Apparatus and method to configure antenna beam width
Using High-beam and low-beam transmission signals that have different antenna tilts, different beam-widths, and different polarizations than one another may provide performance advantages in wireless networks. The high-beam transmission signal and the low-beam transmission signal may have orthogonal polarizations. For example, the high-beam transmission signal and the low-beam transmission signal may be linearly polarized signals having different electromagnetic field (E-field) polarization angles with respect to the y-axis, e.g., +/− forty-five degrees with respect to a vertically polarized wave. As another example, the high-beam transmission signal may be a vertically polarized signal, and the low-beam transmission signal may be a horizontally polarized signal, or vice-versa. In addition to having orthogonal polarizations, the low-beam transmission signal may have a greater antenna beam down-tilt angle, and a wider beam-width than the high-beam transmission signal.
1. A method comprising:
generating two signals;
obtaining a low-beam signal and a high-beam signal by applying different beamforming weight vectors to the two signals; and
concurrently transmitting, by an access point, the low-beam signal and the high-beam signal over different polarizations of a common cross-polarized antenna to emit a low-beam transmission signal and a high-beam transmission signal, wherein the low-beam transmission signal has more antenna down-tilt, a wider beam-width, and a different polarization than the high-beam transmission signal, wherein a beam-width angle of the low-beam transmission signal is at least twice as wide as a beam-width angle of the high-beam transmission signal, the beam-width angle of the low-beam transmission signal being an angle between negative three decibel (−3 dB) points of main lobe of the low-beam transmission signal, and the beam-width angle of the high-beam transmission signal being an angle between −3 dB points of main lobe of the high-beam transmission signal.
2. The method of claim 1 , wherein the low-beam transmission signal and the high-beam transmission signal are linearly polarized signals having different electromagnetic field (E-field) polarization angles with respect to y-axis, the y-axis corresponding to a vertically polarized wave.
3. The method of claim 2 , wherein the low-beam transmission signal and the high-beam transmission signal have orthogonal E-field polarization angles.
4. The method of claim 3 , wherein the high-beam transmission signal comprises a forty-five degree E-field angle with respect to the y-axis, and the low-beam transmission signal comprises a negative forty-five degree E-field angle with respect to the y-axis, or
wherein the high-beam transmission signal comprises a negative forty-five degree E-field angle with respect to the y-axis, and the low-beam transmission signal comprises a forty-five degree E-field angle with respect to the y-axis.
5. The method of claim 3 , wherein the high-beam transmission signal comprises a vertically polarized signal, and the low-beam transmission signal comprises a horizontally polarized signal, or
wherein the high-beam transmission signal comprises a horizontally polarized signal, and the low-beam transmission signal comprises a vertically polarized signal.
6. The method of claim 2 , wherein an antenna down-tilt of the low-beam transmission signal is at least three degrees greater than an antenna down-tilt of the high-beam transmission signal.
7. The method of claim 6 , wherein the antenna down-tilt of the low-beam transmission signal is at least six degrees greater than the antenna down-tilt of the high-beam transmission signal.
8. The method of claim 1 , wherein the high-beam transmission signal comprises a forty-five degree electromagnetic field (E-field) polarization angle with respect to y-axis, an eight degree antenna down tilt, and a four degree beam-width angle, and
wherein the low-beam transmission signal comprises a negative forty-five degree electromagnetic field (E-field) polarization angle with respect to the y-axis, a fourteen degree antenna down tilt, and an eight degree beam-width angle, the y-axis corresponding to a vertically polarized wave.
9. The method of claim 1 , wherein the low-beam transmission signal and the high-beam transmission signal are circularly or elliptically polarized signals having different electromagnetic field (E-field) polarization angles with respect to x-axis and y-axis at a given point in space and time, the y-axis corresponding to a vertically polarized wave, and the x-axis corresponding to a horizontally polarized wave.
10. The method of claim 1 , wherein obtaining the low-beam signal and the high-beam signal by applying different beamforming weight vectors to the two signals comprises:
obtaining the low-beam signal by applying a first beamforming weight vector to a first component signal; and
obtaining the high-beam signal by applying a second beamforming weight vector to a second component signal, wherein the first beamforming weight vector provides upper side-lobe suppression for the low-beam signal, and wherein the second beamforming weight vector provides lower side-lobe suppression for the high-beam signal.
11. The method of claim 10 , wherein the first beamforming weight vector provides upper side-lobe suppression for the low-beam signal by suppressing a secondary lobe of the low-beam signal having a same elevation angle as a primary-lobe of the high-beam signal, and
wherein the second beamforming weight vector provides lower side-lobe suppression for the high-beam signal by suppressing a secondary lobe of the high-beam signal having a same elevation angle as a primary-lobe of the low-beam signal.
