Small cell beam-forming antennas
A small cell cellular base station includes an eight port radio and an eight-port base station antenna that has four linear arrays of dual-polarized radiating elements. Each of the linear arrays has a different azimuth boresight pointing direction and each dual-polarized radiating element includes first and second radiators that have respective directional radiation patterns. The radio is configured to determine and apply a first set of amplitude and phase weights to RF signals that are received through the eight ports of the antenna, and to apply a second set of amplitude and phase weights to RF signals that are output by the radio to the eight ports of the antenna.
1. A method of operating a base station antenna that includes at least a first linear array of dual-polarized radiating elements and a second linear array of dual-polarized radiating elements, each dual-polarized radiating element including a first polarization radiator that radiates at a first polarization and a second polarization radiator that radiates at a second polarization that is orthogonal to the first polarization, the first and second linear arrays having different azimuth boresight pointing directions, the method comprising:
transmitting a first data stream to a first user using a multi-input-multi-output (“MIMO”) transmission scheme using the first and second linear arrays; and
transmitting a second data stream to a second user while operating the base station antenna in a beam-forming mode using the first and second linear arrays.
2. The method of claim 1 , wherein the first user is closer to the base station antenna than the second user.
3. The method of claim 1 , the base station antenna further comprising a third linear array of dual-polarized radiating elements and a fourth linear array of dual-polarized radiating elements, wherein at least two of the first through fourth linear arrays point in opposite directions, wherein the azimuth pointing directions of each of the first through fourth linear arrays is offset from the azimuth pointing directions of each of the three other of the first through fourth linear arrays by about 90 degrees, 180 degrees and 270 degrees, respectively.
4. The method of claim 3 , wherein the first data stream is transmitted using a 4xMIMO transmission technique, where the first and second linear arrays are used together to transmit a first data stream at a first polarization and to transmit a second data stream at a second polarization, and the third and fourth four linear arrays are used together to transmit a third data stream at the first polarization and to transmit a fourth data stream at the second polarization.
5. The method of claim 3 , wherein the first through fourth linear arrays are used to transmit the second data stream in the beam-forming mode.
6. The method of claim 5 , wherein the base station antenna operates in a beam-forming mode and also simultaneously operates using a 2xMIMO transmission technique by transmitting the second data stream through the first through fourth linear arrays at a first polarization while simultaneously transmitting a third data stream through the first through fourth linear arrays to the second user at a second polarization.
7. The method of claim 1 , further comprising:
using a radio to sample a channel between the base station and a selected one of a plurality of users, and based on the channel sampling, determining whether data will be transmitted to the selected user using beam-forming alone or using beam-forming in conjunction with MIMO transmission techniques.
8. A method of operating a base station antenna that includes through fourth linear arrays of dual-polarized radiating elements, where the azimuth pointing directions of each of the first through fourth linear arrays is offset from the azimuth pointing directions of each of the three other of the first through fourth linear arrays by about 90°, 180° and 270°, respectively, each dual-polarized radiating element including a first polarization radiator that radiates at a first polarization and a second polarization radiator that radiates at a second polarization that is orthogonal to the first polarization, the method comprising:
using a radio to sample a channel between the base station and a selected one of a plurality of users and, based on the channel sampling, determining whether data will be transmitted to the selected user using the first and second linear arrays in a beam-forming mode or using the first and second linear arrays to transmit using a 4×MIMO transmission technique.