Switched ethernet fronthaul architecture for cloud-radio access networks

A fronthaul design for current and future mobile networks based on the transport of sampled radio signals from/to base station baseband processing units to/from remote radio heads (RRHs) is presented. The design is a pure-Ethernet switched architecture that uses virtual local area network identifiers for the RRHs and flow identifiers for the antenna ports and is compatible with current standardization definitions. A comprehensive analysis for the limits of the Ethernet fronthaul in terms of the total number of antennas that can be supported is carried out, based on the latency imposed by the Ethernet network. The analysis assumes the transportation of control and management and timing information [based on the precision-time protocol (PTP)] but is valid for other types of background traffic (for example, that generated by the implementation of different Long-Term Evolution functional subdivisions in a fronthaul with mixed processing). A low-cost test bed using "smart small factor pluggable" in-line probes is presented and used to obtain measurements from an Ethernet fronthaul, transporting mixed traffic. The measurements show how background traffic affects hybrid-automatic repeat request retransmissions and are used to validate the analysis. The effects of contention of PTP packets are discussed, and a simple solution to overcome the effects of contention is proposed.