Frame generating apparatus and frame generating method

Abstract

A frame generating apparatus accommodating a client signal in an optical data transfer unit frame with a higher bit rate than the client signal includes a deserializer, a plurality of generic mapping procedure circuits, and a serializer. The deserializer deserializes the client signal into parallel signals, the number of parallel signals corresponding to the number of tributary slots used in the optical data transfer unit frame. The plurality of generic mapping procedure circuits inserts data and stuff into a frame accommodating portion of the optical data transfer unit frame based on a difference in the bit rate between the client signal and the optical data transfer unit frame. The serializer serializes the parallel signals output from the plurality of generic mapping procedure circuits.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

N×Cn mod(the total number of bytes in a signal accommodating portion)≥Cn   (2)

N: an address assigned to the frame accommodating portion of the ODTU frame

Cn: (the bit rate of the ODUj signal)/(the bit rate of the ODTU frame)×(the total number of bytes in the frame accommodating portion of the ODTU frame)

mod: an operator for calculating a remainder (modulo)

In this case, the number of pieces of stuff to be inserted into the signal accommodating portion of the ODTU frame may be calculated by subtracting Cn from the total number of bytes in the signal accommodating portion. Next, the number of pieces of stuff when the above expression (2) is satisfied will be described. For example, a description will be given about accommodating ODU0 in OPU4 by using one set of tributary slots (TS). In this case, the total number of bytes (B) in the signal accommodating portion in 1TS is 15200. The number of TS's (Nts) used for accommodation is 1. The bit rate (fc) of ODU0 is 1.244160000 Gbps (typical value). The bit rate (fs) of 1TS in OPU4 is 1.301709251 (typical value). Thus, the number of bytes to be accommodated Cn is 14528 according to the following expression (3). In expression (3), “Int” indicates rounding up the number after the decimal point.
Cn=Int((fc/Nts)/fs×B)=Int(1.244160000/1)/1.301709251×15200)=14528   (3)

The above example shows mapping ODUj (j=0) into ODTU with a tributary slot occupation of OTU. For the case of mapping ODUj into ODTU that is occupied m tributary slots of OTU, m GMP processing circuits are uses with same Cn value. Therefore, data of ODUj or stuff are inserted into ODTU frame with m granularity manner.

Next, addresses assigned to the frame accommodating portion of the ODTU frame will be described with reference to FIGS. 12A and 12B. The addresses are sequentially assigned in accordance with the number of TS's in each row of each signal accommodating portion. Referring to FIG. 12A, when the number of TS's is 1, addresses are sequentially assigned in each row of the signal accommodating portion.

Referring to FIG. 12B, when the number of TS's is 4, addresses are sequentially assigned in units of four columns in each row of the signal accommodating portion. Specifically, addresses 1A to 1D for tributary slots A to D, where A<B<C<D, are sequentially assigned to the 1st to 4th columns of the signal accommodating portion. Likewise, addresses 2A to 2D for tributary slots A to D, where A<B<C<D, are sequentially assigned to the 5th to 8th columns of the signal accommodating section. That is, when “n” number of TS's is used, addresses are assigned to concatenate ODTU of 1TS by n.

FIG. 13 is a diagram illustrating stuff bytes inserted into the signal accommodating portion in accordance with the above expression (2). In FIG. 13, “S” corresponds to a stuff byte. As illustrated in FIG. 13, stuff bytes are inserted into the signal accommodating portion in a dispersed manner. Accordingly, jitter may be effectively suppressed when stuff bytes are removed in a receiver side compared to when stuff bytes are continuously inserted.

FIGS. 14A and 14B are diagrams illustrating storage of information for GMP in an ODTU OH unit. Referring to FIG. 14A, when 1TS is used, overhead information for the TS is given to an ODTU frame. Referring to FIG. 14B, when 4TS (TS#A to #D, where A<B<C<D) is used, overhead information for each TS is given to an ODTU frame. The overhead information includes information about the number of pieces of stuff calculated in the above expression (2). The information about the number of pieces of stuff is the same in the overhead corresponding to each TS.

FIG. 15 is a diagram illustrating an example of an OPUk OH unit. Referring to FIG. 15, an OTU4/ODU4/OPU4 frame stores, in the 15th column and the 4th row, information indicating the correspondence between tributary slot numbers and tributary ports. Specifically, the OTU4/ODU4/OPU4 frame stores a signal for identifying port numbers of 80 tributary slots using seven bits. Accordingly, the number of tributary slots used for accommodating an ODUj signal in the OTU4/ODU4/OPU4 frame may be determined.

