Multi-carrier CDMA system for cellular mobile communication with two-way path-adapted array antennas — A path modeled design

As an extension of the paper [1], we propose in this paper a multi-carrier CDMA modulation system for cellular mobile communication with two-way transmitter-receiver broadband far-field antenna array adaptation to the propagation path characteristics. We assume the frequency band is shared between the two directions and the same array antenna is used at each station for transmission and reception. Also assumed is error-free measurement of the transmittance from each of the transmitters to the array elements of the receivers. In the uplink, power control is employed at the side of the mobile transmitters based on the downlink reception. Based on the path model of propagation in the analysis, it is shown that the array-carrier MLE (Maximum Likelihood Estimate) reception of the code-division multiplexed symbols realizes array-enhanced bandwidth-limited Rake reception. It was confirmed by simulation, assuming independently Rayleigh-distributed path model, that the system, both in downlink and in uplink, gives much better BER versus SNR per bit performance than that of the carrier-only MLE reception employing transmitter-directed antennas. Because of the optimality of the reception, the transmitter array adaptation has nothing to do but optimally to deliver transmitted power to the paths so as the total expected arriving power at the receiver be maximum. Owing to the reciprocity of propagation by using the same antenna array for reception and transmission, the transmitter array adaptation can make use of the measurement, at the receiver, of the transmittance with omni-directional transmission to derive the optimum transmitter array weighting. The algorithm achieves two way uplink downlink optimization without interchanging any measured information.