JP4392373B2 - Communication method, transmission timing notification device, edge device, program, and storage medium - Google Patents

Description

  The present invention relates to a communication method for preventing data corruption due to collision between signals generated by connecting a plurality of edge devices on the user side and external devices by branching transmission lines, and in particular, tolerance of data loss. The present invention relates to a communication method for transmitting data with low loss with low loss.

  In recent years, with an increase in data traffic, a demand for a large-capacity optical transmission system is increasing. As these types, wavelength multiplexing systems such as WDM (Wavelength Division Multiplexing), time division multiplexing systems such as optical TDM (Time Division Multiplexing), and packet multiplexing systems such as optical burst switching and optical packet switching are currently proposed. Among them, GEPON (Gigabit Ethernet (registered trademark) Passive Optical Network) exists as a broadcast-type optical transmission system (Non-patent Document 1).

  GEPON is realized on a tree-like network without a loop. A coupler (splitter) that branches an optical signal is provided at a branch point of the network. In GEPON, there are an optical network unit (ONU) and an optical line terminal (OLT) as devices that transmit optical signals. The ONU has a user (a personal computer or the like) arranged downstream, and plays a role of converting data from the user into an optical signal and transmitting it to another ONU. The optical signal transmitted from the ONU is once terminated by the OLT and sent to another ONU. At this time, if optical signals are transmitted from a plurality of ONUs at the same time, the signals collide with each other in the network. Therefore, in GEPON, which requires adjustment of ONU signal transfer timing, the OLT transfers optical signals to the ONU. This adjustment is performed by notifying the start time and end time.

  An intermediate point of GEPON is that an optical signal reaches all ONUs physically connected by an optical fiber (transmission line) constituting the network. When the optical signal is transferred from the OLT to the ONU, the signal level is attenuated by a coupler which is a branch point of the network. Since the amount of attenuation depends on the number of branches of the coupler, the amount of attenuation increases as the number of ONUs existing ahead of the coupler increases. To solve this problem, consider using an optical transmission system using a multipoint-to-multipoint optical path that can limit the number of branches at a branch point.

This method is a technique that uses an edge device that transmits an optical signal and a switch device that branches the optical signal and guides it to a destination of the signal, and performs optical transmission over a network made of optical fibers. By using not only a coupler but also a switch as a branch point of the network, it can be guided only to a place where an optical signal is desired to be sent. Each edge device uses this optical signal to transmit data to other edge devices to which the signal reaches. By using this method, the attenuation of the optical signal is reduced, and a longer interval optical signal can be transmitted. Further, by reducing the number of optical fibers through which signals pass, it becomes possible to use optical signals having the same wavelength in different optical fibers, and the use efficiency of optical signals in the entire network is improved.
“Knowing the latest technology of FTTH”, Nikkei Network, pp.43-61, Jun.2004

  In an optical transmission method using a multipoint-to-multipoint path, more data is carried, and so improvement of the path utilization rate is an issue. As a method for realizing this, there is a method for reducing the data loss rate by avoiding data corruption due to signal collision by predetermining the time at which the edge device transmits a signal as in the time division multiplex transmission method. is there. At this time, the use efficiency is further improved by setting the time when the edge device finishes signal transmission and the time when another edge device starts signal transmission to the same time. At this time, an important factor that determines the performance of the system is the accuracy of the time that each edge device is viewing. If each edge device sees exactly the same time, the occurrence of a collision or time during which no signal is transmitted can be avoided.

  However, each edge device has a device for managing time, and it is very difficult to set all of them to the same time. In addition, fluctuations occur in the time managed by the managing device itself, so it is difficult to always notify the time at the same interval. Even in such a case, the edge device transmits the data on the signal based on the information that it has, but because the time fluctuates, the data transmitted assuming that there is no signal from other edge devices There is a case of loss due to a signal from the edge device. In a transmission method in which a class exists in the way of handling data, data that does not allow loss is also carried. Therefore, avoiding such a situation is important in terms of quality improvement.

