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Time slot synchronization method for satellite-borne AIS signal receiving system

A technology for time slot synchronization and signal reception, which is applied in time division multiplexing systems, multiplexing communications, electrical components, etc. It can solve the problem that phase-locked loops cannot complete carrier synchronization, and achieve less resource occupation and execution efficiency. High, step-by-step effects

Active Publication Date: 2014-08-13
SHANGHAI SPACEFLIGHT INST OF TT&C & TELECOMM
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Generally, the receiving system uses phase-locked technology to synchronize the carrier of the received signal, but the phase-locked loop synchronization is suitable for signals with a certain length of time, because it takes a certain amount of time for the phase-locked loop to complete the synchronization. For short-term burst signals such as AIS , the PLL cannot complete the carrier synchronization

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  • Time slot synchronization method for satellite-borne AIS signal receiving system
  • Time slot synchronization method for satellite-borne AIS signal receiving system
  • Time slot synchronization method for satellite-borne AIS signal receiving system

Examples

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Embodiment 1

[0033] Such as figure 1 Shown, a kind of time slot synchronization method that is used for space-borne AIS signal receiving system comprises the following steps:

[0034] Step S1, the initialization step, in an AIS time slot, from the received continuous signal, take out a certain length of signal segments at regular intervals, a total of M signal segments, and perform discrete Fourier transform on each signal segment respectively transforming, transforming the time-domain signal into a frequency-domain signal to obtain M frequency-domain signals;

[0035] Step S2, the correlation calculation step, presets N local reference frequency domain signals, performs correlation calculations on the M frequency domain signals obtained in step S1 and N local reference frequency domain signals respectively, and obtains M×N correlation values; among them, the local The reference frequency domain signal includes a reference signal sequence without frequency offset and a cyclic shift sequen...

Embodiment 2

[0039] Compared with embodiment 1, this embodiment differs in that:

[0040] Step S1, the discrete Fourier transform in the initialization step is specifically:

[0041] The first 32-bit symbols of the AIS data packet are used for synchronization, that is, the first 32-bit symbols in each group of AIS signals received are used as synchronization reference signals. The first 32 symbols include a 24-bit synchronization symbol (Training sequence), the specific symbol is 0101...0101; and a start flag (Start flag) 8 bits, the specific symbol is 01111110.

[0042] Assume that the time length of one symbol is the interval for taking signal segments from the received signal, and take out P pieces of data from the continuous received signal every other time interval, and the P pieces of data form a data group, thus obtaining M pieces of data Data group; wherein, P is 32 multiplied by the sampling rate, and the sampling rate is the number of sampling points of each symbol. Discrete Fo...

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Abstract

The invention discloses a time slot synchronization method for a satellite-borne AIS signal receiving system. The method includes the following steps that in an AIS time slot, M signal segments of a certain length are taken out at intervals from received continuous signals, discrete Fourier transform is conducted on each signal segment, and time domain signals are converted into frequency domain signals; correlation operations are conducted on the frequency domain signals and local reference frequency domain signals respectively, so that M*N correlation values are obtained; the maximum value is obtained from the correlation values, start time of the received signal segment corresponding to the maximum value serves as synchronization time, a frequency deviation value of the local reference signal corresponding to the maximum value serves as a synchronizing frequency point, and therefore time slot synchronization is conducted according to the obtained synchronization time and the synchronizing frequency point. The method has the following advantages that time slot synchronization of the satellite-borne AIS signal receiving system can be effectively achieved, the steps are simple, the method is easy to achieve, occupied resources are few, and execution efficiency is high.

Description

technical field [0001] The invention belongs to the technical field of signal time slot synchronization, and in particular relates to a time slot synchronization method used in a satellite-borne AIS signal receiving system. Background technique [0002] In 2002, the International Maritime Organization (IMO) proposed the automatic identification system (Automatic Identification System, AIS) and made it mandatory for use on ships. AIS is an electronic communication device installed on ships. The AIS system can continuously broadcast information such as the position of the own ship and receive signals broadcast by surrounding ships, so that the ship can grasp the status of the surrounding ships and ensure the safety of navigation. [0003] The ship automatic identification system (AIS) uses the SOTDMA communication protocol, which is equivalent to one minute as one frame, and each frame is divided into 2250 time slots, and the time width of a time slot is 26.67ms. Each ship use...

Claims

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Application Information

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IPC IPC(8): H04J3/06
Inventor 方诗峰刘婧张喆李洪星
Owner SHANGHAI SPACEFLIGHT INST OF TT&C & TELECOMM