Error detection/correction and fault detection/recovery – Pulse or data error handling – Digital data error correction
Patent
1998-04-17
2000-12-19
Tu, Trinh L.
Error detection/correction and fault detection/recovery
Pulse or data error handling
Digital data error correction
714798, 714799, H04L 118
Patent
active
061638692
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for retransmitting data transmitted incorrectly (ARQ), in which method, for the purpose of transmission between subscribers having in each case at least one transmit section and at least one receive section, a data stream at the transmitting subscriber's end is subdivided into data words having a predeterminable length and is combined to form data words and the individual data words are temporarily stored in a transmit buffer, are transmitted, if necessary via a transmit unit, and are received by the receiving subscriber, if necessary in a receive unit and, after temporary storage in a receive buffer are output, in which arrangement an error which has occurred during the transmission is detected and a command for retransmission of the data word transmitted incorrectly is issued via the transmit section of the receiving subscriber and the receive section of the transmitting subscriber to the transmit section of the transmitting subscriber.
Such known ARQ methods are used for securing error-free data transmission in various applications. For this purpose, the transmitted data word, after having been received, is checked by means of a fixed routine in an error detection unit. If an incorrect data word occurs, the transmitting subscriber is requested to repeat this data word until the correctness of the transmission is confirmed at the receiving subscriber's end.
In this arrangement, however, the disturbance causing the incorrect transmission may occur relatively frequently over a prolonged period of time as a result of which the incorrect data words are requested again and again by the receiving subscriber during which time no further data can be transmitted. For this reason, the transmitted-information rate may decrease steeply.
On the basis of the methods mentioned initially, the invention has the object of improving such a method with the aim of being able to keep the data throughput constant between transmitting and receiving subscriber.
According to the invention, this is achieved by the ARQ retransmissions of the data transmitted incorrectly being carried out via a predeterminable proportion, which is constant in the time average, of the number of data words transmitted within the averaged period of time.
As a result, an excess transmission capacity is continuously available during the data transmission. If a data word is received incorrectly, the receiver only requests a retransmission for as long as this is possible in connection with the excess capacity available in the time average so that the nominal data throughput can be kept constant without being influenced by the retransmissions. The ARQ retransmissions of the data transmitted incorrectly are thus carried out via a constant predeterminable proportion of the number of data words transmitted within a predeterminable period of time in each case. The duration of the period of time over which the averaging over time is carried out is essentially limited by the storage capacity of the transmit or receive ARQ buffer used. In the case of incorrect transmission, a signal with higher redundancy is transmitted.
In this connection, the method according to the invention is basically suitable for all types of data transmission but especially for data streams which need a constant bit rate in order to maintain timing relationships between various units which applies, for example, to coded and possibly compressed data as are necessary for video and/or audio transmission.
To obtain a high-quality transmission, it is advantageous to select the proportion of the retransmissions carried out in the time average to be between 2 and 7%.
In this connection, it has been found to be especially advantageous if this proportion is specified to be approximately 3.3% since it is possible in this case to achieve a very high constant transmission rate with good transmission quality.
According to another variant of the invention, it can be provided for the data words to be transmitted from the transmit buffer faster than they are written into
REFERENCES:
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patent: 5719883 (1998-02-01), Ayanoglu
IEEE Transaction on Communications, "An Improved Selective-Repeat ARQ Strategy", E.J. Weldon Jr., vol. Com-30, No. 3, Mar. 1982, pp. 480-486.
M. Nakamura et al., "Performance Evaluation for ARQ Schemes in Power and/or Bandwidth Limited Systems", The Transactions of the IEICE, vol. E72, No. 5, May 1989, pp. 494-501.
"A New Selective Retransmitted ARQ System", IEEE Global Telecommunications Conference Record, vol. 3, Nov. 29, 1993, pp. 1815-1821.
R. Fantacci, "Performance Evaluation of Efficient Continous ARQ Protocols", IEEE Transactions on Communications, vol. 38, No. 6, Jun. 1990, pp. 773-781.
H. Bruneel et al., "On the Throughput Performance of Some Continuous ARQ Strategies with Repeated Transmissions", IEEE Transactions on Communications, vol. Com-34, No. 3, Mar. 1986, pp. 244-249.
Abraham Esaw
Ericsson Austria Aktiengesellschaft
Tu Trinh L.
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