CN107659321B - Automatic frequency hopping AIS single channel receiver - Google Patents

Automatic frequency hopping AIS single channel receiver Download PDF

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CN107659321B
CN107659321B CN201711079704.2A CN201711079704A CN107659321B CN 107659321 B CN107659321 B CN 107659321B CN 201711079704 A CN201711079704 A CN 201711079704A CN 107659321 B CN107659321 B CN 107659321B
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frequency
frequency hopping
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receiving module
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CN107659321A (en
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袁海峰
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Shenzhen Quark Elec Technologies Co ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/0003—Software-defined radio [SDR] systems, i.e. systems wherein components typically implemented in hardware, e.g. filters or modulators/demodulators, are implented using software, e.g. by involving an AD or DA conversion stage such that at least part of the signal processing is performed in the digital domain
    • H04B1/0028—Software-defined radio [SDR] systems, i.e. systems wherein components typically implemented in hardware, e.g. filters or modulators/demodulators, are implented using software, e.g. by involving an AD or DA conversion stage such that at least part of the signal processing is performed in the digital domain wherein the AD/DA conversion occurs at baseband stage
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/06—Receivers
    • H04B1/16—Circuits
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/713—Spread spectrum techniques using frequency hopping
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B17/00—Monitoring; Testing
    • H04B17/20—Monitoring; Testing of receivers
    • H04B17/29—Performance testing

Abstract

The invention discloses an automatic frequency hopping AIS single-channel receiver, which comprises a GPS radio-frequency front end, a GPS receiving module, an AIS radio-frequency front end, an AIS receiving module and a baseband information processing module, wherein the GPS radio-frequency front end is connected with the GPS receiving module; the AIS radio frequency front end is connected with an AIS receiving module, and the AIS receiving module is connected with a baseband information processing module. The automatic frequency hopping receiver device detects the congestion condition of the AIS two channels in real time, and accordingly the receiver is set to work in a fixed frequency hopping mode or a dynamic frequency hopping mode. And the receiver detects the time slot conflict random characteristics of the two channels in real time in a dynamic frequency hopping mode, the time slot conflict is preferably selected to be less, and the AIS time slot works by utilizing higher frequency points. The application of the invention can obviously shorten the locking time of the surrounding AIS transmitters and improve the quantity of the received effective information.

Description

Automatic frequency hopping AIS single channel receiver
Technical Field
The invention relates to the technical field of Automatic Identification Systems (AIS) of ships, in particular to an Automatic frequency hopping AIS single-channel receiver.
Background
In recent years, with the rapid development of ship science and technology and the rise of ocean economy, the position of marine transportation is increasingly remarkable, and the world shipping market is expanded and developed unprecedentedly. The rapid development of the world shipping industry brings great economic benefits and makes marine traffic conditions more and more complex.
The AIS system is an effective safety system for collision avoidance, navigation and navigation aid on the sea. According to the mandatory requirements of the International Maritime Organization (IMO), all international vessels of 300 tons or more and non-international vessels of 500 tons or more are currently equipped with AIS equipment. Although the equipment is not forcibly installed on the small-sized ship at present, the AIS is gradually popularized and applied to the aspects of sea area perception, sea surface monitoring, sea rescue, auxiliary identification, leisure, environmental protection, smuggling, terrorism attack and the like due to the self-reporting characteristic and the gradual reduction of the manufacturing cost of the AIS.
The International Telecommunications Union (ITU) and the international maritime organization are the subject of the AIS technical standards. The AIS transmitter operates on two VHF channels (161.975MHz and 162.025MHz), and operates to alternately transmit AIS information on the two channels. The AIS communication protocol divides each minute into 2250 time slots on two frequency channels, one time slot having a time width of 26.67ms, each ship transmitting a signal using one time slot at a time. The AIS system adopts a Time Division Multiple Access (TDMA) communication system to exchange and identify digital information between a ship and a shore base so as to achieve the purpose of collision avoidance. In order to achieve the function of exchanging information between various terminal devices by autonomous networking on the channel, in the international standard, according to different stages of terminal device networking, an isochronous multiple Access mode such as Random Access TDMA (ramtdma), Incremental TDMA (ITDMA), Fixed Access TDMA (FATDMA), Self-Organized TDMA (SOTDMA), and Carrier-Sense TDMA (CSTDMA) is designed in sequence.
