Signal transfer device, signal transfer method, and program

Abstract

This signal transferring device includes: a receiving unit which receives frames from a user terminal; a first determining unit which determines a priority traffic class on the basis of first information contained in each frame; a second determining unit which, if a frame relating to a priority traffic class is received, determines a frequency shift of the frame relative to a time slot of the host device, on the basis of a distribution of the frames relative to the time slot; a first queue which holds the frames; a first gate opening and closing unit which adjusts a timing at which a gate of the first queue is released, if a frequency shift has occurred; a second queue which holds frames sent from the first queue; a storage unit which stores second information indicating, for each time slot, the priority traffic class that is being transmitted; a second gate opening and closing unit which controls a timing at which a gate of the second queue is released, on the basis of the second information; and a transmitting unit which transmits the frames sent from the second queue.

Description

[Technical field]

[0001] One aspect of the present invention relates to a signal transfer device, a signal transfer method, and a program. [Background technology]

[0002] Time Sensitive Networking (TSN) is known as a technology for minimizing delays in devices caused by congestion at relay nodes and suppressing the occurrence of delay fluctuations. TSN is based on time synchronization between devices, for example, using the Precision Time Protocol (PTP).

[0003] Time-Aware Shaper (TAS) is a well-known technology that can be applied to TSN. TAS is a method that is particularly effective when the priority traffic class has periodicity, and performs scheduling for the priority traffic class and switches communication availability.

[0004] One example of TSN is a network system that transfers data between multiple user terminals via a communication network in which multiple signal transfer devices are connected to each other. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2014-86857 Summary of the Invention [Problem to be solved by the invention]

[0006] However, even in time-synchronized TSN, if frequency synchronization is not achieved, frequency deviation will increase. When frequency deviation occurs in a user terminal, the distribution of frames will shift with respect to time slots in the signal transfer device. When frames shift due to frequency deviation, collisions between frames will occur at the junction point of the signal transfer device, which may result in increased delays for priority traffic classes and discarded frames. When a maximum delay is specified, this increased delay will be a problem.

[0007] The present invention has been made in light of the above-mentioned circumstances, and an object of the present invention is to provide a signal transfer device, a signal transfer method, and a program that are capable of avoiding collisions between priority traffic classes. [Means for solving the problem]

[0008] A signal forwarding device according to one embodiment of the present invention is a signal forwarding device connected to a communication network for data communication between a plurality of user terminals, and includes a receiving unit that receives frames from a user terminal, a first determination unit that determines a priority traffic class based on first information included in the frame, a second determination unit that, when a frame related to a priority traffic class is received, determines a frequency shift of the frame relative to a time slot based on a distribution of the frame relative to the time slot of the device, a first queue that holds the frame, a first gate opening / closing unit that adjusts the timing of opening the gate of the first queue when the frequency shift occurs, a second queue that holds frames sent from the first queue, a memory unit that stores second information indicating which priority traffic class is to be transmitted for each time slot, a second gate opening / closing unit that controls the timing of opening the gate of the second queue based on the second information, and a transmitting unit that transmits frames sent from the second queue. When a frequency shift occurs in a high frequency direction, the first gate opening / closing unit adjusts the timing for opening the gate of the first queue so that the frame is delayed until the time slot. Effect of the Invention

[0009] According to one aspect of the present invention, it is possible to provide a signal forwarding device, a signal forwarding method, and a program capable of avoiding collisions between priority traffic classes. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a signal transfer system according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram of a signal transfer device. [Diagram 3] FIG. 3 is a block diagram illustrating an example of a hardware configuration of the signal transfer device. [Figure 4] FIG. 4 is a schematic diagram showing an example of a communication operation of the signal transfer system. [Diagram 5] FIG. 5 is a flowchart illustrating the operation of the signal transfer device. [Figure 6] FIG. 6 is a diagram illustrating an example of the gate control list. [Figure 7] FIG. 7 is a diagram for explaining the direction of frequency shift between frames. [Figure 8] FIG. 8 is a diagram for explaining a timing adjustment operation when a frequency deviation occurs in the high frequency direction. [Figure 9] FIG. 9 is a diagram for explaining a timing adjustment operation when a frequency deviation occurs in the low frequency direction. [Figure 10] FIG. 10 is a flowchart illustrating the operation of the signal transfer device according to the second embodiment of the present invention. [Figure 11A] FIG. 11A is a flowchart illustrating the operation of the signal transfer device according to the third embodiment of the present invention. [Figure 11B] FIG. 11B is a flowchart illustrating the operation of the signal transfer device according to the third embodiment of the present invention. [Figure 12] FIG. 12 is a diagram for explaining a timing adjustment operation when a frequency deviation occurs in the low frequency direction. [Figure 13] FIG. 13 is a block diagram of a signal transfer device according to the fourth embodiment of the present invention. [Figure 14] FIG. 14 is a flowchart illustrating the operation of the signal transfer device. [Figure 15] FIG. 15 is a diagram for explaining a time slot adjustment operation when a frequency deviation occurs. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment will be described with reference to the drawings. In the following description, elements having the same functions and configurations are designated by the same reference numerals, and duplicated description will be omitted.