  The present invention has been made in view of such a situation. When data is transmitted at a predetermined timing using a signal that may cause data corruption due to a collision, the present invention shifts to a clock held by each device. It is an object of the present invention to provide a communication method that can transmit data with low loss to data with low tolerance for data loss even when a problem occurs or when synchronization between devices cannot be successfully performed. To do.

(Communication method)
The present invention that solves the above-described problems (Claim 1) is a communication method for preventing data corruption due to collision of signals generated by connecting a plurality of edge devices on the user side by branching transmission lines. In this communication method, the signal transmission start / end timing of each edge device is determined so as not to collide with signals transmitted by other edge devices. In this communication method, the edge device (1) stores data to be transmitted with different tolerances for loss in the data storage unit according to tolerance, and (2) divides the timing into five or more sections. Then, data is read from the data storage unit and placed in the section so that data with low tolerance for data loss and high reliability is placed in the inner section, and the data arranged in this way It is performed including a procedure of transmitting the signal on the signal from the signal transmission unit.

In this configuration, data to be transmitted is stored for each loss tolerance, and at the time of transmission, the transmission timing is divided into five or more sections, and data with low tolerance is arranged (assigned) in the inner section. For this reason, for example, even when there is a shift in the clock or when synchronization between the devices is not successful, the possibility of the influence reaching the inner section is less than before and after (both ends) of the section. By arranging data in consideration of the allowance for loss in this way, it is possible to transmit data with low loss to data with low allowance for data loss. “Place data with low tolerance in the inner section” is the same as “Place data with high tolerance in the outer section”. Further, it is the same as “Place data with low tolerance in sections other than the earliest and latest sections”.

(Transmission timing notification device)
Further, the present invention (Claim 2 ) is used in the communication method according to Claim 1, and a transmission timing notification for notifying the timing of transmitting data to at least one edge device to be managed among the plurality of edge devices. Device. The transmission timing notification device includes (1) a function of acquiring the start / end timing of signal transmission in each edge device from the external device and storing it in the storage unit, and (2) the stored timing and the It is characterized in that it has a function of notifying the edge device to be managed of signal transmission based on the time of the timepiece device that measures the time managed by the external device.

  In this configuration, the edge timing to be managed is notified of the signal transmission timing. One or a plurality of edge devices may be managed. In the embodiment described later, the transmission timing notification device will be described as existing inside each edge device.

(Edge device)
Further, the present invention (Claim 3 ) is an edge device used in a communication method for preventing data corruption due to collision between signals generated by connecting a plurality of edge devices on the user side by branching transmission lines. is there. The edge device includes (1) a data storage unit that stores data with different tolerances for data loss, and (2) a signal transmission unit that transmits the data stored in the data storage unit on a signal. Prepare. When transmitting the data, this edge device divides the transmission start / end timing into five or more sections, and data with low tolerance for data loss and high reliability is arranged in the inner section. As described above, the data is read from the data storage unit and arranged in the section, and the arranged data is transmitted on the signal via the signal transmission unit.

In this configuration, similarly to the first aspect, it is possible to transmit data with low loss to data with low tolerance for data loss.
In “Best Mode for Carrying Out the Invention” to be described later (see FIGS. 1 and 2 to be described later), a data storage unit is a transfer data storage unit 332, a signal transmission unit is an optical signal transmission / reception unit 333 (related to transmission) Part).

Further, according to the present invention (Claim 4 ), in the configuration of Claim 3 , the edge device comprises: (1) a clock device that counts a time managed by an external device that instructs the timing of signal transmission of each edge device; (2) storage means for storing the start / end timing of signal transmission in the edge device acquired from the external device, and (3) the signal transmission unit transmits a signal based on the timing and the time of the timepiece device. It has a control part which notifies transmission.

  According to this configuration, the timing can be determined appropriately. In “Best Mode for Carrying Out the Invention” described later (see FIGS. 1 and 2 described later), the timepiece device corresponds to the clock 34 and the control unit corresponds to the control unit 311.

