Layer-1 Mobility in Distributed MIMO with Non-Coherent Joint Transmission

Abstract

The Distributed Multiple Input Multiple Output (D-MIMO) network comprises a very large number of distributed Radio Units (RUs), which simultaneously serve multiple User Equipments (UEs) over the same time/frequency resources based on directly measured channel characteristics. Existing research had shown that Coherent Joint Transmission (CJT) in D-MIMO networks could obtain better performance compared to the traditional small cell and cellular massive MIMO network through multiple RUs. Nonetheless, reliable access links become more important at high frequency bands and mobility scenarios that needs robust precoding schemes to utilize the full performance of a D-MIMO network. In this paper, Physical layer (L1) mobility is incorporated in D-MIMO network operating at mmWave. Then centralized and distributed precoding methods are considered to evaluate the spectral efficiencies of mobile UEs with different serving RU subset update periodicities. Moreover, Non-Coherent Joint Transmission (NCJT) among multiple RUs is explored. Through the simulation results, it is shown that serving RU subset (cluster) update and NCJT substantially impact the performance. During UE mobility, frequent serving subset update is necessary for CJT, however, not critical for NCJT.