Joint transmission of precoded and unprecoded sounding reference signals in uplink
Both precoded sounding reference signals (SRS) and unprecoded SRS are transmitted from a UE to an eNB. The UE may transmit both in the same subframe using either TDM or FDM. Or the UE may transmit each in different subframes from each other. The eNB uses some combination of the precoded SRS and the unprecoded SRS in scheduling resources for the UE. The eNB may also provide instruction to the UE for PUSCH precoding for data transmission. The eNB may signal the UE to use the same precoding as for the precoded SRS. The eNB may instead signal the UE to use different precoding by including the precoding information or delta information between the precoding used for the precoded SRS and the selected precoding for the PUSCH data.
1. A method, comprising:
receiving, by a first wireless communications device, a precoded sounding reference signal (SRS) from a second wireless communications device;
receiving, by the first wireless communications device, an unprecoded SRS separate from the precoded SRS from the second wireless communications device;
determining, by the first wireless communications device, a resource scheduling for the second wireless communications device based on a combination of the precoded SRS and the unprecoded SRS;
generating, by the first wireless communications device, a precode instruction for the second wireless communications device for data transmission on an uplink channel, wherein the generating comprises:
determining, by the first wireless communications device, a delta between a desired precoding and an existing precoding used for the precoded SRS; and
including, by the first wireless communications device, the delta as the precode instruction.
2. The method of claim 1 , further comprising:
transmitting, by the first wireless communications device, a resource scheduling message comprising the determined resource scheduling to the second wireless communications device.
3. The method of claim 1 , wherein:
the receiving the precoded SRS comprises receiving during a first symbol period of a subframe, and
the receiving the unprecoded SRS comprises receiving during a second symbol period of the subframe.
4. The method of claim 1 , wherein:
the receiving the precoded SRS comprises receiving during a symbol period of a subframe using a first plurality of frequency resources, and
the receiving the unprecoded SRS comprises receiving during the symbol period of the subframe using a second plurality of frequency resources different from the first plurality of frequency resources.
5. The method of claim 1 , wherein:
the receiving the precoded SRS comprises receiving the precoded SRS during a first subframe, and
the receiving the unprecoded SRS comprises receiving the unprecoded SRS during a second subframe after the first subframe.
6. The method of claim 1 , wherein the precode instruction directs the second wireless communications device to apply a precoding used for the precoded SRS for data transmission.
7. An apparatus, comprising:
a transceiver configured to:
receive a precoded sounding reference signal (SRS) from a wireless communications device; and
receive an unprecoded SRS separate from the precoded SRS from the wireless communications device; and
a processor configured to:
determine a resource scheduling for the second wireless communications device based on a combination of the precoded SRS and the unprecoded SRS;
generate a precode instruction for the wireless communications device for data transmission on an uplink channel;
determine a delta between a desired precoding and an existing precoding used for the precoded SRS; and
include the delta as the precode instruction.
8. The apparatus of claim 7 , wherein the transceiver is further configured to:
transmit a resource scheduling message comprising the determined resource scheduling to the wireless communications device.
9. The apparatus of claim 7 , wherein:
the transceiver is configured to receive the precoded SRS during a first symbol period of a subframe, and
the transceiver is configured to receive the unprecoded SRS during a second symbol period of the subframe.
10. The apparatus of claim 7 , wherein:
the transceiver is configured to receive the precoded SRS during a symbol period of a subframe using a first plurality of frequency resources, and
the transceiver is configured to receive the unprecoded SRS during the symbol period of the subframe using a second plurality of frequency resources different from the first plurality of frequency resources.
11. A non-transitory computer-readable medium having program code recorded thereon, the program code comprising:
code for causing a first wireless communications device to receive a precoded sounding reference signal (SRS) from a second wireless communications device;
code for causing the first wireless communications device to receive an unprecoded SRS separate from the precoded SRS from the second wireless communications device; and
code for causing the first wireless communications device to determine a resource scheduling for the second wireless communications device based on a combination of the precoded SRS and the unprecoded SRS;
code for causing the first wireless communications device to generate a precode instruction for the second wireless communications device for data transmission on an uplink channel, the code for causing the generating further comprises:
code for causing the first wireless communications device to determine a delta between a desired precoding and an existing precoding used for the precoded SRS; and
code for causing the first wireless communications device to include the delta as the precode instruction.
12. The non-transitory computer-readable medium of claim 11 , the code further comprising:
code for causing the first wireless communications device to transmit a resource scheduling message comprising the determined resource scheduling to the second wireless communications device.
13. The non-transitory computer-readable medium of claim 11 , wherein:
the code for causing the first wireless communication device to receive the precoded SRS comprises receipt during a first symbol period of a subframe, and
the code for causing the first wireless communication device to receive the unprecoded SRS comprises receipt during a second symbol period of the subframe.
14. The non-transitory computer-readable medium of claim 11 , wherein:
the code for causing the first wireless communication device to receive the precoded SRS comprises receipt during a symbol period of a subframe using a first plurality of frequency resources, and
the code for causing the first wireless communication device to receive the unprecoded SRS comprises receipt during the symbol period of the subframe using a second plurality of frequency resources different from the first plurality of frequency resources.