Combining channel quality measurements based on sounding reference signals and demodulation reference signals

1. A method of operating a first communication node that communicates by multiple-input-multiple-output, MIMO, wireless communications with a second communication node of a wireless communication system, the method comprising:

receiving a sounding reference signal over a plurality of subcarriers transmitted by the second communication node for MIMO communications;

measuring a channel quality responsive to the sounding reference signal (SRS) to output a first channel quality value, based on generating a Signal-to-Interference-plus-Noise Ratio (SINR) value for each of the plurality of subcarriers of the sounding reference signal;

receiving a demodulation reference signal over a plurality of subcarriers transmitted by the second communication node for MIMO communications;

measuring a channel quality responsive to the demodulation reference signal to output a second channel quality value, based on generating a SINR value for each of the plurality of subcarriers of the demodulation reference signal;

determining a reliability of the first channel quality value and a reliability of the second channel quality value, based on determining a reliability of each of the SINR values for the plurality of subcarriers of the sounding reference signal based on a frequency separation between a subcarrier of the sounding reference signal used to generate the corresponding SINR value and at least one subcarrier of the second communication node controlled by the combined channel quality value, and determining a reliability of each of the SINR values for the plurality of subcarriers of the demodulation reference signal based on a frequency separation between a subcarrier of the demodulation reference signal used to generate the corresponding SINR value and the at least one subcarrier of the second communication node controlled by the combined channel quality value; and

combining the first channel quality value and the second channel quality value while compensating for a difference between the determined reliabilities of the channel quality values to generate a combined channel quality value.

2. The method of claim 1 , further comprising:

controlling scheduling of transmissions by the second communication node, selection of a modulation and coding scheme, or selection of a MIMO transmission mode used by the second communication node for transmission responsive to the combined channel quality value.

3. The method of claim 1 , further comprising:

transmitting a message containing information that controls periodicity, frequency, and/or bandwidth of the sounding reference signal transmitted by the second communication node.

4. A method of operating a first communication node that communicates by multiple-input-multiple-output, MIMO, wireless communications with a second communication node of a wireless communication system, the method comprising:

receiving a sounding reference signal over a plurality of subcarriers transmitted by the second communication node for MIMO communications;

measuring a channel quality responsive to the sounding reference signal (SRS) to output a first channel quality value, based on generating a Signal-to-Interference-plus-Noise Ratio (SINR) value for each of the plurality of subcarriers of the sounding reference signal;

receiving a demodulation reference signal over a plurality of subcarriers transmitted by the second communication node for MIMO communications;

measuring a channel quality responsive to the demodulation reference signal to output a second channel quality value, based on generating a SINR value for each of the plurality of subcarriers of the demodulation reference signal;

determining a reliability of the first channel quality value and a reliability of the second channel quality value, based on determining a reliability of each of the SINR values for the plurality of subcarriers of the sounding reference signal based on a time separation between timing of the demodulation reference signal used to generate the corresponding SINR value and the timing of the data signal from the second communication node, and determining a reliability of each of the SINR values for the plurality of subcarriers of the demodulation reference signal based on a time separation between timing of the demodulation reference signal used to generate the corresponding SINR value and the timing of the data signal from the second communication node; and

combining the first channel quality value and the second channel quality value while compensating for a difference between the determined reliabilities of the channel quality values to generate a combined channel quality value.

5. The method of claim 1 , wherein:

determining the reliability of the SINR values for the plurality of subcarriers of the sounding reference signal comprises determining a power difference between the sounding reference signal used to generate the corresponding SINR value and a data signal from the second communication node.

6. The method of claim 1 , wherein combining the first channel quality value and the second channel quality value while compensating for the determined reliability between the measurements to generate the combined channel quality value comprises:

generating a reliability scale value responsive to a ratio of the reliability of the measurement of the second channel quality value and the reliability of the measurement of the first channel quality value;

scaling at least one of the first channel quality value and the second channel quality value using the reliability scale value; and

combining the first channel quality value and the second channel quality value to generate the combined channel quality value.

