FPGA-based adaptive space-time compression towards 5G MIMO fronthaul

Data compression-assisted radio-over-fiber (RoF) is a candidate solution to improve fronthaul (FH) bandwidth efficiency without losing cell-site simplicity for cloud/centralized radio access network (C-RAN) in fifth-generation (5G) mobile networks. One of the challenges in FH in 5G & beyond lies in MIMO fronthauling, where the FH bandwidth requirement scales (in spatial dimension) with number of antennas and thus cannot be resolved by conventional compression approaches tackling only time dimension. Also, it is desirable to implement FH compressor on real-time hardware to evaluate the implementation complexity, signal quality and processing latency. In this paper, we target 5G MIMO FH, and present field-programmable gate array (FPGA) based hardware design, characterization and evaluation of our proposed adaptive space-time FH compression technique. We experimentally demonstrate 8-antenna MIMO FH uplink enabled by the FPGA-based compressor. 48 Gb/s CPRI-equivalent rate encapsulating 1024QAM 5G new radio (NR)-like signals is transported using only 2.5 GBd optical PAM4, achieving <1.25% EVM with low processing latency. The FPGA demonstration indicates the feasibility of the space-time compression technique towards practice, which may be employed in not only FH network, but also other applications such as indoor MIMO distributed antenna system (DAS) or converged fiber-wireless transmission systems.