5G Wireless Fronthaul Interface

5G wireless communication demands more spectrum resources than 4G, for enhanced mobile broadband (eMBB), ultra-reliable and low-latency communication (URLLC), and massive machine type communication (mMTC). Currently, 5G uses the sub 6GHz FR1 spectrum that supports a maximum bandwidth of 100Mb/s, five times that of 4G LTE. When there are 64 channels and the bandwidth is 100MHz, the common public radio interface (CPRI) protocol requires at least 100Gb/s for fronthaul channels. However, in 2017, the industry was not ready for 100Gb/s optical transceiver modules. Therefore, the enhanced CPRI (eCPRI) protocol was developed.

The eCPRI protocol defines multiple split modes. An interface of a higher protocol layer requires a lower transmission bandwidth. In mainstream split scenarios, some physical-layer signal processing functions are transferred from the baseband to the antenna side, requiring only 25Gb/s from the fronthaul interface. In recent years, the requirements for mainstream fronthaul optical transceiver modules have evolved from 10Gb/s in the 4G era to 25Gb/s in the 5G era.