Long-distance carrier digital communication system

Abstract

The invention relates to a long-distance carrier wave digital communication system which comprises a low-voltage power supply and a plurality of digital telephones, and the low-voltage power supply and the digital telephones are connected with a carrier wave bus. The digital telephone comprises a power supply base plate, an audio processing plate, a carrier communication plate and telephone input and output accessories, wherein the power supply base plate, the audio processing plate and the carrier communication plate are connected with one another through interfaces; wherein serial port communication is carried out between the power supply base plate and the carrier communication plate, the communication content comprises time, on-off states, audio data, a bus occupation mode sent to the carrier communication plate on the power supply base plate and a local set control mode returned to the power supply base plate by the carrier communication plate. The long-distance carrier digital call system is free of a central node and a switch, low-voltage power supply is achieved, hot plugging can be achieved, and installation and maintenance are easy; multi-party conversation can be realized at the same time, and the longest communication distance between the telephones can reach several kilometers.

Description

Technical Field

[0001] The present invention relates to the field of digital communication, and in particular to a long-distance carrier digital communication system. Background Art

[0002] The communication distance of carrier digital telephone communication, the number of connected phones, the number of phones that can talk at the same time, and the ease of installation and maintenance have always been the core indicators for evaluating the quality of the carrier communication system. In the general process, the carrier signal is usually coupled to the power line. When the transmission distance is longer, the signal attenuation will become more serious. Therefore, the communication distance between points is limited. However, in order to extend the communication distance, a repeater is generally used to extend the signal. However, the separate access to the relay circuit board not only increases the system cost but also increases the difficulty of installation and maintenance.

[0003] Based on this, it is necessary to propose a solution to overcome the shortcomings of the current existing technology. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a long-distance carrier digital communication system.

[0005] In order to achieve the above object, the long distance carrier digital communication system of the present invention is as follows:

[0006] The long-distance carrier digital call system has the following main features: it includes a low-voltage power supply and several digital telephones, and the low-voltage power supply and digital telephones are all connected to the carrier bus; the digital telephones include a power baseboard, an audio processing board, a carrier communication board and telephone input and output accessories, and the power baseboard, audio processing board and carrier communication board are all interconnected through interfaces; wherein serial port communication is performed between the power baseboard and the carrier communication board, and the communication content includes time, switch status, audio data, bus occupancy mode sent from the power baseboard to the carrier communication board, and local setting control mode returned from the carrier communication board to the power baseboard.

[0007] Preferably, the system is the application layer software of the carrier communication board and is designed with a baseboard serial port receiving task, and the processing flow is as follows:

[0008] The carrier communication board described in (1.1) receives the task and determines whether there is a data frame from the power baseboard. If not, repeat this step, otherwise, enter (1.2);

[0009] (1.2) Determine whether the current data frame is an AT command frame. If so, execute the corresponding AT command. Otherwise, directly enter (1.3);

[0010] (1.3) Determine again whether the data frame of the power baseboard is included. If so, cache the data of the power baseboard. Otherwise, return to step (1.1).

[0011] Preferably, the system is an application layer software design of the carrier communication board with a carrier data receiving task, and the processing flow is as follows:

[0012] (2.1) Start executing the carrier receiving task and determine whether there is a carrier frame at present. If not, repeat this step. Otherwise, directly enter (2.2);

[0013] (2.2) Extracting carrier data, controlling the sending time, updating the data list, obtaining the bus occupation mode of other machines, setting the local state and other machine table, forwarding carrier data, and sending the other machine data to the power supply backplane are executed in sequence, thereby completing the reception of carrier data.

[0014] Preferably, the system is an application layer software design of the carrier communication board with a carrier active sending task, and the processing flow is as follows:

[0015] (3.1) Start executing the carrier active sending task, extract the current operating status of the digital telephone and generate the occupied carrier control word;

[0016] (3.2) Determine whether it is necessary to occupy the carrier line to send the task. If not, directly perform short delay processing. Otherwise, enter (3.3);

[0017] (3.3) Determine whether the sending time of the current corresponding task has arrived. If so, perform carrier sending processing and then short delay. Otherwise, perform short delay processing directly.

