An information transmission manner has evolved from optical fiber transmission to microwave transmission. However, because spectrum resources of a commonly-used frequency band in a microwave transmission manner are limited, multi-input multi-output (MIMO for short) has become a future development trend of microwave technologies.
Distributed MIMO is main architecture in microwave MIMO, and is highly compatible and easy to be installed. Due to independence of an ODU (Out Door Unit, digital microwave transceiver), sources of carriers at a sending end and carriers at a receiving end are different, which brings a serious synchronization problem to a system.
In an existing wireless communication system, because a carrier frequency is low, a carrier frequency offset is not serious and does not have a great effect on the system. Therefore, a method of performing channel estimation or frequency offset estimation separately is usually adopted. However, in a microwave communication system with a high carrier frequency, the method in wireless communication is not applicable. At present, no method is put forward to satisfactorily solve a carrier frequency offset of a channel in the microwave communication system.