A typical AIS terminal includes a transmitter and two receivers. The transmitter alternately transmits the AIS information on the two frequency channels according to the AIS protocol, while the two receivers synchronously receive and parse the AIS information on the two frequency channels. Terminals without a transmitter are called AIS receivers, while devices with only one receiver are called single channel receivers. And the single-channel receiver is alternately switched on the two frequency points to receive the AIS information. Compared with a dual-channel receiver, the single-channel receiver has the characteristics of low power consumption, small volume, low requirement on baseband processing capacity and the like. At present, many maritime AIS terminal devices are not simple and have navigation functions, and have multiple functions of entertainment, communication, safety, weather, tide and the like. For such terminal equipment, the power consumption of each functional module directly affects the operation duration of the whole terminal. And the requirements for the baseband processing capability directly affect the actual engineering problems of the volume, the heat dissipation and the like of the whole terminal equipment. Therefore, under the background that portable intelligent terminals are increasingly popularized, the AIS single-channel receiver with lower power consumption and lower requirements on baseband processing capacity is designed to have important practical significance.
Since the AIS single channel receiver only listens to one channel at any time and receives signals of one channel, the single channel receiver receives half of the information compared to the dual channel receiver. From this point of view, the performance of a single channel receiver is also only half of that of a dual channel, but this is not the case in practical applications. First, most commercial AIS transmitters on the market transmit information on a certain frequency channel, and then switch to another frequency channel to apply for a time slot for retransmission. Therefore, a single channel receiver will, with a high probability, capture the information it transmits in a certain channel. The AIS standard protocol provides that the transmitter alternately transmits AIS messages on both frequency channels, so there is a low probability that messages transmitted on both frequency channels will be missed. In fact, a dual channel receiver has a large amount of redundant information in the signal received on both channels simultaneously. Secondly, in hardware design, compared with a dual-channel receiver, the radio frequency front end part theoretically reduces the insertion loss of 3dBm because a splitter is not needed to divide the radio frequency signal into two paths. In practical application, with the same radio frequency front end design, a single-channel receiver can have 1.8 to 2.5dBm higher sensitivity than a double-channel receiver. The improvement of the sensitivity also improves the monitoring and receiving range and the probability of capturing AIS signals.
Disclosure of Invention
The present invention aims to provide an automatic frequency hopping AIS single channel receiver to solve the problems in the background art.
In order to achieve the purpose, the invention provides the following technical scheme:
an automatic frequency hopping AIS single-channel receiver comprises a GPS radio-frequency front end, a GPS receiving module, an AIS radio-frequency front end, an AIS receiving module and a baseband information processing module, wherein the GPS radio-frequency front end is connected with the GPS receiving module, the GPS receiving module is connected with the baseband information processing module, and the GPS receiving module carries out down-conversion, signal amplification and analog-to-digital conversion on a radio-frequency signal sent by the GPS radio-frequency front end and then sends the signal to the baseband information processing module; the AIS radio frequency front end is connected with the AIS receiving module, the AIS receiving module is connected with the baseband information processing module, and the AIS receiving module carries out filtering, down-conversion, intermediate frequency filtering and analog-to-digital conversion on radio frequency signals sent from the AIS radio frequency front end and then sends the radio frequency signals into the baseband information processing module.