[0018] Preferably, the carrier frame is generated and sent in the following manner:

[0019] (2.1.1) The carrier transmission task of receiving instructions or data begins;

[0020] (2.1.2) Set the address, identification, and sending station address of the next station, and fill in the transparent word and magic word;

[0021] (2.1.3) Set the current frame as the downlink frame and set the data source address;

[0022] (2.1.4) Fill the payload with the serial port buffer and calculate the cyclic redundancy check code crc, payload and frame byte count;

[0023] (2.1.5) Carrier transmission: the carrier transmission task of the corresponding instruction or data is completed.

[0024] Preferably, when the carrier acquires a new frame, the sending time point is calculated in the following manner:

[0025] (2.2.1) Start calculating the sending time point;

[0026] (2.2.2) Sort the current data source list and calculate the sequence number of the received frame data source after sorting;

[0027] (2.2.3) Determine whether the current data source sequence number is the largest. If so, the reference of the current sending time point is the remainder of the system time% sending cycle. Otherwise, the current reference remains unchanged.

[0028] (2.2.4) Calculate the sequence number of the local machine after sorting, and determine whether the current local sequence number is the largest. If so, the sending time point = (reference time + sorting number × time slice) % sending period. Otherwise, the sending time point of the local machine is not adjusted.

[0029] (2.2.5) Calculation of the sending time point is completed.

[0030] Preferably, the carrier data source list is updated in the following manner:

[0031] (2.3.1) Start updating the data source list;

[0032] (2.3.2) Determine whether the current data source address exists. If not, add a new data source. Otherwise, go directly to (2.3.3);

[0033] (2.3.3) Determine whether the current identifier is a new identifier. If not, end the list update directly. Otherwise, go directly to (2.3.4);

[0034] (2.3.4) Calculate the current identification interval, where the audio missing frame count is the difference between the new and old identifications;

[0035] (2.3.5) Determine whether there is a missing frame at present. If yes, calculate the missing audio time and accumulate the missing audio time. Otherwise, directly enter (2.3.6);

[0036] (2.3.6) Determine whether the current interval time is larger. If so, replace the maximum identification interval first. Otherwise, directly record the current identification system time;

[0037] (2.3.7) Set the remaining time for deleting the data source and end the data source list update.

[0038] The long-distance carrier digital call system of the present invention has no central node, no switch, low-voltage power supply, hot-swappable, and simple installation and maintenance. The system does not specify the wiring method, and communication can be achieved by simply hanging it on the power supply line, which simplifies installation and maintenance. The number of telephones connected to the system at the same time can reach dozens, which can meet most application scenarios; multi-party calls can be realized at the same time (limited to a maximum of three parties at the same time due to the influence of carrier bandwidth); telephones at any location can be interchanged, and installation and maintenance are further simplified; the longest communication distance between telephones can reach several kilometers; and during the call, any telephone can start broadcasting at the same time, and all telephones in the system can receive the broadcasting; and a driver's telephone is set in the system, which can be inserted into the three-party call and can also start the alarm state of the entire network. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a structural block diagram of the long-distance carrier digital communication system of the present invention.

[0040] Figure 2 The figure is a schematic diagram of the structure of a single digital telephone of the present invention.

[0041] Figure 3 It is a schematic diagram of the composition structure of the power base plate of the present invention.

[0042] Figure 4 The figure is a schematic diagram of the structure of the audio processing board of the present invention.

[0043] Figure 5 It is a schematic diagram of the composition structure of the carrier communication board of the present invention.

[0044] Figure 6 A schematic diagram of the data structure for communication between the carrier communication board and the power baseboard defined in the present invention.

[0045] Figure 7 A schematic diagram of the application layer design task of the carrier communication board of the present invention.

[0046] Figure 8 The figure is a schematic diagram of a possible digital telephone wiring method in practical application of the long-distance carrier digital communication system of the present invention.

[0047] Fig. 9 It is a schematic diagram of the data structure of the carrier receiving and transmitting frame of the present invention.

[0048] Fig.10 It is a schematic diagram of a data source information list of the present invention.

[0049] Fig.11 The present invention is a flowchart of the process of carrier frame generation and transmission.

