Achieved Data Rate of Cooperative MIMO in Measured Channels

Abstract

This paper evaluates the achieved data rate of a cooperative Multiple Input Multiple Output (MIMO) system in real measured channels. The achieved data is computed according to an iterative algorithm, which determines the linear transmit and receive beamforming filters that maximize the sum-rate. This method allows us to design the transmit filter with a simple algorithm. The Channel State Information (CSI) of all channels is assumed to be known at the transmitters, and cooperation between (BSs) in sharing the CSI is considered. MIMO channels in different scenarios were measured in a typical propagation environment using two BSs and four handsets, similar to smartphones, held by different users. Users were located at different distances from each other, and at different orientations with respect to each other. We computed the received data rate for four different groups of handsets at a fixed SNR of 15 dB. Using the algorithm, we investigated how the experimental and theoretical capacity is influenced by cross-correlation between the individual user linkages arising from one antenna at the BS, and by imbalance in the power of the different linkages. The system performs best when the handsets are separated by at least 1 m. Furthermore, both in theory and in practice, the algorithm is more sensitive to power imbalance rather than cross-correlation.