In some critical application in WSN there is huge demand for authentication. Irreversible modification where made in watermarked data according to previous watermarking based approach. So by using new technique on the basis of prediction error expansion and DCT we are going to achieve the integrity of data in WSN. The authentication scheme based on this technique allows reversible modification in which sensor nodes placed at different location gather the stream data and non-overlapping authentication group composed of two adjacent data group. The first data group is going to compute watermark bits and these beats are embedded into consecutive group before transmission .Verification and complete restoration is done by the sink. According to this paper live copy of data element is buffered rather than entire data group which highly reduce the delay.