[0050] Fig.12This is a flow chart of the update process of the data source list of the present invention.

[0051] Fig.13 It is a schematic diagram of the worst wiring method in practical application of the long-distance carrier digital communication system of the present invention.

[0052] Fig.14 This is a flow chart for calculating the sending time point within the cycle of the present invention.

[0053] Fig.15 The figure is a schematic diagram of verifying a three-party conversation in actual application of the long-distance carrier digital conversation system of the present invention. DETAILED DESCRIPTION

[0054] In order to more clearly describe the technical content of the present invention, further description is given below in conjunction with specific embodiments.

[0055] Before describing in detail embodiments according to the present invention, it should be noted that, hereinafter, the terms "comprises", "includes" or any other variations are intended to cover non-exclusive inclusion, whereby a process, method, article or apparatus comprising a series of elements includes not only these elements, but also other elements not explicitly listed or inherent to such process, method, article or apparatus.

[0056] See also Figure 1 As shown, the long-distance carrier digital call system includes a low-voltage power supply and several digital telephones, and the low-voltage power supply and digital telephones are all connected to the carrier bus; the digital telephones include a power baseboard, an audio processing board, a carrier communication board and telephone input and output accessories, and the power baseboard, audio processing board and carrier communication board are all interconnected through interfaces; wherein serial port communication is performed between the power baseboard and the carrier communication board, and the communication content includes time, switch status, audio data, bus occupancy mode sent from the power baseboard to the carrier communication board, and local setting control mode returned by the carrier communication board to the power baseboard.

[0057] As a preferred embodiment of the present invention, the system is an application layer software design of the carrier communication board with a baseboard serial port receiving task, and the processing flow is as follows:

[0058] The carrier communication board described in (1.1) receives the task and determines whether there is a data frame from the power baseboard. If not, repeat this step, otherwise, enter (1.2);

[0059] (1.2) Determine whether the current data frame is an AT command frame. If so, execute the corresponding AT command. Otherwise, directly enter (1.3);

[0060] (1.3) Determine again whether the data frame of the power baseboard is included. If so, cache the data of the power baseboard. Otherwise, return to step (1.1).

[0061] As a preferred embodiment of the present invention, the system is an application layer software design of the carrier communication board with a carrier data receiving task, and the processing flow is as follows:

[0062] (2.1) Start executing the carrier receiving task and determine whether there is a carrier frame at present. If not, repeat this step. Otherwise, directly enter (2.2);

[0063] (2.2) Extracting carrier data, controlling the sending time, updating the data list, obtaining the bus occupation mode of other machines, setting the local state and other machine table, forwarding carrier data, and sending the other machine data to the power supply backplane are executed in sequence, thereby completing the reception of carrier data.

[0064] As a preferred embodiment of the present invention, the system is the application layer software of the carrier communication board, which is designed with a carrier active sending task, and the processing flow is as follows:

[0065] (3.1) Start executing the carrier active sending task, extract the current operating status of the digital telephone and generate the occupied carrier control word;

[0066] (3.2) Determine whether it is necessary to occupy the carrier line to send the task. If not, directly perform short delay processing. Otherwise, enter (3.3);

[0067] (3.3) Determine whether the sending time of the current corresponding task has arrived. If so, perform carrier sending processing and then short delay. Otherwise, perform short delay processing directly.

[0068] As a preferred embodiment of the present invention, the carrier frame is generated and sent in the following manner:

[0069] (2.1.1) The carrier transmission task of receiving instructions or data begins;

[0070] (2.1.2) Set the address, identification, and sending station address of the next station, and fill in the transparent word and magic word;

[0071] (2.1.3) Set the current frame as the downlink frame and set the data source address;

[0072] (2.1.4) Fill the payload with the serial port buffer and calculate the cyclic redundancy check code crc, payload and frame byte count;

[0073] (2.1.5) Carrier transmission: the carrier transmission task of the corresponding instruction or data is completed.

