DOA Estimation for MC-CDMA Uplink Transmissions
We consider the uplink of an MC-CDMA network and assume that the base station is endowed with a uniform linear array. Transmission takes place over a multipath channel and the goal is the estimation of the directions of arrival (DOAs) of the signal from the active users. In a multi-user scenario difficulties are due primarily to the large number of parameters involved in the estimation of the DOAs which makes this problem much more challenging than in single-user transmissions. The solution we propose allows estimating the DOAs of different users independently, thereby leading to significant reduction in the system complexity. In the presence of multipath propagation, however, estimating the DOAs of a given user through maximum likelihood methods remains a formidable task since it involves a search over a multidimensional domain. Therefore, we look for simpler solutions and discuss two alternative schemes based on the SAGE and ESPRIT algorithms.
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