Apparatus and method for full-dimensional MIMO with one-dimensional CSI feedback

1. A method for wireless communication, comprising:

dividing a two-dimensional antenna array to a plurality of sub-arrays, wherein each of the plurality of sub-arrays comprises a same number of antenna elements;

mapping the two-dimensional antenna array into a one-dimensional vertical channel state information reference signal (CSI-RS) port array for receiving elevation CSI feedback and a one-dimensional horizontal CSI-RS port array for receiving azimuth CSI feedback, wherein the mapping includes applying intra-sub-array antenna aggregation in each of the plurality of sub-arrays and applying inter-sub-array antenna aggregation among the plurality of sub-arrays, wherein the one-dimensional vertical CSI-RS port array includes an M-port cross-polarized CSI-RS array for M-port elevation CSI feedback, wherein the one-dimensional horizontal CSI-RS port array includes an N-port cross-polarized CSI-RS array for N-port azimuth CSI feedback, and M represents a column number or a subset of the column number of the two-dimensional antenna array and N represent a row number or a subset of the row number of the two-dimensional antenna array, wherein the applying the inter-sub-array antenna aggregation includes utilizing inter-sub-array aggregation weight vectors for the mapping, and wherein the inter-sub-array aggregation weight vector for the mapping to the one-dimensional vertical CSI-RS port array and the inter-sub-array aggregation weight vector for the mapping to the one-dimensional horizontal CSI-RS port array are selected so that patterns of the one-dimensional vertical CSI-RS port array and one-dimensional horizontal CSI-RS port array are complementary to each other; and

transmitting one or more elevation CSI-RS from the one-dimensional vertical CSI-RS port array and one or more azimuth CSI-RS from the one-dimensional horizontal CSI-RS port array.

2. The method of claim 1 , wherein numbers of CSI ports of the elevation CSI feedback and of the azimuth CSI feedback for the subset of antenna elements of the two-dimensional antenna array are determined based on a capability of a user equipment (UE).

3. A method for wireless communication, comprising:

dividing a two-dimensional antenna array to a plurality of sub-arrays, wherein each of the plurality of sub-arrays comprises a same number of antenna elements;

mapping the two-dimensional antenna array into a one-dimensional vertical channel state information reference signal (CSI-RS) port array for receiving elevation CSI feedback and a one-dimensional horizontal CSI-RS port array for receiving azimuth CSI feedback, wherein the mapping includes applying intra-sub-array antenna aggregation in each of the plurality of sub-arrays and applying inter-sub-array antenna aggregation among the plurality of sub-arrays; and

transmitting one or more elevation CSI-RS from the one-dimensional vertical CSI-RS port array and one or more azimuth CSI-RS from the one-dimensional horizontal CSI-RS port array,

wherein the applying the intra-sub-array antenna aggregation includes aggregating all rows of the antenna elements in each of the plurality of sub-arrays to form a plurality of aggregated vertical sub-arrays and aggregating all columns of the antenna elements in each of the plurality of sub-arrays to form a plurality of aggregated horizontal sub-arrays, wherein the applying the inter-sub-array antenna aggregation includes utilizing inter-sub-array aggregation weight vectors for the mapping, and wherein the inter-sub-array aggregation weight vector for the mapping to the one-dimensional vertical CSI-RS port array and the inter-sub-array aggregation weight vector for the mapping to the one-dimensional horizontal CSI-RS port array are selected so that patterns of the one-dimensional vertical CSI-RS port array and one-dimensional horizontal CSI-RS port array are complementary to each other.

4. The method of claim 3 , wherein the applying the inter-sub-array antenna aggregation includes aggregating the plurality of aggregated vertical sub-arrays to form the one-dimensional vertical CSI-RS port array and aggregating the plurality of aggregated horizontal sub-arrays to form the one-dimensional horizontal CSI-RS port array.

