Digital selective call modulation and demodulation device

Abstract

The invention provides a digital selective call modulation and demodulation device, and relates to the technical field of marine safety communication, the device comprises a modulation function module, a demodulation function module and a network interface function module, the network interface function module comprises a receiver interface, a service control interface and a transmitter interface which are realized based on a preset network protocol, the service control interface performs signaling interaction and data transmission with an external service control system, the receiver interface receives to-be-demodulated data transmitted by an external receiver, and the demodulation function module demodulates the to-be-demodulated data to obtain demodulated data; the modulation function module modulates the to-be-modulated data to obtain message data, and the transmitter interface sends the message data to an external transmitter. The method does not depend on hardware equipment any more, modulation-demodulation and adaptation services can be completed through network modulation, the limitation defect of a use scene is overcome, and the use reliability, the service expansibility and the deployment flexibility of a GMDSS service system can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of maritime safety communications, and in particular to a digital selective calling modulation and demodulation device. Background Art

[0002] The Global Maritime Distress and Safety System (GMDSS) is an indispensable means to ensure the safety of ships at sea. Through maritime safety communication facilities, it can effectively support daily ship traffic safety management and maritime law enforcement, and broadcast maritime safety information, which is extremely important for preventing maritime accidents. GMDSS is mainly composed of three parts: satellite communication system, ground radio communication system and maritime safety information broadcasting system.

[0003] Digital Selective Calling Terminals (DSC) is a standard for transmitting predefined digital information through medium frequency (MF), high frequency (HF) and very high frequency (VHF) maritime radio systems. Ships use the DSC calling system for distress alarms and distress relays, and coast stations use the DSC calling system to receive DSC messages and transmit receipt confirmation signals.

[0004] Existing DSC equipment uses dedicated modem components to achieve modulation and demodulation. Dedicated modem components rely on dedicated hardware devices and rely on dedicated lines for transmission, which has limited usage scenarios. Summary of the invention

[0005] The present invention provides a digital selective call modulation and demodulation device, which is used to solve the defects that a dedicated modem device depends on dedicated hardware equipment, relies on a dedicated line for transmission, and has limited use scenarios.

[0006] The present invention provides a digital selective call modulation and demodulation device, comprising a modulation function module, a demodulation function module and a network interface function module. The network interface function module comprises a receiver interface, a service control interface and a transmitter interface implemented based on a preset network protocol. The service control interface performs signaling interaction and data transmission with an external service control system. The receiver interface is used to receive data to be demodulated transmitted by an external receiver and send the data to be demodulated to the demodulation function module. The demodulation function module is used to demodulate the data to be demodulated to obtain demodulated data. The modulation function module is used to modulate the data to be modulated to obtain message data and send it to the transmitter interface. The transmitter interface is used to send the message data to an external transmitter.

[0007] As an embodiment, the demodulation function module is used to demodulate the data to be demodulated to obtain demodulated data, including: Performing synchronization detection on the data to be demodulated to determine whether the data to be demodulated meets a preset synchronization condition; The data to be demodulated that meets the synchronization condition is demodulated based on time diversity and a preset demodulation method to obtain demodulated data.

[0008] As an embodiment, the data to be demodulated includes a dot pattern sequence, the demodulation function module includes a local dot pattern sequence corresponding to the dot pattern, and the synchronous detection of the data to be demodulated to determine whether the data to be demodulated meets the preset synchronization condition includes: Performing coarse synchronization on the data to be demodulated based on the local dot pattern sequence to obtain a coarse synchronization position of the data to be demodulated; Performing bit synchronization on the data to be demodulated according to the coarse synchronization position to determine the bit synchronization position of the data to be demodulated; Determining a phase adjustment sequence of the data to be demodulated according to the bit synchronization position; The phase adjustment sequence is demodulated to determine whether the phase adjustment sequence is detected correctly. If it is correct, it is determined that the data to be demodulated meets the preset synchronization condition and the detection is stopped; otherwise, the bit synchronization position is delayed, the updated phase adjustment sequence is determined and the detection is continued until the detection is correct or the delay number of the bit synchronization position reaches a preset value. If the delay number of the bit synchronization position reaches the preset value and the updated phase adjustment sequence is still not detected correctly, it is determined that the data to be demodulated does not meet the preset synchronization condition.