FIG. 16 is a diagram illustrating another example of the OPUk OH unit. The difference from the example illustrated in FIG. 15 is that the OTU4/ODU4/OPU4 frame stores, in the 15th column and the 3rd row, types of client signals accommodated in respective tributary slots (ODU0, ODU1, ODU2, ODU3, and ODU2e). By having this type of OH, the types of accommodated client signals may be identified.

In this embodiment, a description has been given about frame generation for transmitting a client signal having a bit rate under 100 Gbps at a bit rate of 100 Gbps. However, this embodiment is not limited thereto. This embodiment may also be applied to frame generation for transmitting a low-bit-rate client signal at a higher bit rate. In this case, too, an operation speed required for a GMP circuit may be decreased by deserializing a client signal into parallel signals the number of which corresponds to the number of multiple frames of an ODTU frame.

In this embodiment, the number of tributary slots in each set is 80, but the number is not limited thereto. In this case, when the number of GMP processing circuits 22 is the same as the number of tributary slots in each set, an advantage of this embodiment may be obtained.

An embodiment of the present invention has been described in detail. The present invention is not limited to this specific embodiment, and various modifications and changes are acceptable within the scope of the present invention described in the following claims.

According to the frame generating apparatus and frame generating method disclosed in the specification, ODTU frames applicable to the GMP method may be generated.

All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.

Claims

1. A frame generating apparatus that accommodates a client signal in an optical data transfer unit frame with a higher bit rate than the client signal, the frame generating apparatus comprising:

a deserializer that deserializes the client signal into m parallel signals where m is corresponding to the number of tributary slots used in the optical data transfer unit frame;

m generic mapping procedure circuits that inserts data and stuff into a frame accommodating portion of the optical data transfer unit frame based on a difference in the bit rate between the client signal and the optical data transfer unit frame; and

a serializer that serializes the m parallel signals output from m generic mapping procedure circuits,

wherein m generic mapping procedure circuits that in accordance with an address inserts data into the frame accommodating portion of the optical data transfer unit frame when a first expression (N×Cn) mod Tb<Cn is satisfied, and inserts stuff into the frame accommodating portion of the optical data transfer unit frame when a second expression (N×Cn) mod Tb≥Cn is satisfied, “N” representing the address assigned to the frame accommodating portion of the optical data transfer unit frame, “Cn” representing (a bit rate of the client signal)÷(a bit rate of the optical data transfer unit frame)×(the total number of bytes in the frame accommodating portion of the optical data transfer unit frame),“Tb” representing the total number of bytes in a signal accommodating portion, and “mod” representing a remainder operator.

2. The frame generating apparatus according to claim 1, further comprising:

an optical data transfer unit generator accommodating a signal from the serializer in the optical data transfer unit frame,

wherein the frame accommodating portion includes a plurality of rows, and

wherein the optical data transfer unit generator sequentially assigns addresses in accordance with the number of tributary slots in each row of the frame accommodating portion.

3. The frame generating apparatus according to claim 2,

wherein the optical data transfer unit generator accommodates the signal from the serializer in the optical data transfer unit frame by regarding two types of optical data transfer unit frames of eighty types of optical data transfer unit frames as one set and forty sets of the optical data transfer unit frames as one multi-frame cycle.

4. A frame generating method for accommodating mapping a client signal in into an optical data transfer unit frame with a higher bit rate than the client signal, the method comprising:

mapping a group of m successive bytes of the client signal into a group of m successive bytes of the optical data transfer unit frame, where m is the number of tributary slots of the optical data transfer unit frame;

deserializing, by an apparatus, the client signal into parallel signals, the number of parallel signals corresponding to the number of tributary slots used in the optical data transfer unit frame;

inserting, by an apparatus, data and stuff into a frame accommodating portion of the optical data transfer unit frame based on a difference in bit rate between the client signal and the optical data transfer unit frame; and

serializing, by an apparatus, the parallel signals after inserting data and stuff into the frame accommodating portion of the optical data transfer unit frame, wherein data is inserted inserting data into the a frame accommodating portion of the optical data transfer unit frame in accordance with an address when a first expression (N×Cn) mod Tb<Cn is satisfied, and inserting stuff is inserted into the frame accommodating portion in accordance with an address when a second expression (N×Cn) mod Tb>Cn Tb≥Cn is satisfied, “N” representing the address assigned to the frame accommodating portion of the optical data transfer unit frame, “Cn” representing (a bit rate of the client signal)÷(a bit rate of the optical data transfer unit frame)×(the a total number of bytes in the frame accommodating portion of the optical data transfer unit frame), “Tb” representing the total number of bytes in a signal accommodating portion the frame accommodating portion of the optical data transfer unit frame, and “mod” representing a remainder operator.

5. The method according to claim 4,

wherein the stuff is inserted into the frame accommodating portion of the optical data transfer unit frame in a dispersed manner.

