Constant modulus algorithm - performance poor? The question is based on a research article titled, "Novel Robust Blind Equalizer for QAM Signals
Using Iterative Weighted-Least-Mean-Square
Algorithm"

The Authors have proposed an equalization scheme for channel equalization for QAM symbols. The Authors in the last page, Table I present their results. The first column result is for Constant Modulus lagorithm given below: 

5 (dB) 6.36 ; 10 (dB) 9.90 ;15 (dB) 15.12; 25 (dB) 18.0

with the plot 

The Authors say that the values are in dB, but I don't undertstand why the SIR curve is increasing. In general, lesser the value of SIR, better is the perofrmance. But the curve shows the opposite. So, does CMA not work for QAM? 

Moreover, their proposed method the values for which are also higher for high SNR. So, when the noise level is low both CMA and their method is perfroming badly?
The constant modulus algorithm does not work for QAM because QAM is not a constant modulus signal (amplitude at the symbol decisions is not constant), such as BPSK and QPSK. 

SIR is the "Signal to Interference Ratio" and the greater the SIR the better the performance, not the other way around as you describe. With a higher SIR, the signal is stronger relative to the interference.