Blind joint estimation of channel order and the number of active users in direct sequence code-division multiple-access multi-path channels

A new, reliable and computationally efficient blind method is proposed for joint estimation of channel order and number of active users in a direct sequence code-division multiple-access system with multi-path fading channel. The proposed method (i) exploits a parametric model used for equalisation of multi-path channels in finite impulse response multi-input multi-output systems, (ii) first, estimates rank of correlation matrix of observation, by combining the subspace method and information-theoretic criteria, (iii) then, estimates simultaneously channel order and number of active users, by using the estimated rank and the model parameter, without any prior information, (iv) uses only a single antenna, in contrast to the previous methods, while having the ability to jointly estimate higher numbers of active users and channel order in lower signal-to-noise ratios. Numerical results show that the proposed method can estimate higher number of users and also has higher detection probability when using minimum mean square error algorithm.