5G wireless signal coverage will gradually move from high-value areas to low- and medium-value areas. The low- and medium-value areas have a wide area and sparse personnel distribution. The cost of 5G wireless signal coverage will increase significantly, the utilization rate of 5G base stations will decrease significantly, the cost will rise, and the utilization rate will increase.
The decline will lead to a longer payback period. The use of 5G digital optical fiber repeaters for 5G wireless signal coverage will be a major trend. The overlapping coverage problem generated by 5G digital optical fiber repeaters during application needs to be avoided during the survey and design. The article explores The basic overview application of digital optical fiber repeater is given.
The 5G digital optical fiber repeater has two duplex modes. The working principles of the time division duplex 5G digital optical fiber repeater and the frequency division duplex 5G digital optical fiber repeater are quite different. Downlink of time division duplex 5G digital optical fiber repeater:
The near-end unit couples the 5G NR RRU downlink RF signal through a coupler (usually a 40dB coupler), and enters the RF switch unit of the near-end unit through the feeder. The unit RF switch unit controls the turn-on and turn-off time of the RF switch unit through the 5G baseband synchronization signal demodulated by the FPGA, which is synchronized with the 5G NR RRU signal.
The 5G NR RRU downlink RF signal enters the near-end unit frequency conversion module, and the frequency is converted into an intermediate frequency signal. The near-end unit ADC/DAC module converts the digital signal into the near-end unit FPGA module. The near-end unit FPGA module performs baseband synchronous demodulation on the digital signal, demodulates the baseband synchronization signal of the 5G NR RRU, and the baseband synchronization signal controls the near-end unit.
The radio frequency switch completes the time slot synchronization with the 5G NR RRU; the near-end unit FPGA module also filters the digital signal, delays adjustment, DPD and other processing, and frames the baseband synchronization signal according to the CPRI protocol into a digital signal of the CPRI protocol. , the digital signal of the CPRI protocol is transmitted to the remote unit through the optical fiber of the near-end unit optical transceiver, and the optical transceiver of the remote unit receives the digital signal of the CPRI protocol transmitted by the optical transceiverof the near-end unit and enters the remote unit FPGA module.
The FPGA module of the remote unit demodulates the digital signal and the baseband synchronization signal. The baseband synchronization signal completes the control of the remote radio frequency switch. The digital signal enters the ADC/DAC module of the remote unit and is converted into an intermediate frequency signal and enters the remote frequency conversion module.
The remote frequency conversion The module converts the intermediate frequency signal into a 5G NR RRU downlink radio frequency signal and enters the low-noise module of the remote power amplifier for power amplification. After amplification, the 5G NR RRU downlink radio frequency signal can be used as a signal for the room division system, beautification antenna, and base station antenna through the remote radio frequency switch. source to complete the coverage of the coverage area.
Uplink: The indoor distribution system, the beautification antenna, and the base station antenna receive the 5G NR RRU uplink RF signal transmitted by the 5G terminal through air coupling and enter the remote RF switch. The remote RF switch completes the clock synchronization with the 5G NR RRU through the baseband synchronization signal , the 5G NR RRU uplink RF signal enters the low-noise module of the remote power amplifier for low-noise amplification and then enters the remote frequency conversion module.
The remote frequency conversion module converts the 5G NR RRU uplink RF signal into an intermediate frequency signal and then enters the remote unit ADC/DAC module , convert into digital signal and enter the remote unit FPGA module, the remote unit FPGA module filters, delay adjustment, DPD and other processing of the digital signal, and then frames it according to the CPRI protocol into a digital signal of the CPRI protocol, a digital signal of the CPRI protocol The optical module of the remote unit is transmitted to the near-end unit through the optical fiber, and the optical module of the near-end unit receives the digital signal of the CPRI protocol transmitted by the optical module of the near-end unit and enters the FPGA module of the remote unit. The digital signal is called out and enters the ADC/DAC module of the near-end unit.
The ADC/DAC module of the near-end unit converts the digital signal into an intermediate frequency signal and enters the near-end frequency conversion module. The near-end frequency conversion module converts the intermediate frequency signal into a 5G NR RRU. After the end RF switch, the backhaul to the 5G NR RRU is the transmission link.
Time division duplex and frequency division duplex 5G digital optical fiber repeaters are similar in the digital processing part, and the equipment delay of 5G digital optical fiber repeater is mainly generated by digital processing.
Therefore, time division duplex and frequency division duplex 5G The equipment delay of the digital optical fiber repeater is basically the same, which is about 7us. The delay of the 5G digital optical fiber repeater is inversely proportional to the out-of-band suppression index of the 5G digital optical fiber repeater. The delay increases, and the out-of-band suppression index That’s good, as the delay decreases, the out-of-band suppression index is poor. Therefore, the delay and the out-of-band suppression index need to be comprehensively considered.
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