In today's environment where intelligent devices are increasing day by day, the application of MIMO technology is quite critical. We can adopt different working modes according to different conditions and different wireless environments. The agreement defines the following seven MIMO working modes:
(1) Single-antenna working mode: It is also known as the SISO (Single-Input Single-Output) system, which uses a single antenna to transmit signals and a single antenna to receive signals.
(2) Open-loop transmit diversity: Using the mathematical method of complex conjugates, orthogonal spatial channels are formed on multiple antennas, and the same data stream is sent to improve transmission reliability.
(3) Open-loop spatial multiplexing: Artificially create "multipath effect" on different antennas, and one antenna transmits normally. Other antennas introduce a phase offset link. The transmission relationship of multiple antennas constitutes a complex matrix, and different data streams are transmitted in parallel. This complex matrix is randomly selected at the transmitting end, independent of the feedback result at the receiving end, which is open-loop spatial multiplexing.
(4) Closed-loop spatial multiplexing: When transmitting multiple data streams in parallel, the transmitter selects a complex matrix that creates "multipath effects" according to the feedback channel estimation results, which is closed-loop spatial multiplexing.
(5) MU-MIMO: Allows the transmitter to transmit data with multiple users at the same time.
(6) Closed-loop RANK=1 precoding: that is, space diversity technology. WLAN communication technology As a special case of closed-loop spatial multiplexing, only one data stream is transmitted, that is to say, the rank of the spatial channel is Rank=1. This working mode plays a role in improving transmission reliability, and is actually a way of transmitting diversity.
(7) Beamforming: Beamforming is also called a smart antenna. By phase-weighting the correlation of the output signals of multiple antennas, the signals form in-phase superposition in a certain direction and form phase cancellation in other directions, thereby achieving signal gain. .
この記事をシェア
