Codebook design for composite beamforming in next-generation mmWave systems

1. A method of communicating between a transmitter and a receiver in a wireless communication system, comprising:

selecting a beamformer from a beamforming codebook; and

transmitting a signal from antenna elements using the selected beamformer by adjusting a gain and a phase of the signal, the antenna elements corresponding to an absolute value and an angle of a respective complex beamforming coefficient from the selected beamformer, wherein the respective complex beamforming coefficient is obtained by:

calculating beamforming coefficients of the antenna elements for a composite beam as a summation of beamforming coefficients of corresponding ones of the antenna elements of a beamforming vector for the plurality of disjoint beam lobes of the composite beam; and

normalizing the beamforming vector of the calculated beamforming coefficients such that an absolute value of an m-th beamforming coefficient of the beamforming vector for a constituent beam lobe q is proportional to sinc(δq(η+m)), wherein δq and n are two constant values and sinc(x) is a function defined as sin(x)/x, where sin(x) is the sinusoidal function;

wherein the beamformer is a composite beam comprised of a plurality of disjoint beam qlobes, and each of the plurality of disjoint beam lobes covers a desired angular interval.

2. The method of claim 1 , wherein the antenna elements are arranged in tandem in two parallel lines of a particular distance, and wherein the antenna elements in a line from among the two parallel lines are uniformly placed.

3. The method of claim 2 , wherein the antenna elements are dipole or cross-dipole or patch antennas.

4. The method of claim 2 , wherein the beamforming coefficients of tandem ones of the antenna elements have a same absolute value.

5. The method of claim 4 , wherein a difference in a phase of tandem ones of the antenna elements is set to achieve a desired isolation between a radiated signal in unwanted directions and intended directions.

6. The method of claim 1 , wherein the beamforming codebook is a hierarchical codebook comprising:

a first layer codebook which is comprised of plurality of beamforming codewords for a given set of beams; and

a second layer codebook which is comprised of plurality of index sets, wherein an index set denotes a composition of a composite codebook in terms of its constituent beams.

7. The method of claim 1 , wherein an absolute value of beamforming coefficients of a beamforming codeword is constant.

8. The method of claim 1 , wherein a codeword of the beamforming codebook can be decomposed as a linear summation of a particular number of phase vectors, wherein a phase vector is a vector for which an absolute value of the elements of the vector is constant.

9. A base station in a wireless communication system, comprising:

a memory device for storing program code; and

a hardware processor operatively coupled to the memory device for running the program code to:

select a beamformer from a beamforming codebook; and

transmit a signal from antenna elements using the selected beamformer by adjusting a gain and a phase of the signal, the antenna elements corresponding to an absolute value and an angle of a respective complex beamforming coefficient from the selected beamformer, wherein the respective complex beamforming coefficient is obtained by the hardware processor by:

calculating beamforming coefficients of the antenna elements for a composite beam as a summation of beamforming coefficients of corresponding ones of the antenna elements of a beamforming vector for the plurality of disjoint beam lobes of the composite beam; and

normalizing the beamforming vector of the calculated beamforming coefficients such that an absolute value of an m-th beamforming coefficient of the beamforming vector for a constituent beam lobe q is proportional to sinc(δq(n+m)), wherein δq and η are two constant values and sinc(x) is a function defined as sin(x)/x, where sin(x) is the sinusoidal function;

wherein the beamformer is a composite beam comprised of a plurality of disjoint beam lobes, and each of the plurality of disjoint beam lobes covers a desired angular interval.

10. The base station of claim 9 , wherein the antenna elements are arranged in tandem in two parallel lines of a particular distance, and wherein the antenna elements in a line from among the two parallel lines are uniformly placed.

11. The base station of claim 10 , wherein the antenna elements are dipole or cross-dipole or patch antennas.

12. The base station of claim 10 , wherein the beamforming coefficients of tandem ones of the antenna elements have a same absolute value.

13. The base station of claim 12 , wherein a difference in a phase of tandem ones of the antenna elements is set to achieve a desired isolation between a radiated signal in unwanted directions and intended directions.

14. The base station of claim 9 , wherein the beamforming codebook is a hierarchical codebook comprising:

a first layer codebook which is comprised of plurality of beamforming codewords for a given set of beams; and

a second layer codebook which is comprised of plurality of index sets, wherein an index set denotes a composition of a composite codebook in terms of its constituent beams.

15. The base station of claim 9 , wherein an absolute value of beamforming coefficients of a beamforming codeword is constant.

16. The base station of claim 9 , wherein a codeword of the beamforming codebook can be decomposed as a linear summation of a particular number of phase vectors, wherein a phase vector is a vector for which an absolute value of the elements of the vector is constant.