Method and apparatus for switching data between bitstreams of a time division multiplexed network

• US 6,430,180 B1
• Filed: 05/04/2000
• Issued: 08/06/2002
• Est. Priority Date: 11/06/1997
• Status: Expired due to Term

• Current Assignee: Net Insight Intellectual Property AB (Net Insight AB)
• Original Assignee: Net Insight AB
• Inventors: Gauffin, Lars, Roos, Joachim, Holm, Lukas, Bohm, Christer
• Primary Examiner(s): TON, DANG T
• Application Number:
  US09/565,205
• Time in Patent Office: 824 Days
• Field of Search: 370/441, 370/535, 370/537, 370/501, 370/502, 370/503, 370/442, 370/389, 370/428, 370/413, 370/351, 370/352, 370/347, 370/342, 370/369, 370/371, 370/372, 370/358, 370/360, 370/363, 370/367, 370/370, 370/368, 370/374, 370/375, 370/376, 370/378, 370/379, 370/380, 370/381, 370/506, 370/507, 370/509, 370/510, 370/512, 370/468, 370/465, 370/437, 370/337
• US Class Current: 370/369
• CPC Class Codes: H04J 2203/001 using a shared central buffer
• CPC Class Codes: H04J 2203/0032 Fibre
• CPC Class Codes: H04J 2203/0044 Bus, e.g. DQDB
• CPC Class Codes: H04J 2203/0091 Time slot assignment
• CPC Class Codes: H04J 3/0602 Systems characterised by the synchronising information used
• CPC Class Codes: H04Q 11/04 for time-division multiplexing H04Q11/0001 takes precedence

Abstract

A method and an apparatus for switching data between a set of input bitstreams and a set of output bitstreams in a circuit switched time division multiplexed network is presented. Each bitstream is divided into recurring frames and each frame is divided into time slots. Each one of the input bitstreams is received, and frames of time slot data thereof are temporarily stored in a set of memories. Each of the memories is used for storing frames of a respective bitstream of the input bitstreams. For each frame of each one of the output bitstreams, and sequentially in accordance with the order that the time slot data are to be transmitted in the respective output frame, time slot data is selectively read from frames presently temporarily stored in the set of memories, and is then transmitted into allocated time slots of the output bitstreams.

Claims

1. A method for switching data in time and space between a set of input bitstreams and a set of output bitstreams in a circuit switched time division multiplexed network, each of said bitstreams being divided into recurring frames and each of said frames being divided into time slots, said method comprising the steps of:

receiving each one of said input bitstreams;

temporarily storing frames of time slot data from said input bitstreams, wherein frames from different input bitstreams are stored in respective memory means of a set of memory means;

providing each time slot of an output frame of each one of said output bitstreams with an identification designating whether or not the respective time slot of said output bitstreams is to receive time slot data from any one of said input bitstreams and, if so, from which time slot data entry of said memory means that said time slot data is to be collected;

selectively reading, for each output frame of each one of said output bitstreams, time slot data from the frames temporarily stored in said set of memory means in accordance with said identification of each time slot, wherein said selective reading for each of said output bitstreams is performed independent of the other output bitstreams, and wherein said selective reading causes the time slot data to be read sequentially in accordance with the order that said time slot data are to be transmitted in the respective output frame; and

transmitting said time slot data, as selectively read from said temporarily stored frames, into allocated time slots of said output bitstreams.

2. A method as claimed in claim 1, wherein said independency is provided by performing said selective reading over lines private to each output bitstream.

3. A method as claimed in claim 1, wherein said step of temporarily storing comprises temporarily storing time slot data from respective recurring time slot positing in the sequences of time slots of said input bitstreams in respective time slot data entries of said memory means.

4. A method as claimed in claim 1, wherein said step of selectively reading comprises the steps of:

reading, for sequential time slots of a frame of a bitstream of said output bitstreams, respective provided identifications of time slot data entries of said set of memory means, said time slot data entries providing time slot data for said time slots; and

selectively reading, for said time slots of said frame, time slot data from said time slot data entries based upon said identifications.

5. A method as claimed in claim 1, comprising the steps of receiving an additional bitstream and reading, for a time slot of a frame of at least one bitstream of said output bitstreams, said time slot being allocated to receive time slot data from said additional bitstream, time slot data from said additional bitstream based upon an identification indicating that said time slot is arranged to receive time slot data from said additional bitstream.

6. A method as claimed in claim 1, comprising the step of providing each time slot of a frame of each one of said output bitstreams with an identification designating whether or not the respective time slot of said output bitstreams is to receive time slot data from any one of said input bitstreams and, if so, from which time slot data entry of said memory means that said time slot data is to be collected.

7. A method as claimed in claim 1, comprising the step of providing a set of identification updates and associated timing information relating to when said identifications are to be updated using said identification updates, and updating said identifications with said set of identification updates at the timing designated by said associated timing information.

8. A method as claimed in claim 1, comprising the steps of, for each one of said input bitstreams, detecting a frame synchronization signal and, based thereupon, synchronizing said temporary storing of frames into the respective memory means of said set of memory means.

