Transmitter

Abstract

The purpose of the present disclosure is to provide a transmitter for wireless communication capable of setting a transmission path for which a delay is guaranteed on the basis of an arbitrary probability. A transmitter according to the present disclosure connects two or more transmission paths to perform wireless communication with a receiver, the transmitter being configured to execute: processing for calculating a plurality of candidates for a combination of transmission paths; distribution calculation processing for calculating a total delay probability distribution for each candidate on the basis of the delay probability distribution of each of the transmission paths; determination processing for determining, from among the candidates, a combination to be used for data transmission on the basis of the total delay probability distribution; and processing for distributing and transmitting data to be transmitted to transmission paths included in the determined combination.

Description

Transmitter

[0001] The present disclosure relates to a technique for setting a transmission path based on a delay probability distribution.

[0002] In redundancy technology that replicates data and transmits it over multiple paths, simply increasing the number of transmission paths can lead to increased delay times. For this reason, techniques are known for optimizing transmission paths to satisfy delay requirements. For example, Patent Literature 1 discloses a technique that calculates an end-to-end delay threshold and the number of redundant paths for each path based on topology information, line information, and design parameter information, and then calculates candidate paths for each path based on the end-to-end delay threshold and the number of redundant paths.

[0003] It is known that the delay time in each transmission path is not fixed but is actually a probability distribution. However, the above method does not take into account statistical information about the delay.

[0004] On the other hand, Patent Document 2 discloses a communication device that determines the priority of each flow based on statistical information about the delay allowable for transmitted and received signals. The statistical information includes at least one of the minimum, maximum, and average values ​​of the delay time required for data transfer.

[0005] JP 2019-161279 A JP 2019-110404 A

[0006] In order to guarantee the delay for a set transmission route based on probability, route optimization that takes into account the probability distribution of delay is required. However, even in the method of Patent Document 2 that takes into account statistical information on delay, only discrete values ​​such as the minimum, maximum, and average values ​​of delay are considered.

[0007] In order to solve the above-mentioned problems, an object of the present disclosure is to provide a wireless communication transmitter that can set a transmission path with guaranteed delay based on an arbitrary probability.

[0008] An aspect of the present disclosure is a transmitter that connects two or more transmission paths with a receiver and performs wireless communication, and is preferably configured to perform the following: a process of calculating multiple candidate combinations of the transmission paths; a distribution calculation process of calculating a total delay probability distribution for each candidate based on the delay probability distribution of each of the transmission paths; a determination process of determining from the candidates the combination to be used for transmitting data based on the total delay probability distribution; and a process of distributing and transmitting data to be transmitted to the transmission paths included in the determined combination.

[0009] The transmitter of the present disclosure calculates multiple candidate combinations of transmission paths. Furthermore, the transmitter determines a combination to be used for data transmission from among the candidates based on the total delay probability distribution calculated for the candidates. This makes it possible to provide a wireless communication transmitter that can set a transmission path with guaranteed delay based on an arbitrary probability.

[0010] FIG. 1 is a schematic diagram showing the relationship between the number of transmission paths and delay in wireless communication, according to a prerequisite technology of the present disclosure. FIG. 2 is a schematic diagram showing factors of delay in wireless communication and delay probability distributions for each factor, according to a prerequisite technology of the present disclosure. FIG. 3 is a configuration example of a wireless communication system, according to a first embodiment of the present disclosure. FIG. 4 is a block diagram showing a detailed configuration example of a transmitter, according to a first embodiment of the present disclosure. FIG. 5 is a diagram explaining a delay probability distribution acquired by a transmitter, according to a first embodiment of the present disclosure. FIG. 6 is a diagram explaining a cumulative delay probability distribution calculated by a transmitter, according to a first embodiment of the present disclosure. FIG. 7 is a diagram explaining a total delay probability distribution calculated by a transmitter, according to a first embodiment of the present disclosure. FIG. 8 is a diagram explaining a decision process performed by a transmitter, according to a first embodiment of the present disclosure. FIG. 9 is a block diagram showing a detailed configuration example of a transmitter, according to a second embodiment of the present disclosure.

