI and the RRC configuration, which one or multiple OFDM symbols of the plurality of OFDM symbols should be used to transmit DM-RS for the PUSCH transmission; and
transmitting the DM-RS for the PUSCH transmission in the one or multiple OFDM symbols.
2. The method of claim 1 , wherein the potential DM-RS transmission schedules are associated with different time-domain positions of DM-RSs.
3. The method of claim 1 , wherein the potential DM-RS transmission schedules are associated with respective numbers of OFDM symbols used for transmitting DM-RSs.
4. The method of claim 1 , wherein the determining of which one or multiple OFDM symbols should be used to transmit DM-RS for the PUSCH transmission is based at least on a format of the DCI.
5. The method of claim 1 , wherein the determining of which one or multiple OFDM symbols should be used to transmit DM-RS for the PUSCH transmission is based further on a duration of the PUSCH transmission.
6. The method of claim 1 , wherein the RRC configuration further indicates the position of a first OFDM symbol within a slot to be used for DM-RS transmission.
7. The method of claim 1 , wherein the DCI is associated with an uplink grant associated with the PUSCH transmission.
8. The method of claim 1 , wherein at least one of the potential DM-RS transmission schedules is associated with using a single OFDM symbol of a slot for DM-RS transmission.
9. A wireless transmit receive unit (WTRU), comprising:
a processor configured to:
receive a radio resource control (RRC) configuration indicating a plurality of potential demodulation reference signal (DM-RS) transmission schedules associated with a Physical Uplink Shared Channel (PUSCH);
receive downlink control information (DCI) associated with a PUSCH transmission, the PUSCH transmission to be performed over a plurality of Orthogonal Frequency-Division Multiplexing (OFDM) symbols;
determine, based at least on the DCI and the RRC configuration, which one or multiple OFDM symbols of the plurality of OFDM symbols should be used to transmit DM-RS for the PUSCH transmission; and
transmit the DM-RS for the PUSCH transmission in the one or multiple OFDM symbols.
10. The WTRU of claim 9 , wherein the potential DM-RS transmission schedules are associated with different time-domain positions of DM-RSs.
11. The WTRU of claim 9 , wherein the potential DM-RS transmission schedules are associated with respective numbers of OFDM symbols used for transmitting DM-RSs.
12. The WTRU of claim 9 , wherein the processor is configured to determine which one or multiple OFDM symbols should be used to transmit DM-RS for the PUSCH transmission based at least on a format of the DCI.
13. The WTRU of claim 9 , wherein the processor is configured to determine which one or multiple OFDM symbols should be used to transmit DM-RS for the PUSCH transmission based further on a duration of the PUSCH transmission.
14. The WTRU of claim 9 , wherein the RRC configuration further indicates the position of a first OFDM symbol within a slot to be used for DM-RS transmission.
15. The WTRU of claim 9 , wherein the DCI is associated with an uplink grant for the PUSCH transmission.
16. The WTRU of claim 9 , wherein at least one of the potential DM-RS transmission schedules is associated with using a single OFDM symbol of a slot for DM-RS transmission.