JP2008022307A - Communication synchronizing method and communication terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication synchronizing method by which communication terminals can be synchronized with each other with no collision of communication without requiring a reference station. <P>SOLUTION: A communication terminal X receives transmission data of a plurality of other communication terminals for a period of one frame after transmitting data, and measures transmission timing and a deviation amount Δ (step 20). The transmission timing is corrected by using the deviation amount Δ and a deviation amount Δ<SB>i</SB>of the communication terminal X itself, and transmission timing which is one frame later is predicted (step 22). A deviation amount Δ<SB>i+1</SB>of the communication terminal X itself is found from the predicted transmission timing (step 24). Data are transmitted with a deviation of the deviation amount Δ<SB>i</SB>. At this time, information on the deviation amount Δ<SB>i+1</SB>is included in the transmission data (step 26). The value of Δ<SB>i+1</SB>is substituted in Δ<SB>i</SB>, and (i+1) is substituted in (i) (step 28). A return to the step 20 is made. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In a communication system in which a plurality of communication terminals communicate with each other by a time division multiple access method, communication synchronization that can synchronize communication between a plurality of communication terminals without a base station serving as a reference for communication synchronization is provided. It is about the method.

  As a method for synchronizing transmission timing between communication terminals when a plurality of communication terminals communicate without having a reference station such as a base station, the method of Patent Document 1 is known.

In the method of Patent Document 1, an ID number and a group number are attached to a communication terminal, transmission is performed at a timing specific to the ID number, and the order of transmission is determined in the order of the ID number. And when the communication terminal receives the transmission data of another communication terminal, the same group number is adjusted by adjusting its own reception timing at any time after the end of reception based on the terminal data included in the data. Communication within a group composed of communication terminals marked with is synchronized.
JP2003-143056

  However, in the method of Patent Document 1, since each communication terminal operates autonomously, the communication terminals may operate without considering each other's operation, and communication may collide. Further, communication cannot be synchronized between groups having different group numbers.

  Therefore, an object of the present invention is a communication synchronization method for synchronizing communication so that no collision occurs in a communication system having no reference station.

  In a communication synchronization method for synchronizing a communication system configured by a plurality of first communication terminals that perform communication by a time division multiple access method, the data transmitted by the first communication terminal has a transmission timing at the next data transmission. The amount of shift (hereinafter referred to as “amount of shifting transmission timing” is referred to as “shift amount” in this specification) is included, and the shift amount of the first communication terminal of itself is the previous data transmission time. The shift amount of the first communication terminal of itself, the transmission timing of the other first communication terminal measured by receiving the transmission data of the other first communication terminal for one frame, and the other first The communication synchronization method is characterized in that when the first communication terminal transmits data, the transmission timing is changed based on the shift amount obtained at the previous data transmission when the first communication terminal transmits data.

  In this way, by including the shift amount at the next data transmission in the transmission data and exchanging the shift amount between the communication terminals, the communication terminal that has received the transmission data can transmit the data in advance to the terminal that transmitted the data. The next transmission timing can be predicted, and it can be estimated how much the own transmission timing should be shifted without causing a collision. By repeating such a shift amount several times, the shift amount of each communication terminal becomes zero. That is, communication is synchronized in this communication system.

  In addition, even if some communication terminals withdraw from this communication method, since the exchange of the shift amount is continued between the remaining communication terminals, the communication is synchronized in the communication system configured by the remaining communication terminals. .

  In the communication synchronization system according to the first aspect of the invention, communication can be synchronized not only in a group composed of a plurality of communication terminals and communicating with each other but also in a plurality of groups. This is because if there is at least one communication terminal belonging to a plurality of groups in common, the amount of shift can be exchanged with all the communication terminals of the plurality of groups via the shift amount of the communication terminals belonging to the common group.

  The second invention is the measurement according to the first invention, wherein when the second communication terminal joins the communication system, the second communication terminal receives the transmission data of the first communication terminal for one frame. The shift amount of the second communication terminal is obtained from the transmission timing of the first communication terminal and the shift amount of the first communication terminal, and data is transmitted by shifting the transmission timing by the shift amount of the second communication terminal. The communication synchronization method is characterized in that the transmission data at the time of subscribing to the communication system and subscribing to the second communication terminal includes information that the shift amount is zero.