[0011] <Base Technology> First, as a base technology, we will explain why there is an optimal solution for the number of transmission paths that minimizes delay. FIG. 1 is a schematic diagram showing the relationship between the number of transmission paths and delay in wireless communication, according to the base technology of the present disclosure. In FIG. 1, the horizontal axis represents the number of transmission paths used, and the vertical axis represents the magnitude of delay. Near point A, where the number of transmission paths is extremely small, large delays occur due to frequent data retransmissions. This tendency is particularly pronounced when the packet error rate (PER) is high on each transmission path. In general, this delay can be reduced up to point B due to the effect of redundancy achieved by increasing the number of transmission paths.

[0012] On the other hand, if the number of transmission paths is further increased from point B, the delay time begins to increase. This is because the total delay time is dominated by the path with the longest delay time, due to the receiver's requirement to wait for all packets distributed to multiple transmission paths to arrive.

[0013] From the above, it can be said that there exists an optimal solution for the number of transmission paths that minimizes delay.

[0014] 2 is a schematic diagram showing factors of delay in wireless communication and delay probability distribution for each factor, according to the base technology of the present disclosure. Examples of factors that cause delay include transmission waiting in the CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) algorithm. This is a delay that occurs in the L2 layer, one of the layers defined in the OSI (Open Systems Interconnection) reference model. Meanwhile, in the higher L4 layer, delays occur due to retransmissions.

[0015] Hereinafter, a delay probability distribution that does not include data retransmission, such as delay based on the CSMA / CA algorithm, will be referred to as a first delay probability distribution 10. On the other hand, a delay probability distribution due to retransmission will be referred to as a second delay probability distribution 20.

[0016] 2, the left side represents the delay probability distribution for the first transmission path, and the right side represents the delay probability distribution for the second transmission path. FIG. 2 shows that the first delay probability distribution 10 and the second delay probability distribution 20 differ depending on the transmission path.

[0017] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The same or corresponding components will be denoted by the same reference numerals, and repeated description may be omitted.

[0018] 3 illustrates a configuration example of a wireless communication system 100 according to a first embodiment of the present disclosure. The wireless communication system 100 includes a transmitter 110 and a receiver 120. The transmitter 110 and the receiver 120 connect two or more transmission paths 50(1), 50(2), ... to perform wireless communication.

[0019] 4 is a block diagram showing a detailed configuration example of the transmitter 110 according to the first embodiment of the present disclosure. The communicators 113(1), 113(2), ... respectively connect the transmission paths 50(1), 50(2), ... to the receiver 120. The communicators 113 are digital or analog signal processing circuits, antennas, etc. The collection circuit 112 executes a collection process to collect information on the probability of delay occurrence in each transmission path 50.

[0020] Here, the information on the probability of occurrence of delay means information necessary to acquire the delay probability distribution of each transmission path 50. For example, the information is information on the probability of occurrence of an error in each transmission path 50, such as PER, but is not limited to this.

[0021] The analysis circuit 114 calculates the cumulative delay probability distribution 30 for each transmission path 50 from the collected information on the probability of delay occurrence. Furthermore, the analysis circuit 114 calculates a plurality of candidate combinations of the transmission paths 50.

[0022] For example, if there are three transmission paths 50, there are four candidate combinations: transmission path 50(1) and transmission path 50(2), transmission path 50(2) and transmission path 50(3), transmission path 50(1) and transmission path 50(3), and transmission path 50(1), transmission path 50(2), and transmission path 50(3). Note that a single path may be included in the combinations, in which case, in addition to the four above, the candidates include transmission path 50(1), transmission path 50(2), and transmission path 50(3).