[0009] As an embodiment, performing bit synchronization on the data to be demodulated according to the coarse synchronization position to determine the bit synchronization position of the data to be demodulated includes: Performing bit synchronization on the data to be demodulated according to the coarse synchronization position; Based on a predetermined frequency offset estimation result, frequency offset compensation is performed on the data to be demodulated that has completed bit synchronization, and a bit synchronization position of the data to be demodulated after compensation is determined.

[0010] As an embodiment, the demodulating the data to be demodulated that meets the synchronization condition based on time diversity and a preset demodulation method to obtain demodulated data includes: Determining whether the to-be-demodulated data meeting the synchronization condition is diversity based on the time diversity, and if it is diversity, performing soft information merging; The combined data to be demodulated or the non-diversity data to be demodulated are demodulated based on a preset demodulation method to obtain demodulated data.

[0011] As an embodiment, after obtaining the demodulated data, the method further includes: The demodulated data is checked based on an error checking method to obtain a check result.

[0012] As an embodiment, the calling frequency band of the external transmitter includes the MF frequency band, the HF frequency band and the VHF frequency band. If the calling frequency band is the MF frequency band or the HF frequency band, the dot pattern calling length of the message data is 200 bits or 20 bits. If the calling frequency band is the VHF frequency band, the dot pattern calling length of the message data is 200 bits.

[0013] As an embodiment, the receiver interface, the service control interface and the transmitter interface all include IP network interfaces.

[0014] As an embodiment, the network interface function module is also used to respond to management and control instructions issued by the user based on any network node to implement one or more functions of remote status viewing, fault diagnosis, upgrade maintenance and business operations.

[0015] As an embodiment, the modulation function module, the demodulation function module and the network interface function module are deployed on a server of a preset architecture.

[0016] The present invention provides a digital selective call modem device, which is software-based through a modulation function module, a demodulation function module and a network interface function module, and is network-based based on a receiver interface, a service control interface and a transmitter interface implemented based on a preset network protocol. The digital selective call modem device is no longer dependent on hardware devices, and can complete modulation and demodulation and adaptation services through network calls, thereby solving the limitations and defects of usage scenarios, and can effectively improve the use reliability, service scalability and deployment flexibility of the GMDSS service system, and adapt to the development needs of system networking and softwareization. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 It is a structural schematic diagram of an existing DSC device.

[0019] Figure 2 This is one of the structural schematic diagrams of a digital selective call modulation and demodulation device provided by the present invention.

[0020] Figure 3 This is the second structural schematic diagram of a digital selective call modulation and demodulation device provided by the present invention.

[0021] Figure 4 This is one of the demodulation flow diagrams of the demodulation function module provided by the present invention.

[0022] Figure 5 This is the second demodulation flow diagram of the demodulation function module provided by the present invention.

[0023] In the figure: 100 - modulation function module, 200 - demodulation function module, 300 - network interface function module, 310 - receiver interface, 320 - service control interface, 330 - transmitter interface. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Figure 1 It is a structural diagram of the existing DSC equipment, such as Figure 1 As shown in the figure, the components of existing DSC equipment are all hardware, and the modem mainly realizes the conversion between digital baseband signals and audio (1700Hz) frequency shift keying (FSK) signals. There are generally two methods to realize DSC modulation and demodulation, one is called direct frequency modulation method and the other is called frequency keying method. Direct frequency modulation method is to use the input baseband pulse to control a certain parameter of an oscillator to achieve the purpose of changing the oscillation frequency. Frequency keying method is to use the switch circuit controlled by the rectangular pulse sequence to select two different independent frequency sources. Generally speaking, the frequency keying method uses two independent oscillators to obtain a phase-discontinuous FSK signal; while the direct frequency modulation method f1 and f2 are generated by the same resonant circuit, and a phase-continuous FSK signal is obtained.

