Data packet discard notification

• US 6,330,435 B1
• Filed: 03/18/1999
• Issued: 12/11/2001
• Est. Priority Date: 03/18/1999
• Status: Expired due to Term

• Current Assignee: Wi-Fi One, LLC (Inception Holdings, LLC)
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Khan, Farooq, Lazraq, Tawfik
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): Tran, Congvan
• Application Number:
  US09/271,319
• Time in Patent Office: 999 Days
• Field of Search: 455/412, 455/403, 455/575, 455/466, 370/229, 370/230, 370/235, 370/237, 370/236, 370/356, 370/365, 340/7.52, 340/7.3
• US Class Current: 455/412.1
• CPC Class Codes: H04L 1/1809 Selective-repeat protocols
• CPC Class Codes: H04L 1/1877 for semi-reliable protocols, e.g. for less sensitive applications like streaming video buffer level management for video bitstream control arrangements H04N21/44004

Abstract

An algorithm complementary to the Selective Repeat ARQ technique is provided, that allows obsolete or otherwise superfluous packets to be safely discarded at the transmitter when using the Selective Repeat ARQ technique. Thus, clogging of ARQ buffers and deadlocking of the system can be avoided, and data transfer in mobile wireless environments using Selective Repeat ARQ can be made more efficient. In accordance with various embodiments of the algorithm, a data packet discard notification (DPDN) message is sent by the transmitter to the receiver to indicate to the receiver which packets the transmitter has discarded, so that the receiver need no longer expect to receive them. The DPDN message can be sent when the transmitter discards packets. The DPDN message can also be sent in response to a communication such as a request or negative acknowledgment that is sent by the receiver to the transmitter.

Claims

1. A method for discarding data packets in a system having a transmitter and a receiver, wherein the method is complementary to the Selective Repeat Automatic Repeat Request protocol and comprises the steps of:

transmitting a data packet discard notification message from the transmitter to the receiver indicating data packets the transmitter has discarded;

receiving the data packet discard notification message;

computing which data packets have been discarded by the transmitter based on the data packet discard notification message;

removing entries from a first list indicating data packets expected to be received from the transmitter, wherein the entries correspond to data packets identified in the computing step.

2. The method of claim 1, wherein the data packet discard notification message contains a field indicating a format of the message.

3. The method of claim 1, wherein:

the data packet discard notification message includes at least one pair of a data packet sequence number field and a length field; and

for each at least one pair, the data packet sequence number field indicates a first data packet to be discarded by the receiver and the length field indicates a number of data packets immediately preceding the first data packet, that are to be discarded by the receiver.

4. The method of claim 1, wherein:

the data packet discard notification message includes at least one pair of a data packet sequence number field and a length field; and

for each at least one pair, the data packet sequence number field indicates a first data packet to be discarded by the receiver and the length field indicates a number of data packets nearest the first data packet, that are to be discarded by the receiver.

5. The method of claim 1, wherein:

the data packet discard notification message includes at least one pair of a data packet sequence number field and a length field; and

for each at least one pair, the data packet sequence number field indicates a first data packet to be discarded by the receiver and the length field indicates a number of data packets immediately following the first data packet, that are to be discarded by the receiver.

6. The method of claim 1, wherein the data packet discard notification message includes a sequence number field for each data packet to be discarded by the receiver.

7. The method of claim 1, wherein the data packet discard notification message includes a bitmap and at least one pair of a data packet sequence number field and a length field, for each pair the length field designates a portion of the bitmap, the pair designates a group of data packets, and the portion of the bitmap indicates which of the group of data packets are to be discarded by the receiver.

8. The method of claim 7, wherein the data packets in the group are sequentially adjacent and the data packet sequence number field identifies a data packet at one end of the group.

9. The method of claim 7, wherein a sequence of the at least one pair together with the at least one length field indicates which portions of the bitmap correspond to different pairs of the at least one pair.

10. The method of claim 1, wherein the data packet discard notification message includes at least one pair of a data packet sequence number field and a bitmap, the data packet sequence number field and the bitmap together designate a group of data packets, and the bitmap indicates which of the group of data packets are to be discarded by the receiver.

11. The method of claim 1, further comprising the steps of:

when the data packet discard notification message is not received by the receiver, updating the data packet discard notification message to include any data packets discarded by the transmitter after the data packet discard notification message was sent; and

sending the updated data packet discard notification message to the receiver.

12. The method of claim 1, further comprising the steps of:

transmitting a retransmission request from the receiver to the transmitter;

receiving the retransmission request at the transmitter;

determining whether any data packets indicated in the retransmission request have been discarded by the transmitter; and

when data packets indicated in the retransmission request are determined to have been discarded by the transmitter, sending a data packet discard notification message from the transmitter to the receiver indicating that the data packets have been discarded by the transmitter.

13. The method of claim 1, further comprising the steps of:

identifying any data packets indicated in the data packet discard notification message that do not have corresponding entries in the first list;

adding entries to a second list indicating data packets expected not to be received from the transmitter, wherein the entries correspond to the data packets identified in the identifying step;

periodically comparing the first and second lists to identify matching entries; and

removing the identified matching entries from the first and second lists.