JP6086964B1 - Frame transmission system and frame transmission apparatus - Google Patents

Abstract

The present invention provides a transmission system with improved resistance against bit errors in OH information transmitted using multiframes. In a frame transmission system for transmitting a frame of an optical transmission network (OTN), overhead is transmitted in the form of a multi-frame in synchronization with a cycle of n times the multi-frame cycle of OTN (n is an integer of 2 or more). The (OH) information is changed, and the OH information is converted into multi-frames and transmitted repeatedly n times during a period of n times the multi-frame period of OTN (n is an integer of 2 or more). Also, the n OH information is compared, and the OTN frame is processed using the OH information having the largest number of matches. The period that is n times the multiframe period may be a period that corresponds to the number of OTN frames that is the least common multiple of the number of OTN frames that are identified based on two or more of MFAS, OFMI, and LLM of OTN. it can. [Selection] Figure 4

Description

  The present invention relates to a frame transmission system and a frame transmission apparatus for transmitting a frame storing digital data, and more particularly to an “optical transmission network” (OTN) which is a communication standard used in a backbone communication network. The present invention relates to a frame transmission system and a frame transmission apparatus that transmit compliant frames.

  The current backbone communication network is an optical transport network (OTN) recommended by the International Telecommunication Union-Telecommunication Standardization Sector (ITU-T). ) Is widely used. OTN is transparent to accommodate a variety of client signals such as Ethernet (registered trademark) and Synchronous Digital Hierarchy (SDH), monitoring and control systems that are aware of wavelength division multiplexing (WDM) signal management. Defines the bit rate, mapping method, etc. (See Non-Patent Document 1)

  FIG. 1 is a diagram for explaining the frame structure of OTN. Note that the overhead of storing address information and various monitoring signals used when transmitting data is added to the beginning of various frames constituting the OTN frame, but in the following, the overhead is abbreviated as OH and stored in OH. Information and signals transmitted in this manner will be abbreviated as OH information. The OPUk frame 110 includes a payload area 112 in which a client signal 100 such as Ethernet (registered trademark) or SDH is accommodated, and an OPUk (Optical Channel Payload Unit-k) OH area 114 that is OH that provides accommodation information of the client signal. Composed. The ODUk frame 110 is provided with an ODUk (Optical Channel Data Unit-k) OH124, which is an OH that provides (stores) signals for end-to-end path monitoring and performance monitoring. Is done. The ODUk frame 120 provides (stores) signals for maintenance and operation functions necessary for transmission of an optical channel, which is signal transmission between 3R playback (Re-amplification, reshaping, and retiming) points. Transport Unit-k) OH 134 and a code 136 for providing a Forward Error Correction (FEC) function are added to form an OTUk frame 130.

  The OTN has a function of collecting a plurality of OTN frames as one group and transmitting predetermined OH information using the one group of OTN frames. A plurality of OTN frames used for transmission of the predetermined OH information is called “multiframe”, and transmission of predetermined OH information using a plurality of OTN frames constituting the multiframe is called multiframe.

  Hereinafter, the concept of multiframe will be described by taking “Multiplex Structure Identifier” (MSI) transmitted using a plurality of OPUk OHs as an example.

  FIG. 2A is a diagram for explaining the OTN frame structure described in FIG. 1 in more detail. Frame synchronization (FA) OH230 is defined in the first to seventh columns of the first row of the OTN frame, and OTUk OH134 is defined in the following eight to fourteenth rows. ODUk OH124 is defined in the 1st to 14th columns of the 2nd to 4th rows. The OPUk OH 114 is defined in the 15th to 16th columns of the 1st to 4th rows, and the payload 112 is defined in the 17th to 3824th columns of the 1st to 4th rows. An OTUk FEC code 136 is defined in the 3825 to 4080 columns of the first to fourth rows.

