What are the parameters that need to be considered in specific use?

The antenna is also an important part of the wireless system. What are the parameters that need to be considered in specific use?  

The antenna is a passive device and will not increase the power of the output signal. It just changes the signal distribution in space to increase the signal strength in a certain direction. In use, you need to focus on several parameters such as its operating frequency, antenna gain, polarization direction, and beam width.