Digital optical fiber repeater is different from the previous analog optical fiber repeater, which converts the radio frequency signal into an intermediate frequency digital signal through frequency conversion, and then transmits it through optical fiber. The specific working principle is: the near-end machine will be from.NodeBThe received base station downlink signal is converted into a low intermediate frequency signal orI/Qsignal, this signal passes throughADCIt is converted into a digital signal, then packaged into serial data according to a certain frame format, and then sent to the remote machine through the optical fiber. The remote machine is de-framed by the baseband processing unit to recover the low intermediate frequency signal or.I/QSignal,DACIt is converted into an analog signal, converted into a radio frequency, and then transmitted by the transmitting subsystem; the remote terminal sends the received uplink signal of the mobile terminal to the receiving end of the base station through the reverse process.

Digital fiber optic repeater andRRUYou can use the existing mature Ethernet digital fiber transmission technology to transmit baseband signals, and jointly comply with the standard.OBSAIInterface andCPRIinterface. Digital fiber optic repeater andRRUAll of the remote units can be used as signal sources of the indoor distribution system and can be replaced with each other. Which one to choose depends on the indoor service and carrier frequency requirements of the macro base station. If the macro base station has rich capacity and many carrier frequencies, it is more appropriate to use digital optical fiber repeater to reduce sector scrambling codes. If the indoor business needs are large, you should chooseRRUas a signal source. Such as convention and exhibition centers, large office buildings and other business demand is large, should consider digital fiber optic repeater,RRUand joint networking of macro base stations.

In terms of coverage distance, both can be used as a base station remote system, and a digital fiber repeater can be used as a carrier pool remote,RRUCan be used as baseband pool remote. The distance of the carrier pool depends on the coverage radius of the cell and the transmission speed of the light on the optical fiber. The digital signal propagates in the optical fiber, and its dynamic range is larger than that of the analog signal, so that the remote machine can achieve greater signal coverage. At the same time, the digital signal does not attenuate with the attenuation of the optical signal, so its transmission distance is further increased. According to the calculation, the distance can exceed40km, as the baseband pool'sRRUCan be extended further without distance restrictions.

In the use of scrambling codes, the scrambling code of the radio frequency signal of the digital optical fiber repeater is always the same as that of the donor base station, and the digital optical fiber repeater does not increase the hardware capacity and orthogonal code capacity of the base station channel board, so if it is widely used in the sector, it will not increase the scrambling code.RRUThe radio remote unit is a new sector, which is composed of the remaining channel board and baseband processing equipment of the base station, and extends to a certain distance through the optical fiber system. Some people call it the baseband pool technology, and some people call it the extended microcellular technology. In short, it has hardware capacity and new scrambling and synchronization codes. DueRRUWith the performance of the base station, a large number of scrambling codes and neighbor cell lists will inevitably be added in the sector of the macro base station, resulting in the increase of pilot pollution and soft handover, which is a problem to be paid attention to in network optimization.