  FIG. 2B shows the configuration of the FA OH 230 in the OTN frame. In FA OH, a frame alignment signal (FAS) 232 is defined in the first 6 bytes (corresponding to the first row to the sixth column of the OTN frame), followed by one byte (in the first row, the seventh column). A multi-frame alignment signal (MFAS) 234 is defined. MFAS is equivalent to a counter, and the value of MFAS (MFAS value) is incremented from 0 (“0000 0000” in the bit string) to 255 (“1111 1111”) each time one OTN frame 130 is transmitted. To be granted. When the MFAS value reaches 255, it returns to 0 and is incremented again. A group of OTN frames having an MFAS value of 0 to an OTN frame of No. 255 can constitute a “multiframe”. In this specification, one period of a multiframe is referred to as a “multiframe period”.

  FIG. 2 (c) shows a more detailed configuration of the OPUk OH 114, and particularly shows a configuration of OPU4 OH information transmitted using a plurality of OPU4 OHs. The information of OPU4 OH is OH information transmitted in a multi-frame manner. In each of the 15th and 16th columns of the first to third rows of the OTN frame, a stuff control (Justification Control, JC) byte is defined. Payload Structure Identifier (PSI) is defined in the 15th column of the 4th row of the OTN frame, and OPU Multi-Frame Identifier (OMFI) is defined in the 16th column of the 4th row. Yes. Although only one PSI (1 byte) is defined in one OTN frame 130, the PSI transmitted in 256 OTN frames constituting one multiframe is integrated, so that FIG. OH information (OPU4 OH information (256 bytes in total)) as shown in the right figure of FIG. As described above, the OPU4 OH information transmitted in a multi-frame using a multi-frame composed of 256 OTN frames is one of the OH information.

  Among the information of OPU4 OH, 80 bytes obtained by accumulating the PSI of the OTN frames whose MFAS 234 values are 2 to 81 constitute a multiplex structure extension (MSI) 244. The MSI stores information indicating how client signals are accommodated in the OPUk payload 112. More specifically, each byte of the MSI indicates whether the tributor slot (TS) is arranged in the OPUk payload 112, and if the TS is arranged, the number of the tributary port of the TS (TS destination). Show. TS is a slot to which a tributary unit to which a client signal is mapped is further mapped.

  With reference to FIG. 3, transmission / reception of an OTN frame will be described. FIG. 3A is a diagram illustrating the configuration of a frame transmission system that transmits and receives an OTN frame. The frame transmission system 300 in FIG. 3A includes a plurality of frame transmission apparatuses A320, a plurality of frame transmission apparatuses B360, and a network 340 connecting these frame transmission apparatuses. Normally, the frame transmission apparatus has both a function for transmitting and receiving an OTN frame, but for the sake of simplicity of explanation, the frame transmission apparatus A320 has a configuration having only a transmission function, and the frame transmission apparatus B360 has a reception function. A description will be given assuming that the configuration has only functions.

  The frame transmission apparatus A320 on the transmission side includes an OTN framer 322 that accommodates a client signal in the OTN frame having the configuration shown in FIG. 1, and an optical transmitter that converts an OTN frame of an electrical signal output from the OTN framer into an optical signal ( TX) 324. The frame transmission apparatus A320 normally includes an optical wavelength division multiplexing (WDM) apparatus 326 that wavelength-multiplexes a set of a plurality of OTN framers 322 and an optical transmitter 324 and optical signals having different wavelengths output from the plurality of optical transmitters. With. The wavelength-multiplexed optical signal is transmitted to the network 340.

  The reception-side frame transmission apparatus B 360 includes an optical receiver (RX) 364 that converts an optical signal received via the network 340 into an OTN frame of an electrical signal, and an OTN framer 362 that separates a client signal from the OTN frame. . In addition, the frame transmission apparatus B 360 normally includes a set of a plurality of OTN framers and optical receivers, and an optical wavelength division multiplexing (WDM) apparatus 366. Since the optical signal received via the network 340 is wavelength-multiplexed, it is separated into an optical signal having a single wavelength by an optical wavelength multiplexing (WDM) device 366. Each optical signal is converted into an OTN frame of an electrical signal by the optical receiver 364, and then the client signal is separated by the OTN framer 362.