Further, according to the present invention (Claim 5 ), in the configuration of Claim 3 , the edge device comprises: (1) a clock device that counts a time managed by an external device that instructs the timing of signal transmission of each edge device; (2) Storage means for storing start / end timing of signal transmission in another edge device acquired from the external device, (3) Based on start / end timing of signal transmission in the other edge device And a control unit that determines the start / end timing of signal transmission in its own edge device and notifies the signal transmission unit of signal transmission based on this timing and the time of the timepiece device. And

  According to this configuration, it is possible to appropriately determine its own timing based on the timing of another edge device.

(Program / Media)
A program according to the present invention (Claim 6 ) causes a computer to execute the communication method according to Claim 1 . A storage medium of the present invention (Claim 7 ) stores the program according to Claim 6 .

  According to the present invention, even when there is a shift in the clock held by each device, or even when synchronization between devices is not successful, data is transmitted with low loss for data with a low tolerance for data loss. It becomes possible.

  Hereinafter, the best mode (hereinafter referred to as “embodiment”) for carrying out the communication method, transmission timing notification device, edge device, program, and storage medium of the present invention will be described in detail.

≪First embodiment≫
In the first embodiment, signals are transmitted from a plurality of edge devices using optical signals that may cause data corruption due to collisions between the signals, and the transmitted signals pass through the same path to each other, and for each edge device. In a communication method in which the time for which a signal can be output is determined, the transmission (transfer) timing (order within the timing) is determined according to the tolerance for data with different degrees of tolerance (tolerance) for data loss. In this way, it is possible to transmit data at a loss rate according to the tolerance.

[Overall configuration of communication system]
FIG. 1 is a diagram illustrating an overall configuration of a communication system to which a communication method and the like according to the present embodiment are applied, and a configuration of an ONU as an edge device.
As shown in FIG. 1, the communication system includes an OLT 1 installed in the accommodation station and ONUs 3 (3 a, 3 b) installed in a plurality of user homes via an optical fiber (transmission line) F via a switch 2. Connected to the network. In this figure, only two ONUs 3 are shown, but the number is not particularly limited. In this embodiment, the OLT 1 corresponds to an external device, and the ONU 3 corresponds to an edge device. Incidentally, as an external device, there is a router in addition to the OLT 1.

[OLT (external device)]
The OLT 1 has a function of assigning an identifier (LLID) for identifying each ONU 3. The OLT 1 has a function of obtaining each transmission delay time when communicating with each ONU 3 and managing this transmission delay time in association with the identifier described above. For this reason, as will be described later, the ONU 3 is configured to adjust the time of the clock provided in the ONU 3 using the time described in the control frame transmitted by the OLT 1. The OLT 1 determines in advance the timing at which each ONU 3 transmits a signal to the network, and notifies each ONU 3 of the timing.

[switch]
The switch 2 is configured by an optical cross connect (OXC) or the like, and has a function of guiding an optical signal only to the destination of the optical signal. Incidentally, in the switch 2, optical signals collide with each other for reasons such as not switching data on a packet basis, and data corruption occurs due to the collision between the signals.

[ONU (edge device)]
A personal computer (hereinafter referred to as “personal computer”) PC is connected to each ONU 3 via a cable C of Gigabit Ethernet (registered trademark). Each ONU 3 converts an electrical signal transmitted by the personal computer PC via the cable C into an optical signal, and is directed to the network (switch 2) under the management of the OLT 1 so that the optical signals do not collide with each other in the network. It is configured to transmit at a predetermined timing. In addition, about the basic communication method which transmits so that optical signals may not collide by this OLT1 and ONU3, what was described in the above-mentioned nonpatent literature 1 is applied, and description is abbreviate | omitted.

  However, in the communication method in which each ONU 3 transmits an optical signal as in Non-Patent Document 1, the optical signals collide with each other when the ONU 3 has a clock shift, or when the ONUs 3 cannot synchronize well. And data corruption occurs.