Further: the method comprises the steps that a receiver receives AIS information alternately sent on two frequency channels, detects the congestion conditions of the two AIS channels, accordingly sets the receiver to work in a fixed frequency hopping mode or an automatic frequency hopping mode, when the AIS channels are in an unsaturated and non-congestion state, the receiver works in the fixed frequency hopping mode, and otherwise, the receiver enters the automatic frequency hopping mode; the receiver only has a group of AIS receiving units, the receiving units work alternately on two frequency points of AIS, the switching time on the two frequency points is dynamically adjusted according to the congestion and time slot conflict characteristic situation on each frequency point, and the processing steps of the automatic frequency hopping realization method are as follows:
step (1): the single-channel AIS receiver finishes initialization, starts working when working in a fixed frequency hopping mode, sets the frequency hopping interval time T value in the fixed frequency hopping mode to be T1, sets the system standard congestion rate P to be P1, and then enters the step (2);
step (2): the single-channel receiver is configured at a first frequency point (hereinafter referred to as frequency point A), works for a time length of T1, the baseband information processing module synchronously detects the load rate PA of the channel A in a time period of T1, judges whether the load rate PA of the channel A is higher than P1, if yes, the system executes the step (4) and switches to an automatic frequency hopping mode, otherwise, the process of the step (3) is executed;
and (3): the single-channel receiver is configured at a second frequency point (hereinafter referred to as frequency point B), works for T1 time duration, and then executes the process of the step (2);
and (4): the system switches to an automatic frequency hopping mode, and then enters the step (5);
and (5): the single-channel receiver is configured at a first frequency point A, the frequency hopping interval time T is T2, and the baseband information processing module is according to a formula
Figure GDA0002351649000000041
The time slot conflict random characteristic value D of the frequency point A is calculated by the mathematical modelAThen entering step (6); in the above formula, tiIndicating that the ith information is transmitted on the t-th time slot;
and (6): the single-channel receiver is configured at a second frequency point B, the frequency hopping interval time T is T2, and the baseband information processing module is according to a formula
Figure GDA0002351649000000042
The time slot conflict random characteristic value D of the frequency point B is calculated by the mathematical modelBThen entering step (7);
and (7): compare the updated DAAnd DBA value that if the former is small, the process of step (8) is performed, otherwise step (9) is performed;
configuring a single-channel receiver to work at a first frequency point A, and updating a frequency hopping interval time T-T2- β, wherein β is a number larger than 1;
step (9), configuring the single-channel receiver to work at a second frequency point B, and updating the frequency hopping interval time T-T2- β, wherein β is a number larger than 1 as in step (8);
step (10): judging whether the frequency hopping time T under the automatic frequency hopping mode is larger than the frequency hopping time T1 under the fixed frequency hopping mode, if so, executing the step (2); otherwise, executing step (11);
step (11): the receiver works in the set frequency point and the frequency hopping interval time, and the baseband information processing module works according to the formula
Figure GDA0002351649000000043
The time slot collision random characteristic value D in the time for executing the step is calculated and the value D is updated to the latest time slot collision random characteristic value of the channel, and then the step (7) is executed.
Further: the GPS radio frequency front end is externally connected with a GPS antenna, receives radio frequency signals and sends the processed radio frequency signals to a GPS receiving module; the AIS radio frequency front end is externally connected with an AIS antenna and used for receiving radio frequency signals, and the received radio frequency signals are sent to the AIS receiving module after front end processing is completed.
Further: the GPS radio frequency front end module comprises: low noise amplifier and band pass filter, low noise amplifier receives the radio frequency signal who comes from the antenna to accomplish the front end signal amplification function, band pass filter and low noise amplifier are connected, realize the filtering to the front end signal, filter the noise, allow the effective signal of GPS frequency channel to pass through, and send the radio frequency signal after will handling to GPS receiving module.
Further: the GPS receiving module comprises: a down converter, an intermediate frequency amplifier and an analog-to-digital converter; the down converter receives a radio frequency signal from a GPS radio frequency front end, outputs an intermediate frequency signal after frequency mixing, the intermediate frequency signal is subjected to signal amplification through an intermediate frequency amplifier, and then is subjected to conversion from an analog signal to a digital signal through an analog-to-digital converter, and the digital signal is input into the baseband information processing module.
Further: the AIS radio frequency front end includes: the low-pass filter is connected with the AIS antenna and used for carrying out high-frequency filtering on the received wireless signals, the low-noise amplifier is connected with the low-pass filter and used for amplifying the radio-frequency signals passing through the low-pass filter and then sending the radio-frequency signals to the AIS receiving module.
Further: the AIS receiving module comprises a sound meter filter, a down converter, an intermediate frequency filter and an analog-to-digital converter, wherein the sound meter filter is connected with a low noise amplifier at the front end of AIS radio frequency to receive radio frequency signals, the signals are converted from the radio frequency signals to the intermediate frequency signals through the down converter, then the intermediate frequency signals are input to the intermediate frequency filter to be subjected to band-pass filtering, and the analog-to-digital converter is connected with the intermediate frequency filter to finish the digital processing of the intermediate frequency signals sent from the intermediate frequency filter; the digital signal sent by the analog-to-digital converter is input to the baseband information processing module.