[0074] As a preferred implementation of the present invention, when the carrier acquires a new frame, the sending time point is calculated in the following manner:

[0075] (2.2.1) Start calculating the sending time point;

[0076] (2.2.2) Sort the current data source list and calculate the sequence number of the received frame data source after sorting;

[0077] (2.2.3) Determine whether the current data source sequence number is the largest. If so, the reference of the current sending time point is the remainder of the system time% sending cycle. Otherwise, the current reference remains unchanged.

[0078] (2.2.4) Calculate the sequence number of the local machine after sorting, and determine whether the current local sequence number is the largest. If so, the sending time point = (reference time + sorting number × time slice) % sending period. Otherwise, the sending time point of the local machine is not adjusted.

[0079] (2.2.5) Calculation of the sending time point is completed.

[0080] As a preferred embodiment of the present invention, the carrier data source list is updated in the following manner:

[0081] (2.3.1) Start updating the data source list;

[0082] (2.3.2) Determine whether the current data source address exists. If not, add a new data source. Otherwise, go directly to (2.3.3);

[0083] (2.3.3) Determine whether the current identifier is a new identifier. If not, end the list update directly. Otherwise, go directly to (2.3.4);

[0084] (2.3.4) Calculate the current identification interval, where the audio missing frame count is the difference between the new and old identifications;

[0085] (2.3.5) Determine whether there is a missing frame at present. If yes, calculate the missing audio time and accumulate the missing audio time. Otherwise, directly enter (2.3.6);

[0086] (2.3.6) Determine whether the current interval time is larger. If so, replace the maximum identification interval first. Otherwise, directly record the current identification system time;

[0087] (2.3.7) Set the remaining time for deleting the data source and end the data source list update.

[0088] like Figure 1 As shown, the system has a simple structure and only includes a low-voltage power supply and multiple digital telephones. It has no requirements for wiring methods and is very simple to install and maintain. Among them, the power supply line is the communication line.

[0089] In order to achieve multi-party calls, a higher audio compression rate consumes less transmission bandwidth. Therefore, this technical solution uses a high audio compression dedicated DSP, which can generate a frame of audio code with only 6 bytes every 20ms.

[0090] On this basis, the transmission control on the carrier power line is the core part of this technical solution. In order to facilitate installation and maintenance, digital telephones need to be interchangeable at will. Therefore, the serial port is used for transmission between the carrier board and the bottom instead of the network port, bypassing the configuration of the IP address, which can also save hardware costs.

[0091] In this communication system, each telephone node realizes the function of mutual relay through software. Since the IP protocol is not used, the link layer of the carrier can be programmed directly. Because the IP layer is bypassed and the MAC address is used directly for distinction, there is no need to configure the IP address during construction, and the installation and maintenance of the telephone will be extremely simple.

[0092] In this regard, the design goal of this technical solution is: any phone can initiate a call, and through broadcasting, call the other phone to start the call. After the other phone picks up the phone, the two parties enter the call. If other devices continue to pick up the phone, a multi-party call can be started. A maximum of three people can talk. After more than three parties, the phone that picks up the phone later enters the urging state. If the phone that picks up the phone later is the driver's phone, one of the devices will be kicked out, and the three-party call will still be retained. During the call, if any phone presses the broadcast button, the phone will become a shouting phone, and the remaining phones in the entire network that have not picked up the phone will broadcast the voice of the shouting phone. The driver's phone is also equipped with an alarm pedal. At any time, the alarm pedal will cause all network devices to enter the alarm state and play the alarm audio.

[0093] Therefore, the phone is in four states at any time: on-hook monitoring state, alarm state, talking (shouting) state, and urging to hang up state. The switching of the four states is not only related to the switch state of the phone (including off-hook, broadcast button, alarm switch, driver configuration), but also related to the carrier line occupation of other phones on the bus.

[0094] Therefore, the carrier board software application layer of the present invention needs to transmit the status and audio data obtained by the local telephone from the baseboard, and also control the telephone's occupation of the carrier line.

[0095] like Figure 6 As shown, serial communication is carried out between the carrier communication board and the power baseboard. The communication content includes time, switch status, audio data, as well as the bus occupancy mode sent from the baseboard to the carrier board and the local setting control returned by the carrier board to the baseboard.