  Therefore, as shown in FIG. 1, in this embodiment, the ONU 3 includes a transmission timing notification device 31, a signaling device 32, a transfer device 33, a clock 34, and the like.

  The transmission timing notification device 31 notifies the transfer device 33 of the timing (transmission start time / transmission end time) at which data to be transferred (appropriately referred to as “transfer data”) is transmitted on the optical signal. Have This timing is acquired from the OLT 1 through the signaling device 32 for the purpose of adjusting the communication timing between the ONUs 3.

  The signaling device 32 has a function of acquiring the transmission timing of the ONU 3 from the OLT 1 as described above.

  The transfer device 33 has a function of transmitting transfer data on an optical signal to the network at the timing notified from the transmission timing notification device 31. Therefore, as illustrated in FIG. 1, the transfer device 33 includes an electrical signal transmission / reception unit 331, a transfer data storage unit 332, an optical signal transmission / reception unit 333, and the like.

  The electric signal transmission / reception unit 331 has a function of transmitting / receiving an electric signal to / from the personal computer PC. Thereby, it becomes possible to receive the transfer data transmitted by the personal computer PC on the electric signal. The transfer data storage unit 332 has a function of storing transfer data having different tolerances for data loss by tolerance (by class). The optical signal transmission / reception unit 333 has a function of transmitting / receiving an optical signal to / from the network. As a result, the transfer data transmitted by the personal computer PC can be transmitted to the network with the optical signal.

  The electrical signal transmission / reception unit 331 classifies the transfer data by tolerance (by class), for example, class 3 for moving images, class 2 for text, class 1 for text, and a predetermined size (data length). ) And stored in the transfer data storage unit 332. In addition, the optical signal transmission / reception unit 333 reads predetermined transfer data in consideration of this class, and transmits the data on the optical signal to the network. Details of storage / reading of the transfer data (functions of the transfer data storage unit 332 and the optical signal transmission / reception unit 333) will be described later with reference to FIGS.

  The clock 34 measures the time set by the clock of the OLT 1. The time adjustment is performed using the method described in Non-Patent Document 1. Incidentally, the clock 34 is configured to include, for example, a quartz clock, and is inexpensive but is not accurate. For this reason, it can be said that the time which the clock 34 ticks easily shifts.

[Configuration of transmission timing notification device]
FIG. 2 is a diagram illustrating a configuration of the transmission timing notification apparatus of FIG.
As shown in FIG. 2, the transmission timing notification device 31 includes a control unit 311, a timing storage unit 312, and the like.

  The control unit 311 corresponds to the function of notifying the ONU 3 (transfer device 33) of signal transmission based on the timing stored in the timing storage unit 312 and the time of the clock 34 that measures the time managed by the OLT 1. To do. Further, the control unit 311 reads the transmission timing stored in the timing storage unit 312, refers to the time of the clock 34, and transmits the optical signal by the transfer device 33 at the transmission timing (transmission start time / transmission end time). It has a function of determining whether or not there is a timing and notifying the transfer apparatus 33 of the timing.

  The timing storage unit 312 has a function of storing timing for transmitting an optical signal. As described above, this timing is obtained through the signaling device 32 that the OLT 1 has notified each ONU 3.

  Note that the timing storage unit 312 acquires and stores the transmission timing of each other ONU 3 via the signaling device 32, and the control unit 311 transmits its own transmission in a vacant time zone during which the other ONU 3 does not transmit. The timing may be set (determined). In addition, the transmission timing notification device 31 may include the clock 34.