[0012] [1] First embodiment [1-1] Configuration of signal transmission system 1 Fig. 1 is a schematic diagram of a signal transfer system 1 according to a first embodiment of the present invention. The signal transfer system 1 includes a plurality of signal transfer devices (TR) 10 and a plurality of locations BA. Fig. 1 shows three signal transfer devices 10-1 to 10-3 and three locations BA1 to BA3 as an example.

[0013] The signal transfer devices 10-1 to 10-3 are connected to each other to configure a communication network NW. When there is no need to distinguish between the signal transfer devices 10-1 to 10-3, they will be referred to as the signal transfer device 10.

[0014] Each of the multiple locations BA includes an edge device (EG) 11 and multiple user terminals (US) 12. As an example, the first location BA1 includes an edge device 11-1 and a user terminal 12-1. The second location BA2 includes an edge device 11-2 and a user terminal 12-2. The third location BA3 includes an edge device 11-3 and user terminals 12-3 and 12-4. When it is not necessary to distinguish between the edge devices 11-1 to 11-3, they are referred to as edge devices 11. When it is not necessary to distinguish between the user terminals 12-1 to 12-4, they are referred to as user terminals 12. The user terminals 12 are devices used by users and are also called end terminals.

[0015] At a first point BA1, a user terminal 12-1 is connected to an edge device 11-1. The edge device 11-1 and the user terminal 12-1 constitute a communication network. The edge device 11-1 communicates frames with the user terminal 12-1. The edge device 11-1 is connected to a signal forwarding device 10-1.

[0016] At the second point BA2, the user terminal 12-2 is connected to the edge device 11-2. The edge device 11-2 and the user terminal 12-2 configure a communication network. The edge device 11-2 communicates frames with the user terminal 12-2. The edge device 11-2 is connected to the signal forwarding device 10-2.

[0017] At the third point BA3, the user terminals 12-3 and 12-4 are connected to the edge device 11-3. The edge device 11-3 and the user terminals 12-3 and 12-4 form a communication network. The edge device 11-3 communicates frames with the user terminals 12-3 and 12-4. The edge device 11-3 is connected to the signal forwarding device 10-3.

[0018] The first location BA1, the second location BA2, and the third location BA3 can communicate frames with each other via a communication network NW. A frame is the smallest unit of data transmitted and received between devices. Data transfer between multiple edge devices 11 is performed via multiple signal forwarding devices 10. The first location BA1, the second location BA2, and the third location BA3 may be configured to be included in the same communication network. Frames are forwarded via a first user terminal, a first edge device, a first signal forwarding device, a second signal forwarding device, a second edge device, and a second user terminal.

[0019] The signal forwarding system 1 constitutes TSN (Time Sensitive Networking). The devices included in the signal forwarding system 1 are time-synchronized, for example, by using PTP (Precision Time Protocol). That is, the multiple signal forwarding devices 10, the multiple edge devices 11, and the multiple user terminals 12 are time-synchronized. The multiple signal forwarding devices 10 are time-synchronized and frequency-synchronized. The frequency synchronization is realized, for example, by using a synchronous clock. On the other hand, the multiple edge devices 11 and the multiple user terminals 12 are time-synchronized but not frequency-synchronized.

[0020] [1-2] Configuration of signal transfer device 10 Next, the configuration of the signal forwarding device 10 will be described. The signal forwarding device 10 executes the function of a TAS (Time Aware Shaper). In the TAS, during a period when traffic for which delay control is to be performed, whose transmission timing is controlled, arrives at the device, only the priority traffic class is forwarded and other priority traffic classes are not forwarded, and during a period when traffic for which delay control is to be performed does not arrive, other priority traffic classes are forwarded. This operation is repeated periodically. As a result, traffic for which delay control is to be performed can be forwarded without being kept waiting by the forwarding of other priority traffic classes.

[0021] 2 is a block diagram of the signal transfer device 10. The signal transfer device 10 includes a receiver 20, a transmitter 30, a time information storage unit 40, a GCL storage unit 41, an input port PT1, and an output port PT2.

[0022] The input port PT1 receives frames from other signal transfer devices 10, and also receives frames from the corresponding edge device 11. The frames input to the input port PT are sent to the receiver 20.

[0023] The receiver 20 includes a frame receiving unit 21, a priority traffic class determining unit 22, a frequency deviation determining unit 23, a TS (time slot) adjustment queue 24, and a TS adjustment gate opening / closing unit 25.

