Analog MIMO Radio-Over-Copper Downlink With Space-Frequency to Space-Frequency Multiplexing for Multi-User 5G Indoor Deployments

Analog MIMO Radio-Over-Copper Downlink With Space-Frequency to Space-Frequency Multiplexing for Multi-User 5G Indoor Deployments

Analog MIMO Radio-Over-Copper Downlink With Space-Frequency to Space-Frequency Multiplexing for Multi-User 5G Indoor Deployments
Analog MIMO Radio-Over-Copper Downlink With Space-Frequency to Space-Frequency Multiplexing for Multi-User 5G Indoor Deployments

Abstract:

Radio access network (RAN) centralization is at the basis of current mobile networks, in which BaseBand Units (BBUs) and radio antenna units (RAUs) exchange over the FrontHaul (FH) digitized radio-frequency signals through protocols such as the common public radio interface. However, such architecture, as it stands, does not scale to the demands of multiple-antennas 5G systems, thus leading to drastic RAN paradigm changes. Differently from digital RAN architectures, we propose to overcome bandwidth/latency issues due to digitization by employing an all-analog FH for multiple-antenna RAUs based on the analog radio-over-copper (A-RoC) paradigm. The A-RoC is an alternative/complementary solution to FH for the last 200 m, such as for indoor, to reuse existing local area network (LAN) cables with remarkable economic benefits. Although LAN cables contain 4 twisted-pairs with up to 500 MHz bandwidth/ea., their usage is limited by cable attenuation and crosstalk among pairs. This paper demonstrates that a judicious mapping of each radio-frequency signal of each antenna onto a combination of cable pair-frequency allocations, referred to as space-frequency to space-frequency multiplexing, optimized together with the design of the digital precoding at the BBU, substantially mitigates the cable impairments. The LAN cables can be exploited for last 100-200 m analog transport FH to meet the requirements of 5G indoor networks.

Published in: IEEE Transactions on Wireless Communications ( Volume: 18 , Issue: 5 , May 2019 )