[0023] Furthermore, the analysis circuit 114 calculates a total delay probability distribution 40 for each candidate based on the cumulative delay probability distribution 30 for each transmission path 50. Furthermore, the analysis circuit 114 executes a determination process to determine, from the candidates, a combination of transmission paths 50 whose delay satisfies a predetermined probability based on the total delay probability distribution 40.

[0024] The analysis circuit 114 notifies the control circuit 115 of the determined combination of transmission paths 50 .

[0025] The control circuit 115 receives data 60 from the upper layer and performs flow control. The control circuit 115 copies the data 60 based on the number of transmission paths 50 included in the determined combination. Furthermore, the control circuit 115 distributes the copied data 60 to each communication device 113 responsible for the transmission paths 50 included in the combination. The communication device 113 that receives the data 60 from the control circuit 115 transmits the data 60 to the receiver 120 via the transmission path 50 that it is responsible for.

[0026] The processing performed by the transmitter 110 may be executed by a program using a computer having a CPU and memory and storing a program in the memory. Alternatively, the processing may be executed by a program using an integrated circuit such as an FPGA (Field Programmable Gate Array). The program may be provided by being recorded on a storage medium or via a network. This point is common to all of the following embodiments.

[0027] 5 is a diagram illustrating a delay probability distribution acquired by the transmitter 110 according to the first embodiment of the present disclosure. In FIG. 5, the upper part represents the delay probability distribution for the transmission path 50(1), and the lower part represents the delay probability distribution for the transmission path 50(2).

[0028] In the collection process, the magnitude of delay in each transmission path 50 is collected separately for each delay factor. This allows a delay probability distribution for each delay factor to be obtained. That is, the acquired delay probability distribution includes the above-mentioned first delay probability distribution 10 that does not include retransmission and the second delay probability distribution 20 due to retransmission.

[0029] It should be noted that the transmission waiting time in the CSMA / CA algorithm varies depending on the priority of the data 60, the number of other transmitters attempting to transmit to the same receiver 120, etc. Therefore, it should be noted that there are multiple first delay probability distributions 10 in both the transmission path 50(1) and the transmission path 50(2).

[0030] Therefore, hereinafter, the multiple first delay probability distributions 10 in the transmission path 50(1) will be referred to as first delay probability distributions 11 with different symbols, and when it is necessary to distinguish between them, they will be referred to as first delay probability distribution 11(1), first delay probability distribution 11(2), .... Similarly, the multiple first delay probability distributions 10 in the transmission path 50(1) will be referred to as first delay probability distributions 12, and when it is necessary to distinguish between them, they will be referred to as first delay probability distribution 12(1), first delay probability distribution 12(2), .... Furthermore, the second delay probability distribution 20 in the transmission path 50(1) will be referred to as second delay probability distribution 21, and the second delay probability distribution 20 in the transmission path 50(2) will be referred to as second delay probability distribution 22.

[0031] FIG. 6 is a diagram illustrating a cumulative delay probability distribution 30 calculated by the transmitter 110 according to the first embodiment of the present disclosure. In FIG. 6, the upper part represents the cumulative delay probability distribution 30(1) for the transmission path 50(1), and the lower part represents the cumulative delay probability distribution 30(2) for the transmission path 50(2). The cumulative delay probability distribution 30 is calculated by finding the sum of the delay probability distributions for each delay factor. For example, the cumulative delay probability distribution 30(1) for the transmission path 50(1) is calculated as the sum of the first delay probability distribution 11(1), the first delay probability distribution 11(2), ..., and the second delay probability distribution 21. Similarly, the cumulative delay probability distribution 30(2) for the transmission path 50(2) is calculated as the sum of the first delay probability distribution 12(1), the first delay probability distribution 12(2), ..., and the second delay probability distribution 22.

[0032] Note that because the delay probability distributions for two types of delay factors are added together, a two-stage increase appears in the cumulative delay probability distribution 30. That is, in the cumulative delay probability distribution 30(1) in the upper part of Figure 6, the first increase C comes from the first delay probability distribution 11, which does not include retransmissions. On the other hand, the second increase D comes from the second delay probability distribution 21, which does not include retransmissions.

