Vectorial channel estimation for uplink MC-CDMA in beyond 3G wireless systems

In beyond 3G wireless systems the bandwidth efficiency can be increased with the use of adaptive antenna arrays. This paper focus on a key issue for adaptive antenna arrays, that is, channel parameters estimation including direction-of-arrival (DOA). In order to estimate DOA, the channel frequency responses for the links between the mobile users and each of base station array elements are estimated by pilot-aided minimum mean square error (MMSK) algorithm. This estimator is not sensitive to the channel statistics. Based on frequency response estimatives DOA´s of impinging multipath components to the base station are estimated by a low complex maximum likelihood (ML) approach. Furthermore an uplink burst structure with specifically designed midamble field for multiuser channel estimation in MC-CDMA is proposed. The performance is assessed in terms of channel estimation errors for a MC-CDMA TDD system over fast and slow fading mobile channels.