A communication method, comprising: sending, by a cable modem terminal system, CMTS, a reference signal within a first time period by using a valid subcarrier in a first spectrum, wherein the first time period is a time period within which none of cable modems, CMs, connected to the CMTS sends a signal in the first spectrum, wherein the valid subcarrier is a subcarrier that is in a channel and that can be used to carry a signal; performing, by the CMTS based on an interfering signal received by the CMTS within the first time period, channel interference estimation on a channel that is used during signal reception of the CMTS and that occupies the first spectrum, wherein the interfering signal is a signal obtained after the reference signal sent by the CMTS passes through the channel; canceling, by the CMTS based on a result of the channel interference estimation, interference from a first signal of the CMTS to a second signal received by the CMTS, wherein the first signal is a signal sent by the CMTS by using a subcarrier in the first spectrum, and the second signal is a signal sent by a first CM in all the CMs by using a subcarrier in the first spectrum; performing, by the CMTS, time domain interleaving with a depth of M on N continuous unused subcarrier block symbols, wherein each of the N continuous unused subcarrier block symbols comprises a next codeword pointer, NCP, and a forward error correction, FEC, codeword, M and N are integers greater than o, and N > M - 1, an unused subcarrier block is set to from an orthogonal frequency division multiplexing, OFDM, symbol that does not carry service information before interleaving; and generating, by the CMTS, the reference signal, wherein a reference sequence corresponding to the reference signal is carried in N+1-M interleaved symbols. sending, by a cable modem terminal system, CMTS, a reference signal within a first time period by using a valid subcarrier in a first spectrum, wherein the first time period is a time period within which none of cable modems, CMs, connected to the CMTS sends a signal in the first spectrum, wherein the valid subcarrier is a subcarrier that is in a channel and that can be used to carry a signal; performing, by the CMTS based on an interfering signal received by the CMTS within the first time period, channel interference estimation on a channel that is used during signal reception of the CMTS and that occupies the first spectrum, wherein the interfering signal is a signal obtained after the reference signal sent by the CMTS passes through the channel; canceling, by the CMTS based on a result of the channel interference estimation, interference from a first signal of the CMTS to a second signal received by the CMTS, wherein the first signal is a signal sent by the CMTS by using a subcarrier in the first spectrum, and the second signal is a signal sent by a first CM in all the CMs by using a subcarrier in the first spectrum; performing, by the CMTS, time domain interleaving with a depth of M on N continuous unused subcarrier block symbols, wherein each of the N continuous unused subcarrier block symbols comprises a next codeword pointer, NCP, and a forward error correction, FEC, codeword, M and N are integers greater than o, and N > M - 1, an unused subcarrier block is set to from an orthogonal frequency division multiplexing, OFDM, symbol that does not carry service information before interleaving; and generating, by the CMTS, the reference signal, wherein a reference sequence corresponding to the reference signal is carried in N+1-M interleaved symbols.