| Input: . |
| Output: . |
| 1: Zero padding and the length of is changed from to . |
| 2: Let . |
| 3: For ; ++ do |
| 4:Tear apart the spectrum randomly by and , where and |
| denote the expressions of and in frequency-domain, respectively, and . |
| 5:Apply a flat window function to expand the spectrum range. |
| (1) Let be the window function in frequency-domain, |
| where and denote the cutoff frequencies of the passband and stopband, respectively, |
| and denotes the ripple amplitude, whose reference value is , where is a positive integer. |
| (2) Compute , where denotes the expression of in time-domain. |
| The length of is . |
| 6:Subsample in frequency-domain. Letting be the data length after subsampling, |
| we have with . |
| 7:Map with a hash function. |
| (1) Define a hash function . |
| (2) Define an offset function . |
| (3) Let denote the support set of the largest coefficients in . The preimage set of is , |
| whose size is , where and . |
| (4) Obtain the largest spectrum coefficients as |
|
| (5) Record the nonzero position of . |
| 8: End for |
| 9: Letting be the occurrence times of coordinate in the sets and only retaining the coordinate whose occurrence |
| times are larger than , we have , and the rest terms are zeroes. |
| 10: For each coordinate in , we obtain the corresponding spectrum coefficients with and . |
| 11: Return , where denotes computing the median of a sequence. |