  As described above, even when the second communication terminal joins a certain communication system, the first communication terminal exchanges the shift amount. Therefore, the second communication terminal uses a plurality of shift amounts based on the shift amount. The next transmission timing of the first communication terminal can be predicted. Therefore, the second communication terminal can join the communication without colliding. After joining the second communication terminal, the shift amount is exchanged between the first communication terminal and the second communication terminal as in the first aspect of the invention, so that the communication system including the second communication terminal can communicate. Be synchronized.

  In a third aspect based on the first aspect or the second aspect, the shift amount predicts a transmission timing after one frame from the transmission timing and the shift amount, and the predicted transmission timing is set to one slot of the own communication terminal. This is an amount that matches the transmission frequency that is the most frequent when viewed from the length. If the shift amount is 1/2 slot length or less, the transmission timing is delayed by the shift amount, and the shift amount is 1/2 slot. If it is greater than the length, the communication synchronization method is characterized in that the transmission timing is advanced by a value obtained by subtracting the shift amount from the length of one slot.

Hereinafter, the method for obtaining the shift amount will be described in more detail.
First, as seen from the division timing of the communication terminal for which the shift amount is to be obtained, how much the predicted transmission timing of other communication terminals deviates from the one-slot length of the communication terminal for which the shift amount is to be obtained. Measure whether or not Therefore, the measured deviation is a value between 0 and 1 slot length. Then, the distribution of the deviation (for example, a histogram is formed with time on the horizontal axis and frequency on the vertical axis) is examined. From the result, the most frequent frequency is set as the shift amount.

  When there are a plurality of the most frequent magnitudes, the smallest deviation may be set as the shift amount as in the fourth invention.

  Further, as in the fifth aspect, instead of using the most frequent shift amount as the shift amount, the average shift may be used as the shift amount. In addition, the median value may be shifted. The average may be simple as an arithmetic average as in the sixth invention, but may be a weighted average. Further, the shift amount may be obtained in consideration of dispersion.

  According to a seventh aspect of the present invention, there is provided a communication terminal for performing communication by a time division multiple access method, wherein the communication terminal transmits data including transmission data including information on a shift amount at the next data transmission, and other communication Data receiving means for receiving transmission data of the terminal for one frame, transmission timing determining means for determining the transmission timing of each communication terminal from the reception timing of transmission data of other communication terminals received by the data receiving means, and transmission timing Shift amount determining means for determining the shift amount of the own communication terminal from the transmission timing of each communication terminal obtained by the determining means and the shift amount of each communication terminal included in the transmission data of the other communication terminal, and the shift amount Transmission timing changing means for changing the transmission timing of the own communication terminal based on the shift amount obtained by the determining means It is a communication terminal.

  The shift amount determination means includes a transmission timing correction means for correcting the transmission timing of each communication terminal from the transmission timing of each communication terminal and the shift amount of each communication terminal, and a shift amount determination for obtaining a shift amount from the corrected transmission timing. You may be comprised from two means of a means.

  According to the present invention, since communication terminals exchange information of a shift amount with each other, a communication collision does not occur between terminals without using a signal from an external system as a time reference such as a base station, and completely It becomes possible to synchronize time division timing autonomously. In particular, in the second invention, even when a communication terminal newly joins the communication system, the communication terminal that wants to join can know the transmission timing and the shift amount by receiving the data. You can join the communication without.

  The present invention is a method of synchronizing communication when a plurality of communication terminals are communicating by a time division multiple access method without having a base station that serves as a reference for communication synchronization. It is assumed that the communication terminal is in a receiving state while not transmitting data. Further, it is assumed that the frame length and the slot length are fixed to specific values.

