Efficient SRS resource indication methods

1. A method in a network node, operable in a cellular wireless communication network, of receiving an uplink transmission from a wireless device, the method comprising:

transmitting signaling configuring a wireless device with a plurality of Sounding Reference Signal (SRS) resources;

transmitting an indication, in a physical layer downlink control channel, of a selected plurality of SRS resources selected from among the plurality of configured SRS resources; and

receiving a plurality of multiple-input multiple-output (MIMO) layers of a PUSCH transmission,

wherein the selected plurality of SRS resources map to respective ones of the plurality of MIMO layers,

wherein the indication of the selected plurality of SRS resources includes SRS resource indexes with a fixed order that corresponds to an order in which the SRS resources of the selected plurality of SRS resources are mapped to the MIMO layers, and

wherein a size of a field used for the indication of SRS resource indexes is determined according to a maximum number of MIMO layers that the wireless device is configured to transmit.

2. The method of claim 1 , wherein the indication of the selected plurality of SRS resources indicates an entry of a table, wherein the table includes only one entry for each possible ordering of a combination of SRS resources.

3. The method of claim 1 , wherein the signaling configuring the wireless device with a plurality of SRS resources indicates groupings of the plurality of SRS resources into a plurality of SRS resource groups, each group comprising a plurality of SRS resources and wherein each of the SRS resources of the selected plurality of SRS resources are selected from the same SRS resource group.

4. A method in a wireless device, operable in a wireless communication network, of transmitting an uplink transmission, the method comprising:

receiving signaling configuring the wireless device with a plurality of Sounding Reference Signal (SRS) resources;

receiving an indication, in a physical layer downlink control channel, of a selected plurality of SRS resources selected from among the plurality of configured SRS resources; and

transmitting a plurality of multiple-input multiple-output (MIMO) layers of a PUSCH transmission,

wherein the selected plurality of SRS resources map to respective ones of the plurality of MIMO layers,

wherein the indication of the selected plurality of SRS resources includes SRS resource indexes with a fixed order that corresponds to an order in which the SRS resources of the selected plurality of SRS resources are mapped to the MIMO layers, and

wherein a size of a field used for the indication of SRS resource indexes is determined according to a maximum number of MIMO layers that the wireless device is configured to transmit.

5. The method of claim 4 , wherein the indication of the selected plurality of SRS resources indicates an entry of a table, wherein the table includes only one entry for each possible ordering of a combination of SRS resources.

6. The method of claim 4 , wherein the signaling configuring the wireless device with a plurality of SRS resources indicates groupings of the plurality of SRS resources into a plurality of SRS resource groups, each group comprising a plurality of SRS resources and wherein each of the SRS resources of the selected plurality of SRS resources are selected from the same SRS resource group.

7. A network node for receiving an uplink transmission from a wireless device in a wireless communication network, the network node comprising:

an antenna configured to send and receive wireless signals; and

a transceiver connected to the antenna and to processing circuitry, and configured to condition signals communicated between the antenna and the processing circuitry, the processing circuitry being configured to carry out a method comprising:

transmitting signaling configuring a wireless device with a plurality of Sounding Reference Signal (SRS) resources;

transmitting an indication, in a physical layer downlink control channel, of a selected plurality of SRS resources selected from among the plurality of configured SRS resources; and

receiving a plurality of multiple-input multiple-output (MIMO) layers of a PUSCH transmission,

wherein the selected plurality of SRS resources map to respective ones of the plurality of MIMO layers,

wherein the indication of the selected plurality of SRS resources includes SRS resource indexes with a fixed order that corresponds to an order in which the SRS resources of the selected plurality of SRS resources are mapped to the MIMO layers, and

wherein a size of a field used for the indication of SRS resource indexes is determined according to a maximum number of MIMO layers that the wireless device is configured to transmit.

8. The network node of claim 7 , wherein the indication of the selected plurality of SRS resources indicates an entry of a table, wherein the table includes only one entry for each possible ordering of a combination of SRS resources.

9. The network node of claim 7 , wherein the signaling configuring the wireless device with a plurality of SRS resources indicates groupings of the plurality of SRS resources into a plurality of SRS resource groups, each group comprising a plurality of SRS resources and wherein each of the SRS resources of the selected plurality of SRS resources are selected from the same SRS resource group.

10. A wireless device operable in a wireless communication network to transmit an uplink transmission, the wireless device comprising:

an antenna configured to send and receive wireless signals; and

a transceiver connected to the antenna and to processing circuitry, and configured to condition signals communicated between the antenna and the processing circuitry, the processing circuitry being configured to carry out a method comprising:

receiving signaling configuring the wireless device with a plurality of Sounding Reference Signal (SRS) resources;

receiving an indication, in a physical layer downlink control channel, of a selected plurality of SRS resources selected from among the plurality of configured SRS resources; and

transmitting a plurality of multiple-input multiple-output (MIMO) layers of a PUSCH transmission,

wherein the selected plurality of SRS resources map to respective ones of the plurality of MIMO layers,

wherein the indication of the selected plurality of SRS resources includes SRS resource indexes with a fixed order that corresponds to an order in which the SRS resources in the selected plurality of SRS resources are mapped to the MIMO layers, and

wherein a size of a field used for the indication of SRS resource indexes is determined according to a maximum number of MIMO layers that the wireless device is configured to transmit.

11. The wireless device of claim 10 , wherein the indication of the selected plurality of SRS resources indicates an entry of a table, wherein the table includes only one entry for each possible ordering of a combination of SRS resources.

12. The wireless device of claim 10 , wherein the signaling configuring the wireless device with a plurality of SRS resources indicates groupings of the plurality of SRS resources into a plurality of SRS resource groups, each group comprising a plurality of SRS resources and wherein each of the SRS resources of the selected plurality of SRS resources are selected from the same SRS resource group.