Method and apparatus enabling synchronous transfer mode, variable length and packet mode access for multiple services over a broadband communication network

• US 6,055,242 A
• Filed: 03/06/1997
• Issued: 04/25/2000
• Est. Priority Date: 03/20/1996
• Status: Expired due to Term

• Current Assignee: Alcatel-Lucent USA, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Dravida, Subrahmanyam, Kustka, George John, Magill, Peter D., Siller, Curtis A., Sriram, Kotikalapudi, Doshi, Bharat Tarachand
• Primary Examiner(s): Pham, Chi H.
• Assistant Examiner(s): YAO, KWANG BIN
• Application Number:
  US08/812,469
• Time in Patent Office: 1,146 Days
• Field of Search: 370/389, 370/395, 370/442, 370/443, 370/458, 370/459, 370/460, 370/461, 370/468, 370/508, 370/470, 370/471, 370/473, 370/474, 370/477, 370/485, 370/487, 370/489, 370/490
• US Class Current: 370/458
• 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 12/2801 Broadband local area networks
• CPC Class Codes: H04N 21/6118 involving cable transmission, e.g. using a cable modem
• CPC Class Codes: H04N 21/6168 involving cable transmission, e.g. using a cable modem
• CPC Class Codes: H04N 7/17309 Transmission or handling of upstream communications

Abstract

The specification relates to a broadband multiple access protocol for bi-directional hybrid fiber/coax (HFC) networks. The protocol supports downstream broadcast transmission from headend to cable modem, and also provides for allocation of bandwidth for cable modems to transmit back to the headend. Although the present invention is described in relation to an HFC network, it is also equally applicable to a wireless communications environment. The protocol supports different access modes such as synchronous transfer mode, asynchronous transfer mode, and variable length data. The protocol adapts to changing demands for a mix of circuit and packet mode applications and allocates upstream and downstream bandwidth in response to the a variety of bursty and isochronous traffic sources. In order to satisfy the quality of service requirements of varied applications, while maintaining high bandwidth efficiency, the protocol utilizes a frame structure with frame partitioning into regions; one region dedicated to STM payload and asynchronous, second region dedicated to ATM and VL payloads, messaging and control.

Claims

1. A method for transmission of synchronous transfer mode (STM) payloads and asynchronous variable length (VL) payloads over a bi-directional broadband communications network having a source and a destination, said method comprising the steps of:

dividing said transmission into a series of successive time frames;

partitioning each of said time frames into a first region and a second region, said first region and said second region separated with a boundary;

allocating at least one time slot to said first region whenever at least one of said STM payloads is available for said transmission;

dividing said second region into a plurality of basic slots, said plurality of basic slots allocated and assigned for said transmission of said asynchronous VL payloads; and

dynamically adjusting the position of said boundary within each of said time frames, to facilitate transmission bandwidth allocation for said source.

2. The method in accordance with claim 1 wherein said plurality of basic slots within said second region are additionally allocated and assigned for transmission of asynchronous transfer mode (ATM) payloads.

3. The method in accordance with claim 1 wherein said transmission is an upstream transmission.

4. The method in accordance with claim 3 wherein said plurality of basic slots within said second region are also allocated and assigned for transmission of asynchronous transfer mode (ATM) payloads.

5. The method in accordance with claim 4 wherein:

said source is a station; and

said destination is a common controller.

6. The method in accordance with claim 5 further comprising the steps of:

subdividing said plurality of basic slots within said second region into an upstream slow control region, a contention region, and a reserved region;

requesting a basic slot allocation within said reserved region of subsequent frames via said contention region; and

transmitting said asynchronous VL payloads and said ATM payloads upstream via said plurality of basic slots within said reserved region.

7. The method in accordance with claim 3 wherein:

said source is a headend; and

said destination is a cable modem.

8. The method in accordance with claim 7 further comprising the steps of:

subdividing said plurality of basic slots within said second region into an upstream slow control region, a contention region, and a reserved region;

requesting a basic slot allocation within said reserved region of subsequent frames via said contention region; and

transmitting said asynchronous VL payloads and said ATM payloads upstream via said plurality of basic slots within said reserved region.

9. The method in accordance with claim 8 wherein said upstream ATM payloads are appended with a bandwidth request field (BRF), said BRF a means of requesting a quantity of additional bandwidth in subsequent upstream frames, said BRF transmitted upstream in said reserved region such that said BRF is not subject to a collision.

10. The method in accordance with claim 8 wherein said upstream VL payloads are appended with a bandwidth request field (BRF), said BRF a means of requesting a quantity of additional bandwidth in subsequent upstream frames;

said BRF transmitted upstream in said reserved region and therefore said BRF not subject to a collision.