  The basic idea of the present invention is that information indicating how much the communication terminal shifts the transmission timing at the next transmission (hereinafter, the amount of time to be advanced or delayed is referred to as “shift amount”). It is to be included in the transmission data. When other communication terminals receive the shift amount information, it is possible to predict a future transmission timing distribution, prevent a communication collision, and adjust the transmission timing.

  The communication synchronization mechanism of the present invention based on this basic concept will be described with reference to the flowcharts of FIGS. 1 is a flowchart regarding a method in which a communication terminal (hereinafter referred to as communication terminal X) that has not yet started communication with another communication terminal newly joins a group in which a plurality of communication terminals are communicating, These are the flowcharts regarding the method of synchronizing communication, when the communication terminal X has already participated in communication of several other communication terminals.

First, the flowchart of FIG. 1 will be described.
The communication terminal X that wants to participate in communication receives transmission data of all other communication terminals that can be received for one frame from a certain point of time, and measures their transmission timing and shift amount Δ (step 10). . The transmission timing is corrected using the shift amount Δ, and the transmission timings of all other communication terminals that can be received after one frame are predicted (step 12). From the predicted transmission timing, an empty slot (a section in which the transmission interval is longer than one slot length) is specified, and the shift amount Δ of the communication terminal X itself is obtained (step 14). Data is transmitted to the empty slot by shifting the shift amount Δ, that is, it participates in communication. At this time, information of the shift amount Δ ₀ = 0 is included in the transmission data (step 16). Thereafter, the process proceeds to step 20 in FIG.

Next, the flowchart of FIG. 2 will be described.
First, after transmitting data, the communication terminal X receives transmission data of all other communication terminals that can be received for one frame, and measures their transmission timing and shift amount Δ (step 20). . The transmission timing is corrected using the shift amount Δ and the shift amount Δ _i of the communication terminal X itself, and the transmission timings of all the other communication terminals that can be received after one frame are predicted (step 22). . From the predicted transmission timing, the shift amount Δ _{i + 1} of the communication terminal X itself is obtained (step 24). The data is transmitted with the shift amount Δ _i shifted. At this time, information of the shift amount Δ _{i + 1} is included in the transmission data (step 26). Delta _i assigns the value of delta _{i + 1,} the substitutes i + 1 to i (step 28). Return to step 20.

  Next, the correction of the transmission timing in step 12 and step 22 and the method of obtaining the shift amount in step 14 and step 24 will be described in detail. First, from the transmission timing measurement data in steps 10 and 20, the distribution of the timing at which the other communication terminal has transmitted one slot length is examined with reference to the one slot length of the communication terminal for which the shift amount is obtained. The transmission timing is corrected from the shift amount and the shift amount of other communication terminals. For example, if the transmission timing of a certain communication terminal Y is 0.4 slot length and the shift amount of the communication terminal Y is 0.1 slot length, the corrected transmission timing is 0.5 slot length. Next, a histogram is created from the corrected transmission timing, with the horizontal axis representing time and the vertical axis representing frequency. The most frequent timing in this histogram is set as the shift amount. If the shift amount is selected in this way, the sum of the shift amounts of the communication terminals becomes small, so that synchronization can be performed efficiently. If there are multiple timings with the highest frequency, the one with the shortest shift amount is selected. If the shift amount is 1/2 slot length or less, the transmission timing is delayed by the shift amount, and if the shift amount is greater than 1/2 slot length, the transmission timing is advanced by a value obtained by subtracting the shift amount from 1 slot length. Shall.

  For example, in the case of the transmission timing distribution as shown in the histogram of FIG. 3, when the above method of obtaining the shift amount is applied, in the example of FIG. 3a, the shift amount is 1/2 slot length (1/2 slot length). In the example of FIG. 3b, the shift amount is 3/4 slot length (1/4 slot length advanced), and in the example of FIG. 3c, the shift amount is 1/4 slot length (1/4 slot length delayed). Become.

  The method for obtaining the shift amount described above is merely an example, and the shift amount may be obtained from a simple average or a weighted average of the histogram, or dispersion may be taken into consideration.

  According to the method shown in the flowcharts of FIGS. 1 and 2, communication can be joined without causing a collision, and communication can be synchronized.