[0026] The modulation and demodulation functions of existing DSC equipment are implemented using dedicated modem devices, which rely on dedicated hardware devices. The existing technology relies on dedicated hardware devices and cannot be implemented on general commercial X86 servers. Its transceiver interface is an analog audio interface and cannot be called over the network. Dedicated modem devices are implemented using traditional dedicated signal processing circuit technology, relying on dedicated chips such as single-chip microcomputers and digital signal processing. They have diverse interfaces, single functions, and rely on dedicated lines for transmission, which determines the limitations of their use and has the following defects: 1) The realization of business functions depends on dedicated hardware. Often one device (module) can only complete one business, with single functions, non-interchangeability, inflexible adjustment, and difficult expansion; 2) Existing technologies rely on dedicated equipment, and their interfaces and protocols are diverse and difficult to unify, making it difficult to achieve centralized management and allocation of channel resources, and unable to meet the development needs of intelligent system control; 3) The existing technology has high costs for system maintenance, testing, maintenance, upgrading and replacement, and has high requirements for testing equipment and technical personnel; 4) In terms of system deployment, existing technologies rely on dedicated lines for data transmission, cannot be seamlessly connected to IP networks, cannot be directly transmitted on IP networks, have high requirements for locations, and cannot be flexibly deployed; 5) In the prior art, hard detection is usually used for signal detection at the receiving end, and a direct judgment is made to compare whether the dot patterns of 0 / 1 are consistent, thereby determining whether a signal is captured; 6) In the prior art, in the demodulation of the signal at the receiving end, non-coherent demodulation is usually performed directly, ignoring the influence of the system frequency offset and the time selective fading channel during the transmission process on the signal.

[0027] To solve at least one of the above-mentioned defects, the present invention provides a digital selective call modulation and demodulation device, which is described in detail below with reference to the accompanying drawings.

[0028] Figure 2 FIG. 1 is one of the structural diagrams of a digital selective call modulation and demodulation device provided by the present invention. Figure 2 As shown, the present invention provides a digital selective call modulation and demodulation device, including a modulation function module 100, a demodulation function module 200 and a network interface function module 300, wherein the network interface function module 300 includes a receiver interface 310, a service control interface 320 and a transmitter interface 330 implemented based on a preset network protocol.

[0029] The service control interface 320 performs signaling interaction and data transmission with an external service control system. The external service control system can be mounted on any network node, and the external service control system performs signaling interaction and data transmission with the service control interface 320 based on the network protocol to implement functions such as signaling verification, protocol analysis, and packet assembly.

[0030] The receiver interface 310 is used to receive the data to be demodulated transmitted by the external receiver, and send the data to be demodulated to the demodulation function module 200. The demodulation function module 200 is used to demodulate the data to be demodulated to obtain the demodulated data. The data to be demodulated can be pulse code modulation (PCM) audio data. The demodulation function module 200 can demodulate the PCM audio data into networked DSC message data. After the demodulation function module 200 completes the data demodulation, it feeds back the receiving status information to the receiver interface 310.

[0031] The modulation function module 100 is used to modulate the data to be modulated, obtain the message data and send it to the transmitter interface 330, and the transmitter interface 330 is used to send the message data to the external transmitter. The data to be modulated is PCM audio data. The external service control system sends the PCM audio data to the modulation function module 100 through the service control interface 320. The modulation function module 100 modulates the PCM audio data into networked DSC message data and sends it to the transmitter interface 330. The transmitter interface 330 sends the modulated DSC message data to the external transmitter based on the standard real-time transport protocol (RTP) so that the external transmitter can transmit. The external transmitter feeds back the transmission status information to the transmitter interface 330.