[0096] The carrier board communicates with the base board. Every time the base board produces a new voice packet, it will send the data to the carrier board. The carrier board will cache the data and send it at the appropriate time. The communication data structure is as follows: Figure 6 .

[0097] The appropriate sending time is very important for communication. If it is not properly controlled, data conflicts are likely to occur on the network, affecting the sending and receiving results.

[0098] The carrier board will receive data sent by other machines on the carrier bus, and its format is also Figure 6 After obtaining the data from other machines, it may be forwarded, and the baseboard will be notified to change the state of the local machine or modify the list of other machines on the baseboard.

[0099] For this reason, Figure 7 As shown, the software of the carrier board application layer is designed with three tasks, including the baseboard serial port receiving task, the carrier data receiving task and the carrier active sending task.

[0100] In a specific embodiment of the present invention, for better explanation, there is provided Figure 8 A possible wiring method is shown, its problems are pointed out, and a solution is given.

[0101] Figure 8 This is a possible way to wire telephones. Assuming that the longest distance of the carrier is 300 meters, since the point-to-point distance is within the range, telephone 1 can communicate normally with its neighbor telephone 3, but not with telephones 2 and 4. Similarly, telephone 3 can communicate normally with telephone 1, telephone 2, telephone 4, and telephone 6, but not with other telephones. In order to broadcast the entire network, the command frame and data frame of telephone 1 need to pass through telephone 1, telephone 3, telephone 6, and telephone 9 before reaching telephone 10 and telephone 8. It can be seen that during the transmission process, some telephones must forward the source data to achieve full network broadcasting.

[0102] Because the wiring cannot be predicted, the present invention requires that each telephone must broadcast and forward the data source once. However, at this time, for telephone 6, in addition to a frame of data sent by telephone 3 during data downlink, telephone 5, telephone 7, and telephone 9 will also forward data frames. Phone 6 will receive data frames sent by the data source multiple times. Without a reasonable mechanism, phone 6 will repeatedly send the frame, and other phones will also repeat it, resulting in serious bus congestion and communication jam.

[0103] exist Figure 8 In the example, the phenomenon of phone 6 will also occur in phone 3 and phone 9. With more complicated wiring, the above situation is more serious.

[0104] Therefore, a reasonable mechanism needs to be designed to ensure that each phone can forward once and only once during the communication process to ensure smooth communication. To this end, the present invention introduces a data source + data identification method to achieve the above goal.

[0105] Based on this, we first define the transceiver frame format of the carrier link layer. The transceiver frame format is defined as follows: Fig. 9 As shown, the data source information list is as follows Fig.10 shown.

[0106] The generation of carrier frames only needs to follow Fig.10 Just fill in the data in the corresponding position as shown. To prevent frame transmission errors, a CRC check is added to the end of the frame. There is an 8-byte frame source identifier in the data structure. This identifier is used for forwarding control. In order to avoid the trouble caused by data overflow of this identifier, an 8-byte integer is directly defined. When each node sends a new frame of data, the identifier will be incremented.

[0107] Figure 8 In the process, a node may receive data from the same data source multiple times from neighboring nodes.

[0108] During the receiving process, the carrier will enter the data source and identifier into the data source table. When a new frame of data is received, it can compare whether the identifier in the same data source is the latest. If and only if the identifier of the latest data source is the latest, the frame of data will be processed. This ensures that each phone sends and forwards the frame of each data source only once.

[0109] In this way, the bandwidth can be reasonably utilized during the transmission of a frame of data, without excessive occupancy and without loss.

[0110] The update flow chart of the data source list is as follows: Fig.12 As shown in the figure, after the above design, a frame of data can be transmitted smoothly between all phones. However, when multiple nodes send data at the same time, bus conflicts are still inevitable, resulting in audio loss during the transmission of multiple phones. Figure 7 The sending time control described in is the key to coordinating multi-machine calls.

[0111] The key to solving this problem is to divide the multi-device calls into time slices. In each time slice, only one data source phone can broadcast to the entire network. Three devices are needed to talk, which is divided into four time slices with some margin.

