Space-frequency to space-frequency for MIMO radio over copper

Centralized Radio Access Network (C-RAN) architecture is considered the only viable solution to handle the complex interference scenarios generated by massive antenna and small cell deployment foreseen for next generation (5G) mobile networks. The fronthaul links used to exchange the signal between Base Band Units (BBUs) and Remote Radio Heads (RRHs) are conventionally based on optical fiber, due to its huge bandwidth. In this paper we propose the radio over copper (RoC) as a complementary technology for the fronthaul architectures leveraging on the pre-existing LAN cables that are largely deployed in buildings and enterprises. To fully exploit the capabilities of LAN cable over the last 50-200m, a joint space and frequency division multiplexing is proposed. In particular, the main contribution of the paper is to prove that a smart mapping between the radio antennas/spectrum and the copper cable space/frequency dimensions allows an efficient communication over the RRH-BBU link with performances that are comparable to those achieved by an ideal fronthauling where BBU and RRH are assumed to be co-located. Validation is on the radio-link capabilities of RoC over Cat-6 cable to meet the demand for massive MIMO technology.