[0032] It can be understood that the present invention software-izes the digital selective call modem device through the modulation function module 100, the demodulation function module 200 and the network interface function module 300, and networks the digital selective call modem device based on the receiver interface 310, the service control interface 320 and the transmitter interface 330 implemented based on the preset network protocol. It is no longer dependent on hardware equipment, and can complete modulation and demodulation and adaptation services through network calls, thereby solving the limitations and defects of the usage scenarios, and can effectively improve the reliability, service scalability and deployment flexibility of the GMDSS service system, and meet the development needs of system networking and softwareization.

[0033] Figure 3 FIG. 2 is a second structural diagram of a digital selective call modulation and demodulation device provided by the present invention. Figure 3 As shown, based on the above embodiment, as an optional embodiment, the receiver interface 310, the service control interface 320 and the transmitter interface 330 all include IP network interfaces. Correspondingly, the network interface function module 300 is an Internet Protocol (IP) interface function module.

[0034] It is understandable that the present invention converts the service data of the DSC device into IP, and can directly transmit the service data losslessly, ensure the high sampling rate of the sound source, and realize high-fidelity audio transmission, which solves the defect that in the traditional transceiver service process, there is more than one A / D and D / A conversion between the voice transmission of each device, which are all lossy conversions and cannot realize high-fidelity transmission. The present invention is used in conjunction with a new generation of networked transceivers and a new generation of GMDSS service systems to easily realize IP data flow.

[0035] Based on the above embodiment, as an optional embodiment, the calling frequency band of the external transmitter includes the MF frequency band, the HF frequency band and the VHF frequency band. If the calling frequency band is the MF frequency band or the HF frequency band, the dot pattern calling length of the message data is 200 bits or 20 bits. If the calling frequency band is the VHF frequency band, the dot pattern calling length of the message data is 200 bits.

[0036] The DSC message data includes a dot pattern, a phase adjustment sequence, a call content, a sequence end character and an error check character arranged in sequence, wherein the dot pattern is an alternating BY or YB sequence bit synchronization signal (i.e., 010101... or 101010...). The phase adjustment sequence provides phase information for the receiver in the GMDSS service system to allow the phase adjustment of the correction bit and accurately determine the position of the character in the call sequence. At the same time, in order to reduce pseudo-synchronization caused by bit errors in the dot pattern, character synchronization should be obtained using character recognition rather than recognizing changes in, for example, the dot pattern.

[0037] The phase adjustment sequence consists of specific characters sent alternately in the DX and RX positions. Six DX characters are sent. The phase adjustment character in the DX position is the signal with symbol number 125 in Table 2. The phase adjustment character in the RX position specifies the starting position of the information sequence (i.e., the format indicator) and is composed of the signals with symbol numbers 111, 110, 109, 108, 107, 106, 105 and 104 in Table 2. Phase adjustment is considered to be completed when two DXs and one RX, two RXs and one DX, or three RXs are successfully received in the DX or RX position, respectively. The three phase adjustment characters can be in consecutive or non-consecutive positions, but in both cases, all bits of the phase adjustment sequence should be detected to obtain the correct 3-character code pattern. The call is rejected only when the correct code pattern cannot be found in any position of the phase adjustment sequence.

[0038] The sequence end characters have the following meanings: 117: RCK RQ This call requires receipt confirmation and is only used for single calls and automatic / semi-automatic calls; 122: RCK BQ This call is a response to a call requesting confirmation of receipt. It is used for single calls, automatic / semi-automatic calls, and all distress forwarding confirmations. 127: For all other calls.

[0039] The end-of-sequence character is transmitted three times in succession in the DX position and once in the RX position.

[0040] The 7 information bits of the error check character shall be equal to the least significant bit of the modulo 2 sum of the corresponding bits of all information characters (i.e. vertical even parity check). The format indicator and the end of sequence character are information characters. The phase adjustment character and the retransmit (RX) character are not information characters. Only one format indicator and one end of sequence character are used. The error check character shall also be sent in the DX and RX positions.

[0041] It can be understood that the present invention provides a software modulation solution that no longer relies on hardware devices and can complete modulation through network calls, thereby solving the limitations of usage scenarios.

