What is SU-MIMO?
SU-MIMO (Single-User MIMO) is an application of MIMO technology where the base station communicates with a single UE using multiple spatial streams simultaneously. By exploiting multiple independent propagation paths between the transmit and receive antenna arrays, SU-MIMO multiplies the achievable data rate for that user — up to the minimum of the number of transmit and receive antenna layers. SU-MIMO is the primary technique for maximizing peak throughput to individual users in both LTE and 5G NR.
How Does SU-MIMO Work?
In SU-MIMO, the gNB transmitter maps different data streams onto separate spatial layers and precodes them for transmission across the antenna array. The UE receiver uses advanced algorithms (MMSE, SIC) to separate and decode the spatial streams. The number of usable layers depends on the channel rank — the number of independent spatial paths between gNB and UE, which in turn depends on antenna count, antenna spacing, and the scattering environment. In 5G NR, SU-MIMO supports up to 8 layers in the downlink (requiring 8 Rx antennas at the UE) and up to 4 layers in the uplink. The UE reports channel rank and preferred precoding via RI (Rank Indicator) and PMI (Precoding Matrix Indicator) feedback.
Use Cases
Peak data rate delivery to individual 5G NR users, high-throughput FWA connections, enterprise dedicated capacity, eMBB services in low-density environments, and mmWave backhaul using high-rank MIMO.
3GPP / Standards Reference
3GPP TS 38.211 (NR MIMO layer mapping), 3GPP TS 38.214 (NR MIMO feedback and scheduling), 3GPP TS 38.306 (NR UE radio capabilities — max layers)
Related Terms
MU-MIMO | MIMO | Massive MIMO | Beamforming | gNB
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