Method and apparatus for tracking data packets in a packet data communication system

• US 6,134,237 A
• Filed: 09/30/1997
• Issued: 10/17/2000
• Est. Priority Date: 09/30/1997
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Brailean, Karen A., Boxall, Robert F.
• Primary Examiner(s): Kizou, Hassan
• Assistant Examiner(s): Pezzlo, John
• Application Number:
  US08/940,299
• Time in Patent Office: 1,113 Days
• Field of Search: 370/394, 370/384, 370/242, 370/245, 370/248, 370/349, 455/464, 380/270, 709/225, 375/222
• US Class Current: 370/394
• CPC Class Codes: H04L 1/1809 Selective-repeat protocols
• CPC Class Codes: H04L 2001/125 Arrangements for preventing errors in the return channel

Abstract

A packet data communication system (100) employs a method and apparatus for tracking data packets in the packet data communication system. A sending communication device (e.g., 101) transmits a data packet (130) to a receiving communication device (e.g., 105), wherein the data packet includes a respective packet sequence number (131). Responsive to the transmission, the sending device increases a transmit tracking number (V(S)) that is used to indicate the packet sequence number of the data packet that is next in sequence to be transmitted. Upon receiving the data packet, the receiving device transmits an acknowledgment data packet (140) to the sending device, wherein the acknowledgment data packet includes a receive tracking number (139). The receive tracking number indicates the packet sequence number of the data packet that the receiving device expects to receive next. Upon receiving the acknowledgment data packet, the sending device determines whether a communication error occurred based on the receive tracking number and the transmit tracking number.

Claims

1. A method for tracking data packets in a packet data communication system, the method comprising the steps of:

transmitting, by a first communication device, a data packet to a second communication device;

increasing, by the first communication device responsive to the step of transmitting, a transmit tracking number, wherein the transmit tracking number indicates a packet sequence number of a data packet that is next in sequence to be transmitted;

receiving, by the second communication device, the data packet transmitted by the first communication device;

transmitting, by the second communication device, an acknowledgment data packet to the first communication device, wherein the acknowledgment data packet includes a receive tracking number that indicates a packet sequence number of a data packet that is next in sequence to be received;

receiving, by the first communication device, the acknowledgment data packet;

comparing, by the first communication device, the receive tracking number and the transmit tracking number; and

when the receive tracking number is greater than the transmit tracking number, determining that a communication error occurred.

2. The method of claim 1, wherein the communication error comprises a software error that occurred in at least one of the first communication device and the second communication device.

3. The method of claim 1, further comprising the step of determining that a communication error did not occur when the receive tracking number is less than or equal to the transmit tracking number.

4. The method of claim 1, wherein the acknowledgment data packet comprises a plurality of data blocks, the method further comprising the steps of:

at the second communication device and prior to the step of transmitting the acknowledgment data packet;

inputting a predetermined value into a portion of a first data block of the plurality of data blocks reserved for the receive tracking number;

determining a data integrity indicator for the plurality of data blocks;

inputting the data integrity indicator into a portion of a second data block of the plurality of data blocks; and

replacing the predetermined value with the receive tracking number, such that the acknowledgment data packet, when transmitted, includes the receive tracking number and the data integrity indicator.

5. The method of claim 4, further comprising the steps of:

at the first communication device and responsive to the step of receiving the acknowledgment data packet;

replacing the receive tracking number with the predetermined value;

determining a second data integrity indicator for the plurality of data blocks;

comparing the second data integrity indicator with the data integrity indicator in the second data block;

when the second data integrity indicator does not equal the data integrity indicator in the second data block, determining that the acknowledgment data packet is corrupted.

6. The method of claim 1, wherein the acknowledgment data packet comprises a plurality of data blocks, the method further comprising the steps of:

at the second communication device and prior to the step of transmitting the acknowledgment data packet;

determining a data integrity indicator for the plurality of data blocks less a portion of a first data block of the plurality of data blocks reserved for the receive tracking number;

inputting the data integrity indicator into a portion of a second data block of the plurality of data blocks; and

inputting the receive tracking number into the portion of the first data block reserved for the receive tracking number, such that the acknowledgment data packet, when transmitted, includes the receive tracking number and the data integrity indicator.

7. The method of claim 6, further comprising the steps of:

at the first communication device and responsive to the step of receiving the acknowledgment data packet;

determining a second data integrity indicator for the plurality of data blocks less the portion of the first data block containing the receive tracking number;

comparing the second data integrity indicator with the data integrity indicator in the portion of the second data block; and

when the second data integrity indicator does not equal the data integrity indicator in the portion of the second data block, determining that the acknowledgment data packet is corrupted.

