Rate adaptation in a wireless communication system

• US 20020152342A1
• Filed: 02/09/2001
• Published: 10/17/2002
• Est. Priority Date: 02/09/2001
• Status: Active Grant

• Current Assignee: Alcatel-Lucent USA, Inc. (Nokia Corporation)
• Original Assignee: Arnab Das, Farooq Ullah Khan
• Inventors: Das, Arnab, Khan, Farooq Ullah
• Granted Patent: US 6,721,834 B2
• Time in Patent Office: Days
• US Class Current: 710/117
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0006 by adapting the transmission format
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0025 Transmission of mode-switching indication
• CPC Class Codes: H04L 1/0069 Puncturing patterns
• CPC Class Codes: H04L 1/08 by repeating transmission, e.g. Verdan system H04L1/1858 and H04L1/189 take precedence
• CPC Class Codes: H04L 1/1819 with retransmission of additional or different redundancy
• CPC Class Codes: Y02D 30/50 in wire-line communication networks, e.g. low power modes or reduced link rate

Abstract

Disclosed is a method of data rate adaptation based on channel conditions. In the present invention, data is initially transmitted at a first data rate based on a measured first channel condition and, if a NACK is received, the data is retransmitted. The data retransmitted is at a rate which is based on the condition of the channel during or before the transmission of the NACK. The data retransmission rate can also be based on the actual channel condition at the time of the first transmission plus the condition of the channel before or during the transmission of the NACK.

Claims

1. A method of transmitting data comprising the steps of:

a) transmitting data in a time slot n;

b) receiving channel condition information during a different time slot from a receiver to which the data was intended, indicating that receipt of the transmitted data was not successful; and

c) determining a data rate for retransmission of the data based on the received channel condition information.

2. The method of claim 1, wherein the step of determining the data rate for retransmission comprises the step of estimating the channel condition prior to retransmission.

3. The method of claim 1, wherein the step of determining the data rate for retransmission comprises estimating the amount of redundancy of data needed for successful decoding.

4. The method of claim 1 further comprising the step of:

receiving channel quality information for a second time slot from the receiver, and using the channel quality information for the first and second time slots to determine the data rate for retransmission.

5. The method of claim 4 wherein the second time slot is a slot that is subsequent to the first time slot.

6. The method of claim 4 wherein the first and second data transmissions are identical.

7. The method of claim 4 wherein the first data transmission may be soft combined with the second data transmission.

8. The method of claim 4 comprising the additional step of:

receiving, prior to the step of determining the first data rate, a rate indication message indicating the first data rate for the receiver.

9. The method of claim 4 comprising the additional step of:

receiving, after the step of determining the first data rate and prior to the step of determining the second data rate, a rate indication message indicating the second data rate for the receiver.

10. The method of claim 4 wherein the first data rate is a higher data rate than a data rate indicated in a received rate indication message.

11. The method of claim 4 wherein the second data rate is a higher data rate than a data rate indicated in a received rate indication message.

12. The method of claim 4 comprising the additional step of:

receiving, prior to the step of determining the first data rate, a plurality of rate indication messages indicating the data rates for a plurality of receivers.

13. The method of claim 12 comprising the additional step of:

selecting a receiver from the plurality of receivers to which to transmit data using the received plurality of rate indication messages.

14. The method of claim 13, wherein the selected receiver is a receiver associated with a rate indication message indicating a highest data rate.

16. The method of claim 15 wherein the data that is retransmitted is at the same rate as the data that is transmitted.

17. The method of claim 15 wherein the data that is retransmitted is at a higher rate than the data that is transmitted.

18. The method of claim 15 wherein the data that is retransmitted is at a lower rate than the data that is transmitted.

15. A method of transmitting data comprising the steps of:

transmitting data to a receiver at a first rate;

receiving from the receiver channel condition information and information indicating a non-successful receive of the data;

determining a new rate for the retransmission of the data based on the received channel information; and

retransmitting the data to the receiver.