Multiple Input Multiple Output Measurements and Modeling in Manhattan

Narrowband MIMO measurements using 16 transmitters and 16 receivers at 2.11 GHz were carried out in Manhattan. Measured median capacities of the full 16´16 array were found to be 35 bps/Hz at 10 dB system SNR, which is within 80% of the Rayleigh iid channel capacity. Subarray capacities for a 2´2 and 4´4 systems were found to be 5.5 and 10 bps/Hz, respectively, which is within 90% of the corresponding median Rayleigh iid capacities. Correlation model parameters are derived from data and used to predict capacities, which are then compared to measured capacities. It was found that the spatial MIMO channel statistics are well represented by the separate transmitter and receiver correlation matrices, with a median relative error in capacity of 3%, in contrast to the 18% median relative error observed by assuming the antennas to be uncorrelated. A reduced parameter model, consisting of 4 parameters, has been developed to generate correlation matrices. When these correlation matrices are used to impose spatial correlation on the synthetic H matrices, the median relative error in capacity between measured and synthetic channels was found to be 3%. Furthermore, the set of 4 covariance parameters is, in turn, modeled as a correlated Gaussian random vector with 4 elements. Its statistics are completely described by a 4-element vector mean and a 4´4 covariance matrix. The resulting set of 20 parameters is used to generate different realizations of the covariance matrices. These covariance matrices are, in turn, used to generate correlated H matrices with capacities that are consistent with measurements collected in Manhattan. The spatial channel model reportedallows simulations of H matrices for arbitrary antenna configurations, consistent with the NYC measurements. These channel matrices may be used to test receiver algorithms in system performance studies. These results may also be used for antenna array design, as the decay of remote antenna correlation with antenna separation has been reported here. An important finding for the base transmitter array was that the antennas were largely uncorrelated even at antenna separation as small as two wavelengths.