  The client signal separation process in the frame transmission apparatus B 360 will be described in further detail. FIG. 3B is a diagram for explaining client signal separation processing in the OTN framer of the frame transmission apparatus B. The OTN framer 362 includes an OH reception buffer 386, a control unit 382, and a separator 388. The OH reception buffer 386 of the OTN framer 362 stores the OH (OPUk-OH, ODUk-OH, OTUk-OH, FA OH) of the received OTN frame. The control unit of the OTN framer decodes the MFAS included in the FA OH of the received OTN frame. When the control unit 382 finds an OTN frame whose MFAS value is 0, the control unit 382 recognizes that the OTN frame is the first OTN frame in one multiframe. The OH reception buffer 386 stores OH of at least one multiframe (that is, 256) OTN frames. The control unit 382 accumulates PSI bytes of one multi-frame OTN frame to form PSI (OH information) composed of 256 bytes. The control unit 382 analyzes 256 bytes of PSI (OH information) (more specifically, analyzes 80 bytes of MSI included in the PSI), and thus 256 OTN frames constituting one multiframe. It is possible to grasp how the client signal is accommodated. The OTN framer separator 388 separates the client signal from the OTN frame based on the MSI analyzed by the control unit 382.

  As described above, OTN provides a function for accommodating a variety of client signals and transmitting the network. However, client signal accommodation information is transmitted using an 80-byte MSI obtained from one multiframe. Shared between devices.

International Telecommunication Union, “Interfaces for the optical transport network,” Recommendation ITU-T G.709 / Y.1331, February 2012

  As shown in FIG. 2A, an FEC code is assigned to the OTN frame. The OTN framer of the frame transmission apparatus can correct the bit error using the FEC code even if a bit error has occurred in the received OTN frame.

  However, even such an OTN FEC function is not universal, and if the bit error exceeds a predetermined allowable value, the OTN framer may not be able to correct the bit error included in the OTN frame. If bit errors remain in OH information such as information and signals stored and transmitted in OH, the function based on the OH information does not operate as expected. For example, in the above example, it is assumed that a bit error remains in the PSI 242 in the OPUk OH 114 of one OTN frame 130 out of 256 OTN frames constituting the multiframe. In this case, the 80-byte MSI obtained from one multiframe is not correct information, but the OH information (MSI) in which this error remains is misidentified as correct information (the OH information (MSI) is misidentified as being changed). Thus, the OTN framer 362 in the frame transmission device B 360 on the receiving side separates the client signal from the OTN frame. Therefore, the OTN framer 362 cannot correctly separate the client signal from the OTN frame.

  As described above, in the OTN, a plurality of OTN frames are grouped into one, and a function of transmitting predetermined OH information in a multiframe using the group of OTN frames (multiframe) is provided. When even one bit error remains in the OH information transmitted using, there is a problem that the receiving-side frame transmission apparatus cannot correctly execute the processing based on the OH information.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a transmission system and a frame transmission apparatus that have improved resistance to bit errors remaining in OH information transmitted and received over the entire multiframe. There is to do.

In order to achieve such an object, one embodiment of the present invention is a frame transmission system for an optical transmission network (OTN) frame. The frame transmission system includes a frame transmission device that transmits an OTN frame and a frame reception device that receives an OTN frame transmitted by the frame transmission device. The frame transmission device includes a first multi-frame included in the OTN frame. The value of the first overhead (OH) information for counting the period of the frame and the value of the second OH information for counting the period of the second multiframe included in the OTN frame are predetermined values. The frame reception device is configured to change the accommodation information of the client signal to be transmitted in the form of multi-frames in the first multi-frame period in synchronization with the timing coincident with the first multi-frame period. The value of the OH information of 1 and the value of the second OH information included in the received OTN frame are predetermined values. Is recognized as a timing at which the accommodation information of the client signal transmitted in a multi-frame in the first multi-frame cycle is changed .

One embodiment of the present invention is a frame transmission device that receives an OTN frame. The frame transmission apparatus includes a first overhead (OH) information value for counting the period of the first multiframe included in the received OTN frame, and the second multiframe included in the received OTN frame. At the timing when the value of the second OH information for counting the period of the frame coincides with a predetermined value, the accommodation information of the client signal that is transmitted in a multiframe with the first multiframe period is changed. It is configured to be recognized as timing . Frame transmission apparatus is configured to process the OTN frame received on the basis of the housing information which is changed in synchronization with the recognized timing.