Compared with the prior art, the invention has the beneficial effects that:
compared with the common double-channel receiver in the market, the invention has the advantages that the power consumption of the power supply, the hardware volume and the requirement on the baseband processing capacity are obviously reduced. The characteristics can better meet the requirements of offshore portable equipment, and have a positive promoting effect on the development of AIS receivers.
The invention is different from other single-channel receivers with fixed frequency hopping time, detects the load conditions of the two AIS receiving channels in real time, dynamically adjusts the working time of the single-channel receiver in the two AIS receiving channels according to the random characteristic of time slot conflict, and optimizes the number of AIS information received in unit time to the maximum extent, thereby improving the information capture time and the receiving number of the single-channel receiver. The invention has carried on many times and repeated the test in Shenzhen snake mouth harbor and England Nanompton harbor. The test result shows that compared with the similar single-channel receiver with fixed frequency hopping time, the acquisition time and the information receiving quantity are obviously improved.
Drawings
Fig. 1 is a schematic diagram of an automatic frequency hopping AIS single-channel receiver system.
Fig. 2 is a schematic structural diagram of a GPS rf front end and a GPS receiving module in an automatic frequency hopping AIS single channel receiver.
Fig. 3 is a schematic structural diagram of an AIS radio frequency front end and an AIS receiving module in an automatic frequency hopping AIS single channel receiver.
Fig. 4 is a schematic flow chart of a software algorithm in an automatic frequency hopping AIS single-channel receiver.
In the figure: the device comprises a 1-GPS radio frequency front end, a 1.1-low noise amplifier, a 1.2-band pass filter, a 2-GPS receiving module, a 2.1-down converter, a 2.2-intermediate frequency amplifier, a 2.3-analog-to-digital converter, a 3-AIS radio frequency front end, a 3.1-low pass filter, a 3.2-low noise amplifier, a 4-AIS receiving module, a 4.1-acoustic meter filter, a 4.2-down converter, a 4.3-intermediate frequency filter, a 4.4-analog-to-digital converter and a 5-baseband information processing module.
Detailed Description
Referring to fig. 1, in an embodiment of the present invention, an automatic frequency hopping AIS single channel receiver includes a GPS radio frequency front end (1), a GPS receiving module (2), an AIS radio frequency front end (3), an AIS receiving module (4), and a baseband information processing module (5).
The GPS radio frequency front end (1) is externally connected with a GPS antenna, receives radio frequency signals and sends the processed radio frequency signals to the GPS receiving module (2) for further processing. The GPS receiving module (2) is connected with the GPS radio frequency front end (1), and after the GPS receiving module (2) carries out down-conversion, signal amplification and analog-to-digital conversion on the radio frequency signals sent by the GPS radio frequency front end (1), the signals are sent to the baseband information processing module (5) for digital processing.
The AIS radio frequency front end (3) is externally connected with an AIS antenna and used for receiving radio frequency signals. The received radio frequency signals are sent to an AIS receiving module (4) for further processing after front-end processing is completed.
The AIS receiving module (4) is connected with the AIS radio frequency front end (3), and the AIS receiving module (4) sends radio frequency signals sent from the AIS radio frequency front end (3) to the baseband information processing module (5) after down-conversion, intermediate frequency amplification and analog-to-digital conversion, and then carries out digital processing on the next step.
The baseband information processing module (5) is connected with the GPS receiving module (2) and the AIS receiving module (4). The baseband information processing module completes the following functions:
1. and receiving the digital signal from the GPS receiving module (2) to finish the analysis of the position information.
2. And receiving the digital signals from the AIS receiving module (4) to complete the signal detection and decoding on the frequency point where the AIS signals are located.
3. And detecting the load rates of two AIS channels, and configuring the AIS receiver to switch between a fixed frequency hopping mode and an automatic frequency hopping mode according to the load rate values of the channels. The AIS receiver enters into an automatic frequency hopping mode only when the time slot conflict occurs in the system, otherwise, the AIS receiver switches and works at two frequency points according to fixed time.
4. And under the automatic frequency hopping mode, detecting the randomness of time slot collision in real time, thereby dynamically switching the working channel of the receiver. And the baseband processing module compares the average time slot conflict ratio of the two frequency points in real time and configures more working time of the AIS receiver at the frequency point with the small time slot conflict ratio.