8. A method for a first communication device to track data packets transmitted to a second communication device, the method comprising the steps of:

transmitting a data packet to the second communication device;

increasing, responsive to the step of transmitting, a transmit tracking number, wherein the transmit tracking number indicates a packet sequence number of a data packet that is next in sequence to be transmitted;

receiving an acknowledgment data packet from the second communication device, wherein the acknowledgment data packet includes a receive tracking number that indicates a packet sequence number of a data packet that is next in sequence to be received by the second communication device;

comparing, by the first communication device, the receive tracking number and the transmit tracking number; and

when the receive tracking number is greater than the transmit tracking number, determining that a communication error occurred.

9. The method of claim 8, further comprising the step of determining that a communication error did not occur when the receive tracking number is less than or equal to the transmit tracking number.

10. The method of claim 8, wherein the acknowledgment data packet comprises a plurality of data blocks and wherein the method further comprises the steps of:

responsive to the step of receiving the acknowledgment data packet;

replacing the receive tracking number with a predetermined value;

determining a first data integrity indicator for the plurality of data blocks;

comparing the first data integrity indicator with a second data integrity indicator that is positioned within a predetermined data block of the plurality of data blocks; and

when the first data integrity indicator does not equal the second data integrity indicator, determining that the acknowledgment data packet is corrupted.

11. The method of claim 8, wherein the acknowledgment data packet comprises a plurality of data blocks and wherein the method further comprises the steps of:

responsive to the step of receiving the acknowledgment data packet;

determining a first data integrity indicator for the plurality of data blocks less a portion of a first data block of the plurality of data blocks containing the receive tracking number;

comparing the first data integrity indicator with a second data integrity indicator that is positioned within a portion of a second data block of the plurality of data blocks; and

when the first data integrity indicator does not equal the second data integrity indicator, determining that the acknowledgment data packet is corrupted.

12. A method for a first communication device to track data packets received from a second communication device, the method comprising the steps of:

receiving a data packet transmitted by the second communication device;

generating an acknowledgment data packet, wherein the acknowledgment data packet comprises at least one data block;

inputting a predetermined value into a portion of the at least one data block reserved for a receive tracking number, wherein the receive tracking number indicates a packet sequence number of a data packet that is next in sequence to be received;

determining a data integrity indicator for the at least one data block;

inputting the data integrity indicator into a portion of the at least one data block reserved for the data integrity indicator;

determining the receive tracking number;

replacing the predetermined value with the receive tracking number; and

transmitting the acknowledgment data packet to the second communication device, such that the acknowledgment data packet includes the receive tracking number and the data integrity indicator.

13. The method of claim 12, wherein the acknowledgment data packet comprises a plurality of data blocks and further includes user data of the first communication device.

14. A communication device in a packet data communication system, the communication device comprising:

a transmitter that transmits a data packet to a target communication device;

a receiver that receives an acknowledgment data packet indicating receipt of the data packet from the target communication device, the acknowledgment data packet including a receive tracking number that indicates a packet sequence number of a data packet that is next in sequence to be received by the target communication device; and

a computer readable memory device, coupled to the transmitter and the receiver, that has stored therein a computer program that, when executed, performs the following functions;

increases a transmit tracking number upon transmission of the data packet, wherein the transmit tracking number indicates a packet sequence number of a data packet that is next in sequence to be transmitted by the communication device; and

upon reception of the acknowledgment data packet, compares the receive tracking number to the transmit tracking number and when the receive tracking number is greater than the transmit tracking number, determines that a communication error occurred.

15. The communication device of claim 14, wherein the communication device comprises a base station.

16. The communication device of claim 15, wherein the communication device further comprises a data controller.

17. The communication device of claim 14, wherein the communication device comprises a mobile or portable two-way radio device.

18. In a packet data communication system that includes a wireless communication unit and a data controller operably coupled to a base station, a method for the data controller to track data packets transmitted to the wireless communication unit, the method comprising the steps of:

providing, by the data controller, a data packet to the base station;

receiving, by the data controller, a confirmation message from the base station indicating that the data packet has been transmitted;

updating, by the data controller, responsive to the confirmation message, a transmit tracking number, wherein the transmit tracking number indicates a packet sequence number of a data packet that is next in sequence to be transmitted;

receiving, by the data controller via the base station, an acknowledgment data packet from the wireless communication unit, wherein the acknowledgment data packet includes a receive tracking number that indicates a packet sequence number of a data packet that is next in sequence to be received by the wireless communication unit; and

when the receive tracking number is later in sequence than the transmit tracking number, determining, by the data controller, that a communication error occurred.