Microwave Mobile Communications
Microwave Mobile Communications
On Limits of Wireless Communications in a Fading Environment when UsingMultiple Antennas
Wireless Personal Communications: An International Journal
Keyholes, correlations, and capacities of multielement transmit and receive antennas
IEEE Transactions on Wireless Communications
MIMO channel capacity and modeling issues on a measured indoor radio channel at 5.8 GHz
IEEE Transactions on Wireless Communications
IEEE Transactions on Information Theory
Optimal transmitter eigen-beamforming and space-time block coding based on channel correlations
IEEE Transactions on Information Theory
MIMO channel modeling and the principle of maximum entropy
IEEE Transactions on Information Theory
A simple transmit diversity technique for wireless communications
IEEE Journal on Selected Areas in Communications
Capacity limits of MIMO channels
IEEE Journal on Selected Areas in Communications
Comparison of MIMO antenna configurations in picocell and microcell environments
IEEE Journal on Selected Areas in Communications
Polarized MIMO channels in 3-D: models, measurements and mutual information
IEEE Journal on Selected Areas in Communications
Empirical comparison of MIMO and beamforming schemes for outdoor-indoor scenarios
IEEE Transactions on Wireless Communications
Hi-index | 0.01 |
MIMO systems are usually associated with high scattering isotropic propagation while the use of directive antennas is associated with free space conditions. We found outdoor-indoor channels to be in between these two extremes, in the sense that we observed directivity - and - MIMO gain, for the same ensemble of channels. Our observation is based on measurements with directive (8 dB) and dipole antennas. Median MIMO capacities were found to be about 80% of the ideal (Rayleigh i.i.d.), at 5 dB Signal to Noise Ratio (SNR), for both types of antennas. Using properly aimed directive antennas, the SNR was found on average to be 5.4 dB above that obtainable with dipoles, somewhat less than the 7 dB antenna gain difference. Thus, isotropic propagation, which would have negated directivity gains, cannot be justified in general. We empirically established that aiming for largest received power is the best array pointing strategy with directive antennas. Combining MIMO processing and angular search resulted on average in gains of 70% over the median capacities obtained with dipoles. Therefore it may in some cases be convenient to arrange subgroups of antennas for beamforming, and then process the thus reduced number of radio channels for MIMO gain.