A communications apparatus, comprising: a first radio module, providing a first wireless communications service and communicating with a first communications device in compliance with a first protocol; a second radio module, providing a second wireless communications service and communicating with a second communications device in compliance with a second protocol; and a transmission noise suppression device (370; 500; 800), coupled to at least one of the first radio module and second radio module and operative to process a plurality of downlink signals received by the first radio module to cancel transmission noise comprised in the plurality of downlink signals, wherein the transmission noise is generated when the second radio module is processing a plurality of uplink signals to be transmitted, the communications apparatus being characterized by: the downlink signals comprise a plurality of first downlink signals and a plurality of second downlink signals, and the transmission noise suppression device (370; 500; 800) comprises: a filter (410; 510; 810), coupled to a first path for receiving the first downlink signals, filtering the first downlink signals according to a plurality of filter parameters to obtain a plurality of filtered signals; a parameter estimator (420; 520; 820), coupled to the filter (410; 510; 810), receiving the first downlink signals from the first path and the second downlink signals from a second path, and estimating the filter parameters according to the first downlink signals and the second downlink signals; and a subtractor (430; 530; 830), coupled to the filter (410; 510; 810) and subtracting the second downlink signals from the filtered signals to obtain a plurality of processed signals, wherein the transmission noise does not manifest in the processed signals. a first radio module, providing a first wireless communications service and communicating with a first communications device in compliance with a first protocol; a second radio module, providing a second wireless communications service and communicating with a second communications device in compliance with a second protocol; and a transmission noise suppression device (370; 500; 800), coupled to at least one of the first radio module and second radio module and operative to process a plurality of downlink signals received by the first radio module to cancel transmission noise comprised in the plurality of downlink signals, wherein the transmission noise is generated when the second radio module is processing a plurality of uplink signals to be transmitted, the communications apparatus being characterized by: the downlink signals comprise a plurality of first downlink signals and a plurality of second downlink signals, and the transmission noise suppression device (370; 500; 800) comprises: a filter (410; 510; 810), coupled to a first path for receiving the first downlink signals, filtering the first downlink signals according to a plurality of filter parameters to obtain a plurality of filtered signals; a parameter estimator (420; 520; 820), coupled to the filter (410; 510; 810), receiving the first downlink signals from the first path and the second downlink signals from a second path, and estimating the filter parameters according to the first downlink signals and the second downlink signals; and a subtractor (430; 530; 830), coupled to the filter (410; 510; 810) and subtracting the second downlink signals from the filtered signals to obtain a plurality of processed signals, wherein the transmission noise does not manifest in the processed signals. the downlink signals comprise a plurality of first downlink signals and a plurality of second downlink signals, and the transmission noise suppression device (370; 500; 800) comprises: a filter (410; 510; 810), coupled to a first path for receiving the first downlink signals, filtering the first downlink signals according to a plurality of filter parameters to obtain a plurality of filtered signals; a parameter estimator (420; 520; 820), coupled to the filter (410; 510; 810), receiving the first downlink signals from the first path and the second downlink signals from a second path, and estimating the filter parameters according to the first downlink signals and the second downlink signals; and a subtractor (430; 530; 830), coupled to the filter (410; 510; 810) and subtracting the second downlink signals from the filtered signals to obtain a plurality of processed signals, wherein the transmission noise does not manifest in the processed signals.