Method for structuring of digital data which can be transferred in both directions on a passive optical network (PON) in a PON TDMA system

• US 6,347,096 B1
• Filed: 01/21/1999
• Issued: 02/12/2002
• Est. Priority Date: 05/27/1996
• Status: Expired due to Term

• Current Assignee: Italtel SPA (Italtel Group SPA), Siemens Communications Incorporated (Siemens AG)
• Original Assignee: Italtel SPA (Italtel Group SPA), Seimens Information and Communication Networks SPA
• Inventors: DʼAscoli, Lucio, Podesta, Angelo, Serio, Franco, Castoldi, Pierluigi, Profumo, Alberto
• Primary Examiner(s): Nguyen, Chau
• Assistant Examiner(s): Nguyen, Phuongchau Ba
• Application Number:
  US09/194,442
• Time in Patent Office: 1,118 Days
• Field of Search: 370/395, 370/442, 370/458, 370/470, 370/486, 370/487, 370/490, 370/471, 370/476, 370/395.1
• US Class Current: 370/476
• CPC Class Codes: H04J 14/08 Time-division multiplex systems
• CPC Class Codes: H04J 3/1694 Allocation of channels in TDM/TDMA networks, e.g. distributed multiplexers Passive Optical Networks H04Q11/0062
• CPC Class Codes: H04L 2012/561 Star, e.g. cross-connect, concentrator, subscriber group equipment, remote electronics
• CPC Class Codes: H04Q 11/0067 Provisions for optical access or distribution networks, e.g. Gigabit Ethernet Passive Optical Network (GE-PON), ATM-based Passive Optical Network (A-PON), PON-Ring
• CPC Class Codes: H04Q 2011/0079 Operation or maintenance aspects

Abstract

A method for transmission of data through an optical network includes defining transmission frames for upstream and downstream directions between an optical line termination and at least one optical network unit of an optical network. A multiple frame is defined consisting of an integer number multiple of a group of frames. A distinct value is assigned to a header portion of a useful field of a first fundamental block in the first frame of each multi-frame. The distinct value complies with a requisite composition of a header portion of the asynchronous transfer mode. A useful field is assigned to a fundamental block within the multi-frame such that each slot of the fundamental block has a digital data format compatible with the synchronous digital hierarchy. The remaining fundamental blocks with in a multi-frame have slots assigned to a digital data format compatible with an asynchronous transfer mode system such that digital data from both a broadband source and a narrowband source may be transmitted over the same optical network in an efficient manner.

Claims

1. A method for transmission of data through an optical network, the method comprising the steps of:

defining transmission frames for both the downstream and upstream directions between an optical line termination and at least one optical network unit of the optical network, each frame having constant duration;

defining an integer number of N slots for said frames, in each transmission direction, so that a one-to-one relation exists between each slot forming part of the downstream frame structure and each slot forming part of the upstream frame structure, is always valid;

defining m fundamental blocks for each slot in the downstream direction m being an integer number of higher than 1, each one of fundamental blocks consisting of a useful field and an auxiliary field;

defining a predetermined number of slots in the upstream direction and allocating a guard field, a preamble field and an useful field in each slot;

defining a multi-frame consisting of an integer number multiple k multiplied by a group of four, of said frames;

assigning a distinct value to a header portion of the useful field of the first fundamental block of the first slot of the first frame of each multi-frame, the distinct value being different from the values assigned to the header portions of the useful field of all the other fundamental blocks, and the distinct value complying with a requisite composition of the header portion of an asynchronous transfer mode cell;

assigning the useful of one of said m fundamental blocks of each slot to the transmission digital data in a first formate compatible with the synchronous digital hierarchy (SDH) and in particular assigning;

i) the first part of the bytes of said useful field to the transmission of a synchronous alignment word, and

ii) the remaining bytes of said useful field to contain said formatted digital data;

assigning the remaining of said fundamental blocks in a second format compatible with an asynchronous transfer mode system of each slot to the transmission of digital data.

