NG-RAN and 5G-NR

65G-NR Radio Interface – MIMO and Beamforming

6.1. Multiplexing techniques

6.1.1. MIMO mechanism

The MIMO mechanism improves radio data rate by performing spatial multiplexing of multiple signals. Each signal is transmitted on several antennas and received on multiple antennas, and all signals share the same time–frequency resource.

SU-MIMO (Single User – Multiple Input Multiple Output) refers to the transmission from a base station to one mobile, using the same frequency and time resource, on two antennas (2x2 MIMO) (Figure 6.1), on four antennas (4x4 MIMO) or on eight antennas (8x8 MIMO).

Figure 6.1. SU-MIMO mechanism

MU-MIMO (Multi User – MIMO) refers to the transmission from a radio node to different mobiles, using the same frequency and time resource, on two antennas (2x2 MIMO) (Figure 6.2), on four antennas (4x4 MIMO) or on eight antennas (8x8 MIMO).

Figure 6.2. MU-MIMO mechanism

The receivers receive the components y₁ and y₂ which are the product of the components x₁ and respectively x₂ (the signals transmitted) by the transmission matrix H. The signal x₁ (respectively x₂) is transmitted by the transmitter Tx1 (respectively Tx2). The signal y₁ (respectively y₂) is received by the receiver Rx1 (respectively Rx2). The transmission matrix H contains the transfer functions ...