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MIMO (Multiple-Input Multiple-Output) transmission, a key technology for 5G, enables large-scale connections by spatially multiplexing signals at the same time and frequency, thereby contributing to higher capacity and speed in communications.
MIMO also enables precoding, eigenmode transmission, and signal detection.
In order to obtain these advantages, the channel must be accurately estimated from the received signal at the base station.
Once an accurate channel is obtained, it is possible to maximize network throughput by precoding the transmitted signal on the downlink or to completely separate the received signal on the uplink.
Generally, spatial multiplexed signals are separated by estimating the channel information from the pilot signal and applying spatial filtering based on the estimated channel information.
In principle, as the number of spatial multiplexes becomes large, the pilot length should be increased for the channel estimation.
However, while the accuracy of channel estimation improves when long pilot sequences are added, the overhead also increases, which is undesirable from the viewpoint of transmission efficiency.
Therefore, in large-scale MIMO, a system that can estimate the channel from relatively short pilot sequences with unknown channel matrices is currently required. |
IEEE/ICACT20230070 Slide.03
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