2. The method according to claim 1, characterized in that the m auxiliary bytes of each slot are used to carry from the optical line termination to the at least one optical network unit enabling controls or permitting the transmission of the enabled optical line termination in a certain slot of the upstream frame structure.

3. The method according to claim 1, further comprising dedicating the useful field of said fundamental blocks to the transport of said first digital data, organized as 53-byte ATM cells, used in the context of broad band digital networks (B-ISDN) while the useful field of one and only one of said m fundamental blocks of one or more of said slots is dedicated to the transport of said digital data, pertaining to narrow band signal sources, organized in a digital stream having rated speed equal to 1544 kb/s or 2048 kb/s, or in first level tributary transport modules (TU-11 or TU-12) as defined in the context of the synchronous digital hierarchy (SDH);

arranging a fifth byte of said header portion to comply with a compositional standard for the header portion of the asynchronous transfer mode cell and introducing in the payload portion of said dedicated useful field a frame of a digital data stream or of a first level tributary transport module (TU-12 or (TU-11),

in an upstream transmission, aligning a data structure of said useful field to coincide with each slot of the downstream data structure, where the useful field on one and only one of said m fundamental blocks is dedicated to the transport of said digital data.

4. The method according to claim 1, where the downstream line transmission speed is 622.080 Mbit/s, equal to that defined for STM-4, a synchronous transport module level 4, of the SDH hierarchy, according to Recommendation ITU-U G.709, and the frame consists of 9720 bytes and has a 125 μ

s duration, with a frame repetition rate of 8 KHz.

5. The method according to claim 1, wherein each slot of the downstream frame structure consists of 162 bytes and contains three of the fundamental blocks.

6. The method according to claim 5, wherein each slot of the downstream frame structure corresponds to a slot in the upstream data structure consisting of 81 bytes, the upstream bit transmission speed being equal to one-half of the downstream transmission speed.

7. The method according to claim 6, wherein the useful field of a first one of said three fundamental blocks of one or more of the 60 slots of the frame, is dedicated to the transmission of said first format, while the second and third blocks are dedicated to the transmission of second format.

8. The method according to claim 1 further comprising, the step of arranging an auxiliary field serially before the useful field in one of the m fundamental blocks.

9. The method according to claim 1, wherein said first format supports a tributary transport module TU-12, as defined in the recommendation G.709.

10. The method according to claim 1 further comprising identifying the useful field of one of the fundamental blocks of one or more slots by a header, different from all other headers, and dedicating its payload to the transport of service and maintenance data relevant to a broad band PON access system including the optical line termination and the at least one network unit.

11. The method according to claim 1 further comprising dedicating the payload of the useful field of the first block of the first slot of each frame, for the header portion to the transport of service and maintenance data relevant to a broad band PON access system including the optical line termination and at least one network unit.

12. A method for transmission of data through an optical network, the method comprising the steps of:

defining transmission frames for transmission in upstream and downstream directions between an optical line termination and at least one optical network unit of the optical network;

organizing the transmission frames into a multi-frame including an integer number multiple of the defined transmission frames;

assigning a distinct value to a header portion in a first frame of the multi-frame, the distinct value complying with a requisite composition of a header portion of an asynchronous transfer mode cell;

assigning a useful field to a primary fundamental block within the multi-frame such that each slot of the primary fundamental block has a first data format compatible with a synchronous digital hierarchy; and

assigning slots in secondary fundamental blocks within the multi-frame to a second data format compatible with an asynchronous transfer mode system such that digital data from both a broadband source and a narrowband source may be transmitted via the multi-frame over the optical network in an efficient manner.

13. The method according to claim 12 further comprising the step of:

defining an integer number of N slots for said frames in the upstream direction and N slots in the downstream direction.

14. The method according to claim 13 further comprising the step of defining m fundamental blocks of the primary and secondary blocks for each of the N slots in the downstream direction from the optical line termination to the at least one network unit, each of the m fundamental blocks including a useful field and an auxiliary field, where m is an integer number greater than 1.