  Hereinafter, specific examples of the present invention will be described with reference to the drawings. However, the present invention is not limited to these examples.

  First, in the first embodiment, there are two terminals, that is, communication terminal A and communication terminal B, and communication between the two parties is not performed, and each performs the processing shown in the flowchart of FIG. 2 independently. The manner in which communication is synchronized will be described.

In the first embodiment, the communication terminal A and the communication terminal B each have the communication timing as shown in FIG. 4A, and the timing is shown by dividing each slot length by a solid line. The transmission interval T1 (1 frame length) between the communication terminals A and B is 100 ms, the transmission time T2 (1 slot length) is 1 ms, and the transmission interval T3 between the communication terminal A and the communication terminal B is 0.1 ms. . When data is not transmitted, both the communication terminal A and the communication terminal B are in a receiving state, and the transmission interval and the transmission time are not changed. Further, since the communication terminal A and the communication terminal B each independently perform the processing shown in the flowchart of FIG. 2, the shift amount Δ _A (0) = 0 of the communication terminal A and the shift amount Δ _B (0 of the communication terminal B) ) = 0.

  Assume that the communication terminal B first notices the presence of the communication terminal A in such a state. That is, a state in which the communication terminal B can receive the transmission data of the communication terminal A between the end of transmission of the communication terminal B and before the start of transmission of the communication terminal A (for example, communication by the movement of the communication terminal A) This is a case where the communication terminal A has entered the receivable range of the terminal B and the communication terminal B observes the transmission data of the communication terminal A in the process of step 20. Since the communication terminal A has not received the transmission data of the communication terminal B, the presence of the communication terminal B is not yet noticed.

At this time, since the communication terminal B is not communicating with another communication terminal, the process proceeds to step 10 to communicate with the new communication terminal A. As a result of the observation in step 10, the transmission timing of the communication terminal A is the transmission timing shown in FIG. 4a, and the timing of the 1-slot length of the communication terminal A viewed from the 1-slot length of the communication terminal B (in other words, the communication terminal B T4 was 0.9 ms and the shift amount Δ _A (0) = 0 of the communication terminal A was measured. Therefore, in the process of step 12, even if it correct | amends from shift amount (DELTA) _A (0) of the communication terminal A, the transmission timing of the communication terminal A does not change, but is a timing of 0.9 ms.

Next, the free slot and the shift amount are obtained by the processing of step 14, but since the communication is between the two, only the communication terminal A exists as the other communication terminal, and naturally the timing with the highest frequency is that of the communication terminal A. This is the transmission timing, and the shift amount Δ _B = 0.9 ms. When the shift amount is shorter than 1/2 slot length, the transmission timing is delayed by the shift amount, and when the shift amount is longer than 1/2 slot length, the transmission timing corresponding to the value obtained by subtracting the shift amount from 1 slot length is set. Shall be fast. Therefore, in this case, the 0.1 ms transmission timing is advanced. It can also be seen that slots other than the slots 100 and 101 are empty slots. Here, it is assumed that the slot 102 closest to the transmission timing of the communication terminal A is selected.

Next, the communication terminal B transmits data including information “shift amount Δ _B (0) = 0” to the slot 102 by accelerating the transmission timing by 0.1 ms in the process of step 16, and the communication terminal A Participate in communication with. Thereafter, the process proceeds to step 20 in FIG.

On the other hand, the communication terminal A receives the data of the communication terminal B by the process of step 20, and observes that the timing of 1 slot length of the communication terminal B is 0 ms and the shift amount Δ _B (0) = 0. . Since the timing after correction in step 22 is 0 ms, Δ _A (1) = 0 is obtained in step 24. In step 26, since Δ _A (0) = 0, the transmission timing is not changed, and data is transmitted together with the information of Δ _A (1) = 0. Then, after the process of step 28, the process returns to step 20.

