Let X and Y are random variables. According to Appendix B, Eq. (21), Proposition 4 and Proposition 5, we can obtain the mean From Eq. (19), we have: E[ null In Section 2, we propose CWDA. Next, we analyze the gap between CWDA and CWDA-Relaxation, i.e., the difference between In Section 6, we make further discussion and analysis on the conditions for CWDA to be satisfied. Theorem 2. Let X N (0,c First, we show the following two theorems: Theorem 4. Because the approximation is widely used in the proof of Theorem 1, it is necessary to verify it numerically. Since Eq. (55), we find that Note that, the approximation is widely used in the proof of Eq.(57) and Eq.(58).