[0033] By calculating the cumulative delay probability distribution 30, it is possible to statistically grasp the magnitude of delay on each transmission path 50. The dashed lines in the upper and lower parts of Figure 6 indicate the magnitude of delay that gives a predetermined probability in the cumulative delay probability distribution 30(1) and cumulative delay probability distribution 30(2). In other words, this means that the magnitude of delay on each transmission path 50 is smaller than the value indicated by the dashed line at that probability.

[0034] 7 is a diagram illustrating a total delay probability distribution 40 calculated by the transmitter 110 according to the first embodiment of the present disclosure. The total delay probability distribution 40 is calculated by finding the sum of the cumulative delay probability distributions 30 for each transmission path 50. In FIG. 7, the total delay probability distribution 40 is calculated as the sum of the cumulative delay probability distribution 30(1) for the transmission path 50(1) and the cumulative delay probability distribution 30(2) for the transmission path 50(2). This makes it possible to statistically grasp the magnitude of delay when the transmission path 50(1) and the transmission path 50(2) are combined among the multiple transmission paths 50.

[0035] The transmitter 110 determines the magnitude of delay based on percentiles or the like for the calculated total delay probability distribution 40. The dashed line in Fig. 7 indicates the magnitude of delay determined based on the 99th percentile. In other words, it can be said that there is a 99% probability that the magnitude of delay in the combination of transmission path 50(1) and transmission path 50(2) will be smaller than the value indicated by the dashed line. However, the percentile value here is an example and is not limited thereto.

[0036] FIG. 8 is a diagram illustrating a determination process performed by the transmitter 110 according to the first embodiment of the present disclosure. In the determination process, the magnitude of delay that provides a predetermined probability is determined from the total delay probability distribution 40 for each candidate combination. The magnitude of delay for each candidate is compared, and the combination of transmission paths 50 with the smallest magnitude of delay is selected as the combination to be used for transmitting data 60. FIG. 8 shows the total delay probability distribution 40 for multiple candidate combinations. The upper part of FIG. 8 shows the total delay probability distribution 40(1) for the combination of transmission path 50(1) and transmission path 50(2). The lower part shows the total delay probability distribution 40(2) for the combination of transmission path 50(2) and transmission path 50(3). Note that there are other candidate combinations, but they are omitted here.

[0037] In FIG. 8, the magnitude of delay determined based on the 99th percentile is shown by a dashed line. From the position of the dashed line, the magnitude of delay (d １２ ), the magnitude of delay (d ２３It is clear that the delay is smaller when the transmission path 50 is smaller than the transmission path 50 ...

[0038] In this way, the transmitter 110 of the present disclosure calculates multiple candidate combinations of transmission paths 50. Furthermore, the transmitter 110 determines a combination to be used for transmitting data 60 from the candidates based on the total delay probability distribution 40 calculated for the candidates. This makes it possible to provide a wireless communication transmitter 110 that can set a transmission path 50 with a guaranteed delay based on an arbitrary probability. In this case, it is also possible to use a combination of transmission paths 50 that minimizes delay.

[0039] <First Modification of First Embodiment> It has been described that in the determination process, the combination of transmission paths 50 with the smallest delay based on the total delay probability distribution 40 is selected as the combination to be used for transmitting the data 60. However, the combination to be used for transmitting the data 60 is not limited to the combination of transmission paths 50 with the smallest delay. For example, it may be a combination of transmission paths 50 that satisfies a predetermined delay magnitude with a predetermined probability or higher and that uses the fewest number of transmission paths 50. This makes it possible to set a transmission path 50 that satisfies a predetermined delay magnitude with a predetermined probability and reduces the burden associated with redundant transmission of the data 60. This point is common to all of the following embodiments.

