A Full Field-of-View Self-Steering Beamformer for 5G mm-Wave Fiber-Wireless Mobile Fronthaul

摘要

The upcoming new radio access allows ultra-high data rate using millimeter-wave (mm-Wave) frequencies, while it normally suffers from large path loss. To compensate for path loss, phased arrays for both the transmitter and receiver are used. The 5G new radio (NR) three beam management process proceeds as follows: The transmitted beam is first swept in the downlink direction from the remote radio unit (RRU) to the user equipment (UE), and then the uplink beam is aligned to determine which beam direction has the best reception quality, and vice versa. However, this sequential beam management requires that the RX must be able to perform both beam detection and steering across all the reception angles. Moreover, due to the narrow beamwidth of the phased array operation, a "quantum leap" performance improvement of the receiver operating at mm-Wave is required. In this article, a self-steering array beamformer (SSA-BF) receiving system is proposed, which is composed of a home-designed IC package with zero DC power consumption and a 4-element antenna array. We first conduct the measurement without the antenna, and the SSA-BF receiver shows a significant array factor enhancement with negligible SNR degradation over full field-of-view (FoV) (incidence angle = +/- 90 degrees), <3 ms fast beam alignment time, and it can support enhanced mobile data-rate up to 10 and 7.8 Gb/s with 20x100 MHz carrier aggregation OFDM in back-to-back and over 25-km fiber transmission, respectively. Moreover, a broadside 3-dB beamwidth +/- 80 degrees and broadband 17-36 GHz antenna is designed for the proposed SSA-BF receiver in a 5G fiber-wireless access. The SSA-BF receiving system with the 1 x 4 antenna array is designed at 28 GHz, and it shows the normalized array gain better than 3- and 6-dB degradation over broad FoV incidence = +/- 68 degrees and +/- 85 degrees, respectively. Without any external tuning controls, the proposed SSA-BF achieves the state-of-the-art autonomous beamforming for 6 Gb/s 64-QAM signal over 50-cm wireless distance, achieving a substantial array factor improvement. To the best of authors' knowledge, this is the first demonstration of a high-speed switching SSA-BF receiver in a fiber-wireless integrated radio access as a true enabler for mm-Wave mobile fronthaul applications