[0024] The frame receiving unit 21 receives frames via the input port PT1. The frames received by the frame receiving unit 21 include frames from the signal transfer device 10 adjacent to the own device and frames from the edge device 11 connected to the own device.

[0025] The priority traffic class determination unit 22 determines the priority traffic class based on information included in the received frame. The priority traffic class is information for classifying data according to its type. The priority traffic class can be used to prioritize frames.

[0026] The frequency deviation determining unit 23 receives the time information stored in the time information storage unit 40. The frequency deviation determining unit 23 determines the frequency deviation of the frame with respect to the time slot of the own device in the priority traffic class determined by the priority traffic class determining unit 22.

[0027] The TS adjustment queue 24 holds the frames until the transmission timing in order to match the frames with the time slots of the own device.

[0028] The TS adjustment gate opening / closing unit 25 controls the timing for opening the gate of the TS adjustment queue 24. The TS adjustment gate opening / closing unit 25 adjusts the timing for opening the gate of the TS adjustment queue 24 in accordance with the frequency shift determined by the frequency shift determination unit 23. When the gate of the TS adjustment queue 24 is opened, a frame is output from the TS adjustment queue 24.

[0029] The transmitter 30 includes a transmission queue 31 , a transmission gate opening / closing unit 32 , and a frame transmitting unit 33 .

[0030] The transmit queue 31 holds frames sent from the receiver 20 for each priority traffic class.

[0031] The transmission gate opening / closing unit 32 controls the timing to open the gate of the transmission queue 31. The transmission gate opening / closing unit 32 controls the timing to open the gate of the transmission queue 31 based on the time information stored in the time information storage unit 40 and the GCL stored in the GCL storage unit 41. When the gate of the transmission queue 31 is opened, a frame is output from the transmission queue 31.

[0032] The frame transmitting unit 33 transmits a frame via the output port PT2 to the signal transfer device 10 adjacent to its own device or to the edge device 11 connected to its own device.

[0033] The time information storage unit 40 stores the time information. The time information stored in the time information storage unit 40 is sent to the frequency deviation determination unit 23 and the transmission gate opening / closing unit 32. Time synchronization is achieved by the time information stored in the time information storage unit 40.

[0034] The GCL storage unit 41 stores a gate control list (GCL). The gate control list GCL is information for determining which priority traffic class is to be transmitted at any timing within one period. The GCL stored in the GCL storage unit 41 is sent to the transmission gate opening / closing unit 32.

[0035] (Hardware configuration of the signal transfer device 10) FIG. 3 is a block diagram showing an example of a hardware configuration of the signal transfer device 10. As shown in FIG.

[0036] The signal transfer device 10 can be configured by a computer, as shown in Fig. 3. The signal transfer device 10 has a hardware processor 101 such as a CPU (Central Processing Unit). In the signal transfer device 10, a program memory 102, a data memory 103, an input / output interface 104, and a communication interface 105 are connected to the processor 101 via a bus 106.

[0037] The program memory 102 is a non-transient tangible computer-readable storage medium, and is configured by combining, for example, a non-volatile memory such as a hard disk drive (HDD) or a solid state drive (SSD) that can be written and read at any time, and a non-volatile memory such as a ROM. This program memory 102 stores programs required for the processor 101 to execute various control processes according to the present embodiment. That is, the priority traffic class determination unit 22, the frequency deviation determination unit 23, the TS adjustment gate opening / closing unit 25, and the transmission gate opening / closing unit 32 shown in FIG. 2 may all be realized by having the processor 101 read and execute the programs stored in the program memory 102. Note that some or all of these processing function units may be realized in various other forms, including integrated circuits such as an application specific integrated circuit (ASIC) or a field-programmable gate array (FPGA).

[0038] The data memory 103 is a tangible computer-readable storage medium, and is configured, for example, by combining the above-mentioned non-volatile memory with a volatile memory such as a RAM (Random Access Memory). This data memory 103 is used to store various data acquired and created in the course of various processes. That is, in the data memory 103, an area for storing various data is allocated as appropriate in the course of various processes. The data memory 103 includes the GCL storage unit 41, the time information storage unit 40, the TS adjustment queue 24, and the transmission queue 31 shown in FIG. 2.

[0039] The input / output interface 104 is the input port PT1 and the output port PT2 shown in FIG. 2, and the signal transfer device 10 and the edge device 11 can be connected via the input / output interface 104.

[0040] The communication interface 105 performs communication interface processing between the device and an external device connected to the device itself. The communication interface 105 corresponds to the frame receiving unit 21 and the frame transmitting unit 33 shown in Fig. 2. The communication interface 105 may include a communication module according to a communication medium, a communication method, and a communication protocol.

