A data-rate adaptable modem solution for millimeter-wave wireless fronthaul networks

For dense small cell deployment in centralized baseband architecture, wireless fronthaul is a cost efficient and flexible alternative to fiber-based fronthaul links. Due to the available wide bandwidth, millimeter-wave technology is the most promising choice to realize multi-gigabit wireless transmission of the common public radio interface (CPRI). In this paper, we present a novel differential encoding scheme for differential quadrature phase-shift keying (D-QPSK) modulation, which enables data-rate adaptable CPRI transmission without modification of a standard receiver. A multi-rate D-QPSK modulator/demodulator (modem) is implemented and tested for data rates up to 10 Gbps, limited by the bandwidth of the microwave components in use. This modem is verified to fulfill the CPRI specifications with respect to multi-rate, low latency and high system performance. Therefore, it is proposed for the implementation of wireless CPRI links at millimeter-wave bands.