Method and apparatus for synchronization between MAC and physical layers in a wireless communication system when transporting ATM cells

• US 6,771,660 B1
• Filed: 10/25/2000
• Issued: 08/03/2004
• Est. Priority Date: 10/29/1999
• Status: Expired

• Current Assignee: Zarbana Digital Fund LLC (Intellectual Ventures LLC)
• Original Assignee: Ensemble Communications Inc (Quarterhill Inc. (f/k/a Wi-LAN Inc.))
• Inventors: Bourlas, Yair, Stanwood, Kenneth L., Behar, Jacques
• Primary Examiner(s): CANGIALOSI, SALVATORE A
• Application Number:
  US09/696,934
• Time in Patent Office: 1,378 Days
• Field of Search: 370/337, 370/338, 370/350, 370/352, 370/465, 370/466, 370/468, 370/473, 370/474, 370/503
• US Class Current: 370/466
• CPC Class Codes: H04L 2012/5607 Radio
• CPC Class Codes: H04L 2012/5627 Fault tolerance and recovery
• CPC Class Codes: H04L 2012/5648 Packet discarding, e.g. EPD, PTD
• CPC Class Codes: H04L 69/324 in the data link layer [OSI layer 2], e.g. HDLC
• CPC Class Codes: H04L 9/40 Network security protocols
• CPC Class Codes: H04W 80/02 Data link layer protocols

Abstract

The present invention is a novel method and apparatus for efficiently transporting and synchronizing data between the Media Access Control (MAC) and physical communication protocol layers in a wireless communication system. An inventive method and apparatus for transporting and synchronizing to fixed-length ATM cell boundaries and for protecting against the potential misinsertion of ATM cells has been described. An inventive ATM packet format is described. The ATM packet format is used by the present invention for the transportation and synchronization of ATM cells. The ATM packets include fields that are used to detect errors occurring within each ATM cell. ATM cells are transported in exactly two TC/PHY packets, or TDUs. ATM header information is contained in the first TDU only. No ATM header information is carried by the second TDU. An entire ATM cell is discarded if an uncorrectable error is detected in the first TDU. If no uncorrectable error occurs in the first TDU, the second TDU is checked for errors. If an undetectable error exists in the second TDU, no discard action is taken. The error is noted, and both TDUs are passed through to the higher MAC communication layers. The inventive method protects against errors occurring in the ATM header because the ATM header is always carried in the first TDU. Consequently, misinsertion of ATM cells is also prevented.

Claims

1. A method of synchronizing and transporting data in a wireless communication system, wherein the wireless communication system includes a plurality of customer premise equipment (CPE) in communication with associated and corresponding base stations, and wherein the base stations maintain uplink and downlink sub-frame maps representative of bandwidth allocations in uplink and downlink communication links, and wherein the base stations each include an associated and corresponding media access control (MAC) having a plurality of MAC data messages, and wherein the MAC transports a MAC data message through a MAC data packet that is mapped to at least one Transmission Convergence Data Unit (TDU) in a layered data transport architecture, and wherein the data includes ATM cell data configured into at least one ATM cell, the method comprising the steps of:

(a) obtaining a first Transmission Convergence Data Unit (TDU), wherein the first TDU includes an ATM header for a selected ATM cell, and wherein the first TDU includes ATM data bytes of the selected ATM cell;

(b) determining whether an uncorrectable data error is present in the first TDU obtained in step (a);

(c) obtaining a second TDU, wherein the second TDU includes remaining data bytes of the selected ATM cell;

(d) determining whether an uncorrectable data error is present in the second TDU obtained in step (c);

(e) discarding the entire selected ATM cell by discarding both the first and second TDUs if an uncorrectable data error is found in the first TDU, and then returning to step (a) to obtain a next selected ATM cell, else proceeding to step (f);

(f) noting that an error condition exists if an uncorrectable data error is found in the second TDU obtained in step (c); and

(g) passing the entire selected ATM cell to high level communication layers of the MAC and returning to step (a) to obtain a next selected ATM cell.

2. The method of synchronizing and transporting data of claim 1, wherein the MAC data packets are segmented into fixed-length ATM cells for transportation in the wireless communication system.

3. The method of synchronizing and transporting data of claim 2, wherein the MAC data packets are segmented into fixed length ATM cells upon transmission and reassembled into MAC data packets upon reception in accordance with a pre-defined Segmentation and Reassembly (SAR) process.