[0041] [1-3] Operation Next, the operation of the signal forwarding system 1 configured as above will be described. Fig. 4 is a schematic diagram showing an example of the communication operation of the signal forwarding system 1. In this embodiment, as shown in Fig. 4, as an example, a case will be described in which an operation of transmitting a frame from a user terminal 12-1 included in a first point BA1 to a user terminal 12-3 included in a third point BA3 and an operation of transmitting a frame from a user terminal 12-2 included in a second point BA2 to a user terminal 12-4 included in a third point BA3 are performed in parallel. The following description of the signal forwarding device 10 corresponds to the operation of the signal forwarding device 10-3 in Fig. 4.

[0042] 5 is a flowchart illustrating the operation of the signal transfer device 10. The signal transfer system 1 controls the timing of transmission and reception by performing time synchronization in order to suppress delays within the device.

[0043] The signal forwarding device 10 has a plurality of time slots, and forwards data to a priority traffic class determined for each time slot. In the example of Fig. 4, there is traffic corresponding to a path passing through the edge device 11-1, the signal forwarding device 10-1, the signal forwarding device 10-3, and the edge device 11-3, and traffic corresponding to a path passing through the edge device 11-2, the signal forwarding device 10-2, the signal forwarding device 10-3, and the edge device 11-3.

[0044] In the gate control list (GCL) stored in the GCL storage unit 41, opening and closing of the gate according to the priority is defined for each time slot. The gate of a specific queue is opened based on the gate control list, so that frames of a specific priority are transferred. FIG. 6 is a diagram for explaining an example of the gate control list. The time slot (TS) specifies the timing for opening the gate of the corresponding queue. The time slots TS0 to TS4 are one period. The time lengths of the time slots TS0 to TS4 are, for example, 20 μs, 10 μs, 15 μs, 15 μs, and 100 μs, and may be different for each time slot. Here, VLAN-CoS (Class of Service) is used as an identifier for controlling the gate for the queue, and it is possible to control the opening (gate open) and closing (gate close) of the queue gate. The CoS value represents the priority of the priority traffic class, and the priority order is 0, which is the lowest, and 7, which is the highest. Based on the priority of the eight classes, eight queues and gates are provided for each egress port, and eight gates are controlled for each time slot. The GCL may be configured to open multiple gates at the same time.

[0045] First, the frame receiving unit 21 receives a frame from another signal transfer device 10 (step S100).

[0046] Next, the priority traffic class determination unit 22 determines the priority traffic class based on information included in the received frame, for example, a PCP (Priority Code Point) value (step S101). The PCP value is information indicating the priority of traffic. As the information indicating the priority of traffic, traffic class information included in the frame may be used, or an identifier for determining the priority of traffic may be added to the frame.

[0047] Next, the frequency deviation determination unit 23 determines the frequency deviation of the frames for the time slot of the own device based on the distribution of the frames received for the time slot of the own device in the priority traffic class determined by the priority traffic class determination unit 22 (step S102). In step S102, the direction of the frequency deviation is also determined.

[0048] 7 is a diagram explaining the direction of frequency shift of a frame. Time slot TS0 is gate-closed for all priority traffic classes. Time slot TS1 is gate-open only for the traffic priority of the first location BA1. Time slot TS2 is gate-open only for the traffic priority of the second location BA2.

[0049] Fig. 7(a) is a diagram for explaining the timing of traffic expected by the signal forwarding device 10. That is, in Fig. 7(a), frames of the priority traffic class are received so as to coincide with time slots synchronized with the time and frequency of the signal forwarding device 10. In Fig. 7(a), no frequency deviation occurs.

[0050] 7(b) is a diagram for explaining a first example of the timing of a received frame. In this first example, the frame of the priority traffic class is shifted to the right from the time slot. In other words, in the first example, the frame is delayed from the time slot. In this case, it is defined that the frequency of the received frame is shifted to the lower frequency direction.

[0051] 7(c) is a diagram for explaining a second example of the timing of a received frame. In this second example, the frame of the priority traffic class is shifted to the left of the time slot. In other words, in the second example, the frame is ahead of the time slot. In this case, the frequency of the received frame is defined as being shifted in the high frequency direction. The frequency deviation determination unit 23 determines the frequency deviation and also determines whether the deviation is in the high frequency direction or the low frequency direction.

[0052] If a frequency deviation occurs (step S103=Yes), the TS adjustment queue 24 holds the frame until the transmission timing in order to match the frame with the time slot of the own device (step S104). The TS adjustment queue 24 is configured as a FIFO (first-in first-out) queue.

[0053] Next, the TS adjustment gate opening / closing unit 25 adjusts the timing for opening the gate of the TS adjustment queue 24 in accordance with the frequency shift determined by the frequency shift determination unit 23. In other words, the TS adjustment gate opening / closing unit 25 adjusts the timing for transferring the frame to the transmission queue 31.

