A method includes: A transmit end obtains P QAM symbols; the transmit end performs IDWT or DWT on the P QAM symbols, to obtain a first signal matrix with N rows and M columns, and transposes the first signal matrix, to obtain a transposed first transpose matrix, where P, N, and M are all positive integers; and the transmit end outputs the transposed first transpose matrix. Correspondingly, a receive end obtains a second signal matrix with M rows and N columns; the receive end transposes the second signal matrix, to obtain a transposed second transpose matrix; and performs DWT or IDWT on the second transpose matrix, to obtain P QAM symbols.