  FIG. 4B shows a state after the communication terminal B has transmitted data by 0.1 ms earlier by the processing of step 26 and joined the communication. Thus, the communication between the communication terminal A and the communication terminal B is synchronized. Thereafter, the communication terminal A and the communication terminal B repeat the processing of the flowchart of FIG. 2 unless there is a change in environment such as a new communication terminal being detected.

  As described above, both the communication terminal A and the communication terminal B have shifted the transmission timing by the method that the transmission data includes the shift amount and the transmission is shifted at the next transmission time. While avoiding the problem that the transmission of the terminal B collides, it is possible to synchronize without relying on communication with the reference station.

  The second embodiment is a case where there is a group of communication terminals A, B, and C that are performing communication synchronized with each other, and a communication terminal D that is communicating independently of the group. Here, it is assumed that the communication between the groups is synchronized, and the communication terminal D first notices the existence of the group of the communication terminals A, B, and C. Further, one frame length and one slot length are the same as those in the first embodiment.

  The communication terminal D measured the communication timing and the shift amount of the communication terminals A, B, and C by the processing of step 10, and the communication timing was the timing shown in FIG. 5a, and the shift amount was all zero. With the one-slot length of the communication terminal D as a reference, the transmission timings T6 of the communication terminals A, B, and C are all 0.5 ms. Since the shift amount is 0, even if the correction in step 12 is performed, the timing remains 0.5 ms, and in step 14, the shift amount of the communication terminal D becomes 0.5 ms. Therefore, if the transmission is delayed by 0.5 ms in step 16 and the data is transmitted, the communication terminals A, B, C, and D can be synchronized as shown in FIG. Even when there are three or more synchronized communication terminals, a new communication terminal can join the synchronized communication terminal group in synchronization by the same processing.

  In the third embodiment, a communication terminal D that has not yet performed communication is added to the group that performs communication between the communication terminals A, B, and C, and communication is performed between the communication terminals A, B, C, and D. Is the case. One frame length and one slot length are the same as in the first embodiment. Hereinafter, a state in which the communication terminal D joins the communication without colliding by the process shown in the flowchart of FIG. 1 will be described.

  The communication terminals A, B, and C communicate with each other according to the flowchart of FIG. 2 and try to synchronize communication between the communication terminals A, B, and C. Since the communication terminal D has not yet transmitted data, the communication terminals A, B, and C have not detected the presence of the communication terminal D.

The communication terminal D that has not yet started communication measures the received data in the order of the communication terminals B, C, and A for one frame from the timing t ₁ after the end of transmission of the communication terminal A by the process of step 10. Thus, the transmission timings and shift amounts of the communication terminals B, C, and A were measured. The timing after the end of transmission of the communication terminal A is selected as such for ease of explanation, and the communication terminal D may actually measure for one frame at an arbitrary timing. As a result, the transmission timings of the communication terminals A, B, and C are as shown in FIG. 6a. The transmission timing in the 1-slot length with reference to the communication terminal D is T7 (0 ms) for the communication terminal A, T8 (0.9 ms) for the communication terminal B, and T9 (0.6 ms) for the communication terminal C. Further, the shift amounts were Δ _A (0) = 0.5 ms, Δ _B (0) = 0.6 ms, and Δ _C (0) = 0 ms.

Next, the transmission timing is corrected from the shift amount by the processing of step 12. Then, the communication terminal A is 0.5 ms at T7-Δ _A (0), the communication terminal B is 0.5 ms at T8- (1-Δ _B (0)), and the communication terminal C is T9-Δ _C (0). This is 0.6 ms, which is represented as a histogram as shown in FIG. The horizontal axis is time, and the vertical axis is frequency. Next it is a step 14, the highest 0.5ms frequently from 7 is obtained as the shift amount delta _D of the communication terminal D. In addition, since Δ _B (0) = 0.6 ms and Δ _C (0) = 0 ms, the transmission timing of the communication terminal B is 0.4 ms earlier, and the interval between the transmission of the communication terminal B and the transmission of the communication terminal C Can be predicted to be 1.1 ms, that is, 1 slot or more.