[0042] Figure 4 It is one of the demodulation flow diagrams of the demodulation function module provided by the present invention, such as Figure 4 As shown, based on the above embodiment, as an optional embodiment, the demodulation function module 200 is used to demodulate the data to be demodulated to obtain demodulated data, including the following steps.

[0043] Step S1, performing synchronization detection on the data to be demodulated to determine whether the data to be demodulated meets the preset synchronization condition. Specifically, synchronization detection can be performed based on a dot pattern and a phase adjustment sequence to determine whether the data to be demodulated meets the synchronization condition specified by the GMDSS service system.

[0044] Step S2, demodulating the data to be demodulated that meets the synchronization condition based on time diversity and a preset demodulation method to obtain demodulated data.

[0045] As an optional embodiment, the demodulating the data to be demodulated that meets the synchronization condition based on time diversity and a preset demodulation method to obtain demodulated data includes: Step S21, judging whether the to-be-demodulated data meeting the synchronization condition is diversity based on the time diversity, and if it is diversity, performing soft information merging.

[0046] Step S22: demodulate the combined data to be demodulated or the non-diversity data to be demodulated based on a preset demodulation method to obtain demodulated data.

[0047] The principle of time diversity is to divide the time into several time periods (time slices) on the same channel, and each time period is allocated to a specific signal or data stream. In each time slice, only one signal is allowed to be transmitted, and other signals are transmitted in their respective time slices. According to the time slice allocation rules, the received signals are demultiplexed to separate the signals in different time slices.

[0048] The present invention determines whether the data to be demodulated is transmitted using a time diversity scheme. If so, soft information merging is required for the data to be demodulated. If not, demodulation can be performed directly based on a preset demodulation method. The preset demodulation method can use an FSK demodulation method. The principle of the FSK demodulation method is that within a symbol, the received signal is correlated with the signals of two frequency points respectively. The frequency point with the larger correlation value determines that the value within the symbol is the value corresponding to the frequency point. Among them, soft information merging for the data to be demodulated specifically includes merging the same content according to the diversity method.

[0049] It can be understood that the present invention improves the accuracy of judgment through soft detection and can achieve better detection performance.

[0050] Figure 5 FIG. 2 is a second schematic diagram of a demodulation flow of a demodulation function module provided by the present invention. Figure 5 As shown, based on the above embodiment, as an optional embodiment, the data to be demodulated includes a dot pattern sequence, the demodulation function module 200 includes a local dot pattern sequence corresponding to the dot pattern, and the synchronization detection of the data to be demodulated to determine whether the data to be demodulated meets the preset synchronization condition includes: Step S11, performing coarse synchronization on the data to be demodulated based on the local dot pattern sequence to obtain a coarse synchronization position of the data to be demodulated.

[0051] The dot pattern is a known 01 or 10 alternating sequence, which exists in two types: 20 bits and 200 bits. Therefore, signal detection of two bit lengths is performed in parallel. The received sequence is correlated with the local dot pattern modulation sequence by sample point sliding, and the soft information obtained by correlation is accumulated to obtain the sum value. s , if the value s Greater than the set threshold T , then record the position as k , continue to slide back, each time a symbol is added, the sum of the soft information in the sliding window Always greater than the threshold T , until you slide back K Stop detection after symbols.

[0052] Step S12, performing bit synchronization on the data to be demodulated according to the rough synchronization position, and determining the bit synchronization position of the data to be demodulated. Performing optimal sampling point search on the rough synchronization position, and summing a series of soft information Find the position of the maximum value in the equation, and then calculate the starting position of the dot pattern. , completing bit synchronization.

[0053] As an optional embodiment, performing bit synchronization on the data to be demodulated according to the coarse synchronization position to determine the bit synchronization position of the data to be demodulated includes: Step S121, performing bit synchronization on the data to be demodulated according to the coarse synchronization position.

[0054] Step S122, performing frequency offset compensation on the data to be demodulated that has completed bit synchronization based on a predetermined frequency offset estimation result, and determining a bit synchronization position of the data to be demodulated after compensation.

