Millimeter-Wave CRAN with Lens Antenna Arrays

Abstract

Millimeter-wave (mmWave) communication has emerged as a promising candidate for next-generation wireless systems due to the availability of large bandwidth, while cloud radio access network (CRAN), in which low-complexity remote radio heads (RRHs) are deployed to serve users in a distributed manner, is a cost-effective solution to achieve network densification. However, for a CRAN operating over a large bandwidth in the mmWave frequencies, the fronthaul links would be easily saturated by the large amount of sampled and quantized signals to be transferred between RRHs and the central processor. To tackle this problem, we propose in this paper a new architecture for mmWave CRAN with advanced lens antenna arrays at the RRHs. With the energy focusing property, lens antenna arrays are effective in exploiting the angular sparsity of the mmWave channel to simplify the signal processing required to achieve high data rates with multiple antennas, even when the channel is frequency selective. We consider the uplink transmission in a mmWave CRAN with lens antenna arrays and propose a low-complexity quantization bit allocation scheme for multiple antennas at each RRH to meet the stringent fronthaul rate constraint. We compare the proposed mmWave CRAN using lens antenna arrays, with a conventional CRAN using uniform planar arrays at the RRHs, and show that the proposed design achieves significant throughput gains with much lower complexity.