  As described above, according to the present invention, even if a bit error exists in OH information transmitted / received over the entire multiframe, a frame transmission system and a frame transmission apparatus having high resistance to the bit error are provided. can do.

It is a figure explaining the frame structure of OTN. (A) is a diagram for explaining the OTN frame structure in more detail, (b) is a diagram showing the configuration of FA OH in the OTN frame, and (c) is an OPU4 OH transmitted using a plurality of OPU4 OHs. It is a figure which shows the structure of this information. (A) is a figure explaining the structure of the frame transmission system which transmits / receives an OTN frame, (b) is a figure explaining the client signal separation process in the OTN framer of the frame transmission apparatus B. (A) is a figure explaining the structure of the frame transmission system which concerns on one Embodiment of this invention, (b) is a figure explaining the structure of the OTN framer which concerns on one Embodiment of this invention. It is a figure explaining the separation process of the client signal which concerns on one Embodiment of this invention. It is a figure explaining the period of the change of OH information transmitted in multi-frame which concerns on one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. A frame transmission system according to the present invention is a system for transmitting an OTN frame (a frame specified (specified) by the OTN standard), and an OTN multi-frame cycle (multiframe specified by the OTN standard). The OH information to be transmitted in a multi-frame manner is changed in synchronization with a cycle of n times (n is an integer of 2 or more). The changed OH information is transmitted / received during a period n times the multiframe period (over the entire n multiframes). As a result, it is determined whether the change in the OH information is due to the remaining bit error or is made in synchronization with the above period, and the change in the OH information due to the remaining bit error is erroneously recognized as correct information and processed. It is suppressed that it is used for.

  Although the following description shows specific numerical examples, the present invention can be implemented with other numerical values without losing generality. Further, one multiframe in OTN is not limited to the one composed of 256 OTN frames identified by the value of MFAS as described above. For example, it is composed of 80 OTN frames identified by OMFI values or 20 OTN frames identified based on LLM (Logical Lane Marker, 6th column of FA OH) values. One can also constitute one multiframe in OTN. Further, the OH information is not limited to 256-byte PSI formed by accumulating PSI bytes of 256 OTN frames, or 80-byte MSI included in PSI. It can also be applied to other OH information.

(First embodiment)
In the first embodiment of the present invention, the OH information transmitted over the entire multiframe is changed in synchronization with a cycle of n times (n is an integer of 2 or more) of the multiframe cycle specified by OTN (OTN The changed OH information is transmitted n times during a period of n times the multiframe period (n is an integer of 2 or more). Hereinafter, as an example, 256 OTN frames identified by the MFAS are OTN multiframes, and MSI is transmitted over the entire multiframe (multiframe using 256 OTN frames) as the first OH information. A frame transmission system and a frame transmission apparatus according to the embodiment will be described.

  FIG. 4A is a diagram illustrating the configuration of the frame transmission system according to the first embodiment. The transmission system in FIG. 4A is almost the same as the transmission system 300 described with reference to FIG. 4A includes a plurality of frame transmission apparatuses A420, a plurality of frame transmission apparatuses B460, and a network 440 that connects these frame transmission apparatuses. Normally, a frame transmission apparatus has both a function for transmitting and receiving an OTN frame, but for the sake of simplicity of explanation, the frame transmission apparatus A420 has a configuration having only a transmission function, and the frame transmission apparatus B460 has a reception function. A description will be given assuming that the configuration has only functions.

  The transmission-side frame transmission apparatus A 420 includes an OTN framer 422 that accommodates a client signal in the OTN frame having the configuration shown in FIG. 1, and an optical transmitter that converts an OTN frame of an electrical signal output from the OTN framer into an optical signal ( TX) 424. In addition, the frame transmission apparatus A 420 normally includes an optical wavelength division multiplexing (WDM) apparatus 426 that wavelength-multiplexes a set of a plurality of OTN framers 422 and an optical transmitter 424 and optical signals having different wavelengths output from the plurality of optical transmitters. With. The wavelength-multiplexed optical signal is transmitted to the network 440.

