Compressed transport of baseband signals in cloud radio access networks

Abstract

Cloud radio access network (C-RAN) is a next generation wireless access network architecture. In this architecture, common public radio interface (CPRI) links are widely used to transmit baseband signals. Currently, one of the great technical challenges for the C-RAN architecture is the soaring CPRI bandwidth required for data transmission between remote radio unit (RRU) and baseband unit (BBU). In this paper, we propose a novel compression method that exploits the temporal and spectral features of baseband signals, which can achieve high compression ratio (3.56x) and low latency (3.4usec) with limited impact on end-to-end communication performance (error vector magnitude <1.89%). We use a combination of reducing signal sampling, digital automatic gain control, Lloyd-Max quantization and cyclic prefix replacement to compress LTE uplink and downlink signals. Upon verifying the feasibility and validity of the algorithm, we implement the design with field programmable gate array (FPGA) resources.