[Internal configuration of transfer data storage unit]
FIG. 3 is a diagram showing an internal configuration of the transfer data storage unit of FIG.
As shown in FIG. 3, the transfer data storage unit 332 included in the transfer device 33 classifies and stores the transfer data transmitted from the personal computer PC for each path (by destination) (path A, path B,...). . In addition, a first-in first-out buffer (FIFO) is provided for each tolerance of data loss (by class), and transfer data is stored by tolerance (class 1, class 2,...). Here, class 1 has a higher tolerance for loss (sweeter), and class 2 has a lower tolerance for loss than class 1 (stricter). In other words, the larger the class value, the lower the tolerance for loss (higher class), and the classification is such that loss of transfer data is not allowed. By the way, in FIG. 3, the class 1 buffer has four class 1 transfer data, the class 2 buffer has three transfer data, and the class 3 buffer has two transfer data. The number of classes is an example, and the number of classes may be larger than this (for the purpose of the present embodiment, the number is an integer and a value of 2 or more and N or less). Note that high-level transfer data includes streaming data and the like. Moreover, examples of the lower-class transfer data include text data and still image data. Incidentally, the transfer data is stored for each path, but for the first embodiment, the transfer data need only be classified and stored by class.

[Procedure for assigning transfer data by class]
FIG. 4 shows a procedure for dividing the timing (slot) into three or more sections and assigning transfer data by class so that data with low tolerance for data loss and high reliability is arranged in the inner section. FIG.
In FIG. 4, the transmission start time and transmission end time of the optical signal are determined in advance. In the present embodiment, the optical signal transmission / reception unit 333 of the transfer device 33 determines the time length slots that can be accommodated in the arrangementable time area from the ratio for each preset class or the transfer data amount existing in the buffer. It is assumed that the slot is divided into a plurality of slots according to the determined ratio, and transfer data of each class is assigned to each of the divided slots. Here, since the number of classes is N, an example of dividing into 2N-1 slots is shown. Incidentally, only class 1 transfer data can be assigned to the class 1 slot, and only class 2 transfer data or less can be assigned to the class 2 slot. That is, class N or lower transfer data can be assigned to a class N slot. Note that the allocation of each class is symmetric, and data with a low tolerance for data loss comes to the inner slot (section). For this reason, the number of slots after the division does not become less than 3, and becomes an arbitrary integer of 3 or more. The number of slots to be divided (how many sections to divide) can be determined based on an administrator setting or an instruction from an external device such as OLT 1.

[Example of slot division]
FIG. 5 is a diagram showing an example in which slots are divided at a predetermined ratio.
In FIG. 5, a slot having a time length that fits in the arrangeable time area is divided into five slots. That is, the entire slot is assigned one slot to which transfer data of class 3 or less is assigned in the center, two slots to which transfer data of class 2 or less is assigned to both sides, and further, transfer data of class 1 is assigned to the outside thereof. It is divided into two slots. That is, the transfer data of each class is assigned symmetrically. The division ratio (predetermined ratio) is 2 for class 1, 4 for class 2 or less, and 6 for class 3 or less (2: 4: 6, for example, a division ratio in units of time). The division ratio can also be determined based on an administrator setting or an instruction from an external device such as the OLT 1.

[Assignment / Transmission]
FIG. 6 is a diagram showing an operation of assigning transfer data of each class to divided slots.
In FIG. 6, there are two slots for class 1 (SL1 and SL5), two for class 2 and below (SL2 and SL4), and one for class 3 and below (SL3), for a total of five slots. It is divided into (SL1 to SL5). The division ratio is the same as in FIG. The transfer data storage unit 332 has three buffers for class 1 to class 3 for path A (see FIG. 3).
Hereinafter, an operation of assigning the transfer data stored in the three buffers by class to the slots divided into five will be described with reference to FIG. 6 (refer to FIGS. 1 to 5 as appropriate).

  Initially, two pieces of transfer data are stored in the class 1 buffer, two in the class 2 buffer, and four in the class 3 buffer (P1). This transfer data is transmitted from the personal computer PC on the electric signal, and the electric signal transmission / reception unit 331 sorts and arranges it and stores it in the buffer in the transfer data storage unit 332.

First, transfer data of class 1 is assigned to slot SL1 for class 1 (S1).
The optical signal transmission / reception unit 333 extracts one transfer data of class 1 from the buffer of the transfer data storage unit 332 and assigns it to the slot SL1. Thereby, the transfer data of class 1 of the buffer is reduced from two to one (P2).