Next, in the process of step 16, at a timing of the shift amount Δ _D = 0.5 ms, data including information “shift amount Δ _D (0) = 0 ms” is transmitted to the empty slot. Data is transmitted with a delay of 0.5 ms with respect to the empty slot 100 predicted between transmission of the communication terminal B and transmission of the communication terminal C. The process of step 16 is performed after the transmission timing of the communication terminal B is advanced by 0.4 ms based on Δ _B (0) = 0.6 ms. Then, after the processing of step 16, the transmission timing of the communication terminal C is not changed from Δ _C (0) = 0 ms, and then the transmission timing of the communication terminal A is 0. 0 from Δ _A (0) = 0.5 ms. 5ms late. Then, the state shown in FIG. Thus, by following the processing of the flowchart of FIG. 1, the communication terminal D was able to join the communication without causing a collision. Thereafter, the communication terminal D proceeds to step 20, and the communication terminals A, B, C, and D communicate with each other according to the processing of the flowchart of FIG. . Even if there are three or more groups of communication terminals that are being synchronized, each communication terminal has a frequency distribution of the amount of deviation of the slots of other communication terminals based on the slot of its own communication terminal. This is calculated for each communication terminal. The relationship between the amount of slot shift of other communication terminals observed at a certain communication terminal and the frequency thereof is as shown in FIGS. From this frequency distribution, the amount of deviation between the transmission timing of the own communication terminal and the next transmission timing is determined by the method described above.

  In the fourth embodiment, there are communication terminals A and B, and the communication terminal C newly joins, so communication is not performed between the communication terminals A and B, but between the communication terminals A and C and between the communication terminals B and C. This is a case of communication. One frame length and one slot length are the same as in the first embodiment. Further, the communication terminals A and B are operating according to the flowchart of FIG. 2, and the communication terminal C has not yet transmitted data, so the communication terminals A and B have not detected the presence of the communication terminal C. is there. In such a case, a state in which communication is synchronized by following the flowcharts of FIGS.

The communication terminal C measures the communication timing and the shift amount of the communication terminals A, B, and C for one frame length from t _2, which is a timing delayed by 0.2 ms from the end of transmission of the communication terminal B, by the process of step 10. As a result, the communication timing was the timing shown in FIG. 8a, and the shift amounts were all zero. With the one-slot length of the communication terminal C as a reference, the transmission timing T10 of the communication terminal A is 0.3 ms, and the transmission timing T11 of the communication terminal B is 0.8 ms. Since the shift amount is 0, the transmission timing does not change even if the correction in Step 12 is corrected. In Step 14, the shift amount of the communication terminal D is 0.3 ms, which is the smaller shift amount between the transmission timing T10 and the transmission timing T11. .

Next, in step 16, when the information is transmitted together with the information Δ _C (0) = 0 after being delayed by 0.3 ms in the empty slot, the state shown in FIG. 8b is obtained. Thus, the communication between the communication terminals A and C is synchronized. Thereafter, the communication terminal C proceeds to Step 20.

Next, the operation of the communication terminal A will be described. The communication terminal A measures that the transmission timing T12 of the newly joined communication terminal C is 0 ms and the shift amount is 0 by the process of step 20. Since the shift amount of the communication terminal A is 0 and the shift amount of the communication terminal C is 0, there is no correction of the transmission timing in Step 22, and Δ _A (1) = 0 in Step 24, and the transmission timing is determined in Step 26. Data is transmitted together with information of Δ _A (1) = 0 without shifting. Then, after the process of step 28, the process returns to step 20.

Next, the operation of the communication terminal B will be described. The communication terminal B measures that the transmission timing T13 of the newly joined communication terminal C is 0.5 ms and the shift amount is 0 by the process of step 20. Since the shift amount of the communication terminal B is 0 and the shift amount of the communication terminal C is 0, there is no correction of the transmission timing in step 22, and Δ _B (1) = 0.5 ms in step 24, and transmission is performed in step 26. Data is transmitted together with information of Δ _B (1) = 0.5 ms without shifting the timing. Then, after the process of step 28, the process returns to step 20.

