The effects of the channel order and tails on the performance of subspace-based blind signature waveform estimation method in asynchronous DS-CDMA systems are analyzed in theory

and the simulations are carried out.First

we present a signature waveform decomposition model

which means partitioning the signature waveform into the mth-order significant part and the tails

and the corresponding mth-order subspace method is obtained.Secondly

by using matrix perturbation theory

we prove the decomposition validation

which shows that the signature waveform estimation of the mth-order subspace method is close to the mth-order significant part.Finally

from the stable degree of matrix eigenvalue decomposition

the decomposition criterion is derived

which points out that we should avoid modeling the tails and adopt the channel order as small as possible.The simulation results support our theoretical analysis.