[0054] Specifically, if the frequency deviation determination unit 23 determines that there is a deviation in the high frequency direction (step S105=Yes), the TS adjustment gate opening / closing unit 25 controls the timing of opening the gate of the TS adjustment queue 24 so that the frame is delayed by the deviation time α (step S106).

[0055] Fig. 8 is a diagram for explaining the timing adjustment operation when a frequency shift occurs in the high frequency direction. As shown in Fig. 8(a), the frame of the first point BA1 is aligned with the timing of the time slot of the device itself. The frame of the second point BA2 has a frequency shift in the high frequency direction.

[0056] The TS adjustment gate opening / closing unit 25 controls the timing of opening the gate of the TS adjustment queue 24 so that the frame at the second location BA2 is delayed. Specifically, the TS adjustment gate opening / closing unit 25 controls the timing of opening the gate of the TS adjustment queue 24 so that the frame is delayed by the shifted time α. This adjusts the timing of transferring the frame at the second location BA2 to the transmission queue 31, as shown in FIG. 8(b).

[0057] On the other hand, if the frequency deviation judgment unit 23 judges that there is a deviation in the lower frequency direction (step S105=No), the TS adjustment gate opening / closing unit 25 controls the timing of opening the gate of the TS adjustment queue 24 so that the frame is delayed until the time slot of the next period (step S107).

[0058] Fig. 9 is a diagram for explaining the timing adjustment operation when a frequency shift occurs in the low frequency direction. As shown in Fig. 9(a), the frame of the first point BA1 has a frequency shift in the low frequency direction. The frame of the second point BA2 is aligned with the timing of the time slot of the device itself.

[0059] The TS adjustment gate opening / closing unit 25 controls the timing of opening the gate of the TS adjustment queue 24 so that the frame of the first point BA1 is delayed until the time slot of the next period. Specifically, the TS adjustment gate opening / closing unit 25 controls the timing of opening the gate of the TS adjustment queue 24 so that the frame is delayed by "1 period - α", assuming that the shift time is α. This adjusts the timing of transferring the frame of the first point BA1 to the transmission queue 31, as shown in Fig. 9(b).

[0060] On the other hand, if no frequency deviation has occurred (step S103=No), the TS adjustment gate opening / closing unit 25 proceeds to step S108 and sends the frame to the transmission queue 31 without delaying the transmission timing.

[0061] Next, the transmission queue 31 holds frames for each priority traffic class (step S108). That is, the transmission queue 31 has queues in the number corresponding to the priority traffic classes. The transmission queue 31 is made up of FIFO queues provided for each priority traffic class.

[0062] The transmission gate opening / closing unit 32 controls the timing of opening the gate of the transmission queue 31 based on the time information stored in the time information storage unit 40 and the GCL stored in the GCL storage unit 41 (step S109). As a result, frames of the priority traffic class are transferred from the transmission queue 31 to the frame transmitting unit 33.

[0063] The frame transmitting unit 33 transmits the frame to the edge device 11 via the output port PT2 in accordance with the destination information contained in the frame (step S110).

[0064] In this way, even when the signal transfer device 10 receives a frame from an edge device 11 that uses a different frequency, the signal transfer device 10 can transfer the frame while avoiding collision of the frames.

[0065] [1-4] Effects of the first embodiment If frequency synchronization is not achieved between the user terminal 12 and the edge device 11 and the signal forwarding device 10, there is a possibility that frames may move relative to time slots in the signal forwarding device 10.

[0066] According to the first embodiment, when a frequency shift occurs in a frame relative to a time slot, the transmission timing of the frame can be adjusted to match the time slot. This makes it possible to realize a signal transfer device 10 that can avoid collisions of frames between priority traffic classes.

[0067] In addition, the system is designed to determine whether the frequency shift is occurring in the high-frequency direction or the low-frequency direction, and the delay amount is adjusted according to the direction of the frequency shift, thereby enabling more accurate control of the transmission timing.

[0068] [2] Second embodiment In the second embodiment, even if a frequency shift occurs in the traffic, if the frame fits into the time slot, the frame transmission timing is not delayed.

[0069] 10 is a flowchart for explaining the operation of the signal transfer device 10 according to the second embodiment of the present invention. The block configuration of the signal transfer device 10 according to the second embodiment is the same as that of the first embodiment. The operation when there is a deviation in the high frequency direction is the same as that of the first embodiment.

[0070] If the frequency deviation judgment unit 23 judges that there is a deviation in the low frequency direction (step S105=No), the TS adjustment gate opening / closing unit 25 judges whether or not a deviation longer than the allowable timing has occurred (step S200). The allowable timing is the maximum deviation time within the range in which the frame fits within the time slot. The second embodiment assumes that the frame length of the frame to be transmitted and received is smaller than the width of the time slot. In other words, even if a frequency deviation occurs and the frame timing is shifted, the frame will fit within the time slot as long as the deviation time is within the allowable timing. Conversely, if the deviation time is longer than the allowable timing, the frame will not fit within the time slot.