11. A method for downstream transmission of synchronous transfer mode (STM) payloads and asynchronous variable length (VL) payloads over a bi-directional broadband communications network between a headend and at least one cable modem, said method comprising the steps of:

dividing said downstream transmission into a series of successive downteam time frames;

dividing each of said downstream time frames into an integral number of downstream subframes;

partitioning each of said downstream subframes into a downstream first region and a downstream second region;

allocating at least one time slot to said downstream first region whenever at least one of said STM payloads is to be transmitted; and

allocating said asynchronous VL payloads to said downstream second region.

12. The method in accordance with claim 11 further comprising the step of allocating asynchronous transfer mode (ATM) payloads to said downstream second region.

13. The method in accordance with claim 12 wherein an integral number of said successive downstream time frames are transmitted downstream collectively as a master frame.

14. The method in accordance with claim 12 further comprising the steps of:

designating information bytes from each of said downstream subframes into an odd numbered group and an even numbered group;

computing a first forward error correction (FEC) number for said odd numbered group for each of said downstream subframes;

computing a second forward error correction (FEC) number for said even numbered group for each of said downstream subframes;

byte-wise interleaving and appending said first FEC number and said second FEC number to each of said downstream subframes; and

transmitting downstream each of said downstream subframes appended with said first FEC number and said second FEC number while preserving the order of said information bytes in each of said downstream subframes.

15. The method in accordance with claim 14 wherein said byte-wise interleaving and appending of said first FEC number and said second FEC number within each of said downstream subframes preserves application layer interleaving and forward error correction, if said application layer interleaving and forward error correction had previously been performed.

16. The method in accordance with claim 14 wherein delay sensitive traffic within each of said downstream subframes is processed at said at least one cable modem without verifying said first FEC number and said second FEC number, thereby incurring no additional delay due to said at least one cable modem deinterleaving and decoding said first FEC number and said second FEC number.

17. The method in accordance with claim 12 further comprising the steps of:

attaching a VL protocol data unit (PDU) header to each of said downstream VL payloads;

attaching an ATM protocol data unit (PDU) header to each of said downstream ATM payloads; and

attaching an Idle protocol data unit (PDU) header to transmit downstream without payload, said Idle PDU header utilized whenever neither said VL PDU header or said ATM PDU header are being transmitted downstream;

said VL PDU header, said ATM PDU header, and said Idle PDU header being collectively referred to as packet headers.

18. The method in accordance with claim 17 wherein said packet headers are adapted to:

a packet header type identification to said cable modem;

a length quantity describing the length of said VL payload; and

a cable modem address field.

19. The method in accordance with claim 12 further comprising the steps of:

creating a fast control field (FCF) for said downstream transmission; and

transmitting said FCF within said downstream second region of at least one of said downstream subframes for each of said downstream time frames;

said FCF conveying bandwidth allocation information from said headend to said cable modem.

20. The method in accordance with claim 12 further comprising the steps of:

creating a slow control field (SCF) for said downstream transmission; and

transmitting said SCF within said downstream second region of at least one of said downstream subframes for each of said downstream time frames;

said SCF conveying from said head end to said cable modem a plurality of control messages, each of said plurality of control messages capable of transcending said downstream subframe and said downstream time frame.

21. The method in accordance with claim 11 wherein upstream transmission of said STM payloads and asynchronous VL payloads are also enabled, said method further comprising the steps of:

dividing said upstream transmission into a series of successive upstream time frames;

partitioning each of said upstream time frames into an upstream first region and an upstream second region;

allocating at least one upstream time slot to said upstream first region whenever at least one of said STM payloads is to be transmitted; and

dividing said upstream second region into a plurality of basic slots, said plurality of basic slots allocated and assigned for said upstream transmission of said asynchronous VL payloads.

22. The method in accordance with claim 21 further comprising the steps of:

subdividing said plurality of basic slots into an upstream slow control region, a contention region, and a reserved region;

requesting, via said contention region, a basic slot allocation for upstream transmission within said reserved region of subsequent frames; and

transmitting said asynchronous VL payloads upstream within said basic slot allocation.

23. The method in accordance with claim 21 wherein said plurality of basic slots within said second region are also allocated and assigned for upstream transmission of asynchronous transfer mode (ATM) payloads.

24. The method in accordance with claim 23 further comprising the step of allocating asynchronous transfer mode (ATM) payloads to said downstream second region for downstream transmission.

25. The method in accordance with claim 24 further comprising the steps of:

subdividing said plurality of basic slots into an upstream slow control region, a contention region, and a reserved region;

requesting, via said contention region, a basic slot allocation for upstream transmission within said reserved region of subsequent frames;

transmitting upstream messages via said upstream slow control region; and

transmitting upstream said asynchronous VL payloads and said ATM payloads within said basic slot allocation.