[0040] <Variation 2 of Embodiment 1> Note that, since the delay probability distribution may fluctuate, it is desirable to perform the above-mentioned collection process periodically. As a result of the collection process, if a fluctuation is confirmed in the total delay probability distribution 40 of the transmission path 50 in use, and the magnitude of the delay exceeds a threshold, the calculation of the cumulative delay probability distribution, the calculation of the total delay probability distribution, and the determination process are performed again, and the combination of transmission paths 50 is switched to a newly determined combination. This makes it possible to switch to another appropriate transmission path 50 if the delay in the set transmission path 50 worsens. Note that this point is common to all of the following embodiments.

[0041] If necessary, the number of uses of the transmission path 50 may be temporarily increased when switching the transmission path 50. By temporarily increasing the number of uses, it is possible to prevent momentary disconnection and retransmission from occurring when switching, and it is possible to prevent delays in the transmission path 50 from worsening even if only temporarily.

[0042] The interval at which the collection process is performed may be adjusted according to the magnitude of fluctuation in the delay probability distribution of each transmission path 50. This makes it possible to reduce overhead related to the collection process in addition to the above-mentioned effects.

[0043] <Third Modification of First Embodiment> It has been described that the control circuit 115 replicates the data 60 based on the number of transmission paths 50 included in the determined combination. However, the data 60 may be divided instead of replicated. In this case, the control circuit 115 divides the data 60 based on the number of transmission paths 50 included in the determined combination. Furthermore, the control circuit 115 distributes the divided data 60 to the communication devices 113 responsible for the transmission paths 50 included in the combination. When the data 60 is divided and transmitted, retransmission cannot be suppressed, and therefore delays tend to increase compared to when the data 60 is replicated. However, it becomes possible to transmit the data with an expanded bandwidth. Note that division and replication may be combined, such that part of the data 60 is replicated and transmitted, and the other part is separated and transmitted. Note that this point is common to all of the following embodiments.

[0044] Second Embodiment In this embodiment, a transmitter 110 transmits data 60 using a plurality of combinations of transmission paths 50. The following describes changes from the first embodiment.

[0045] 9 is a block diagram showing a detailed configuration example of a transmitter 110 according to a second embodiment of the present disclosure. Similar to the first embodiment, the analysis circuit 114 of this embodiment calculates multiple candidate combinations of transmission paths 50. Furthermore, the analysis circuit 114 executes a determination process. In the determination process of this embodiment, multiple combinations of transmission paths 50 to be used for transmitting data 60 are determined from the candidates.

[0046] First, a combination of transmission paths 50 that will result in a predetermined delay magnitude equal to or greater than a predetermined probability is selected based on the total delay probability distribution 40 for each candidate. If multiple combinations are selected, multiple combinations to be used for transmitting data 60 are determined from the multiple combinations according to the required bandwidth, etc.

[0047] Furthermore, the control circuit 115 divides the original data 60 received from the upper layer based on the number of combinations notified by the analysis circuit 114. Furthermore, the control circuit 115 copies each of the divided data 60 and distributes the copied data 60 to the communication devices 113 according to the combinations.

[0048] For example, if there are five transmission paths 50, the following combinations of transmission paths 50 that can achieve a predetermined delay magnitude with a predetermined probability or higher are selected: A first combination of transmission paths 50(1) and 50(2) A second combination of transmission paths 50(3) and 50(4)

[0049] In this case, the control circuit 115 of the transmitter 110 divides the original data 60 received from the upper layer into first data 61 and second data 62. The first data 61 is duplicated and distributed to the first combination of transmission paths 50(1) and 50(2). Similarly, the second data 62 is duplicated and distributed to the second combination of transmission paths 50(3) and 50(4).

[0050] Each communication device 113 that has received the first data 61 or the second data 62 from the control circuit 115 transmits the data to the receiver 120 via the transmission path 50 that it is responsible for.

