is the conclusion in [36] true. If Sb1b2(w)<0, then it is easy to get the critical point at SRR(w)=−Sb1b2(w) from (13). In this case, MSCx1x2 monotonically decreases to zero as SRR(w) varies in [0,−Sb1b2(w)) and monotonically increases to one as SRR(w) varies in [−Sb1b2(w),+∞). Fig. 1(E) shows that the reference signal may actually decrease or increase MSC. The following should be pointed out: 1) Reference signal power may have a significant impact on MSC (for example, see the curve corresponding to Sb1b2=−1 in Fig. 1(E). In this case, from the curve when reference signal power = 0.5 = 0.5× the power of nonreferential signal b1 or b2, the MSCx1x2 value is sharply changed from 1 to a value below 0.1), and 2) even if reference signal power is greater than the power of nonreferential signals b1 and b2, the effect at a given frequency may not be considerable (for example, see the curve corresponding to Sb1b2=−0.7 in Fig. 1(E). In this case, from the curve when reference signal power = 5 = 5× the power of nonreferential signal b1 or b2, the MSCx1x2 value is not much different from MSCb1b2=Sb1b22=(−0.7)2=0.49).
