A communication signal receiver includes an adder, a slicer, and an infinite impulse response (IIR) filter. The adder performs an addition on a first signal and a filtered signal to generate an output signal. The slicer performs a hard decision on the output signal to generate a detecting result. The IIR filter is coupled to the slicer and the adder for processing the output signal to generate the filtered signal. The communication signal receiver further includes a decoder. The decoder receives and decodes the output signal to generate a decoded output signal, wherein the decoder is a Viterbi decoder.