5. A method for wireless communication, comprising:

dividing a two-dimensional antenna array to a plurality of sub-arrays, wherein each of the plurality of sub-arrays comprises a same number of antenna elements;

mapping the two-dimensional antenna array into a one-dimensional vertical channel state information reference signal (CSI-RS) port array for receiving elevation CSI feedback and a one-dimensional horizontal CSI-RS port array for receiving azimuth CSI feedback, wherein the mapping includes applying intra-sub-array antenna aggregation in each of the plurality of sub-arrays and applying inter-sub-array antenna aggregation among the plurality of sub-arrays, wherein the applying the intra-sub-array antenna aggregation includes utilizing intra-sub-array aggregation weight vectors for the mapping, wherein the applying the inter-sub-array antenna aggregation includes utilizing inter-sub-array aggregation weight vectors for the mapping, and wherein at least one of:

the inter-sub-array aggregation weight vector for the mapping to the one-dimensional vertical CSI-RS port array and the inter-sub-array aggregation weight vector for the mapping to the one-dimensional horizontal CSI-RS port array are selected so that patterns of the one-dimensional vertical CSI-RS port array and one-dimensional horizontal CSI-RS port array are complementary to each other; or

the intra-sub-array aggregation weight vector and inter-sub-array aggregation weight vectors for the mapping to the one-dimensional vertical CSI-RS port array and the one-dimensional horizontal CSI-RS port array are determined based on one or more of: a number of the antenna elements in a column of the two-dimensional antenna array, spacing between the antenna elements, a target down tilt, and elevation dimension coverage; and

transmitting one or more elevation CSI-RS from the one-dimensional vertical CSI-RS port array and one or more azimuth CSI-RS from the one-dimensional horizontal CSI-RS port array.

6. The method of claim 5 , wherein the inter-sub-array aggregation weight vector for the mapping to the one-dimensional vertical CSI-RS port array and the inter-sub-array aggregation weight vector for the mapping to the one-dimensional horizontal CSI-RS port array are selected so that patterns of the one-dimensional vertical CSI-RS port array and one-dimensional horizontal CSI-RS port array are complementary to each other.

7. The method of claim 5 , wherein the intra-sub-array aggregation weight vector and inter-sub-array aggregation weight vectors for the mapping to the one-dimensional vertical CSI-RS port array and the one-dimensional horizontal CSI-RS port array are determined based on one or more of: a number of the antenna elements in a column of the two-dimensional antenna array, spacing between the antenna elements, a target down tilt, and elevation dimension coverage.

8. An apparatus for wireless communication, comprising:

means for dividing a two-dimensional antenna array to a plurality of sub-arrays, wherein each of the plurality of sub-arrays comprises a same number of antenna elements;

means for mapping the two-dimensional antenna array into a one-dimensional vertical channel state information reference signal (CSI-RS) port array for receiving elevation CSI feedback and a one-dimensional horizontal CSI-RS port array for receiving azimuth CSI feedback, wherein the means for mapping includes means for applying intra-sub-array antenna aggregation in each of the plurality of sub-arrays and means for applying inter-sub-array antenna aggregation among the plurality of sub-arrays, wherein the one-dimensional vertical CSI-RS port array includes an M-port cross-polarized CSI-RS array for M-port elevation CSI feedback, wherein the one-dimensional horizontal CSI-RS port array includes an N-port cross-polarized CSI-RS array for N-port azimuth CSI feedback, wherein M represents a column number or a subset of the column number of the two-dimensional antenna array and N represent a row number or a subset of the row number of the two-dimensional antenna array, wherein the means for applying the inter-sub-array antenna aggregation includes means for utilizing inter-sub-array aggregation weight vectors for the mapping, and wherein the inter-sub-array aggregation weight vector for the means for mapping to the one-dimensional vertical CSI-RS port array and the inter-sub-array aggregation weight vector for the means for mapping to the one-dimensional horizontal CSI-RS port array are selected so that patterns of the one-dimensional vertical CSI-RS port array and one-dimensional horizontal CSI-RS port array are complementary to each other; and

means for transmitting one or more elevation CSI-RS from the one-dimensional vertical CSI-RS port array and one or more azimuth CSI-RS from the one-dimensional horizontal CSI-RS port array.

9. The apparatus of claim 8 , wherein numbers of CSI ports of the elevation CSI feedback and of the azimuth CSI feedback for the subset of antenna elements of the two-dimensional antenna array are determined based on a capability of a user equipment (UE).