7. A first communication node comprising:

an antenna array including a plurality of multiple-input-multiple-output, MIMO, antenna elements;

a transceiver coupled to the antenna array, wherein the transceiver is configured to receive communications through the antenna array from a second communication node of a wireless communication system, the received communications including a Sounding Reference Signal, SRS, received over a plurality of subcarriers and a demodulation reference signal received over a plurality of subcarriers; and

a processor coupled to the transceiver and configured to:

measure channel quality responsive to the sounding reference signal to output a first channel quality value based on generating a Signal-to-Interference-plus-Noise Ratio (SINR) value for each of the plurality of subcarriers of the SRS;

measure channel quality responsive to the demodulation reference signal to output a second channel quality value based on generating a Signal-to-Interference-plus-Noise Ratio, SINR, value for each of the plurality of subcarriers of the demodulation reference signal;

determine reliability of the measurements of the first channel quality value based on determining reliability of each of the SINR values for the plurality of subcarriers of the SRS based on a frequency separation between a subcarrier of the sounding reference signal used to measure the corresponding SINR value and at least one subcarrier of the second communication node controlled by the combined channel quality value, and determine reliability of the measurements of the second channel quality value based on determining reliability of each of the SINR values for the plurality of subcarriers of the demodulation reference signal based on a frequency separation between a subcarrier of the demodulation reference signal used to measure the corresponding SINR value and the at least one subcarrier of the second communication node controlled by the combined channel quality value; and

combine the first channel quality value and the second channel quality value while compensating for the determined reliability difference between the measurements to generate a combined channel quality value.

8. The first communication node of claim 7 , wherein the processor is further configured to:

control scheduling of transmissions by the second communication node or selection of a modulation and coding scheme used by the second communication node for transmission responsive to the combined channel quality value.

9. The first communication node of claim 7 , wherein the processor is further configured to:

generate a message containing information for transmission through the transceiver to control periodicity, frequency, and/or bandwidth of the sounding reference signal transmitted by the second communication node.

10. A first communication node comprising:

an antenna array including a plurality of multiple-input-multiple-output (MIMO) antenna elements;

a transceiver coupled to the antenna array, wherein the transceiver is configured to receive communications through the antenna array from a second communication node of a wireless communication system, the received communications including a Sounding Reference Signal (SRS) received over a plurality of subcarriers and a demodulation reference signal received over a plurality of subcarriers; and

a processor coupled to the transceiver and configured to:

measure channel quality responsive to the sounding reference signal to output a first channel quality value, based on generating a Signal-to-Interference-plus-Noise Ratio (SINR) value for each of the plurality of subcarriers of the SRS;

measure channel quality responsive to the demodulation reference signal to output a second channel quality value, based on generating a Signal-to-Interference-plus-Noise Ratio (SINR) value for each of the plurality of subcarriers of the demodulation reference signal;

determine reliability of the measurements of the first channel quality value by determining reliability of each of the SINR values for the plurality of subcarriers of the SRS based on a time separation between timing of the sounding reference signal used to measure the corresponding SINR value and timing of a data signal from the second communication node, and determine reliability of the measurements of the second channel quality value by determining reliability of each of the SINR values for the plurality of subcarriers of the demodulation reference signal based on a time separation between timing of the demodulation reference signal used to measure the corresponding SINR value and the timing of the data signal from the second communication node; and

combine the first channel quality value and the second channel quality value while compensating for the determined reliability difference between the measurements to generate a combined channel quality value.

11. The first communication node of claim 7 , wherein the processor is further configured to combine the first channel quality value and the second channel quality value while compensating for the determined reliability difference between the measurements to generate the combined channel quality value by:

generating a reliability scale value responsive to a ratio of the reliability of the measurement of the second channel quality value and the reliability of the measurement of the first channel quality value;

scaling at least one of the first channel quality value and the second channel quality value using the reliability scale value; and

combining the first channel quality value and the second channel quality value to generate the combined channel quality value.