Independent Code Division Multiple Access in DS-CDMA

An independent component analysis (ICA) based CDMA receiver is proposed, which in addition to the independence of users also exploits the independence of pseudo-codes in user signal separation. The proposed scheme is termed as independent code division multiple access in contrast to orthogonal code division multiple access being used in conventional CDMA receivers. Independence of pseudo-codes has been invoked by introducing the so-called independent Gram-Schmidt process in a deflation based ICA algorithm. The independence via Gram-Schmidt process is claimed by taking the inner product of successive vectors in a nonlinearly transformed Hilbert space, incorporating higher order statistics, instead of that in the original Euclidean space. The proposed receiver has been shown to outperform the existing CDMA receivers, in terms of bit error rate, through simulations. Moreover, the introduction of nonlinear transformation is shown to have no adverse effect on the convergence of the original deflation based ICA algorithm in terms of number of iterations apart from the computational cost of nonlinear transformation at each step. Gold codes are used for the demonstration of the proposed scheme although more work is needed to be done in order to identify the code family more amenable to the independence property.