12. The method of claim 10 , wherein transmitting the low-beam signal and the high-beam signal over different polarizations of the common cross-polarized antenna to emit a low-beam transmission signal and a high-beam transmission signal comprises:
transmitting a single-user multiple-input-multiple-output (SU-MIMO) signal over the common cross-polarized antenna.
13. The method of claim 10 , wherein transmitting the low-beam signal and the high-beam signal over different polarizations of the common cross-polarized antenna to emit a low-beam transmission signal and a high-beam transmission signal comprises:
transmitting a multi-user multiple-input-multiple-output (MU-MIMO) signal over the common cross-polarized antenna, the MU-MIMO signal transporting a first data packet to a first user equipment (UE) via the low-beam transmission signal and a second data packet to a second UE via the high-beam transmission signal, the first data packet and the second data packet being carried over a same time-frequency resources via the low-beam transmission signal and the high-beam transmission signal, respectively.
14. An access point (AP) in a wireless network, the AP comprising:
a common cross-polarized antenna; and
a radio transmitter coupled to the common cross-polarized antenna, wherein the radio transmitter is configured to apply different beamforming weight vectors to two signals to obtain a low-beam signal and a high-beam signal, and to concurrently transmit the low-beam signal and the high-beam signal over different polarizations of the common cross-polarized antenna to emit a low-beam transmission signal and a high-beam transmission signal, wherein the low-beam transmission signal has more antenna down-tilt, a wider beam-width, and a different polarization than the high-beam transmission signal, wherein a beam-width angle of the low-beam transmission signal is at least twice as wide as a beam-width angle of the high-beam transmission signal, the beam-width angle of the low-beam transmission signal being an angle between negative three decibel (−3 dB) points of main lobe of the low-beam transmission signal, and the beam-width angle of the high-beam transmission signal being an angle between −3 dB points of main lobe of the low-beam high-beam transmission signal.
15. The AP of claim 14 , wherein the radio transmitter is configured to apply different beamforming weight vectors to the two signals to obtain the low-beam signal and the high-beam signal by:
applying a first beamforming weight vector to a first component signal to obtain the low-beam signal, wherein the first beamforming weight vector provides upper side-lobe suppression for the low-beam signal by suppressing a secondary lobe of the low-beam signal having a same elevation angle as a primary-lobe of the high-beam signal; and
applying a second beamforming weight vector to a second component signal to obtain the high-beam signal, wherein the second beamforming weight vector provides lower side-lobe suppression for the high-beam signal by suppressing a secondary lobe of the high-beam signal having a same elevation angle as a primary-lobe of the low-beam signal.
16. The AP of claim 14 , wherein the low-beam transmission signal and the high-beam transmission signal are linearly polarized signals having different electromagnetic field (E-field) polarization angles with respect to y-axis, the y-axis corresponding to a vertically polarized wave.
17. The AP of claim 14 , wherein the low-beam transmission signal and the high-beam transmission signal have orthogonal E-field polarization angles.
18. The AP of claim 17 , wherein the high-beam transmission signal comprises a forty-five degree E-field angle with respect to y-axis, and the low-beam transmission signal comprises a negative forty-five degree E-field angle with respect to the y-axis, or
wherein the high-beam transmission signal comprises a negative forty-five degree E-field angle with respect to the y-axis, and the low-beam transmission signal comprises a forty-five degree E-field angle with respect to the y-axis.
19. The AP of claim 17 , wherein the high-beam transmission signal comprises a vertically polarized signal, and the low-beam transmission signal comprises a horizontally polarized signal, or
wherein the high-beam transmission signal comprises a horizontally polarized signal, and the low-beam transmission signal comprises a vertically polarized signal.
20. A computer program product comprising a non-transitory computer readable storage medium storing programming, the programming including instructions to:
generate two signals;
obtain a low-beam signal and a high-beam signal by applying different beamforming weight vectors to the two signals; and
concurrently transmit the low-beam signal and the high-beam signal over different polarizations of a common cross-polarized antenna to emit a low-beam transmission signal and a high-beam transmission signal, wherein the low-beam transmission signal has more antenna down-tilt, a wider beam-width, and a different polarization than the high-beam transmission signal, wherein a beam-width angle of the low-beam transmission signal is at least twice as wide as a beam-width angle of the high-beam transmission signal, the beam-width angle of the low-beam transmission signal being an angle between negative three decibel (−3 dB) points of the main lobe of the low-beam transmission signal, and the beam-width angle of the high-beam transmission signal being an angle between −3 dB points of the main lobe of the high-beam transmission signal.