[0112] go through Fig.12After the data source list is updated, all call nodes will exist in the table. A benchmark is needed for the sending time point. First, the call devices in the list are sorted according to the size of the mac address. The largest mac address is identified as the benchmark for the sending time. The second ranked device is offset by one time slice after the sending time of the largest mac address, the third ranked device is offset by two time slices, and the fourth ranked device is offset by three time slices. The number of devices that can talk at the same time is limited to three. In the worst case, if the fourth device is inserted into the call, one of them will be kicked out. It can be seen that four time slices are sufficient.

[0113] The time of each time slice can be determined according to Figure 8 , increase attenuation on the lines between each phone to ensure that each device can only send signals to neighboring devices.

[0114] Fig.13 This is the worst wiring method for 30 devices to talk. The carrier communication has the most forwarding times. The sending and receiving time between phone 1 and phone 30 is measured. This time can be customized as the time slice for the communication of the 30 phones.

[0115] Of course, the time slice is also affected by the load of a frame of data. The greater the load, the more bandwidth resources are occupied. The load can be adjusted in the subsequent test process.

[0116] Fig.14 To calculate the sending time point flow chart within the cycle, this process is called when the carrier acquires a new frame. With the sending time, Figure 7 In the carrier active sending task, it is determined whether the sending time point has arrived. Only when the bus needs to be occupied and the sending time point has arrived, will it be sent.

[0117] With the above design, when multiple parties are talking, the carrier bus will send data from each party in an orderly manner, and the buses will not conflict with each other.

[0118] Therefore, when 30 telephones are hung on the bus, the 30 telephones are relays for each other, the point-to-point distance is 300 meters, and the maximum transmission distance will increase to 9000 meters. The simulation increases the transmission impedance so that each telephone can only directly transmit with two adjacent nodes. Since the nodes in the present invention play the role of mutual relay, when the audio time carried by each frame is 400ms, three telephones talk without any pressure on the bus, and the audio loss time is 0 in one hour. The verification results are as follows Fig.15 shown.

[0119] During an audio call, the voice frames after audio encoding actually contain many silent frames and comfortable noise frames. Moreover, during a three-party call, the three parties will not speak separately, and there will always be someone speaking and someone listening. Therefore, in order to further save the bandwidth resources of the carrier, the present invention also marks the silent frames and comfortable noise frames during the audio transmission process instead of transmitting the complete frames. At the recipient's end, they are re-synthesized according to the marks, and the system performance is further optimized.

[0120] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention belong.

[0121] It should be understood that each part of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution device.

[0122] A person of ordinary skill in the art may understand that all or part of the steps of the method for implementing the above-mentioned embodiment may be completed by instructing the relevant hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one of the steps of the method embodiment or a combination thereof.

[0123] The storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk, etc.

[0124] In the description of this specification, the description with reference to the terms "an embodiment", "some embodiments", "example", "specific example", or "embodiment" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0125] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

[0126] The long-distance carrier digital call system of the present invention has no central node, no switch, low-voltage power supply, hot-swappable, and simple installation and maintenance. The system does not specify the wiring method, and communication can be achieved by simply hanging it on the power supply line, which simplifies installation and maintenance. The number of telephones connected to the system at the same time can reach dozens, which can meet most application scenarios; multi-party calls can be realized at the same time (limited to a maximum of three parties at the same time due to the influence of carrier bandwidth); telephones at any location can be interchanged, and installation and maintenance are further simplified; the longest communication distance between telephones can reach several kilometers; and during the call, any telephone can start broadcasting at the same time, and all telephones in the system can receive the broadcasting; and a driver's telephone is set in the system, which can be inserted into the three-party call and can also start the alarm state of the entire network.

[0127] In this specification, the present invention has been described with reference to specific embodiments thereof. However, it is apparent that various modifications and variations may be made without departing from the spirit and scope of the present invention. Therefore, the specification and drawings should be regarded as illustrative rather than restrictive.

Claims

1. A long-distance carrier digital communication system, characterized in that: It includes a low-voltage power supply and several digital telephones, and the low-voltage power supply and digital telephones are all connected to the carrier bus; the digital telephones include a power baseboard, an audio processing board, a carrier communication board and telephone input and output accessories, and the power baseboard, audio processing board and carrier communication board are all interconnected through interfaces; wherein serial port communication is performed between the power baseboard and the carrier communication board, and the communication content includes time, switch status, audio data, bus occupancy mode sent from the power baseboard to the carrier communication board, and local setting control mode returned from the carrier communication board to the power baseboard.