  The frame transmission device B 460 on the receiving side includes an optical receiver (RX) 464 that converts an optical signal received through the network 440 into an OTN frame of an electrical signal, and an OTN framer 462 that separates a client signal from the OTN frame. Prepare. The frame transmission apparatus B 460 normally includes a set of a plurality of OTN framers and optical receivers, and an optical wavelength multiplexing apparatus (WDM) 466. Since the optical signal received through the network 440 is wavelength-multiplexed, it is separated into an optical signal having a single wavelength by an optical wavelength multiplexing (WDM) device 466. Each optical signal is converted into an OTN frame of an electrical signal by the optical receiver 464, and then the client signal is separated by the OTN framer 462.

  FIG. 4B is a diagram illustrating the configuration of the OTN framer according to the present embodiment. Note that, unlike the description of FIG. 4A, in the universal implementation, the OTN framer has both a client signal accommodation function and a separation function. Therefore, FIG. 4B shows the configuration of the OTN framer (422, 462) equipped with both the accommodation function and the separation function. The OTN framer (422, 462) receives the OTN frame of the electrical signal output from the optical receiver 464, and stores OH (OPUk-OH, ODUk-OH, OTUk-OH, FA OH) of the received OTN frame. An OH reception buffer 486, a separator 488 that receives the OTN frame stored in the OH reception buffer, separates the client signal contained in the OPUk payload of the OTN frame, and receives the client signal and stores it in the OPUk payload; A multiplexer 484 for providing a predetermined OH to form an OTN frame and outputting it to the optical transmitter 424, and a control unit 482 are provided. Hereinafter, with reference to FIG. 4B, the client signal accommodation processing and separation processing in the OTN framer will be described in detail.

(Containment processing)
The OTN framer multiplexer 484 accommodates the received client signal in the OPUk payload according to the arrangement in the OPUk payload indicated by the 80-byte MSI provided from the control unit 482. Multiplexer 484 further adds OPUk OH, ODUk OH, OTUk OH, and FA OH based on information provided by the control unit to form an OTN frame. Here, OH information transmitted and received in a plurality of OTN frames constituting a multiframe such as MSI is handled as follows. In the MSI example, the multiplexer 484 forms the 256-byte OH information (OPU4 OH information) described in the right diagram of FIG. 2C from the 80-byte MSI provided from the control unit 482, and the FA The first byte of the OH information in the PSI byte of the OTN frame in which the MFAS value in OH is set to 0, the second byte of the OH information in the PSI byte of the OTN frame in which the MFAS value is set to 1, ... The 256th byte of the OH information is sequentially added to the PSI byte of the OTN frame in which the value of MFAS is set to 255. The multiplexer 484 outputs the formed OTN frame to the optical transmitter (TX) 424.

  In the present embodiment, the OTN framer control unit 482 converts the OH information (that is, the MSI value that is the accommodation information of the client signal) by n times the multiframe period of 256 OTN frames identified by the MFAS (n Is changed every period of 2). That is, the OTN framer control unit 482 changes the value of the MSI in synchronization with a cycle that is n times the multiframe cycle. By doing so, the arrangement of the OTN framer in the OPUk payload when accommodating the client signal is always changed from the MSI of the first multiframe among n consecutive multiframes. The same MSI value is always stored in n consecutive multiframes.

  The multiplexer 484 changes the arrangement in the OPUk payload that accommodates the client signal in accordance with the change in the MSI value. Similarly, the separation 488 changes the arrangement (output destination) of the client signal when separating the client signal from the OTN framer to the first multiframe among n consecutive multiframes.

(Separation process)
The OH reception buffer 486 of the OTN framer stores each OH of the received OTN frame. The OTN framer control unit 482 recognizes the first multiframe among n consecutive multiframes (n is an integer of 2 or more) defined in advance using a method described later. The OTN framer control unit 482 refers to the FA OH 230 of the OTN frame included in the multiframe, and decodes the MFAS for the multiframe recognized as the head. At the same time, the control unit 482 accumulates the PSI bytes of the OTN frame included in the head multiframe, and includes 256 bytes of PSI (information of OPU4 OH that is OH information (FIG. 2 (c) right)). The included 80 byte MSI 244 is formed. The control unit 482 provides the MSI to the separator 488. The OTN framer separator 488 separates the client signal from all the OTN frames included in the n multiframes defined in advance based on the MSI provided from the control unit.

