Uplink Joint Reception with LLR Forwarding for Optical Transmission Bandwidth Reduction in Mobile Fronthaul

We propose an uplink joint reception method for coordinated multi-point transmission and reception (CoMP) where the quantized log likelihood ratio (LLR) is forwarded by an optical interface different from the common public radio interface (CPRI), to suppress the explosive increase in the optical transmission bandwidth in the mobile fronthaul (MFH) of the centralized/cloud radio access network (C-RAN) and thus reduce the MFH optical transmission cost of future radio access. To exploit the proposed method, we focus on the split-PHY processing (SPP) architecture for MFH redefinition where the base station (BS) functions are split between modulation and channel coding functions within the PHY (Physical) layer. Numerical simulations of block error rate (BLER) performance confirm a signal to noise ratio (SNR) degradation due to the proposed method in the SPP architecture of less than 3 dB compared with the conventional C-RAN, and an SNR improvement compared to the performance without joint reception of more than 5 dB. Meanwhile, numerical calculations that assume future radio access show that the SPP architecture with the proposed method reduces MFH optical transmission bandwidth by at least 85 % compared to the conventional C-RAN. These results show that the SPP architecture with the proposed method will enable cost-effective MFH deployment.