[0055] The GMDSS service system has frequency deviation. The initial phase of each FSK transmission symbol is different, and when the signal value changes over time due to time selective fading during channel transmission, the frequency deviation is estimated and compensated for after bit synchronization.

[0056] Assume that the received signal sequence is , then the signal sequence of the receiving end-point pattern part is ,in is the length of the end point pattern, and the end point pattern is , the signal symbol rate is , the number of FFT points is N , then the frequency offset estimation result is:

[0057] in, f is the frequency offset estimation result, for y The conjugation signal sequence.

[0058] After determining the frequency offset estimation result, the received signal sequence The effective signal part in the frequency deviation compensation is recorded M is the maximum total length of the call sequence, signal sequence The expression is as follows:

[0059] Step S13, determining the phase adjustment sequence of the data to be demodulated according to the bit synchronization position. Assuming that the length of the dot pattern is 20 or 200 bits, and the bit synchronization position is in the middle of 200 symbols; taking the bit synchronization position as the starting point, the phase adjustment sequence is obtained.

[0060] Step S14, demodulate the phase adjustment sequence to determine whether the phase adjustment sequence is detected correctly. If correct, determine that the data to be demodulated meets the preset synchronization condition and stop detecting. Otherwise, delay the bit synchronization position, determine the updated phase adjustment sequence and continue detecting until the detection is correct or the delay number of the bit synchronization position reaches the preset value. If the delay number of the bit synchronization position reaches the preset value and the updated phase adjustment sequence is still not detected correctly, determine that the data to be demodulated does not meet the preset synchronization condition.

[0061] The phase adjustment sequence is demodulated based on the FSK demodulation method, and it is determined whether the phase adjustment sequence is detected correctly (when two DXs and one RX, two RXs and one DX, or three RXs are successfully received, the phase adjustment is considered to be completed). If the phase adjustment sequence is detected correctly, the detection is stopped; otherwise, one symbol is delayed backwards, and the phase adjustment sequence is continued for detection, with a maximum delay of 200 symbols. If the phase adjustment sequence is not detected correctly after 200 symbols, the call is rejected.

[0062] As an optional embodiment, after obtaining the demodulated data, the method further includes: The demodulated data is checked based on the error checking method to obtain the check result. After the check sequence is demodulated, error checking is performed. The error checking process is: the demodulated signal is used to generate error checking bits, and it is determined whether the generated error checking bits are equal to the demodulated error checking bits. If they are equal, the check is correct, otherwise the check is wrong.

[0063] It can be understood that the present invention provides a variable frequency offset estimation and compensation technology for DSC demodulation, which can further improve the demodulation performance by estimating the frequency offset of the signal that has completed bit synchronization and performing frequency compensation on the useful signal at the receiving end based on the estimated frequency offset.

[0064] Based on the above embodiments, as an optional embodiment, the network interface function module 300 is also used to respond to management and control instructions issued by the user based on any network node to implement one or more functions of remote status viewing, fault diagnosis, upgrade maintenance and business operations.

[0065] It can be understood that the present invention can monitor and manage authorized devices at any node in the network, view the system operating status and operating parameters, and realize intelligent and centralized management and control; users can log in remotely to view the status, diagnose faults, and upgrade and maintain.

[0066] Based on the above embodiment, as an optional embodiment, the modulation function module, the demodulation function module and the network interface function module are deployed on a server of a preset architecture. The server can specifically be a server of X86 architecture. The present invention makes the DSC modulation and demodulation program software-based, network-based and service-based, and deploys it on a server of X86 architecture. The business scale and function can be flexibly configured and adjusted as needed. When the server is in operation, it has the technical effect corresponding to the digital selective call modulation and demodulation device, which will not be described in detail in this embodiment.

[0067] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0068] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A digital selective call modem, characterized in that: It includes a modulation function module, a demodulation function module and a network interface function module. The network interface function module includes a receiver interface, a service control interface and a transmitter interface implemented based on a preset network protocol. The service control interface performs signaling interaction and data transmission with an external service control system. The receiver interface is used to receive data to be demodulated transmitted by an external receiver and send the data to be demodulated to the demodulation function module. The demodulation function module is used to demodulate the data to be demodulated to obtain demodulated data. The modulation function module is used to modulate the data to be modulated, obtain message data and send it to the transmitter interface, and the transmitter interface is used to send the message data to an external transmitter.