Next, transfer data of class 2 or lower is assigned to slot SL2 (S2).
The optical signal transmission / reception unit 333 extracts two class 2 transfer data from the buffer of the data storage unit 332 and assigns them to the slot SL2. Note that a total of two pieces of transfer data, one transfer data of class 1 and one transfer data of class 2, can be assigned to the slot SL2. However, in the present embodiment, it is assumed that data of a higher class is assigned and lower data is assigned if there is a surplus.
Thereby, the transfer data of class 2 becomes 0 (P3). At point P3, the transfer data of class 1 is increased by 1 to 2 (represented by “+1” in the figure). This is because new transfer data is stored in the buffer during step S2. It means that it was done. Incidentally, the number of transfer data of each buffer at the time of the point P3 is six in total, such as two for the class 1 buffer, zero for the class 2 buffer, and four for the class 3 buffer.

Next, transfer data of class 3 or lower is assigned to slot SL3 (S3).
The optical signal transmission / reception unit 333 extracts two pieces of class 3 transfer data from the buffer of the data storage unit 332 and assigns three to the slot SL3. As a result, the total number of transfer data in each buffer at the time point P3.5 is four, such as two for class 1 buffers, one for class 2 buffers, and one for class 3 buffers. It is. At point P3.5, the number of transfer data in the class 2 buffer is 1 instead of 0. This is because one new transfer data of class 2 was stored in the buffer during step S3. I mean.

Next, transfer data of class 3 or lower is assigned to slot SL3 (S3.5).
In step S3 described above, three class 3 transfer data are allocated to the slot SL3. However, the slot SL3 still has a space to allocate three transfer data. For this reason, the optical signal transmission / reception unit 333 allocates class 3, class 2, and class 1 transfer data one by one to the vacant portion of the slot SL3. At this time, there are an assignment method of one transfer data of class 2 and two transfer data of class 1 and an assignment method of one transfer data of class 3 and two transfer data of class 1. However, in the present embodiment, first, high-order transfer data is assigned, and if there is a vacancy, the transfer data one level lower than that is assigned. This ensures that the higher class transfer data is allocated to the inner slot.
As a result, the number of transfer data in each buffer at the time of the point P4 is one, such as one for the class 1 buffer, 0 for the class 2 buffer, and 0 for the class 3 buffer.

Next, transfer data of class 2 or lower is assigned to slot SL4 (S4).
The optical signal transmission / reception unit 333 attempts to take out the transfer data of class 2 from the buffer of the data storage unit 332 and assign it to the slot SL4. However, since there is no class 2 transfer data in the buffer, class 1 transfer data is allocated. However, since there is only one transfer data of class 1, one is assigned.
As a result, the number of transfer data in each buffer at time point P5 is 0 for all of class 1 to class 3.

Finally, class 1 transfer data is assigned to slot SL5 (S5).
Since there is no class 1 transfer data in the buffer of the data storage unit 332, no allocation is performed.

  The transfer device 33 transmits the transfer data thus allocated to the slot on the optical signal to the network.

[Procedure flowchart]
FIG. 7 is a flowchart showing the procedure of the communication method.
Hereinafter, this flowchart will be described with reference to FIG. The main operation is the external device (OLT) 1 from S11 to S14, and each ONU 3 is S15. However, all the operations may be performed by the ONU 3 having a calculation function.

  First, the OLT 1 acquires Multipoint-to-Multipoint path information from the network (S11). Information to be acquired includes node and route information, bandwidth information, and the like. Next, the OLT 1 acquires information on the delay incurred between the branch points of the path and the delay incurred between the adjacent branch points (S12). Subsequently, the OLT 1 calculates the time at which the optical signal transmitted from each edge device passes through the optical fiber constituting the path from the information regarding the delay (S13; passage time calculation). Then, the OLT 1 determines the transmission order of the optical signals of each ONU 3 according to a predetermined algorithm. That is, the transmission timing of each ONU 3 is determined (transmission possible time determination). The ONU 3 is notified of the transmission timing as the determination result (S14).

