In the case of small base station spacing in dense urban areas, which of the following statements about the principles for antenna selection are correct? (Multiple choice)
A . Selection of polarization mode: Due to the difficulty in selecting the site address of the urban base station and the limited installation space of the antenna, it is recommended to use a dual-polarized antenna.
B . Selection of antenna gain: In order to enhance coverage and maximize signal strength, a high gain antenna of 18dBi or more is required;
C . Selection of the direction map: In the urban area, it is mainly considered to improve the frequency reuse degree, so the directional antenna is generally selected.
D . Selection of half-power beamwidth: In order to better control the coverage of the cell to suppress interference, the urban antenna horizontal half-power beamwidth is selected from 60 to 65 degrees.
Answer: A B C D