  As described above, in the frame transmission system according to the first embodiment, the frame transmission device 420 on the transmission side synchronizes with the multiframe period in synchronization with a period that is n times the multiframe period (n is an integer of 2 or more). The OH information transmitted and received is changed throughout, and the receiving side frame transmission apparatus 460 uses the OH information in the first multiframe among the n consecutive multiframes to use the n consecutive multiframes. To handle. As a result, even if a bit error has occurred in OH information in a multiframe other than the head among n consecutive multiframes, OH information including a bit error is ignored, so that bit error resistance is strong. A frame transmission system can be realized.

  In addition, in the frame transmission system 400 according to the first embodiment, various client signal separation processes can be employed. Hereinafter, an example of another embodiment in the client signal separation processing will be described with reference to FIGS. 4B and 5.

  FIG. 5 is a diagram illustrating client signal separation processing according to the first embodiment, taking n = 3 as an example. The OTN framer control unit 482 recognizes the first multiframe among n consecutive multiframes (n is an integer of 3 or more) defined in advance using a method described later. The control unit 482 of the OTN framer refers to the FA OH 230 of the OTN frame included in the multiframe for the multiframe recognized as the head, decodes the MFAS, and determines the OTN frame included in the head multiframe. The PSI bytes are accumulated to form 256 bytes of PSI (OPU4 OH information (right side of FIG. 2 (c)) as OH information) and an 80-byte MSI 244 included therein. The control unit 482 provides the MSI to the separator 488. The control unit 488 decodes the MFAS for each of the multiframes following the head, forms an 80-byte MSI 244, and provides it to the separator.

The control unit 488 further performs the following operation on n MSIs formed from n (n is an integer of 3 or more) consecutive multiframes.
(A) When all the formed MSIs have the same value, the control unit determines that there is no bit error in the MSI information and provides the MSI to the separator.
(B) When even one of the formed MSIs has a different value, the control unit determines that there is a bit error in any of the MSI information, and among the obtained n MSIs, they match each other. The MSI with the largest number is used as the normal MSI, and the MSI is provided to the separator.

  The OTN framer separator 488 separates the client signal from all OTN frames included in three or more predefined multiframes based on the MSI provided from the controller 482.

  As described above, in the frame transmission system according to the first embodiment, in the frame transmission device on the transmission side, the entire multiframe is synchronized with a period of n times the multiframe period (n is an integer of 3 or more). OH information to be transmitted and received is changed, and the receiving side frame transmission apparatus uses n MSIs having the largest number of matching OH information among n consecutive multiframes. A continuous multi-frame is processed. As a result, even if a bit error occurs in OH information in the multiframe including the head among n consecutive multiframes, the OH information including the bit error is ignored. A strong frame transmission system can be realized.

  In order to be able to recognize which multiframe is the head of n consecutive multiframes between the frame transmission device A and the frame transmission device B, for example, the multiframe that is the head (see FIG. 5). In this example, flag information indicating that it is the first multiframe may be added to an undefined OH region in an OTN frame that is included in the multiframe 1) and has an MFAS value of 0. .

(Second Embodiment)
In the second embodiment of the present invention, the “period of n times the multiframe period” described in the first embodiment is different from the number of OTN frames included in a certain multiframe period and one or more other This is a period corresponding to the number of OTN frames that is the least common multiple of the number of OTN frames included in the multiframe period.

  This embodiment will be described with reference to FIG. FIG. 6 is a diagram for explaining a cycle of changing OH information transmitted in a multi-frame format according to the present embodiment. The example illustrates 256 OTN frames identified by MFAS as one multiframe and 80 OTN frames identified by OMFI as another multiframe.

  The configurations of the transmission system and the frame transmission apparatus according to the present embodiment are substantially the same as those described in the first embodiment, and thus description thereof is omitted.

  As shown in FIG. 2C, the OMFI is defined in the fourth row and the 16th column of the OTN frame. A value from 0 (“000 0000” in the bit string) to 79 (“100 1111” in the bit string) is incremented and added in the order of transmission of the OTN frame using the lower 7 bits of 1 byte constituting the OMFI 246. That is, OMFI forms one multiframe with 80 OTN frames. On the other hand, as already described in detail, the MFAS constitutes one multiframe with 256 OTN frames.