6. The method according to claim 4, further comprising:

accommodating a signal from the serializer the data or the stuff in the frame accommodating portion of optical data transfer unit frame,

wherein the frame accommodating portion includes a plurality of rows, and

wherein addresses are sequentially assigned in accordance with the number of tributary slots in each row of the frame accommodating portion in accommodating the signal from the serializer.

7. The method according to claim 6,

wherein accommodating the signal from the serializer in data or the stuff in the frame accommodating portion of the optical data transfer unit frame by regarding two types of optical data transfer unit frames of eighty types of optical data transfer unit frames as one set and forty sets of the optical data transfer unit frames as one multi-frame cycle.

8. The method according to claim 4, further comprising:

generating an optical transfer unit frame by multiplexing the plurality of optical data transfer unit frames,

wherein tributary slots have corresponding tributary port numbers, and

wherein the tributary port numbers corresponding to tributary slots are stored in an optical channel payload unit overhead in generating an optical transfer unit frame.

9. The method according to claim 8,

wherein a type of the client signal is further stored in the optical channel payload unit overhead in generating an optical transfer unit frame.

10. A frame generating apparatus comprising:

a deserializer that deserializes a client signal into parallel signals, the number of parallel signals corresponding to the number of tributary slots used in a an optical data transfer unit frame; and

a plurality of generic mapping procedure circuits that in accordance with an address inserts data into a frame accommodating portion of the optical data transfer unit frame when a first expression (N×Cn) mod Tb<Cn is satisfied, and inserts stuff into the frame accommodating portion of the optical data transfer unit frame when a second expression (N×Cn) mod Tb≥Cn is satisfied, “N” representing the address assigned to the frame accommodating portion of the optical data transfer unit frame, “Cn” representing (a bit rate of a client signal)÷(a bit rate of the optical data transfer unit frame)÷×(the total number of bytes in the frame accommodating portion of the optical data transfer unit frame), “Tb” representing the total number of bytes in a signal accommodating portion, and “mod” representing a remainder operator.

11. A frame generating apparatus that accommodates a client signal in an optical data transfer unit frame with a higher bit rate than the client signal, the frame generating apparatus comprising:

a generic mapping procedure circuit that inserts data or stuff into a frame accommodating portion of the optical data transfer unit frame based on a difference in the bit rate between the client signal and the optical data transfer unit frame and maps a group of m successive bytes of the client signal into a group of m successive bytes of the optical data transfer unit frame, where m is the number of tributary slots of the optical data transfer unit frame; and

wherein the generic mapping procedure circuit that in accordance with an address inserts data into the frame accommodating portion of the optical data transfer unit frame when a first expression (N×Cn) mod Tb<Cn is satisfied, and inserts stuff into the frame accommodating portion of the optical data transfer unit frame when a second expression (N×Cn) mod Tb≥Cn is satisfied, “N” representing the address assigned to the frame accommodating portion of the optical data transfer unit frame, “Cn” representing (a bit rate of the client signal)+(a bit rate of the optical data transfer unit frame)×(the total number of bytes in the frame accommodating portion of the optical data transfer unit frame), “Tb” representing the total number of bytes in a signal accommodating portion, and “mod” representing a remainder operator.

12. The frame generating apparatus according to claim 11, wherein the client signal is optical data unit (ODU) and the optical data transfer unit frame is optical data transfer unit (ODTU).

13. The frame generating apparatus according to claim 11, wherein the optical data transfer unit frame is optical data payload unit (OPU) and the client signal is a signal with a lower bit rate than the OPU.

14. The frame generating apparatus according to claim 11, wherein the optical data transfer unit frame is optical data payload unit (OPU) and the client signal is Ethernet signal.

15. The frame generating apparatus according to claim 11, wherein the generic mapping procedure circuits insert stuff into the frame accommodating portion of the optical data transfer frame in a dispersed manner.

16. The frame generating apparatus according to claim 11, further comprising:

an optical data transfer unit generator accommodating a client signal in the optical data transfer unit frame,

wherein the frame accommodating portion includes a plurality of rows, and

wherein the optical data transfer unit generator sequentially assigns addresses in accordance with m in each row of the frame accommodating portion, where m is the number of tributary slots of the optical data transfer unit frame.

17. The frame generating apparatus according to claim 11, further comprising:

an optical frame unit frame generator generating an optical transfer unit frame,

wherein tributary slots have corresponding tributary port numbers, and

wherein the optical transfer unit frame generator stores the tributary port numbers corresponding to the tributary slots in an optical channel payload unit overhead.

18. The frame generating apparatus according to claim 17, wherein the optical transfer unit frame generator further stores a type of the client signal in the optical channel payload unit overhead.