  Each ONU 3 transmits a signal according to the time (timing) notified in S14 (S15). Specifically, as described above, the control unit 311 notifies the ONU 3 (transfer device 33) of signal transmission based on the timing stored in the timing storage unit 312 and the time of the clock 34, and the transfer. The device 33 transmits a signal.

  At the time of this transmission, in the first embodiment, the transfer device 33 classifies the transfer data transmitted from the personal computer PC into classes with different loss tolerances and stores them in a buffer. In addition, the transfer device 33 divides a slot having a length of time that falls within the notified timing (arrangeable time area) into three or more, and the data slot has a higher tolerance for data loss at the center (inside) of the divided slots. Allocate transfer data. In other words, the determined timing is divided into three or more sections, and data with a low tolerance for data loss and high reliability is arranged in the inner section.

[Transmission timing and passage timing]
FIG. 8 is a diagram showing the transmission timing of each edge unit (ONU) and the signal passing timing of each switch.
In FIG. 8, time advances from the left to the right of the table. In addition, horizontal rows described with reference numerals 3a, 3b, 3c, and 3d in the table indicate the transmission timing (transmission start time / transmission end time) of the optical signal of each ONU 3. In addition, horizontal rows indicated by reference numerals 2a and 2b in the table indicate the passage timing (passage start time / passage end time) of each optical signal in the switches 2a and 2b (nodes). As described above, the transmission timing of the optical signal in each ONU 3 and the transmission timing of the optical signal in each switch 2 are managed. However, when the clock 34 is deviated or the synchronization between the devices is successfully performed. Collisions between optical signals occur when they cannot be taken.
However, since the data is arranged as shown in the upper diagram of FIG. 8, that is, the high-class transfer data is sandwiched between the low-class transfer data. It can be transferred with little loss.
In the lower part of FIG. 8, the numbers such as “1”, “1.25”, and “1.5” attached to the link are the time required for the optical signal to pass through the link (between nodes).

  As described above, according to the first embodiment, even if the clocks held by the respective devices are shifted to each other or the synchronization between the devices cannot be successfully performed, the rate of loss of transfer data having a small loss tolerance is reduced. Quality improvement can be realized. In other words, by arranging (allocating) the transfer data in this way, transmission of a signal indicated by the clock (reference numeral 34) of the edge device (for example, the apparatus of reference numeral 3) or the transmission timing notification apparatus (apparatus of reference numeral 31) is started. Even when there is a difference between the time and the transmission end time (timing), data can be transmitted according to the degree of loss allowed by the data.

<< Second Embodiment >>
Next, a second embodiment of the present invention will be described (see FIG. 1 and the like as appropriate).
FIG. 9 is a diagram illustrating an example in which an optical signal can be transmitted at the same time. When performing point-to-point communication on a multipoint-to-multipoint path used to perform many-to-many communication, optical signals do not collide even when optical signals are output simultaneously from multiple ONUs 3a and 3b. There is. That is when two ONUs 3a and 3b transmit optical signals simultaneously. This is because the optical signal transmitted by one ONU 3a does not pass through the same path as the signal transmitted by the other ONU 3b until it arrives at the other ONU 3b.

  For this reason, in the second embodiment, when two ONUs 3 transmit data in a multipoint-to-multipoint path, an optical signal carrying this data is transmitted at the same time (simultaneously). At this time, when a shift occurs in the clock 34, data can be sent correctly as follows.

  That is, in this second embodiment, the ONU 3 stores the transfer data in the data storage means by tolerance and by destination (by path) as shown in FIG. The transfer data is divided into sections, the transfer data is read from the data storage unit 332 so that transfer data with low tolerance of data loss and high reliability is arranged in the inner section, and arranged in the divided sections. The transfer data arranged in (1) is transmitted from the signal transfer unit 333 on the optical signal.