15. The method according to claim 12 further comprising the step of defining a predetermined number of slots in the upstream direction and allocating a guard field, a preamble field and an useful field in each slot.

16. The method according to claim 12 wherein the organizing step comprises defining the multi-frame as including an integer number multiple of a group of four of the transmission frames.

17. The method according to claim 12 wherein the step of assigning the distinct value comprises assigning a distinct value to a header portion of the useful field of the first fundamental block in the first slot in the first frame of each multi-frame, the distinct value being different from the values assigned to the header portions of the useful field of all the other fundamental blocks, and the distinct value complying a requisite composition of the header portion of an asynchronous transfer mode cell.

18. The method according to claim 12 wherein the step of assigning the useful field comprises the following sub-steps:

assigning the useful field of one of the fundamental blocks of each slot to the transmission of digital data in a first format compatible with the synchronous digital hierarchy (SDH);

allocating the first part of the bytes of said useful field to the transmission of a synchronous alignment word, and

allocating the remaining bytes of said useful field to contain said formatted digital data.

19. The method according to claim 12 wherein the primary block comprises a first block and the secondary blocks comprise a second and third blocks, and wherein the useful field is dedicated to the first block.

20. The method according to claim 12 further comprising the step of arranging an auxiliary field serially before a useful field in one of the fundamental blocks.

21. A communications network for transmission of data, the communications network comprising:

a passive optical network having an upstream end and downstream ends;

an optical line termination coupled the upstream end, the optical line termination adapted to transmit a multi-frame composed of a positive integer multiple of frames in a downstream direction, a header portion in a first frame of the multi-frame being compliant with a requisite composition of a header portion of an asynchronous transfer mode cell, the optical line termination assigning a useful field to a primary fundamental block within the multi-frame such that each slot of the primary fundamental block has a first data format compatible with a synchronous digital hierarchy and assigning slots in secondary fundamental blocks within the multi-frame to a second data format compatible with an asynchronous transfer mode system; and

a plurality of optical network units coupled to the downstream ends, the plurality of optical network units adapted to transmit a time division multiple access mode in an upstream direction.

22. The communications network according to claim 21 wherein the optical line termination unit defines an integer number of N slots for the frames in the in the downstream direction.

23. The communications network according to claim 22 wherein the optical line termination defines m fundamental blocks of the primary and secondary blocks for each of the N slots in the downstream direction, each of the m fundamental blocks including a useful field and an auxiliary field, where m is an integer number greater than 1.

24. The communications network according to claim 21 wherein the optical network units define a predetermined number of slots in the upstream direction and allocate a guard field, a preamble field and an useful field in each slot.

25. The communications network according to claim 21 wherein the multi-frame includes an integer number multiple of a group of four of the frames.

26. The communications network according to claim 21 wherein the optical line termination assigns a distinct value to the header portion of the useful field of the first fundamental block in the first slot in the first frame of each multi-frame, the distinct value being different from the values assigned to the header portions of the useful field of all the other fundamental blocks, and the distinct value complying with a requisite composition of the header portion of an asynchronous transfer mode cell.

27. The communications network according to claim 21 wherein the optical line termination assigns the useful field of one of the fundamental blocks of each slot to the transmission of digital data in a first format compatible with the synchronous digital hierarchy (SDH), the optical line termination allocating the first part of the bytes of said useful field to the transmission of a synchronous alignment word, and allocating the remaining bytes of said useful field to contain said formatted digital data.

28. The communications network according to claim 21 wherein the primary block comprises a first block and the secondary blocks comprise a second and third blocks, and wherein the useful field is dedicated to the first block.

29. The communications network according to claim 21 wherein the optical line termination arranges an auxiliary field serially before a useful field in one of the fundamental blocks.

30. The communications network according to claim 21 wherein a broadband exchange and a narrow band exchange are coupled to the optical line termination.

31. The communications network according to claim 21 wherein a broadband network termination and a narrowband network termination are coupled to a corresponding one of the optical networking units.