Comment

1Comments on “Performance Analysis of a 8 to 1000. Elements of the data matrix S were generatedNusing the QPSK constellation and F is chosen as I . OneMDeterministic Channel Estimator for Blockhundred independent realizations of channel coefficients andTransmission Systems With Null Guard10 independent realizations of data blocksS are used (totallyNIntervals”1000 different pairs ofS andh). Traces ofC andC inN hh CR(2) are computed for these 1000 realizations and the averagesBorching Su, Student Member, IEEE,are reported in Table I.and P. P. Vaidyanathan, Fellow, IEEEtr(C )¡tr(C )2 2 CRhhN tr(C )= tr(C )= CRhh v v tr(C )CRAbstract— In the above mentioned paper a Cramer Rao bound 8 ¡ 1:7752 ¡was derived for the performance of a blind channel estimation 12 184:01 1:3373 136:6002algorithm. In this paper an error in the bound is pointed out 14 6:8590 1:0981 5:2462and corrected. It is observed here that the performance of the 16 3:5362 0:9760 2:62331said algorithm does not achieve the Cramer Rao bound. 20 1:7197 0:7414 1:3196100 0:1614 0:1448 0:1147¡2 ¡2In the above paper [1], important work has been done to 1000 1:5149£10 1:4986£10 0.0109analyze the algorithm in [2] which solves a blind channelestimation problem. The performance of the algorithm in [2] TABLE Iin high SNR region was shown to be as in (33) of [1]. COMPARISON OF EQ. (33) IN [1] AND EQ. (2); THE DATA LENGTH PERThe Cramer Rao bound (CRB) of the above mentioned blind BLOCK ISM =12estimation ...