Multicast unitary precoding method for improving fairness between data streams

The invention discloses a multicast unitary precoding method for improving fairness between data streams, which is characterized by that double-current multicast transmission is equivalent to single data stream multicast transmission of two parallel data streams by the aid of a successive interference cancellation receiving technology so as to obtain the quantitative relation between signal-to-noise ratios of the two data streams, and on the basis of a criterion for maximizing the minimum data stream signal-to-noise ratio, an iterative updating machine which supports multiple search paths is adopted to design a unitary matrix precoding matrix so as to improve the signal-to-noise fairness between two data streams and improve the multicast link transmission quality. Compared with existing multi-streaming multicast precoding technologies, the method can obtain the unitary matrix precoding matrix to support double-stream data transmission by a low computational overhead in a scene with large user number in a multicast group, can effectively guarantee the signal-to-noise equilibrium between data flows, and is applicable to a new generation of broadband wireless and mobile communication systems such as 802.11n, TD-HSPA+, TD-LTE, TD-LTE-Advanced and the like.