Demonstration of Analog Millimeter-Wave Fronthaul Link for 64-QAM LTE Signal Transmission

Abstract

Centralized baseband architecture is believed to be cost efficient and to offer high network performance. The fronthaul network, connecting the centralized baseband to distributed remote radios, requires high capacity and low latency transport links, due to the stringent specifications of the data interface, known as common public radio interface (CPRI). Today, fronthaul links are mostly based on digital CPRI over fibers, although it is possible to realize CPRI over wireless technology with the drawback of poor bandwidth efficiency. In this paper, we propose an analog wireless fronthaul concept to enable bandwidth efficient and scalable fronthaul networks. The basic idea is to transport narrow band analog radio signals over millimeter-wave bands instead of multi-gigabit digital signals. The phase and frequency impairments introduced by high frequency carriers are effectively reduced using an analog pilot-based mitigation technique. As a proof-of-concept demonstration, an analog fronthaul link is implemented, and the link performance is verified for 20 MHz 64-QAM LTE transmission over 70/80 GHz (E-band). The measured error vector magnitude (EVM) is about 3% with 10% pilot bandwidth overhead.