[0071] If a delay longer than the allowable timing occurs (step S200=Yes), the TS adjustment gate opening / closing unit 25 controls the timing of opening the gate of the TS adjustment queue 24 so that the frame is delayed until the time slot of the next period (step S107).

[0072] On the other hand, if the difference is within the allowable timing (step S200=No), the TS adjustment gate opening / closing section 25 proceeds to step S108 and sends the frame to the transmission queue 31 without delaying the transmission timing.

[0073] According to the second embodiment, slight frequency deviations are not adjusted (are tolerated), so that delays can be avoided when a slight deviation fits within the time slot width.

[0074] [3] Third embodiment In the third embodiment, when a frequency shift occurs in the traffic, the frame is divided into a first part that fits into the time slot and a second part that does not fit into the time slot, and the first part is transmitted without delay and the second part is transmitted after being delayed until the time slot of the next period.

[0075] 11A and 11B are flowcharts for explaining the operation of the signal transfer device 10 according to the third embodiment of the present invention. The block configuration of the signal transfer device 10 according to the third embodiment is the same as that of the first embodiment. The operation when there is a deviation in the high frequency direction is the same as that of the first embodiment.

[0076] If the frequency deviation judgment unit 23 judges that the frequency deviation is in the lower frequency direction (step S105=No), the TS adjustment gate opening / closing unit 25 judges whether the frame can be transmitted within the time slot (step S300). If the frame can be transmitted within the time slot (step S300=Yes), the process proceeds to step S108.

[0077] If the frame cannot be transmitted within the time slot (step S300=No), the TS adjustment gate opening / closing unit 25 determines whether or not the first part can be transmitted within the time slot when the frame is divided into a first part and a second part (step S301).

[0078] If the first portion of the frame can be transmitted within the time slot (step S301=Yes), the TS adjustment gate opening / closing unit 25 divides the frame into a first portion and a second portion, and controls the timing of opening the gate of the TS adjustment queue 24 so that the first portion is not delayed and the second portion is delayed until the time slot of the next period (step S302). In other words, the TS adjustment gate opening / closing unit 25 sends the first portion of the frame that fits within the time slot to the transmission queue 31 without delay, and sends the second portion that does not fit within the time slot to the transmission queue 31 with a delay until the time slot of the next period.

[0079] If the first portion of the frame cannot be transmitted within the time slot (step S301=No), the TS adjustment gate opening / closing unit 25 controls the timing of opening the gate of the TS adjustment queue 24 so that the frame is delayed until the time slot of the next period (step S303).

[0080] Fig. 12 is a diagram for explaining the timing adjustment operation when a frequency shift occurs in the low frequency direction. As shown in Fig. 12(a), the frame of the first point BA1 has a frequency shift in the low frequency direction. The frame of the second point BA2 is aligned with the timing of the time slot of the device itself.

[0081] The TS adjustment gate opening / closing unit 25 controls the timing of opening the gate of the TS adjustment queue 24 so that the first portion of the frame at the first site BA1 that fits into the time slot is not delayed, and the second portion that does not fit into the time slot is delayed until the time slot of the next period. Specifically, the TS adjustment gate opening / closing unit 25 controls the timing of opening the gate of the TS adjustment queue 24 so that the second portion is delayed by "1 period - β", assuming that the period of the time slot is β. As a result, as shown in Fig. 12(b), the frame at the first site BA1 is divided into a first portion and a second portion, and the first portion and the second portion are transferred to the transmission queue 31 in different time slots.

[0082] The operations from step S108 onwards are the same as those in the first embodiment.

[0083] According to the third embodiment, the first part of the frame that fits into the time slot can be transmitted without delay. Also, only the second part of the frame that does not fit into the time slot can be divided and delayed. This makes it possible to reduce the amount of delay of the frame compared to the first embodiment.

[0084] For example, frame preemption can be used to divide a frame.

[0085] [4] Fourth embodiment In the fourth embodiment, when a frequency shift occurs, the width of the time slot is adjusted to match the frequency that is shifted most toward the lowest frequency.

[0086] [4-1] Configuration of signal transfer device 10 13 is a block diagram of a signal transfer device 10 according to a fourth embodiment of the present invention. The signal transfer device 10 further includes a frequency deviation information storage unit 42. The receiver 20 further includes a TS (time slot) adjustment unit 26.

[0087] The frequency deviation determining unit 23 sends the frequency deviation information calculated in the frequency deviation determining operation to the frequency deviation information storage unit 42 as needed.

[0088] The frequency deviation information storage unit 42 stores multiple pieces of past frequency deviation information calculated in the frequency deviation determination operation by the frequency deviation determination unit 23 at any time. The frequency deviation information storage unit 42 also stores multiple pieces of frequency deviation information received from other signal transfer devices 10 connected to the own device.