5. And under the automatic frequency hopping mode, calculating the maximum interval time of dynamic frequency hopping in real time. And when the configured maximum interval time is longer than the working time of the fixed frequency hopping, configuring the single-channel receiver to return to the working under the fixed frequency hopping mode.
As shown in fig. 2, the GPS rf front end (1) is connected to the GPS receiving module (2) to complete the whole process of converting the rf signal received from the GPS antenna into a digital baseband signal. The GPS radio frequency front end (1) module comprises: low noise amplifier (1.1), band-pass filter (1.2). The low noise amplifier (1.1) receives radio frequency signals from an antenna and completes the function of front end signal amplification. The band-pass filter (1.2) is connected with the low-noise amplifier (1.1), so that the front-end signal is filtered, noise is filtered, and effective signals of a GPS frequency band are allowed to pass.
As shown in fig. 2, the GPS receiving module (2) includes: a down converter (2.1), an intermediate frequency amplifier (2.2) and an analog-to-digital converter (2.3). The down converter (2.1) receives radio frequency signals from a GPS frequency band, and outputs intermediate frequency signals after frequency mixing. The intermediate frequency signal is amplified by an intermediate frequency amplifier (2.2), and then converted from an analog signal to a digital signal by an analog-to-digital converter (2.3). The digital signal is input to a baseband information processing module (5) for further digital signal processing. Preferably, the down-converter (2.1) will use 4.092Mhz as the intermediate frequency.
As shown in fig. 3, the AIS radio frequency front end (3) is connected to the AIS receiving module (4). The AIS radio frequency front end (3) comprises: a low-pass filter (3.1) and a low-noise amplifier (3.2). The low-pass filter (3.1) is connected with the AIS antenna and is used for filtering the received wireless signals at high frequency. The low noise amplifier (3.2) is connected with the low pass filter (3.1), and the low noise amplifier (3.2) amplifies the radio frequency signal passing through the low pass filter (3.1) and then sends the radio frequency signal to the AIS receiving module (4).
As shown in fig. 3, the AIS receiving module (4) includes a sound meter filter (4.1), a down converter (4.2), an intermediate frequency filter (4.3), and an analog-to-digital converter (4.4). The acoustic surface filter (4.1) is connected with a low noise amplifier (3.2) of the AIS radio frequency front end (3), receives radio frequency signals, the signals are converted from the radio frequency signals to intermediate frequency signals through a down converter (4.2), and then the intermediate frequency signals are input to the intermediate frequency filter (4.3) to be subjected to band-pass filtering. The analog-to-digital converter (4.4) is connected with the intermediate frequency filter (4.3) to complete the digital processing of the intermediate frequency signal sent by the intermediate frequency filter (4.3). The digital signal sent by the analog-to-digital converter (4.4) is input into a baseband information processing module (5) for further digital signal processing.
Fig. 4 is a flowchart of a method for indicating bits according to the present embodiment. The process of this embodiment includes the following steps:
step 1: the single-channel AIS receiver completes initialization, and the receiver starts to work under a fixed frequency hopping mode. And setting the value of the frequency hopping interval time T in the fixed frequency hopping mode as T1 and the standard congestion rate P of the system as P1. Then step 2 is entered.
Step 2: the single-channel receiver is configured at a first frequency point (hereinafter referred to as frequency point A) and works for a time length of T1. The baseband information processing module synchronously detects the load rate PA of the channel A in the time period T1. And (4) judging whether the load rate PA of the channel A is higher than P1, if so, executing the step 4 by the system, switching to an automatic frequency hopping mode, and otherwise, executing the process of the step 3.
And step 3: the single-channel receiver is configured at a second frequency point (hereinafter referred to as frequency point B) and works for the time length of T1. The process of step 2 is then performed.
And 4, step 4: the system switches to automatic frequency hopping mode and then proceeds to step 5.
And 5: the single-channel receiver is configured at a first frequency point A, and the frequency hopping interval time T is T2. The baseband information processing module calculates the time slot conflict random characteristic value D of the frequency point A according to the mathematical model of the formulaAThen, step 6 is entered.
Step 6: the single-channel receiver is configured at a second frequency point B, and the frequency hopping interval time T is T2. The baseband information processing module calculates the time slot conflict random characteristic value D of the frequency point B according to the mathematical model of the formulaBThen, step 7 is entered.
