Abstract: A first device receives a first signal sent by a second device, receives a second signal sent by a third device, and determines a first length based on first time, second time, and delay duration. The first time is time at which the first device receives the first signal. The second time is time at which the first device receives the second signal. The first length is a distance from an intersection point of a first straight line on which a terminal device is located and a first transmission line between a first network device and a second network device to the second network device, and the first straight line is perpendicular to the first transmission line.

Abstract: Embodiments of this application provide a leaky coaxial cable and a communication system. The leaky cable includes: an inner conductor, an insulation layer, and an outer conductor, where the insulation layer is configured to separate the inner conductor from the outer conductor; and the outer conductor includes M perforated segments and N non-perforated segments, the M perforated segments and the N non-perforated segments are alternately arranged, at least one of the M perforated segments includes at least three leak holes, spacings between leak holes in each of the at least one perforated segment are the same, and M and N are positive integers greater than or equal to 1.

Abstract: The method includes: obtaining 2N first signals and 2N?1 second signals, where the first signal and the second signal each include M signal points, a signal value, at an even location, of the signal point of the first signal is 0, a signal value, at an odd location or an even location, of the signal point of the second signal is 0, N is a positive integer, and M is a positive even number; performing inverse fast Fourier transform IFFT, inverse Fourier transform IFT, fast Fourier transform FFT, or Fourier transform FT on the 2N first signals and the 2N?1 second signals to determine 2N third signals and 2N?1 fourth signals.

Abstract: A radio over fiber (RoF) system and a nonlinear compensation method, where the RoF system includes a BBU and an RRU, the RRU includes an electrical component, and the BBU includes a downlink and a feedback link. A predistortion module and an optical component are disposed on the downlink, an input end of the feedback link is connected to an output end of the optical component, and the feedback link is configured to feed back, to the predistortion module, a nonlinear signal output by the optical component. The RoF system further includes a temperature detection module configured to detect a temperature value of the electrical component, and transmit the temperature value to the predistortion module. The predistortion module is configured to perform digital predistortion DPD on a baseband signal based on the temperature value and the nonlinear signal.

Abstract: A signal receiving apparatus and method are provided. When a baseband signal is restored, an orthogonal polarization state of light does not need to be precisely controlled. This is easy to implement and can reduce system costs. The apparatus includes an optical splitter configured to split a first polarization multiplexing optical signal into at least two second polarization multiplexing optical signals, and input the two second polarization multiplexing optical signals into at least two optical signal processing modules. An optical signal processing module is configured to couple the second polarization multiplexing optical signal, and input a coupled optical signal to a photoelectric detector configured to convert the coupled optical signal into an analog signal. An analog-to-digital converter is configured to convert the analog signal into a digital signal, and input the digital signal to a digital signal processor configured to process the digital signal to obtain a baseband signal.

Abstract: A radio over fiber (RoF) system and a nonlinear compensation method, where the RoF system includes a BBU and an RRU, the RRU includes an electrical component, and the BBU includes a downlink and a feedback link. A predistortion module and an optical component are disposed on the downlink, an input end of the feedback link is connected to an output end of the optical component, and the feedback link is configured to feed back, to the predistortion module, a nonlinear signal output by the optical component. The RoF system further includes a temperature detection module configured to detect a temperature value of the electrical component, and transmit the temperature value to the predistortion module. The predistortion module is configured to perform digital predistortion DPD on a baseband signal based on the temperature value and the nonlinear signal.

Abstract: This application relates to the field of communications technologies and discloses a transmitter device and a signal processing method. m transmit antenna groups of the transmitter are configured to send m training signals under control of the processor. A target feedback antenna of the transmitter is configured to receive, under control of the processor, a first mixed signal obtained by superimposing the m training signals in space, where a phase difference between the first mixed signal and a second mixed signal obtained by superimposing in space the m training signals received by a receiver device falls within a preset range. A processor of the transmitter is configured to: perform DPD parameter estimation and pre-distortion processing on a to-be-sent signal. The m transmit antenna groups are further configured to send, under control of the processor, the to-be-sent signal on which pre-distortion processing has been performed.

Abstract: This application relates to the field of communications technologies and discloses a transmitter device and a signal processing method. m transmit antenna groups of the transmitter are configured to send m training signals under control of the processor. A target feedback antenna of the transmitter is configured to receive, under control of the processor, a first mixed signal obtained by superimposing the m training signals in space, where a phase difference between the first mixed signal and a second mixed signal obtained by superimposing in space the m training signals received by a receiver device falls within a preset range. A processor of the transmitter is configured to: perform DPD parameter estimation and pre-distortion processing on a to-be-sent signal. The m transmit antenna groups are further configured to send, under control of the processor, the to-be-sent signal on which pre-distortion processing has been performed.