[0051] Here, the method of transmitting using one combination of transmission paths 50 as in the first embodiment has the problem that the bandwidth cannot be widened. By dividing the data 60 into multiple combinations and transmitting them as in the present embodiment, it is possible to increase the available bandwidth.

[0052] <First Modification of Second Embodiment> In order to further increase the bandwidth used, it is also possible to add a separate transmission path 50. In the above example, if the transmission path 50(5) is a path that can independently obtain a predetermined delay magnitude with a predetermined probability or higher, the control circuit 115 may divide the data 60 to be transmitted into three parts, and distribute the divided data 60 to the first combination, the second combination, and the transmission path 50(5), respectively, for transmission.

[0053] Second Modification of Second Embodiment The plurality of combinations determined in the determination process may be determined so as to maximize the bandwidth, thereby making it possible to ensure the maximum bandwidth.

[0054] The present disclosure is not limited to the above-described embodiment, and various modifications can be made in the implementation stage without departing from the spirit of the present disclosure. Furthermore, the modifications may be implemented in appropriate combination, and in such a case, the combined effects can be obtained.

[0055] Aspects of the present disclosure are summarized below as appendices. (Appendix 1) A wireless communication system comprising: a receiver; and a transmitter that connects two or more transmission paths with the receiver and performs wireless communication, wherein the transmitter is configured to execute: a process of calculating multiple candidate combinations of the transmission paths, a distribution calculation process of calculating a total delay probability distribution for each candidate based on the delay probability distribution of each of the transmission paths, a determination process of determining from the candidates the combination to be used for transmitting data based on the total delay probability distribution, and a transmission process of distributing data to be transmitted to the transmission paths included in the determined combination and transmitting the data, and the receiver is configured to execute a process of receiving data transmitted from the transmitter. a transmission program for causing a transmitter, which connects two or more transmission routes and performs wireless communication with a receiver, to execute the following: a process for calculating multiple candidate combinations of the transmission routes, a distribution calculation process for calculating a total delay probability distribution for each of the candidates based on the delay probability distribution of each of the transmission routes, a determination process for determining the combination to be used for data transmission from among the candidates based on the total delay probability distribution, and a transmission process for distributing and transmitting data to be transmitted to the transmission routes included in the determined combination.

[0056] 10, 11, 12 First delay probability distribution 20, 21, 22 Second delay probability distribution 30 Cumulative delay probability distribution 40 Total delay probability distribution 50 Transmission path 60 Data 61 First data 62 Second data 100 Wireless communication system 110 Transmitter 112 Acquisition circuit 113 Communication device 114 Analysis circuit 115 Control circuit 120 Receiver

Claims

1. A transmitter that connects two or more transmission paths to a receiver and performs wireless communication, and is configured to execute the following processes: a process of calculating multiple candidate combinations of the transmission paths; a distribution calculation process of calculating a total delay probability distribution for each candidate based on the delay probability distribution of each of the transmission paths; a determination process of determining from among the candidates the combination to be used for transmitting data based on the total delay probability distribution; and a process of distributing and transmitting data to be transmitted to the transmission paths included in the determined combination.

2. The transmitter of claim 1, wherein the determination process further includes a process of determining, for each candidate, a magnitude of delay that gives a predetermined probability from the total delay probability distribution, and the combination determined in the determination process is the combination that gives the smallest magnitude of delay.

3. The transmitter of claim 1, wherein the determination process further includes a process of selecting a plurality of combinations of the transmission paths that result in a predetermined delay magnitude with a predetermined probability or greater based on a total delay probability distribution for each candidate, and determining these combinations as combinations to be used for transmitting data, and the data to be transmitted is data divided from the original data based on the number of combinations determined.

4. A transmitter as described in any one of claims 1 to 3, further comprising: a process for periodically collecting said information, wherein the delay probability distribution is obtained by collecting information on the probability of delay occurrence for each of said transmission paths; and a process for performing said distribution calculation process and said determination process in response to the collection of said information, and switching the transmission paths to a newly determined combination.

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