[0089] The receiver 20 receives frequency deviation information from another signal transfer device 10 connected to the receiver 20, and stores the received frequency deviation information in the frequency deviation information storage unit 42. The transmitter 30 transmits the frequency deviation information calculated by the receiver 20 to the other signal transfer device 10.

[0090] The TS adjustment unit 26 receives frequency deviation information from the frequency deviation information storage unit 42, and receives a GCL from the GCL storage unit 41. As described above, the GCL includes time slot information. The TS adjustment unit 26 determines the frequency deviation information that is shifted most toward the lowest frequency based on the frequency of its own device and the frequency deviation information stored in the frequency deviation information storage unit 42. The TS adjustment unit 26 adjusts the time slot width based on the determined frequency deviation information. The other configurations are the same as those in the first embodiment.

[0091] [4-2] Operation 14 is a flowchart illustrating the operation of the signal transfer device 10. The operations from step S100 to step S104 are the same as those in the first embodiment.

[0092] The signal transfer device 10 stores a plurality of pieces of frequency deviation information calculated in past signal transfer operations in the frequency deviation information storage unit 42. In addition, the signal transfer device 10 stores a plurality of pieces of frequency deviation information received from other signal transfer devices 10 connected to the own device in the frequency deviation information storage unit 42.

[0093] When a frequency deviation occurs, the TS adjusting unit 26 determines the frequency deviation information that is shifted most toward the lowest frequency based on the frequency of its own device and the frequency deviation information stored in the frequency deviation information storage unit 42 (step S400).

[0094] Next, the TS adjusting unit 26 adjusts the width of the time slot based on the frequency deviation information that is shifted most toward the lowest frequency (step S401).

[0095] Fig. 15 is a diagram for explaining the time slot adjustment operation when a frequency shift occurs. As shown in Fig. 15(a), the frame of the first point BA1 has a frequency shift in the low frequency direction. The frame of the second point BA2 matches the timing of the time slot of the device itself. The frame of the first point BA1 is assumed to be a device that operates at a frequency shifted most in the low frequency direction.

[0096] The TS adjusting unit 26 adjusts the width of the time slot so that the frame of the first point BA1 fits into the time slot. As a result, as shown in FIG. 15(b), the frame of the first point BA1 is adjusted to fit into the corresponding time slot without being delayed.

[0097] There is no need to delay the transmission timing of frames shifted toward lower frequencies due to the adjustment of the time slot width by the TS adjustment unit 26. On the other hand, frames at the second location BA2 are shifted toward higher frequencies due to the adjustment of the time slot width by the TS adjustment unit 26. Similarly, frames at locations other than the first location BA1 are all shifted toward higher frequencies when a frequency shift occurs.

[0098] Next, the TS adjustment gate opening / closing unit 25 controls the timing of opening the gate of the TS adjustment queue 24 so that the frame is delayed by the shifted time α (step S106). The TS adjustment gate opening / closing unit 25 operates based on the time slot adjusted by the TS adjustment unit 26. This adjusts the timing so that the frame shifted in the high frequency direction matches the time slot.

[0099] Next, the transmission queue 31 holds frames for each priority traffic class (step S108).

[0100] The transmission gate opening / closing unit 32 controls the timing of opening the gate of the transmission queue 31 based on the time information stored in the time information storage unit 40, the GCL stored in the GCL storage unit 41, and the time slot adjusted by the TS adjustment unit 26 (step S109). As a result, frames of the priority traffic class are transferred from the transmission queue 31 to the frame transmission unit 33.

[0101] The frame transmitting unit 33 transmits the frame to the edge device 11 via the output port PT2 in accordance with the destination information contained in the frame (step S110).

[0102] [4-3] Effects of the fourth embodiment According to the fourth embodiment, when the frequency is shifted toward a lower frequency, the width of the time slot is adjusted based on the frequency shift information that is shifted the most toward the lower frequency. Therefore, when the frequency is shifted toward a lower frequency, it is not necessary to delay the frame by one period. This makes it possible to reduce the overall delay amount. Other effects are the same as those of the first embodiment.

[0103] [5] Variations Each process according to the above-described embodiment can be stored as a program that can be executed by a processor, which is a computer. Alternatively, the program can be stored in a storage medium of an external storage device, such as a magnetic disk, an optical disk, or a semiconductor memory, and distributed. The processor can then read the program stored in the storage medium of the external storage device, and the processor's operation is controlled by the read program, thereby executing the above-described process. The program can also be provided through a network.