26. The method in accordance with claim 25, wherein a request for a basic slot allocation for upstream transmission in said reserved region of subsequent frames is made, further comprising the steps of:

requesting said basic slot allocation within a bandwidth request field (BRF);

representing said request for said basic slot allocation as an absolute request whenever said request is an initial request; and

representing said request for said basic slot allocation as an incremental request whenever said request is a request for additional bandwidth.

27. The method in accordance with claim 26 further comprising the step of appending said BRF with said upstream transmission of said asynchronous VL payloads and said ATM payloads, said BRF thereby also transmitted within said reserved region.

28. A multiservice protocol for a bi-directional broadband communications system operating between a source and at least one destination, said protocol having a downstream structure and an upstream structure, said downstream structure comprising:

a series of successive downstream frames included within said downstream structure;

a plurality of downstream subframes, said downstream frames comprised of said downstream subframes;

a downstream synchronous region included within said downstream subframes when synchronous transfer mode (STM) payloads are to be transmitted;

at least one downstream STM time slot within said downstream synchronous region when STM payloads are to be transmitted; and

a downstream asynchronous region within said downstream subframes, said downstream asynchronous region utilized for the downstream transmission of asynchronous variable length (VL) payloads.

29. The multiservice protocol in accordance with claim 28 wherein:

said source is a common controller; and

said at least one destination is at least one station.

30. The multiservice protocol in accordance with claim 29 wherein said downstream asynchronous region is further utilized for downstream transmission of asynchronous transfer mode (ATM) payloads.

31. The multiservice protocol in accordance with claim 28 wherein:

said source is a headend; and

said at least one destination is at least one cable modem.

32. The multiservice protocol in accordance with claim 31 wherein said downstream asynchronous region is further utilized for downstream transmission of asynchronous transfer mode (ATM) payloads.

33. The multiservice protocol in accordance with claim 32 further comprising:

a downstream fast control field (FCF), said FCF transmitting bandwidth allocation information to said at least one cable modem, said bandwidth allocation information utilized to configure subsequent said upstream structure from said at least one cable modem to said headend; and

a downstream slow control field (SCF), said SCF transmitting at least one control message to said at least one cable modem, said at least one control message unrestricted by downstream frame and downstream subframe boundaries.

34. The multiservice protocol in accordance with claim 33 wherein:

said downstream FCF is transmitted within said downstream asynchronous region in at least one said downstream subframe per said downstream frame; and

said downstream SCF is transmitted in each said downstream subframe.

35. The multiservice protocol in accordance with claim 31, said upstream structure comprising:

a series of successive upstream frames included within said upstream structure;

a first upstream region within each of said upstream frames;

a second upstream region within each of said upstream frames;

at least one time slot allocated within said first upstream region whenever at least one of said STM payloads is to be transmitted; and

a plurality of basic slots, said plurality of basic slots apportioned throughout the entirety of said second upstream region, said plurality of basic slots allocated and assigned for transmitting upstream said asynchronous VL payloads.

36. The multiservice protocol in accordance with claim 35 wherein said second upstream region is flier utilized for upstream transmission of asynchronous transfer mode (ATM) payloads.

37. A bi-directional broadband communications system having a transmission network wherein at least one cable modem is interconnected with a headend via a transmission medium having a multiple access upstream channel and a broadcast downstream channel, said system capable of transporting synchronous transfer mode (STM) payloads and asynchronous variable length (VL) payloads, comprising:

a cable modem framer for dividing said upstream transmission into a series of successive upstream time frames; and

a headend bandwidth manager transmitting downstream a boundary location for each of said upstream time frames, said boundary location partitioning said frames into a first region and a second region;

said headend bandwidth manager allocating to said first region at least one time slot whenever said cable modem has at least one said STM payload for said upstream transmission;

said cable modem dividing said second region into a plurality of basic slots, said basic slots allocated and assigned for said upstream transmission of said VL payloads; and

said headend bandwidth manager dynamically adjusting said boundary location within said successive upstream time frames to facilitate desired bandwidth allocation for said cable modem.

38. The bi-directional broadband communications system in accordance with claim 37 wherein said plurality of basic slots are also allocated and assigned for said upstream transmission of asynchronous transfer mode (ATM) payloads.