Next, the operation of the communication terminal C that has shifted to step 20 will be described. In the communication terminal C, the transmission timing T14 of the communication terminal A is 0 ms, the transmission timing T15 of the communication terminal B is 0.5 ms, and the shift amount Δ _A (1) = 0, Δ _B (1) = 0. Measure that it is 5 ms. Since the shift amount of the communication terminal C is 0, and the shift amounts Δ _A (1) = 0 and Δ _B (1) = 0.5 ms, the transmission timing of the communication terminal A is not corrected in step 22, and the communication terminal B Is corrected to 0 ms. Therefore, in step 24 Δ _C (1) = 0, and the step 26 without shifting the transmission timing Δ _C (1) = transmits the data together with 0 information. Then, after the process of step 28, the process returns to step 20.

Thereafter, when the communication terminal B delays the transmission timing by Δ _B (1) = 0.5 ms by the process of step 26, the result is as shown in FIG. 8c. Thus, even if communication between the communication terminal A and the communication terminal B is not performed, the communication terminals A, B, and C can be synchronized through the communication terminal C that communicates with both.

  In this case, instead of the communication terminal A, a large number of communication terminals A communicating with each other and the communication terminals not communicating with each other, but a large number of communication terminals communicating with each other The same applies when the communication terminal C newly joins both groups when the group B exists. When the communication terminal C joins the communication terminal group A, as described in the third embodiment, the transmission timing and the next deviation amount are determined from the same number distribution of the deviation amounts of the other communication terminals. A synchronization procedure for joining a group of communication terminals is executed. Similarly, when joining the communication terminal group B, as described in the third embodiment, the self transmission timing and the next deviation amount are determined from the same number distribution of deviation amounts of other communication terminals. A synchronization procedure for joining the communication terminal group is executed. This procedure is executed alternately, but each communication terminal belonging to the communication terminal group A and each communication terminal belonging to the communication terminal group B also obtains the frequency distribution of the amount of deviation of the slots of the other communication terminals as described above. Next, the transmission timing of the communication terminal and the next deviation amount are determined from the frequency distribution. By repeating such a synchronization procedure at each communication terminal, each communication terminal of the communication terminal group A, each communication terminal C, and each communication terminal to the communication terminal group are finally shifted in all communication terminals. It will converge to a state where the quantity is zero. That is, the communication terminal group A and the communication terminal group B are synchronized via the communication terminal C.

  As the synchronization procedure progresses, the communication environment changes and a communication terminal withdraws from the communication terminal group A, a new communication terminal joins, or a part of the communication terminal group A Even if the communication terminal changes so as to communicate with some communication terminals of the communication terminal group B, and further another communication terminal group D joins these groups, the above-mentioned By the process, the process is executed for complete synchronization. Even if the communication environment changes before the entire system is completely synchronized, in the present invention, all communication terminals that can communicate with each other as seen from a certain communication terminal always act in the direction of complete synchronization. Therefore, the most efficient communication environment at that time is realized.

  Example 5 is a communication terminal according to the present invention, and FIG. 7 is a block diagram showing a configuration of the communication terminal. The receiving device 200, the CPU 201, the storage device 202, and the transmission device 203 are configured, and the storage device 202 stores a control program. The data transmission means is the processing procedure of the transmission device 203 and steps 16, 26, the data reception means is the reception device 200, the transmission timing determination means is the processing procedure of steps 10 and 20, and the shift amount determination means is the steps 12, 22, The processing procedures 14 and 24 and the transmission timing changing means are realized in steps 16 and 26.

The operation of this communication terminal will be described below.
The communication terminal performs communication by the time division multiple access method with one frame length and one slot length stored in the storage device 202. When data is not transmitted, data is received. In the processing of steps 10 and 20, the CPU 201 processes the data received by the receiving device 200 based on the control program. Further, the processing in steps 12 and 22 is performed by the CPU 201 based on the control program. Similarly, the processing of steps 14 and 24 is processed by the CPU 201 based on the control program. The processing of steps 16 and 26 is processed by the CPU 201 based on the control program and the transmission device 203. The processing in step 28 is also processed by the CPU 201 based on the control program. The storage device 202 is also used to store the transmission timing, shift amount, and corrected transmission timing used in each step.