2. A digital selective call modulation and demodulation device according to claim 1, characterized in that: The demodulation function module is used to demodulate the data to be demodulated to obtain demodulated data, including: Performing synchronization detection on the data to be demodulated to determine whether the data to be demodulated meets a preset synchronization condition; The data to be demodulated that meets the synchronization condition is demodulated based on time diversity and a preset demodulation method to obtain demodulated data.

3. A digital selective call modulation and demodulation device according to claim 2, characterized in that: The data to be demodulated includes a dot pattern sequence, the demodulation function module includes a local dot pattern sequence corresponding to the dot pattern, and the synchronization detection of the data to be demodulated to determine whether the data to be demodulated meets a preset synchronization condition includes: Performing coarse synchronization on the data to be demodulated based on the local dot pattern sequence to obtain a coarse synchronization position of the data to be demodulated; Performing bit synchronization on the data to be demodulated according to the coarse synchronization position to determine the bit synchronization position of the data to be demodulated; Determining a phase adjustment sequence of the data to be demodulated according to the bit synchronization position; The phase adjustment sequence is demodulated to determine whether the phase adjustment sequence is detected correctly. If it is correct, it is determined that the data to be demodulated meets the preset synchronization condition and the detection is stopped; otherwise, the bit synchronization position is delayed, the updated phase adjustment sequence is determined and the detection is continued until the detection is correct or the delay number of the bit synchronization position reaches a preset value. If the delay number of the bit synchronization position reaches the preset value and the updated phase adjustment sequence is still not detected correctly, it is determined that the data to be demodulated does not meet the preset synchronization condition.

4. A digital selective call modulation and demodulation device according to claim 3, characterized in that: The step of performing bit synchronization on the data to be demodulated according to the coarse synchronization position to determine the bit synchronization position of the data to be demodulated includes: Performing bit synchronization on the data to be demodulated according to the coarse synchronization position; Based on a predetermined frequency offset estimation result, frequency offset compensation is performed on the data to be demodulated that has completed bit synchronization, and a bit synchronization position of the data to be demodulated after compensation is determined.

5. A digital selective call modulation and demodulation device according to claim 2, characterized in that: The method of demodulating the data to be demodulated that meets the synchronization condition based on time diversity and a preset demodulation method to obtain demodulated data includes: Based on the time diversity, determining whether the to-be-demodulated data meeting the synchronization condition is diversity, and if it is diversity, performing soft information merging; The combined data to be demodulated or the non-diversity data to be demodulated are demodulated based on a preset demodulation method to obtain demodulated data.

6. A digital selective call modem device according to claim 5, characterized in that: After obtaining the demodulated data, the method further includes: The demodulated data is checked based on an error checking method to obtain a check result.

7. A digital selective call modulation and demodulation device according to any one of claims 1 to 6, characterized in that: The calling frequency band of the external transmitter includes the MF frequency band, the HF frequency band and the VHF frequency band. If the calling frequency band is the MF frequency band or the HF frequency band, the dot pattern calling length of the message data is 200 bits or 20 bits. If the calling frequency band is the VHF frequency band, the dot pattern calling length of the message data is 200 bits.

8. A digital selective call modulation and demodulation device according to any one of claims 1 to 6, characterized in that: The receiver interface, the service control interface and the transmitter interface all include IP network interfaces.

9. A digital selective call modem device according to claim 8, characterized in that: The network interface function module is also used to respond to the management and control instructions issued by the user based on any network node to implement one or more functions of remote status viewing, fault diagnosis, upgrade maintenance and business operations.

10. A digital selective call modem device according to claim 1, characterized in that: The modulation function module, the demodulation function module and the network interface function module are deployed on a server of a preset architecture.

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