Enabling Uplink MIMO Transmission for 5G NR Multi-Carrier Deployment

Uplink MIMO is a key component of 5G NR standards for improving the data rate. Meanwhile, TDD/FDD multi-carrier deployment is essential for 5G coverage enhancement and latency reduction. Either uplink MIMO or multi-carrier operation requires two concurrent radio frequency (RF) transmitters at UE. However, NR commercial UE is capable of at most two RF transmitters for frequency below 6 GHz. Therefore, dynamic switching of UE RF transmitter between two carriers has been recently introduced in 3GPP Rel-16 to enable uplink MIMO in multi-carrier deployments. Through dynamic transmitter switching and alternative transmission on two carriers, the advantage of more uplink slots in FDD carrier and larger channel bandwidth in TDD carrier can be fully utilized. Simulation results with link adaptation validates that, when 35 microseconds is assumed to perform the switching, dynamic transmitter switching brings 18.2% to 58.1% throughput gain over TDD single carrier transmission with uplink MIMO, and 26.9% to 59.8% throughput gain over FDD and TDD transmission without uplink MIMO.