Communication apparatus and method for communicating using a transmit power difference between antennas

1. A UE for wireless communication, comprising:

a transceiver including a power amplifier;

a first antenna port coupled to the power amplifier to receive power from the power amplifier;

a second antenna port coupled to the power amplifier to receive power from the power amplifier; and

a controller coupled to the transceiver, where the controller determines transmit power difference information corresponding to a transmit power difference between transmit power on the first antenna port and transmit power on the second antenna port,

wherein the transceiver transmits the transmit power difference information,

wherein the second antenna port receives less power from the power amplifier when transmitting sounding reference signals than the first antenna port.

2. The UE according to claim 1 , further comprising a switch coupled between the first antenna port and the power amplifier and coupled between the second antenna port and the power amplifier,

where the controller controls the switch to switch between transmitting sounding reference signals on the first antenna port and transmitting sounding reference signals on the second antenna port.

3. The UE according to claim 1 , wherein the transmit power difference corresponds to the second antenna port receiving less power from the power amplifier when transmitting sounding reference signals than the first antenna port due to power loss between the power amplifier and the second antenna port.

4. The UE according to claim 1 ,

wherein the first antenna port comprises a transmit and receive antenna port, and

wherein the second antenna port comprises an antenna port that has an allowed transmit power reduction of its maximum output power for transmitting sounding reference signals.

5. The UE according to claim 1 , wherein the transmit power difference information comprises the transmit power difference between transmit power for sounding reference signals on the first antenna port and transmit power for sounding reference signals on the second antenna port.

6. The UE according to claim 1 ,

wherein the transceiver receives reference symbols, and

wherein the controller

measures a first received power of the reference symbols on the first antenna port,

measures a second received power of the reference symbols on the second antenna port, and

determines a received power difference by subtracting the second received power from the first received power, where the determined transmit power difference information comprises the determined received power difference.

7. The UE according to claim 6 ,

wherein the received power difference comprises a first received power difference, and

wherein the controller

measures a third received power of the reference symbols on a third antenna port, and

determines a second received power difference by subtracting the third received power from the first received power, and

wherein the transceiver transmits the second received power difference.

8. The UE according to claim 1 ,

wherein the transceiver receives reference symbols, and

wherein the controller

measures a first received power of the reference symbols on the first antenna port,

measures a second received power of the reference symbols on the second antenna port, and

determines a received power ratio between the second received power from the first received power, where the determined transmit power difference information comprises the determined received power ratio.

9. The UE according to claim 1 , wherein the first antenna port comprises a first antenna and the second antenna port comprises a second antenna.

10. A method in a communication device, the method comprising:

determining, at the communication device, transmit power difference information corresponding to a transmit power difference between transmit power on a first antenna port of the device and transmit power on a second antenna port of the device, where the second antenna port is coupled to and uses a same transmit power amplifier as the first antenna port; and

transmitting the transmit power difference information

wherein the second antenna port receives less power from the power amplifier when transmitting sounding reference signals than the first antenna port.

11. The method according to claim 10 , further comprising switching between transmitting sounding reference signals on the first antenna port and transmitting sounding reference signals on the second antenna port using a switch, where the switch is coupled between the first antenna port and the power amplifier and coupled between the second antenna port and the power amplifier.

12. The method according to claim 10 , wherein the transmit power difference corresponds to the second antenna port receiving less power from the power amplifier when transmitting sounding reference signals than the first antenna port due to power loss between the power amplifier and the second antenna port.

13. The method according to claim 10 ,

wherein the first antenna port comprises a transmit and receive antenna port, and

wherein the second antenna port comprises an antenna port that has an allowed transmit power reduction of its maximum output power for transmitting sounding reference signals.

14. The method according to claim 10 , wherein the transmit power difference information comprises the transmit power difference between transmit power for sounding reference signals on the first antenna port and transmit power for sounding reference signals on the second antenna port.

15. The method according to claim 10 , further comprising:

receiving reference symbols;

measuring a first received power of the reference symbols on the first antenna port;

measuring a second received power of the reference symbols on the second antenna port; and

determining a received power difference by subtracting the second received power from the first received power, where the determined transmit power difference information comprises the determined received power difference.

16. The method according to claim 15 ,

wherein the received power difference comprises a first received power difference, and

wherein the method further comprises:

measuring a third received power of the reference symbols on a third antenna port;

determining a second received power difference by subtracting the third received power from the first received power; and

transmitting the second received power difference.

17. The method according to claim 10 , further comprising:

receiving reference symbols;

measuring a first received power of the reference symbols on the first antenna port;

measuring a second received power of the reference symbols on the second antenna port; and

determining a received power ratio between the second received power from the first received power, where the determined transmit power difference information comprises the determined received power ratio.

18. The method according to claim 10 , wherein the first antenna port comprises a first antenna and the second antenna port comprises a second antenna.

19. A processor for wireless communication, comprising:

at least one controller coupled with at least one memory and configured to cause the processor to:

determine transmit power difference information corresponding to a transmit power difference between transmit power on a first antenna port of a device and transmit power on a second antenna port of the device, where the second antenna port is coupled to and uses a same transmit power amplifier as the first antenna port; and

transmit the transmit power difference information

wherein the second antenna port receives less power from the power amplifier when transmitting sounding reference signals than the first antenna port.

20. The processor according to claim 19 , wherein the transmit power difference corresponds to the second antenna port receiving less power from the power amplifier when transmitting sounding reference signals than the first antenna port due to power loss between the power amplifier and the second antenna port.