[0104] The present invention is not limited to the above-mentioned embodiment, and various modifications can be made in the implementation stage without departing from the gist of the invention. In addition, the embodiments may be implemented in appropriate combination, and in that case, the combined effect can be obtained. Furthermore, the above-mentioned embodiment includes various inventions, and various inventions can be extracted by combinations selected from the multiple components disclosed. For example, if the problem can be solved and the effect can be obtained even if some components are deleted from all the components shown in the embodiment, the configuration from which the components are deleted can be extracted as an invention. [Explanation of symbols]

[0105] 1. Signal transmission system 10...Signal transmission device 11…Edge device 12...User terminal 20…Receiver 21...Frame receiver 22... Priority traffic class determination unit 23…Judgment section 24…TS Adjustment Queue 25...TS adjustment gate opening / closing section 26...TS adjustment section 30…Transmitter 31...Transmission queue 32...Transmission gate opening / closing section 33...Frame transmitter 40...Time information storage unit 41...GCL storage section 42...Frequency deviation information storage unit PT1: Input port PT2: Output port 101…Processor 102…Program memory 103...Data memory 104... Input / Output Interface 105...Communication interface 106…Bus BA1~BA3…Base

Claims

1. A signal transfer device connected to a communication network for performing data communication between a plurality of user terminals, A receiving unit for receiving a frame from a user terminal; a first determination unit that determines a priority traffic class based on first information included in the frame; a second determination unit that, when receiving a frame related to a priority traffic class, determines a frequency shift of the frame relative to the time slot based on a distribution of the frame relative to the time slot of the own device; a first queue for holding the frames; a first gate opening / closing unit that adjusts a timing for opening a gate of the first queue when the frequency deviation occurs; a second queue for holding frames sent from the first queue; a storage unit for storing second information indicating which priority traffic class is to be transmitted for each time slot; a second gate opening / closing unit that controls a timing for opening a gate of the second queue based on the second information; a transmission unit for transmitting frames sent from the second queue; Equipped with The first gate opening / closing unit adjusts the timing of opening the gate of the first queue so that the frame is delayed until the time slot when a frequency shift occurs in a high frequency direction. Signal transmission device.

2. The first gate opening / closing unit adjusts the timing of opening the gate of the first queue so that the frame is delayed until the time slot of the next period when a frequency shift occurs in the low frequency direction.

2. The signal transfer device according to claim 1.

3. The first gate opening / closing unit is If a frequency shift occurs in the low frequency direction, it is determined whether or not a time shift longer than an allowable timing occurs; If a delay longer than the allowable timing occurs, the timing for opening the gate of the first queue is adjusted so that the frame is delayed until the time slot of the next period.

2. The signal transfer device according to claim 1.

4. When a frequency shift occurs in a low frequency direction, the first gate opening / closing unit adjusts the timing of opening the gate of the first queue so that a first portion of the frame that fits into the time slot is not delayed and a second portion that does not fit into the time slot is delayed until the time slot of the next period.

2. The signal transfer device according to claim 1.

5. A signal transfer device connected to a communication network for performing data communication between a plurality of user terminals, A receiving unit for receiving a frame from a user terminal; a first determination unit that determines a priority traffic class based on first information included in the frame; a second determination unit that, when receiving a frame related to a priority traffic class, determines a frequency shift of the frame relative to the time slot based on a distribution of the frame relative to the time slot of the own device; a first queue for holding the frames; a first storage unit for storing second information indicating which priority traffic class is to be transmitted for each time slot; A second storage unit for storing frequency deviation information relating to the plurality of user terminals; an adjustment unit that determines first frequency deviation information that is shifted most toward a lower frequency based on a frequency of the own device, the second information, and the frequency deviation information, and adjusts a width of a time slot based on the first frequency deviation information; a first gate opening / closing unit that adjusts a timing for opening a gate of the first queue when the frequency deviation occurs; a second queue for holding frames sent from the first queue; a second gate opening / closing unit that controls a timing for opening a gate of the second queue based on the time slot adjusted by the adjustment unit; a transmission unit for transmitting frames sent from the second queue; A signal transmission device comprising:

6. A signal forwarding method executed by a signal forwarding device connected to a communication network for performing data communication between a plurality of user terminals, comprising: receiving a frame from a user terminal; determining a priority traffic class based on first information included in the frame; When receiving a frame related to a priority traffic class, determining a frequency shift of the frame relative to the time slot based on a distribution of the frame relative to the time slot of the own device; storing said frame in a first queue; When the frequency deviation occurs, a timing for opening the gate of the first queue is adjusted; A frame sent from the first queue is held in a second queue; Controlling the timing of opening the gate of the second queue based on second information indicating which priority traffic class is to be transmitted for each time slot; Transmitting frames sent from the second queue; When a frequency shift occurs in the high frequency direction, the timing for opening the gate of the first queue is adjusted so that the frame is delayed until the time slot. Signal transfer method.

7. A program for causing a computer to function as each unit of the signal transfer device according to any one of claims 1 to 5.

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