9. A method as claimed in claim 1, comprising the steps of, for each one of said output bitstreams, determining a frame synchronization and, based thereupon, synchronizing said selective reading of time slot data and the transmitting thereof into the respective output bitstream.

10. A method as claimed in claim 1, wherein said step of temporarily storing comprises temporarily storing three sequential frames of each one of said input bitstreams.

11. A method as claimed in claim 10, comprising the step of indicating, at each given point in time, which ones of the temporarily stored three sequential frames of each one of said input bitstreams that are currently being written into storage.

12. A method as claimed in claim 10, comprising the step of indicating, at each given point in time, which ones of the temporarily stored three sequential frames of each one of said input bitstreams, that are currently used for the selective reading of time slot data for said output bitstreams.

13. A method as claimed in claim 1, wherein channels on said bitstreams are defined by a respective set of time slots in each frame of the respective bitstream, said time slots being dynamically allocated based upon dynamically changing capacity requirements of the nodes of the network.

14. An apparatus for switching data between a set of input bitstreams and a set of output bitstreams in a circuit switched time division multiplexed network, each of said bitstreams being divided into recurring frames and each of said frames being divided into time slots, said apparatus comprising:

input means for receiving each one of said input bitstreams;

a set of memory means, each memory means being arranged for temporarily storing frames of a respective bitstream of said input bitstreams;

means for selectively reading, for each output frame of each one of said output bitstreams, time slot data from the frames temporarily stored in said set of memory means, wherein said selective reading for each bitstream is performed independent of the other bitstreams, and wherein said selective reading causes the time slot data to be read sequentially in accordance with the order that said time slot data are to be transmitted in the respective output frame; and

output means for transmitting said time slot data, as selectively read by said means for selectively reading, into allocated time slots of said output bitstreams.

15. An apparatus as claimed in claim 14, wherein each one of said memory means is provided with multiple read ports, and wherein each one of said read ports is arranged to serve a respective one of said output bitstreams.

16. An apparatus as claimed in claim 14, wherein said means for selectively reading comprises a set of reading means, each reading means being arranged to read time slot data for a respective bitstream of said output bitstreams.

17. An apparatus as claimed in claim 14, wherein each memory means of said set of memory means comprises a plurality of time slot data entries and wherein each time slot data entry of a memory means of said set of memory means is arranged to store time slot data from a respective recurring time slot position in the sequence of time slots of the input bitstream that is associated with said memory means.

18. An apparatus as claimed in claim 14, wherein said means for selectively reading comprises means for providing, for each one of said output bitstreams, and for those time slots thereof that are allocated to receive time slot data from said input bitstreams, respective identifications of time slot data entries of said set of memory means, wherein said means for selectively reading are arranged to read time slot data for said time slots from said time slot data entries in accordance with said identifications.

19. An apparatus as claimed in claim 14, comprising means for receiving an additional bitstream and means for providing a time slot of a frame of at least one bitstream of said output bitstreams, said time slot being allocated to receive time slot data from said additional bitstream, with an identification related to said additional bitstream for the provision of time slot data therefrom, wherein said means for selectively reading is arranged to read time slot data for said time slot from said additional bitstream based upon said identification.

20. An apparatus as claimed in claim 14, wherein said means for providing identifications is arranged to provide each time slot of a frame of each one of said output bitstreams with an identification designating whether or not the said time slot is to receive time slot data from any one of said input bitstreams and, if so, from which time slot data entry, of said set of memory means, that said time slot data is to be read.

21. An apparatus as claimed in claim 14, comprising:

means for storing a set of identification updates and for storing associated timing information as to when said identifications are to be updated using said identification updates; and

means for updating said identifications using said set of identification updates at the timing designated by said associated timing information.

22. Apparatus as claimed in claim 14, comprising input frame synchronization means for detecting frame synchronization signals for each respective one of said input bitstreams and for synchronizing, based upon said frame synchronization signals, said temporary storing of frames into respective memory means of said set of memory means.

23. An apparatus as claimed in claim 14, comprising output frame synchronization means for determining frame synchronization for each respective one of said output bitstreams and for synchronizing, based thereupon, the selective reading of time slot data from said set of memory means and the transmitting thereof into the respective output bitstream.

24. An apparatus as claimed in claim 14, wherein each one of said memory means comprises three frame storage areas for sequentially and temporarily storing three sequential frames of the respective input bitstream.

25. An apparatus as claimed in claim 24, comprising write pointer means designating, at each given point in time, which frame storage areas, of said set of memory means, that are used for storing the frames that are presently being written from said input bitstreams into said set of memory means.

26. An apparatus as claimed in claim 24, comprising read pointer means designating, at each given point in time, which frame storage areas, of said set of memory means, that are currently used for the selective reading of time slot data for said output bitstreams.

27. An apparatus as claimed in claim 14, comprising means for momentarily offsetting the designation provided by said read pointer means for a time slots of said output bitstreams in order to read time slot data for said time slot from another frame storage area than the one designated by default by said read pointer means.

28. An apparatus as claimed in claim 14, wherein said memory means comprises a random access memory with multiple read ports.