Preparing CSI using a set of zero amplitude parameters

1. An apparatus comprising:

a transceiver; and

a processor coupled to the transceiver, the processor configured to cause the apparatus to:

receive a first channel state information reference signal (“CSI-RS”) from a first base station unit;

receive a second CSI-RS from a second base station unit separate from the first base station unit;

determine, from the first CSI-RS and the second CSI-RS, a total number of non-zero coefficients over a set of layers;

encode the total number of non-zero coefficients by selecting a single codeword from a plurality of candidate codewords in which the selected single codeword identifies the total number of non-zero coefficients;

prepare channel state information (“CSI”), wherein the CSI comprises the selected single codeword encoding of the total number of non-zero coefficients; and

transmit the CSI to at least one base station unit of the first base station unit and the second base station unit.

2. The apparatus of claim 1 , wherein the non-zero coefficients are represented by bits, integers, or values in a range.

3. The apparatus of claim 1 , wherein, to prepare the CSI, the processor is configured to cause the apparatus to prepare a combined CSI for all of at least one transmission layer.

4. The apparatus of claim 1 , wherein each transmission layer in at least one transmission layer comprises multiple beams.

5. The apparatus of claim 1 , wherein the processor is further configured to cause the apparatus to determine a set of zero coefficients and a set of non-zero coefficients over the set of layers, wherein the processor is configured to cause the apparatus to determine the total number of non-zero coefficients over the set of layers based on at least one of the set of non-zero coefficients and the set of zero coefficients.

6. The apparatus of claim 1 , wherein, to encode the total number of non-zero coefficients, the processor is configured to cause the apparatus to encode using a variable length code.

7. The apparatus of claim 1 , wherein a length of each candidate codeword from the plurality of candidate codewords is not more than the number of bits needed to code the total number of non-zero coefficients.

8. The apparatus of claim 7 , wherein the processor is further configured to cause the apparatus to determine locations of zero coefficients to generate a set of location bits, and wherein the CSI further comprises the set of location bits.

9. The apparatus of claim 8 , wherein, to determine the locations of zero coefficients to generate the set of location bits, the processor is configured to cause the apparatus to generate the set of location bits using a combinatorial coding or an enumerative coding.

10. The apparatus of claim 8 , wherein, to determine the locations of zero coefficients to generate the set of location bits, the processor is configured to cause the apparatus to encode locations of non-zero coefficients using a combinatorial coding or an enumerative coding.

11. The apparatus of claim 8 , wherein, to determine the locations of zero coefficients to generate the set of location bits, the processor is configured to cause the apparatus to encode the locations of zero coefficients using a combinatorial coding or an enumerative coding.

12. A method comprising:

receiving a first channel state information reference signal (“CSI-RS”) from a first base station unit;

receiving a second CSI-RS from a second base station unit;

determining, from the first CSI-RS and the second CSI-RS, a total number of non-zero coefficients over a set of layers;

encoding the total number of non-zero coefficients by selecting a single codeword from a plurality of candidate codewords in which the selected single codeword identifies the total number of non-zero coefficients;

preparing a channel state information (“CSI”), wherein the CSI comprises the selected single codeword encoding the total number of non-zero coefficients; and

transmitting the CSI to at least one base station unit of the first base unit and the second base station unit.

13. The method of claim 12 , wherein the non-zero coefficients are represented by bits, integers, or values in a range.

14. The method of claim 12 , wherein preparing the CSI comprises preparing a combined CSI for all of at least one transmission layer.

15. The method of claim 12 , wherein each transmission layer in at least one transmission layer comprises multiple beams.

16. The method of claim 12 , further comprising determining a set of zero coefficients and a set of non-zero coefficients over the set of layers, wherein determining the total number of non-zero coefficients over the set of layers is based on at least one of the set of non-zero coefficients and the set of zero coefficients.

17. The method of claim 12 , wherein encoding the total number of non-zero coefficients comprises encoding using a variable length code.

18. The method of claim 12 , wherein a length of each candidate codeword from the plurality of codewords is not more than the number of bits needed to code the total number of non-zero coefficients.

19. The method of claim 18 , further comprising determining locations of zero coefficients to generate a set of location bits, and wherein the CSI further comprises the set of location bits.

20. The method of claim 19 , wherein determining the locations of zero coefficients to generate the set of location bits comprises encoding one of: locations of non-zero coefficients and locations of zero coefficients, said encoding using a combinatorial coding or an enumerative coding.