10. An apparatus for wireless communication, comprising:

means for dividing a two-dimensional antenna array to a plurality of sub-arrays, wherein each of the plurality of sub-arrays comprises a same number of antenna elements;

means for mapping the two-dimensional antenna array into a one-dimensional vertical channel state information reference signal (CSI-RS) port array for receiving elevation CSI feedback and a one-dimensional horizontal CSI-RS port array for receiving azimuth CSI feedback, wherein the means for mapping includes means for applying intra-sub-array antenna aggregation in each of the plurality of sub-arrays and means for applying inter-sub-array antenna aggregation among the plurality of sub-arrays, wherein the means for applying the intra-sub-array antenna aggregation includes means for aggregating all rows of the antenna elements in each of the plurality of sub-arrays to form a plurality of aggregated vertical sub-arrays and means for aggregating all columns of the antenna elements in each of the plurality of sub-arrays to form a plurality of aggregated horizontal sub-arrays, wherein the means for applying the inter-sub-array antenna aggregation includes means for utilizing inter-sub-array aggregation weight vectors for the mapping, and wherein the inter-sub-array aggregation weight vector for the means for mapping to the one-dimensional vertical CSI-RS port array and the inter-sub-array aggregation weight vector for the means for mapping to the one-dimensional horizontal CSI-RS port array are selected so that patterns of the one-dimensional vertical CSI-RS port array and one-dimensional horizontal CSI-RS port array are complementary to each other; and

means for transmitting one or more elevation CSI-RS from the one-dimensional vertical CSI-RS port array and one or more azimuth CSI-RS from the one-dimensional horizontal CSI-RS port array.

11. The apparatus of claim 10 , wherein the means for applying the inter-sub-array antenna aggregation includes means for aggregating the plurality of aggregated vertical sub-arrays to form the one-dimensional vertical CSI-RS port array and means for aggregating the plurality of aggregated horizontal sub-arrays to form the one-dimensional horizontal CSI-RS port array.

12. An apparatus for wireless communication, comprising:

means for dividing a two-dimensional antenna array to a plurality of sub-arrays, wherein each of the plurality of sub-arrays comprises a same number of antenna elements;

means for mapping the two-dimensional antenna array into a one-dimensional vertical channel state information reference signal (CSI-RS) port array for receiving elevation CSI feedback and a one-dimensional horizontal CSI-RS port array for receiving azimuth CSI feedback, wherein the means for mapping includes means for applying intra-sub-array antenna aggregation in each of the plurality of sub-arrays and means for applying inter-sub-array antenna aggregation among the plurality of sub-arrays, wherein the means for applying the intra-sub-array antenna aggregation includes means for utilizing intra-sub-array aggregation weight vectors for the mapping, wherein the means for applying the inter-sub-array antenna aggregation includes means for utilizing inter-sub-array aggregation weight vectors for the mapping, and wherein at least one of:

the inter-sub-array aggregation weight vector for the means for mapping to the one-dimensional vertical CSI-RS port array and the inter-sub-array aggregation weight vector for the means for mapping to the one-dimensional horizontal CSI-RS port array are selected so that patterns of the one-dimensional vertical CSI-RS port array and one-dimensional horizontal CSI-RS port array are complementary to each other; or

the intra-sub-array aggregation weight vector and inter-sub-array aggregation weight vectors for the means for mapping to the one-dimensional vertical CSI-RS port array and the one-dimensional horizontal CSI-RS port array are determined based on one or more of: a number of the antenna elements in a column of the two-dimensional antenna array, spacing between the antenna elements, a target down tilt, and elevation dimension coverage; and

means for transmitting one or more elevation CSI-RS from the one-dimensional vertical CSI-RS port array and one or more azimuth CSI-RS from the one-dimensional horizontal CSI-RS port array.

13. The apparatus of claim 12 , wherein the inter-sub-array aggregation weight vector for the means for mapping to the one-dimensional vertical CSI-RS port array and the inter-sub-array aggregation weight vector for the means for mapping to the one-dimensional horizontal CSI-RS port array are selected so that patterns of the one-dimensional vertical CSI-RS port array and one-dimensional horizontal CSI-RS port array are complementary to each other.

14. The apparatus of claim 12 , wherein the intra-sub-array aggregation weight vector and inter-sub-array aggregation weight vectors for the means for mapping to the one-dimensional vertical CSI-RS port array and the one-dimensional horizontal CSI-RS port array are determined based on one or more of: a number of the antenna elements in a column of the two-dimensional antenna array, spacing between the antenna elements, a target down tilt, and elevation dimension coverage.