Analog MIMO Radio-over-Copper: Prototype and Preliminary Experimental Results

Analog Multiple-Input Multiple-Output Radio-over-Copper (A-MIMO-RoC) is an effective all-analog FrontHaul (FH) architecture that exploits any pre-existing Local Area Network (LAN) cabling infrastructure of buildings to distribute Radio-Frequency (RF) signals indoors. A-MIMO-RoC, by leveraging a fully analog implementation, completely avoids any dedicated digital interface by using a transparent end-to-end system, with consequent latency, bandwidth and cost benefits. Usually, LAN cables are exploited mainly in the low-frequency spectrum portion, mostly due to the moderate cable attenuation and crosstalk among twisted-pairs. Unlike current systems based on LAN cables, the key feature of the proposed platform is to exploit more efficiently the huge bandwidth capability offered by LAN cables, that contain 4 twisted-pairs reaching up to 500 MHz bandwidth/pair when the length is below 100 m. Several works proposed numerical simulations that assert the feasibility of employing LAN cables for indoor FH applications up to several hundreds of MHz, but an A-MIMO-RoC experimental evaluation is still missing. Here, we present some preliminary results obtained with an A-MIMO-RoC prototype made by low-cost all-analog/all-passive devices along the signal path. This setup demonstrates experimentally the feasibility of the proposed analog relaying of MIMO RF signals over LAN cables up to 400 MHz, thus enabling an efficient exploitation of the LAN cables transport capabilities for 5G indoor applications.Comment: Part of this work has been accepted as a conference publication to ISWCS 201

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

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