In a Hybrid Fiber Coaxial (HFC) network using a Set Top Box (STB) or a cable modem, the cable STB or the cable modem includes respective High-Pass Filters (HPFs) having different passband frequencies to transmit an upstream signal from the cable STB or the cable modem to the HFC network through paths having different passband frequencies depending on states of the HFC network so that the upstream frequency band of 5 to 42 MHz is available.