Wireless communication systems can be classified according to the form of transmitted signals, the status of wireless terminals, the wavelength of electromagnetic waves, the transmission mode, and the communication distance. Today, let's first understand the first three types.

1. According to the classification of transmission signal form, based on the different forms of transmission signals, wireless communication systems can be divided into analog wireless communication systems and digital wireless communication systems.

（1）Analog wireless communication system: An analog wireless communication system directly transmits the collected signals, and the transmitted signals are analog signals.

（2）Digital wireless communication system: A digital wireless communication system converts the collected signals into digital signals before transmission. The transmitted signals only consist of the digits 0 and 1. Digital wireless communication systems are gradually replacing analog wireless communication systems.

2. According to the classification of wireless terminal status, based on the differences in wireless terminal status, wireless communication systems can be divided into fixed wireless communication systems and mobile wireless communication systems.

（1）Fixed wireless communication system: The terminal equipment of a fixed wireless communication system is fixed, such as a fixed telephone communication system.

（2）Mobile wireless communication system: The terminal devices of a mobile wireless communication system are mobile, such as the mobile phone communication system.

3. According to the classification by electromagnetic wave wavelength, based on the different wavelengths of electromagnetic waves, wireless communication systems can be divided into long-wave wireless communication systems, medium-wave wireless communication systems, short-wave wireless communication systems, ultra-short-wave wireless communication systems, microwave wireless communication systems, etc.

（1）Long-wave radio communication system: The long-wave radio communication system refers to the radio communication that utilizes electromagnetic waves with wavelengths greater than 1000m and frequencies lower than 300kHz. It is also known as low-frequency communication. It can be further divided into communication in the long wave (wavelength ranging from 1 to 10km, frequency ranging from 30 to 300kHz), very long wave (wavelength ranging from 10 to 100km, frequency ranging from 3 to 30kHz), extra-long wave (wavelength ranging from 100 to 1000km, frequency ranging from 300 to 3000Hz), super-long wave (wavelength ranging from 1000 to 10000km, frequency ranging from 3 to 30Hz), and extremely long wave (wavelength ranging from 10000 to 100000km, frequency ranging from 3 to 30Hz) bands.      

（2）Medium-wave radio communication system: The medium-wave radio communication system refers to the radio communication conducted using electromagnetic waves with wavelengths ranging from 100 to 1000 meters and frequencies ranging from 300 to 3000 kHz.

（3）Shortwave Radio Communication System: A shortwave radio communication system refers to the radio communication conducted using electromagnetic waves with wavelengths ranging from 10 to 100 meters and frequencies ranging from 3 to 30 MHz.

（4）Ultra-short wave wireless communication system: An ultra-short wave wireless communication system refers to the radio communication conducted using electromagnetic waves with wavelengths ranging from 1 to 10 meters and frequencies ranging from 30 to 300 MHz.

（5）Microwave wireless communication system: A microwave wireless communication system refers to radio communication conducted using electromagnetic waves with wavelengths less than 1m and frequencies higher than 300MHz. It can be further classified into the following bands: decimeter waves (wavelengths ranging from 100 to 1000mm, frequencies ranging from 300 to 3000MHz), centimeter waves (wavelengths ranging from 10 to 100mm, frequencies ranging from 3 to 30GHz), millimeter waves (wavelengths ranging from 1 to 10mm, frequencies ranging from 30 to 300GHz), and sub-millimeter waves (wavelengths ranging from 0.1 to 1mm, frequencies ranging from 300 to 3000GHz).