1. A method for identifying a plurality of symbols transmitted by a transmitter of a wireless communication system according to a plurality of signals received by a receiver of the wireless communication system, the method being implemented in the receiver and for searching a solution point of maximum-likelihood (ML) detection according to the plurality of signals and thereby identifying the plurality of symbols, the method comprising: utilizing a zero-forcing detection to process the plurality of signals and thereby provide a central point; slicing the central point to provide a solution point for the zero-forcing detection; calculating a radius C ZF for the ML detection, the radius C ZF being the distance between the central point and the solution point for the zero-forcing detection, which consequently results in the radius C ZF longer than or equal to a distance C ML from the central point to a solution point of the ML detection; determining a searching range of the ML detection according to the central point and the radius C ZF ; determining one or more qualified solution points according to the plurality of signals and the searching range; and determining one of the one or more qualified solution points as the solution point of the ML detection.