The present invention described above is not limited to the above-described embodiment, and can be widely modified within the scope of its technical idea.
For example, the timing of data transmission (transfer) in the ONU 3 is determined as appropriate and is not limited to a specific determination method. Although the transmission timing notification device 31 has been described as being provided in the ONU 3, it may exist outside the ONU 3. Further, the timing may be notified to a plurality of ONUs 3. The OLT 1 is an example of an external device, and may be a router. Note that a program that causes the ONU 3 to function is transmitted through a network or distributed via a storage medium.

It is a figure which shows the structure of the communication system with which the communication method of this embodiment, etc. are applied, and the structure of ONU as an edge apparatus. It is a figure which shows the structure of the transmission timing notification apparatus of FIG. It is a figure which shows the internal structure of the transfer data memory | storage part of FIG. It is a figure which shows the procedure which divides | segments a timing into three or more areas and allocates transfer data according to a class so that the data loss tolerance with low tolerance of data loss may be arrange | positioned in an inner area. It is a figure which shows the example which divided | segmented the slot by the predetermined | prescribed ratio. It is a figure which shows the operation | movement which allocates the transfer data of each class to the divided slot. It is the flowchart which showed the procedure of the communication method. It is the figure which showed the transmission timing of each edge apparatus, and the passage timing of the signal of each switch .

Explanation of symbols

1 OLT (External device)
2 Switch 3 ONU (Edge device)
31 Transmission Timing Notification Device 311 Control Unit 312 Timing Storage Unit (Storage Unit)
33 Transfer device 332 Transfer data storage unit (data storage unit)
333 Optical signal transmitter / receiver (signal transmitter)
34 Clock (clock device)
F Optical fiber (transmission line)

Claims (7)

A communication method for preventing data corruption due to collisions between signals generated by connecting a plurality of edge devices on the user side by branching transmission lines,
When the start / end timing of signal transmission of each edge device is determined to be a timing that does not collide with a signal transmitted by another edge device,
The edge device is
Procedures for storing data to be transmitted with different tolerances for loss in the data storage unit according to tolerances,
The timing is divided into five or more sections, and data is read from the data storage unit and arranged in the section so that data with low tolerance of data loss and high reliability is arranged in the inner section. The communication method is characterized by executing a procedure of transmitting the data arranged in this way by carrying the signal from the signal transmission unit. A transmission timing notification device that is used in the communication method according to claim 1 and notifies a timing of transmitting data to at least one edge device to be managed among the plurality of edge devices,
A function of acquiring the start / end timing of signal transmission in each edge device from an external device that manages the signal transmission timing of each edge device and storing it in the storage unit,
A transmission timing notification device comprising a function of notifying a managed edge device of signal transmission based on the stored timing and the time of a clock device that measures the time managed by the external device. An edge device used in a communication method for preventing data corruption due to collision between signals generated by connecting a plurality of edge devices on the user side by branching transmission lines,
A data storage unit that stores data with different tolerances for data loss by tolerance,
A signal transmission unit that transmits the data stored in the data storage unit on a signal;
When transmitting the data, the data storage is divided so that the transmission start / end timing is divided into five or more sections, and data requiring low reliability and high reliability is arranged in the inner section. An edge device characterized in that data is read from a unit and arranged in the section, and the data arranged in this way is transmitted on the signal from the signal transmission unit. A clock device that measures the time managed by an external device that instructs the timing of signal transmission of each edge device;
Storage means for storing the start / end timing of signal transmission in the edge device acquired from the external device,
The edge device according to claim 3 , further comprising a control unit that notifies the signal transmission unit of signal transmission based on the timing and the time of the timepiece device. A clock device that measures the time managed by an external device that instructs the timing of signal transmission of each edge device;
Storage means for storing the start / end timing of signal transmission in another edge device, acquired from the external device,
Based on the start / end timing of signal transmission in the other edge device, determine the start / end timing of signal transmission in its own edge device, and based on this timing and the time of the timepiece device, The edge device according to claim 3 , further comprising a control unit that notifies the signal transmission unit of signal transmission. A program causing a computer to execute the communication method according to claim 1 . A storage medium storing the program according to claim 6 .

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