Data packet discard notification

Details Data packet discard notification Data packet discard notification

1999-03-18

2001-12-11

Trost, William (Department: 2683)

Telecommunications

Radiotelephone system

Message storage or retrieval

C455S466000, C370S229000

Reexamination Certificate

active

06330435

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to information transfer in mobile wireless environments, and in particular to management of unacknowledged data frames in Selective Repeat ARQ.
BACKGROUND OF THE INVENTION
In wireless mobile environments, shadowing and multipath fading result in significant cell loss ratio performance degradation. Automatic repeat request (ARQ) and forward error correction (FEC) are frequently used to improve bit error rate (BER) performance. When the communication channel is of poor quality, some messages (e.g., words, cells, etc.) sent by a transmitter to a receiver that are negatively acknowledged (NACKed) or remain unacknowledged by the receiver after a predetermined amount of time after being transmitted (i.e., have timed out), should be stored in ARQ buffers in the transmitter, until they can be successfully transmitted from the transmitter to the receiver or until a period of time expires. A NACK or a timing out can operate as a request from the receiver to the transmitter to retransmit the corresponding message.
In accordance with the well-known Selective Repeat ARQ protocol, when a receiver recognizes that it has not correctly received a particular message, the receiver stores all correctly received messages subsequent to the incorrectly received message in a buffer.
For some messages, after the transmitter has attempted a number of times to retransmit a particular message without success, or after a period of time expires, the message should be discarded from the transmitter's ARQ buffer. However, if the receiver continues to expect discarded messages, the system can go into deadlock.
SUMMARY OF THE INVENTION
In accordance with various embodiments of the invention, 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 cell discard notification (CDN) message is sent by the transmitter to the receiver to indicate to the receiver which cells or packets the transmitter has discarded, and which the receiver need no longer expect to receive.


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European Standard Search Report dated Nov. 22, 1999.

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