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Over-The-Air Apparatus for Large-Scale MIMO Antennas to Create the Full-Rank Channel Matrix
... The author proposed an OTA evaluation method for a massive MIMO antenna that creates a full-rank channel matrix [17]. The results of the Monte Carlo simulation, which included simulation of the proposed OTA testing method, revealed that even though the channel model comprised a limited number of scatterers, a full-rank channel matrix can be created. ...
... The author proposed an OTA testing method in which the scatterers are virtually formed emulating a large number of scatterers [17]. Figure 1 shows the configuration of the proposed fading emulator to enable a full-rank channel matrix for a massive MIMO antenna. ...
... Hence, full-rank status can be achieved by rotating the actual scatterers multiple times, even with a small number of scatterers on the OTA apparatus. Figure 4 shows the average of the 64th eigenvalues through all snapshots as a function of the angular interval between the i-th and (i + 1)-th sets of scatterers with S as a parameter [17]. The green, red, and blue curves indicate the cases where S is 3, 5, and 7, respectively. ...
This paper presents an over-the-air testing method in which a full-rank channel matrix is created for a massive multiple-input multiple-output (MIMO) antenna system utilizing a fading emulator with a small number of scatterers. In the proposed method, in order to mimic a fading emulator with a large number of scatterers, the scatterers are virtually positioned by rotating the massive MIMO antenna. The performance of a 64-element quasi-half-wavelength dipole circular array antenna was evaluated using a two-dimensional fading emulator. The experimental results reveal that a large number of available eigenvalues are obtained from the channel response matrix, confirming that the proposed method, which utilizes a full-rank channel matrix, can be used to assess a massive MIMO antenna system.
... Another is that a large number of scatterers are necessary to create the full-rank channel matrix. Therefore, not only the scope of applications of the proposed method for uplink channels, but also OTA testing methods for downlink channels [41] need to be examined, which will be investigated in future work. ...
This paper presents a method of implementing a 4 × 4 correlation matrix for evaluating the uplink channel properties of multiple-input multiple-output (MIMO) antennas using an over-the-air measurement system. First, the implementation model used to determine the correlation coefficients between the signals received at the base station (BS) antennas via the uplink channel is described. Then, a methodology is introduced to achieve a 4 × 4 correlation matrix for a BS MIMO antenna based on Jakes’ model by setting the initial phases of the secondary wave sources in the two-dimensional channel model. The performance of the uplink channel for a four-element MIMO terminal array antenna is evaluated using a two-dimensional bidirectional fading emulator. The results show that the measured correlation coefficients between the signals received via the uplink channel at the BS antennas using the proposed method are in good agreement with the BS correlation characteristics calculated using Monte Carlo simulation and the theoretical formula, thereby confirming the effectiveness of the proposed method.
A full-polarized multiple input multiple output (MIMO) system, which has transmitting and receiving antennas both composed of co-located tri-polarized electric and magnetic dipoles, possesses a huge and complex correlation matrix. In such a correlation matrix, increasing of some correlation coefficients results in improvement of channel capacity, while increasing of other ones result in more decrement. Therefore, a specific combination of correlation coefficient values may effectively improve the capacity of the entire MIMO channel, yet how to acquire this combination is a problem that needs to be solved. As angle spread of incident wave can affect correlation coefficients to some extent with some regularities, its influence on system performance is studied based on a capacity behavior factor that comprehensively considers all of the correlation coefficients. Variations of important correlation coefficients are analyzed based on some MIMO channel models, and the angle spread of scatterers that can help full-polarized MIMO system to gain higher channel capacity is obtained.KeywordsFull-polarizedMIMOCorrelation coefficientChannel capacity
This paper presents a multiple-input, multiple-output (MIMO) antenna system with the ability to perform full-azimuth beam steering, and with the aim of realizing greater than 20 Gbps vehicular communications. The MIMO antenna described in this paper comprises 64 elements arranged in a daisy chain array structure, where 32 subarrays are formed by pairing elements in each subarray; the antenna yields 32 independent subchannels for MIMO transmission, and covers all communication targets regardless of their position relative to the array. Analytical results reveal that the proposed antenna system can provide a channel capacity of more than 200 bits/s/Hz at a signal-to-noise power ratio (SNR) of 30 dB over the whole azimuth, which is equivalent to 20 Gbps for a bandwidth of 100 MHz. This remarkably high channel capacity is shown to be due to two significant factors; the improved directivity created by the optimum in-phase excitation and the low correlation between the subarrays due to the orthogonal alignment of the array with respect to the incident waves. Over-the-air (OTA) experiments confirm the increase in channel capacity; the proposed antenna can maintain a constant transmission rate over all azimuth angles.