4. The method of synchronizing and transporting data of claim 3, wherein the MAC data packets are segmented in accordance with an ATM adaptation layer, and wherein the ATM adaptation layer is an AAL-5 ATM adaptation layer.

5. The method of synchronizing and transporting data of claim 1, wherein the MAC data packets comprise a MAC header and a MAC payload having a length of n bits.

6. The method of synchronizing and transporting data of claim 1, wherein the length of n bits is variable.

7. The method of synchronizing and transporting data of claim 1, wherein the length of n bits is fixed.

8. The method of synchronizing and transporting data of claim 5, wherein the MAC header further comprises a fragmentation control field, and wherein the fragmentation control field contains information regarding fragmentation of the MAC data message.

9. The method of synchronizing and transporting data of claim 5, wherein the first and the second TDUs comprise:

(a) a TC/PHY payload; and

(b) a TC/PHY header, further comprising a header present field, and wherein the header present field is set to a logical one when a MAC header is present within the TC/PHY payload.

10. The method of synchronizing and transporting data of claim 2, wherein the ATM cells each include an associated ATM header and an associated fixed-length ATM cell data payload.

11. The method of synchronizing and transporting data of claim 10, wherein the ATM cell data payload comprises 48 bytes of ATM cell data.

12. The method of synchronizing and transporting data of claim 2, wherein the first and second TDUs each further include an associated and respective TC CRC field and an associated and respective Forward Error Correction (FEC) field.

13. The method of synchronizing and transporting data of claim 12, wherein the CRC and FEC fields are used during the steps (b) and (d) to detect uncorrectable data errors in the selected ATM cell.

14. An apparatus for synchronizing and transporting data in a wireless communication system, wherein the wireless communication system includes a plurality of customer premise equipment (CPE) in communication with associated and corresponding base stations, and wherein the base stations maintain uplink and downlink sub-frame maps representative of bandwidth allocations in uplink and downlink communication links, and wherein the base stations each include an associated and corresponding media access control (MAC) having a plurality of MAC data messages, and wherein the MAC transports a MAC data message through a MAC data packet that is mapped to at least one Transmission Convergence Data Unit (TDU) in a layered data transport architecture, and wherein the data includes ATM cell data configured into at least one ATM cell, comprising:

(a) means for obtaining first and second Transmission Convergence Data Units (TDUs), wherein the first TDU includes an ATM header for a selected ATM cell, and wherein the TDUs include ATM data bytes of the selected ATM cell;

(b) means for determining whether uncorrectable data errors are present in the first or second TDUs;

(c) means, responsive to the determining means, for discarding the entire selected ATM cell if an uncorrectable error is found in the first TDU; and

(d) means, responsive to the determining means, for noting that an error condition exists if an uncorrectable data error is found only in the second TDU, and for passing the entire selected ATM cell to higher level communication layers of the MAC.

15. The apparatus for synchronizing and transporting data of claim 14, wherein the MAC data packets are segmented into fixed-length ATM cells for transportation in the wireless communication system.

16. The apparatus for synchronizing and transporting data of claim 15, wherein the MAC data packets are segmented into fixed length ATM cells upon transmission and reassembled into MAC data packets upon reception in accordance with a pre-defined Segmentation and Reassembly (SAR) process.

17. The apparatus for synchronizing and transporting data of claim 16, wherein the MAC data packets are segmented in accordance with an ATM adaptation layer, and wherein the ATM adaptation layer is an AAL-5 ATM adaptation layer.

18. The apparatus for synchronizing and transporting data of claim 14, wherein the MAC data packets comprise a MAC header and a MAC payload having a length of n bits.

19. The apparatus for synchronizing and transporting data of claim 14, wherein the means for obtaining the first and second TDUs comprises means for mapping the MAC data packets into Transmission Convergence Data Units.

20. The apparatus for synchronizing and transporting data of claim 19, wherein the mapping means comprises a computer program executable on a computing device.

21. The apparatus for synchronizing and transporting data of claim 14, wherein the first and second TDUs each further include associated and respective TC CRC and Forward Error Correction (FEC) fields, and wherein the means for determining whether uncorrectable data errors are present in the first or second TDUs comprises a computer program, executable on a computing device, and adapted to process the TC CRC and FEC fields.