And 7: compare the updated DAAnd DBThe value is obtained. If the former is small, the process of step 8 is performed, otherwise step 9 is performed.
And 8, configuring the single-channel receiver to work at the first frequency point A, and updating the frequency hopping interval time T-T2- β, wherein β is a number greater than 1, preferably, according to simulation and experimental test results, the value of β is configured to be 1.12.
And 9, configuring the single-channel receiver to work at a second frequency point B, and updating the frequency hopping interval time T-T2- β. like the step 8, β is a number greater than 1. preferably, according to simulation and experimental test results, a value of β is configured to be 1.12.
Step 10: judging whether the frequency hopping time T under the automatic frequency hopping mode is greater than the frequency hopping time T1 under the fixed frequency hopping mode, if so, executing the step 2; otherwise step 11 is performed. The purpose of this step is to set the hop time in the automatic hopping mode to be no longer than the hop time in the fixed hopping mode at any time. And provides a way to go from the automatic frequency hopping mode to the fixed frequency hopping mode.
Step 11: the receiver works in the set frequency point and the frequency hopping interval time. And the baseband information processing module calculates and executes the time slot conflict random characteristic value D in the step time according to a mathematical model of a formula, and updates the value D to the latest time slot conflict random characteristic value of the channel. Then returns to perform step 7.
In the above example, step 7 to step 11 are a cyclic process, and in the automatic frequency hopping mode, when the frequency hopping time is less than the frequency hopping time T1 of the fixed frequency hopping mode, the system detects and updates the time slot collision random eigenvalue of the two channels in real time, and selects the channel with a smaller eigenvalue to operate, thereby achieving the characteristic that the system gives the system the optimal receiving performance.
In the above embodiment, the initial value of the channel switching time T2 of the single channel receiver is less than T1.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

Claims (6)

1. An automatic frequency hopping AIS single channel receiver comprising: GPS radio frequency front end, GPS receiving module, AIS radio frequency front end, AIS receiving module and baseband information processing module, its characterized in that: the GPS radio frequency front end is connected with a GPS receiving module, the GPS receiving module is connected with a baseband information processing module, and the GPS receiving module carries out down-conversion, signal amplification and analog-to-digital conversion on a radio frequency signal sent by the GPS radio frequency front end and then sends the signal to the baseband information processing module; the AIS radio frequency front end is connected with an AIS receiving module, the AIS receiving module is connected with a baseband information processing module, and the AIS receiving module carries out filtering, down-conversion, intermediate frequency filtering and analog-to-digital conversion on radio frequency signals sent from the AIS radio frequency front end and then sends the radio frequency signals to the baseband information processing module; the method comprises the steps that a receiver receives AIS information alternately sent on two frequency channels, detects the congestion conditions of the two AIS channels, accordingly sets the receiver to work in a fixed frequency hopping mode or an automatic frequency hopping mode, when the AIS channels are in an unsaturated and non-congestion state, the receiver works in the fixed frequency hopping mode, and otherwise, the receiver enters the automatic frequency hopping mode; the receiver only has a group of AIS receiving units, the receiving units work alternately on two frequency points of AIS, the switching time on the two frequency points is dynamically adjusted according to the congestion and time slot conflict characteristic situation on each frequency point, and the processing steps of the automatic frequency hopping realization method are as follows:
step (1): the single-channel AIS receiver finishes initialization, starts working when working in a fixed frequency hopping mode, sets the frequency hopping interval time T value in the fixed frequency hopping mode to be T1, sets the system standard congestion rate P to be P1, and then enters the step (2);
step (2): the single-channel receiver is configured at a first frequency point A, the time length of working T1 is long, the baseband information processing module synchronously detects the load rate PA of a channel A in a T1 time period, whether the load rate PA of the channel A is higher than P1 is judged, if yes, the system executes the step (4) and switches to an automatic frequency hopping mode, and if not, the process of the step (3) is executed;
and (3): configuring the single-channel receiver at a second frequency point B, working for T1 time duration, and then executing the process of the step (2);
and (4): the system switches to an automatic frequency hopping mode, and then enters the step (5);
and (5): the single-channel receiver is configured at a first frequency point A, the frequency hopping interval time T is T2, and the baseband information processing module is according to a formula