  The present invention can be applied to a communication system for sharing information such as position and speed between a plurality of automobiles, for example.

flowchart. flowchart. The histogram figure which shows timing distribution. FIG. 3 is a diagram illustrating communication timing according to the first embodiment. The figure which shows the communication timing of Example 2. FIG. The figure which shows the communication timing of Example 3. FIG. FIG. 10 is a histogram diagram showing timing distribution in the third embodiment. The figure which shows the communication timing of Example 4. FIG. FIG. 9 is a block diagram illustrating a configuration of a communication terminal according to a fifth embodiment.

Explanation of symbols

A, B, C, D: Communication terminal T2: 1 slot length 100, 101, 102: Slot

Claims (7)

In a communication synchronization method for synchronizing a communication system configured by a plurality of first communication terminals that perform communication by a time division multiple access method,
The data transmitted by the first communication terminal includes shift amount information that is a shift amount of the transmission timing at the next data transmission,
The shift amount of the first communication terminal of the self is the same as the shift amount of the first communication terminal of the self at the time of the previous data transmission and the transmission data of the other first communication terminal during one frame. Obtained by the transmission timing of the other first communication terminal measured by receiving and the shift amount of the other first communication terminal,
When the first communication terminal transmits data, changing the transmission timing based on the shift amount obtained at the time of the previous data transmission;
A communication synchronization method characterized by the above. When a second communication terminal joins the communication system,
From the transmission timing of the first communication terminal and the shift amount of the first communication terminal, the second communication terminal is measured by receiving the transmission data of the first communication terminal for one frame. And obtaining the shift amount of the second communication terminal,
The second communication terminal transmits data by shifting the transmission timing by the shift amount of the second communication terminal to join the communication system,
The communication synchronization method according to claim 1, wherein the transmission data at the time of joining the second communication terminal includes information that the shift amount is zero. The shift amount predicts the transmission timing after one frame from the transmission timing and the shift amount, and matches the predicted transmission timing with the transmission timing that is the most frequent when viewed on the basis of the length of one slot of the own communication terminal. Is such an amount
If the shift amount is 1/2 slot length or less, the transmission timing is delayed by the shift amount,
If the shift amount is larger than 1/2 slot length, the transmission timing is advanced by a value obtained by subtracting the shift amount from 1 slot length.
The communication synchronization method according to claim 1 or 2, characterized in that   4. The shift amount according to claim 3, wherein when there are a plurality of transmission timings having the highest frequency, the shift amount having a minimum shift amount among the plurality of transmission timings having the highest frequency is set as the shift amount. Communication synchronization method. The shift amount is an amount that predicts the transmission timing after one frame from the transmission timing and the shift amount, and matches the predicted transmission timing with the average value of the transmission timing when viewed on the basis of the length of one slot. ,
If the shift amount is 1/2 slot length or less, the transmission timing is delayed by the shift amount,
If the shift amount is larger than 1/2 slot length, the transmission timing is advanced by a value obtained by subtracting the shift amount from 1 slot length.
The communication synchronization method according to claim 1 or 2, characterized in that   The communication synchronization method according to claim 5, wherein the average value is an arithmetic average value. In communication terminals that communicate using the time division multiple access method,
The communication terminal includes a data transmission unit that transmits transmission data including information on a shift amount that is a shift amount of a transmission timing at the time of next data transmission;
Data receiving means for receiving transmission data of the other communication terminal for one frame;
Transmission timing determining means for determining the transmission timing of each of the communication terminals from the reception timing of transmission data of the other communication terminals received by the data receiving means;
A shift for determining the shift amount of the communication terminal of the communication terminal from the transmission timing of each communication terminal obtained by the transmission timing determination means and the shift amount of each communication terminal included in the transmission data of the other communication terminal. A quantity determining means;
Transmission timing changing means for changing the transmission timing of its own communication terminal based on the shift amount obtained by the shift amount determining means;
A communication terminal comprising:

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