| Summary: | 碩士 === 國立交通大學 === 電信工程系所 === 92 === Multiple-input-multiple-output (MIMO) systems have the potential to achieve very high capacities, depending on the propagation environment. The use of multiple antennas offers extended range and higher throughputs than conventional single antenna communication systems. Large capacity is obtained via the potential decorrelation in the MIMO radio propagation channel since a fully correlated MIMO radio channel only offers one subchannel, while a completely decorrelated MIMO radio channel potentially offers multiple subchannels. The decorrelation effect is dependent on propagation and array arrangement. In this paper, effects of transmitting antenna spacing, multipath angular spreading, signal bandwidth and Tx-Rx distance on the MIMO capacity are investigated through measuremts in indoor environments such as along corridors and classrooms. It is found that (1) When the standard deviation of Tx element spacing is ranging from 1λ to 1.5λ, unequally antenna array spacing may have larger capacity than that of the equal spacing; (2)The MIMO capacity increases as the array element spacing increases and it saturates when the spacing is larger than one wavelength. This reveals that the correlation distance between the elements in indoor environments is about one wavelength; (3) Capacity is increased when the propagation distance decreases, or when rms angle spread increases, or when number of received paths increases. (4) Higher signal bandwidth obtains higher capacity, since more multipath components are resolved, which leads to less spatial correlation.
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