Figure FDA0002351648990000021
The time slot conflict random characteristic value D of the frequency point A is calculated by the mathematical modelAThen entering step (6); in the above formula, tiIndicating that the ith information is transmitted on the t-th time slot;
and (6): sheetThe channel receiver is configured at a second frequency point B, the frequency hopping interval time T is T2, and the baseband information processing module is according to the formula
Figure FDA0002351648990000022
The time slot conflict random characteristic value D of the frequency point B is calculated by the mathematical modelBThen entering step (7);
and (7): compare the updated DAAnd DBA value that if the former is small, the process of step (8) is performed, otherwise step (9) is performed;
configuring a single-channel receiver to work at a first frequency point A, and updating a frequency hopping interval time T-T2- β, wherein β is a number larger than 1;
step (9), configuring the single-channel receiver to work at a second frequency point B, and updating the frequency hopping interval time T-T2- β, wherein β is a number larger than 1 as in step (8);
step (10): judging whether the frequency hopping time T under the automatic frequency hopping mode is larger than the frequency hopping time T1 under the fixed frequency hopping mode, if so, executing the step (2); otherwise, executing step (11);
step (11): the receiver works in the set frequency point and the frequency hopping interval time, and the baseband information processing module works according to the formula
Figure FDA0002351648990000023
The time slot collision random characteristic value D in the time for executing the step is calculated and the value D is updated to the latest time slot collision random characteristic value of the channel, and then the step (7) is executed.
2. The AIS single-channel receiver with automatic frequency hopping according to claim 1, wherein the GPS radio frequency front end is externally connected with a GPS antenna, receives radio frequency signals and sends the processed radio frequency signals to a GPS receiving module; the AIS radio frequency front end is externally connected with an AIS antenna and used for receiving radio frequency signals, and the received radio frequency signals are sent to the AIS receiving module after front end processing is completed.
3. The automatic frequency hopping AIS single channel receiver according to claim 1, wherein the GPS radio frequency front end module includes: low noise amplifier and band pass filter, low noise amplifier receives the radio frequency signal who comes from the antenna to accomplish the front end signal amplification function, band pass filter and low noise amplifier are connected, realize the filtering to the front end signal, filter the noise, allow the effective signal of GPS frequency channel to pass through, and send the radio frequency signal after will handling to GPS receiving module.
4. The AIS single channel receiver with automatic frequency hopping according to claim 1, wherein the GPS receiving module comprises: a down converter, an intermediate frequency amplifier and an analog-to-digital converter; the down converter receives a radio frequency signal from a GPS radio frequency front end, outputs an intermediate frequency signal after frequency mixing, the intermediate frequency signal is subjected to signal amplification through an intermediate frequency amplifier, and then is subjected to conversion from an analog signal to a digital signal through an analog-to-digital converter, and the digital signal is input into the baseband information processing module.
5. The automatic frequency hopping AIS single channel receiver of claim 1, wherein said AIS radio frequency front end includes: the low-pass filter is connected with the AIS antenna and used for carrying out high-frequency filtering on the received wireless signals, the low-noise amplifier is connected with the low-pass filter and used for amplifying the radio-frequency signals passing through the low-pass filter and then sending the radio-frequency signals to the AIS receiving module.
6. The AIS single-channel receiver of claim 1, wherein the AIS receiving module comprises a sound meter filter, a down converter, an intermediate frequency filter and an analog-to-digital converter, the sound meter filter is connected with a low noise amplifier of an AIS radio frequency front end, receives a radio frequency signal, the signal is converted from the radio frequency signal to the intermediate frequency signal through the down converter, then the intermediate frequency signal is input to the intermediate frequency filter for band-pass filtering, and the analog-to-digital converter is connected with the intermediate frequency filter to perform digitization processing on the intermediate frequency signal sent from the intermediate frequency filter; the digital signal sent by the analog-to-digital converter is input to the baseband information processing module.
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CN201725029U (en) * 2009-10-30 2011-01-26 天津七一二通信广播有限公司 Shipborne AIS equipment adopting DDS frequency synthesizer
CN102243308A (en) * 2011-04-25 2011-11-16 上海迦美信芯通讯技术有限公司 Single-channel radiofrequency receiver and frequency planning method thereof
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