  The “least common multiple” between the number 80 of OTN frames included in the multiframe defined by OMFI and the number 256 of OTN frames included in the multiframe defined by MFAS is 1280. That is, as shown in FIG. 6, when OMFI and MFAS values are both 0 and 1280 OTN frames arrive from that point, the next 1281 OTN frame has OMFI and Both values of MFAS become 0 again.

  In the first embodiment, the OH information transmitted / received over the entire multiframe is changed in synchronization with a cycle of n times (n is an integer of 3 or more) the multiframe cycle defined by MFAS. In the second embodiment, this “n times” is the least common multiple of the number 80 of OTN frames included in the multiframe defined by OMFI and the number 256 of OTN frames included in the multiframe defined by MFAS. The multiframe period may be “5 times” corresponding to the period of 1280 OTN frames. Then, the frame transmission apparatus may recognize the timing at which both the OMFI and MFAS values are 0 as multi-frame synchronization timing.

  In the first embodiment, it has been described that flag information indicating the first multiframe is added to an undefined OH area so that multiframe synchronization timing can be recognized between frame transmission apparatuses. On the other hand, in the second embodiment, the OTN framer of the frame transmission apparatus monitors the values of OMFI and MFAS and recognizes that the timing when both of them become 0 is the multi-frame synchronization timing. It is not necessary to use the OH region. That is, the transmission system or the frame transmission apparatus according to the present embodiment can efficiently transmit an OTN frame without being accompanied by an implementation exceeding the OTN standard.

  Instead of monitoring the OMFI and MFAS values, the LLM and MFAS values are monitored, and the timing when both the LLM mod 20 value and the MFAS value are both 0 is recognized as multi-frame synchronization timing. Good. Alternatively, the LLM, OMFI, and MFAS values may be monitored, and the timing at which the LLM mod 20 value and the OMFI and MFAS values become 0 may be recognized as the multiframe synchronization timing.

100 Client signal 110 OPUk frame 112 OPUk payload 114 OPUk overhead 120 ODUk frame 124 ODUk overhead 130 OTUk frame 134 OTUk overhead 136 OTUk FEC
230 Frame synchronization (FA) overhead 232 Frame synchronization signal (FAS)
234 Multi-frame synchronization signal (MFAS)
242 Payload structure identifier (PSI)
244 Multiple Structure Extension (MSI)
246 OPU Multiframe Identifier (OMFI)
300,400 frame transmission system 320,360,420,460 frame transmission device 322,362,422,462 OTN framer 340,440 network 324,424 optical transmitter 326,366,426,466 optical wavelength multiplexing device 364,464 light Receiver 382, 482 Control unit 484 Multiplexer 386, 486 OH Receive buffer 388, 488 Separator

Claims (2)

A frame transmission system comprising: a frame transmission device that transmits an optical transmission network (OTN) frame; and a frame reception device that receives the OTN frame transmitted by the frame transmission device ,
The frame transmitting apparatus includes a first overhead (OH) information value for counting a period of a first multiframe included in the OTN frame, and a second multiframe included in the OTN frame. the value of the second OH information for counting the period in synchronization with the timing that matches the predetermined value, change the receiving information of the client signals to be transmitted by multi-framing in a cycle of the first multiframe It is configured to be so that,
The frame receiving device matches a value of the first OH information included in the received OTN frame with a predetermined value of the second OH information included in the received OTN frame. A frame transmission system configured to recognize, with timing, a timing at which accommodation information of the client signal transmitted in a multiframe and transmitted in a cycle of the first multiframe is changed . A frame transmission apparatus for receiving an optical transmission network (OTN) frame,
The value of the first overhead (OH) information for counting the period of the first multiframe included in the received OTN frame and the period of the second multiframe included in the received OTN frame are counted. Recognizing that the accommodation information of the client signal transmitted in a multi-frame with the period of the first multi-frame is changed at the timing when the value of the second OH information to be matched with the predetermined value, A frame transmission apparatus configured to process a frame of an OTN received based on accommodation information that is changed in synchronization with the recognized timing .