Generally, in typical wireless communication systems, interleavers are deployed after channel coding to distribute burst of errors, so they appear as simple errors. Alternatively, in this paper, a novel seed based random (SBR) post modulation interleaver is reported. SBR interleaver is an attempt to form a unique scrambling matrix in order to interleave the data bits/symbols optimally. Morcover, our study reveals that interleaver can change its position and be introduced even after modulation without affecting the performance of the system. With post modulation interleaving, interleaver size is minimized that implies minimum design complexity. The proposed interleaver is analyzed in terms of the performance parameters called spread and dispersion in burst error environment. For burst error analysis, proposed interleaver is compared with random interleaver to show that, for single error correcting codes, it can deal with much longer burst of errors. To analyze the suitability of proposed post modulation interleaver, the comparison of prc- and post modulation interleaver is carried out.