22. A computer program executable on a computing device, wherein the program is capable of synchronizing and transporting data in a wireless communication system, and wherein the wireless communication system includes a plurality of customer premise equipment (CPE) in communication with associated and corresponding base stations, and wherein the base stations maintain uplink and downlink sub-frame maps representative of bandwidth allocations in uplink and downlink communication links, and wherein the base stations each include an associated and corresponding media access control (MAC) having a plurality of MAC data messages, and wherein the MAC transports a MAC data message through a MAC data packet that is mapped to at least one Transmission Convergence Data Unit (TDU) in a layered data transport architecture, and wherein the data includes ATM cell data configured into at least one ATM cell, comprising:

(a) a first set of instructions for obtaining a MAC data packet;

(b) a second set of instructions for mapping the MAC data packet into a plurality of Transmission Convergence Data Units (TDUs), wherein the TDUs each include ATM cell data;

(c) a third set of instructions for selecting an ATM cell comprising a first and a second TDU, and for obtaining the first TDU, wherein the first TDU includes an ATM header for the selected ATM cell, and wherein the first TDU also includes ATM data bytes of the selected ATM cell;

(d) a fourth set of instructions for obtaining the second TDU, wherein the second TDU includes remaining data bytes of the selected ATM cell;

(e) a fifth set of instructions for determining whether an uncorrectable data error is present in the first TDU, and for discarding the selected ATM cell if an uncorrectable data error is present in the first TDU;

(f) a sixth set of instructions for determining whether an uncorrectable data error is present in the second TDU, and for noting that an error condition exists if an uncorrectable data error is present in the second TDU; and

(g) a seventh set of instructions for passing the selected ATM cell to higher level communication levels of the MAC.

23. The computer program of claim 22, wherein the first and second TDUs each further include an associated and respective TC CRC field and an associated and respective Forward Error Correction (FEC) field.

24. The computer program of claim 23, wherein the CRC and FEC fields are used in determining whether uncorrectable data errors are present in the selected ATM cell.

25. A method of re-synchronizing the transportation of ATM data in a wireless communication system, wherein the wireless communication system includes a plurality of customer premise equipment (CPE) in communication with associated and corresponding base stations having uplink and downlink communication links with the plurality of CPEs, and wherein the base stations maintain uplink and downlink sub-frame maps representative of bandwidth allocations in the uplink and downlink communication links, and wherein the base stations each include an associated and corresponding media access control (MAC) having a plurality of MAC data messages, and wherein the MAC transports a MAC data message through a MAC data packet that is mapped to at least one Transmission Convergence Data Unit (TDU) in a layered data transport architecture wherein each TDU includes ATM data bytes for transportation in the wireless communication system, and wherein each TDU further includes a header present field, and wherein at least one of the communication links may be intermittently disrupted during data transmission, the method comprising the steps of:

(a) detecting a disruption of a communication link during transmission of ATM data;

(b) reestablishing the communication link that was detected as disrupted at step (a);

(c) receiving a TDU;

(d) detecting the header present field of the TDU received at step (c), and if the header present field indicates that a header is present, proceeding to step (e), else returning to step (c); and

(e) resuming data transmission on the disrupted communication link, wherein at most only one MAC data message is lost after reestablishing the communication link in step (b).

26. A method of re-synchronizing the transportation of ATM data in a wireless communication system, wherein the wireless communication system includes a plurality of customer premise equipment (CPE) in communication with associated and corresponding base stations having uplink and downlink communication links with the plurality of CPEs, and wherein the base stations maintain uplink and downlink sub-frame maps representative of bandwidth allocations in the uplink and downlink communication links, and wherein the base stations each include an associated and corresponding media access control (MAC) having a plurality of MAC data messages, and wherein the MAC transports a MAC data message through a MAC data packet that is mapped to at least one Transmission Convergence Data Unit (TDU) in a layered data transport architecture wherein each TDU includes ATM data bytes for transportation in the wireless communication system, and wherein at least one of the communication links may be intermittently disrupted during data transmission, the method comprising the steps of:

(a) detecting a disruption of a communication link during transmission of ATM data;

(b) reestablishing the communication link that was detected as disrupted at step (a);

(c) receiving a first TDU of a selected ATM cell;

(d) determining whether an uncorrectable error is present in the first TDU, and discarding the selected ATM cell if an uncorrectable error is present in the first TDU; and

(e) resuming data transmission on the disrupted communication link, wherein at most only one MAC data message is lost after reestablishing the communication link in step (b).