Adaptive Antenna Arrays for Spatial Multicarrier Access

In this paper, we present and analyze an adaptive antenna array system used for spatial multiple access of single antenna users into a multiple antenna base-station. The system utilizes a multicarrier transmission method called multicarrier orthogonal code division multiplexing (MC-OCDM), which is a generalized form of orthogonal frequency division multiplexing (OFDM). The MC-OCDM multiplexes pilot and data symbols by using orthogonal Hadamard sequences. At the receiving base station, a spatial combiner (beamformer) optimally combines the MC-OCDM decoded data from each antenna and maximizes the signal-to-interference ratio of each user. A space-time decoder is then used for recovering the data symbols of each accessing user by means of maximum signal-to-noise ratio array processing. The system evaluation is based on finding the ergodic capacity region of the multiple access channel which has been shown to increase with increasing number of multipaths until this number exceeds the number of the antennas in the base station array