39. A method for upstream transmission of synchronous transfer mode (STM) payloads and asynchronous variable length (VL) payloads over a bi-directional broadband communications network having a headend and at least one cable modem, said method comprising the steps of:

dividing said upstream transmission into a series of successive time frames;

partitioning said time frames into a first region and a second region, said first region and said second region separated with a boundary;

allocating at least one fixed length time slot to said first region whenever said cable modem has at least one said STM payload for said upstream transmission;

dividing said second region into a plurality of basic slots, said basic slots allocated and assigned for said upstream transmission of said VL payloads; and

dynamically adjusting said boundary position within said frames as determined by said headend, to facilitate a bandwidth allocation for said cable modem.

40. The method in accordance with claim 39 wherein the length of each of said plurality of basic slots provides bandwidth granularity in conformance with transmission quality of service requirements.

41. The method defined in claim 39 further comprising the steps of:

subdividing said basic slots of said second region into an upstream slow control region, a contention region, and a reserved region;

requesting said basic slot allocation in said reserved region in subsequent frames via said contention region; and

transmitting said asynchronous VL payloads upstream via basic slots in said reserved region.

42. A method for upstream transmission and downstream transmission of synchronous transfer mode (STM) payloads, asynchronous transfer mode (ATM) payloads, and asynchronous variable length (VL) payloads over a bi-directional broadband communications network having a headend and at least one cable modem, said method comprising the steps of:

dividing said upstream transmission into a series of successive upstream time frames;

partitioning each of said upstream time frames into an upstream first region and an upstream second region;

dividing said downstream transmission into a series of successive downstream time frames;

dividing said downstream time frames into a plurality of successive downstream time subframes;

partitioning each of said plurality of downstream time subframes into a downstream first region and a downstream second region;

allocating at least one time slot each to said upstream first region and downstream first region, whenever at least one of said STM payloads is to be transmitted; and

assigning a portion of said upstream second region and said downstream second region for conveyance of said asynchronous VL payloads and said ATM payloads.

43. The method in accordance with claim 42 wherein a length of each of said plurality of successive downstream time subframes is selected to minimize delay of said STM payloads.

44. The method in accordance with claim 43 wherein said length of each of said plurality of successive downstream time subframes is 125 microseconds.

45. The method in accordance with claim 42 further comprising the steps of:

queuing a VL PDU at a transmitter for eventual transmission to a receiver;

appending a packet header to said VL PDU; and

including a length field within said packet header;

said length field including a variable, said variable conveying length information of said VL PDU to said at least one cable modem.

46. The method in accordance with claim 45 further comprising the step of including a second variable within the length field;

said second variable equal to a first value if said VL PDU is transmitted completely within one subframe;

said second variable equal to a second value if said VL PDU transmission is started in a previous subframe, but completed within a current subframe;

said second variable equal to a third value if said VL PDU transmission is started within said current subframe, but to be completed in a subsequent subframe; and

said second variable equal to a fourth value if said VL PDU transmission is continued within said current subframe, but to be completed in a subsequent subframe.

47. The method in accordance with claim 42 further comprising the step of including within said downstream transmission a fast control field (FCF), said FCF providing said at least one cable modem with a location for said partitioning each of said upstream time frames into said upstream first region and said upstream second region.

48. The method in accordance with claim 47 wherein said first region is allocated for transmission of said STM payloads.

49. The method in accordance with claim 47 wherein said second region is allocated for transmission of said ATM payloads and said VL payloads.

50. The method in accordance with claim 49 wherein said second region is further allocated for transmission of at least one upstream slow control (USC) message within a USC superslot;

said USC superslot comprised of a plurality of basic slots;

said USC superslot operable for upstream transmission of said at least one USC message; and

said at least one USC message transmitted without reservation and said USC message subject to contention.

51. The method in accordance with claim 47 wherein said FCF contains a downstream MAP, said downstream MAP utilized to provide said at least one cable modem upstream transmission status and upstream reservation grant information at preselected intervals.

52. The method in accordance with claim 42 further comprising the steps of:

incorporating a pointer field (PF) within each of said downstream time subframes;

allocating within each PF a first number of bits, said first number of bits utilized for a cyclical redundancy check (CRC); and

allocating within each PF a second number of bits, said second number of bits utilized to convey the quantity of incomplete variable length transmission within each of said downstream time subframes.

53. A method for transmission of synchronous transfer mode (STM) payloads and asynchronous variable length (VL) payloads, said method comprising the steps of:

dividing said transmission into a series of successive time frames;

partitioning each of said time frames into a first region and a second region, said first region and said region separated with a boundary;

allocating at least one time slot to said first region whenever at least one of said STM payloads is available for said transmission;

dividing said second region into a plurality of basic slots, said plurality of basic slots allocating and assigned for said transmission of said asynchronous VL payloads; and

dynamically adjusting the position of said boundary within each of said time frames, to facilitate transmission bandwith allocation for said source.