2. The long distance carrier digital communication system according to claim 1, characterized in that: The system is the application layer software design of the carrier communication board, which has a baseboard serial port receiving task. The processing flow is as follows: The carrier communication board described in (1.1) receives the task and determines whether there is a data frame from the power baseboard. If not, repeat this step, otherwise, enter (1.2); (1.2) Determine whether the current data frame is an AT command frame. If so, execute the corresponding AT command. Otherwise, directly enter (1.3); (1.3) Determine again whether the data frame of the power baseboard is included. If so, cache the data of the power baseboard. Otherwise, return to step (1.1).

3. The long distance carrier digital communication system according to claim 1, characterized in that: The system is an application layer software design of the carrier communication board with a carrier data receiving task, and the processing flow is as follows: (2.1) Start executing the carrier receiving task and determine whether there is a carrier frame at present. If not, repeat this step. Otherwise, directly enter (2.2); (2.2) Extracting carrier data, controlling the sending time, updating the data list, obtaining the bus occupation mode of other machines, setting the local state and other machine table, forwarding carrier data, and sending the other machine data to the power baseboard are executed in sequence, thereby completing the reception of carrier data.

4. The long distance carrier digital communication system according to claim 1, characterized in that: The system is the application layer software of the carrier communication board, which is designed with a carrier active sending task. The processing flow is as follows: (3.1) Start executing the carrier active sending task, extract the current operating status of the digital telephone and generate the occupied carrier control word; (3.2) Determine whether it is necessary to occupy the carrier line to send the task. If not, directly perform short delay processing. Otherwise, enter (3.3); (3.3) Determine whether the sending time of the current corresponding task has arrived. If so, perform carrier sending processing and then short delay. Otherwise, perform short delay processing directly.

5. The long distance carrier digital communication system according to claim 3, characterized in that: The carrier frame is generated and sent in the following manner: (2.1.1) The carrier transmission task of receiving instructions or data begins; (2.1.2) Set the address, identification, and sending station address of the next station, and fill in the transparent word and magic word; (2.1.3) Set the current frame as the downlink frame and set the data source address; (2.1.4) Fill the payload with the serial port buffer and calculate the cyclic redundancy check code crc, payload and frame byte count; (2.1.5) Carrier transmission: the carrier transmission task of the corresponding instruction or data is completed.

6. The long distance carrier digital communication system according to claim 3, characterized in that: When the carrier acquires a new frame, the sending time is calculated as follows: (2.2.1) Start calculating the sending time point; (2.2.2) Sort the current data source list and calculate the sequence number of the received frame data source after sorting; (2.2.3) Determine whether the current data source sequence number is the largest. If so, the reference of the current sending time point is the remainder of the system time% sending cycle. Otherwise, the current reference remains unchanged. (2.2.4) Calculate the sequence number of the local machine after sorting, and determine whether the current local sequence number is the largest. If so, the sending time point = (reference time + sorting number × time slice) % sending period. Otherwise, the sending time point of the local machine is not adjusted. (2.2.5) Calculation of the sending time point is completed.

7. The long distance carrier digital communication system according to claim 3, characterized in that: Update the carrier data source list in the following manner; (2.3.1) Start updating the data source list; (2.3.2) Determine whether the current data source address exists. If not, add a new data source. Otherwise, go directly to (2.3.3); (2.3.3) Determine whether the current identifier is a new identifier. If not, end the list update directly. Otherwise, go directly to (2.3.4); (2.3.4) Calculate the current identification interval, where the audio missing frame count is the difference between the new and old identifications; (2.3.5) Determine whether there is a missing frame at present. If yes, calculate the missing audio time and accumulate the missing audio time. Otherwise, directly enter (2.3.6); (2.3.6) Determine whether the current interval time is larger. If so, replace the maximum identification interval first. Otherwise, directly record the current identification system time; (2.3.7) Set the remaining time for deleting the data source and end the data source list update.

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