Method for performing link adaptation

• US 20020126694A1
• Filed: 12/27/2001
• Published: 09/12/2002
• Est. Priority Date: 12/28/2000
• Status: Abandoned Application

• Current Assignee: Nokia Corporation
• Original Assignee: Nokia Corporation
• Inventors: Kahola, Mika
• Application Number:
  US10/033,451
• Publication Number:
  US 20020126694A1
• Time in Patent Office: Days
• US Class Current: 370/465
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0016 involving special memory structures, e.g. look-up tables
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0046 Determination of how many bits are transmitted on different sub-channels
• CPC Class Codes: H04L 5/006 Quality of the received signal, e.g. BER, SNR, water filling
• CPC Class Codes: H04W 52/267 taking into account the information rate

Abstract

The invention relates to a method for performing link adaptation in a communication system, in which two communication devices are arranged to communicate with each other in order to transmit information at least partly in a wireless manner. Packets are formed of the information to be transferred, and the packet error rate is defined. In the communication system, at least two different modulation modes can be selected for the connection. The method utilizes fuzzy control in the selection of the modulation mode, wherein at least one of the used variable is said defined packet error rate.

Claims

1. A method for performing link adaptation in a communication system, in which two communication devices are arranged to communicate with in order to transfer information at least partly wirelessly, packets are formed from the information to be transferred, the packet error rate is determined, and for which connection at least two different modulation modes can be selected, wherein the method uses fuzzy control in the selection of the modulation mode, and that at least one of the variables used in fuzzy control is said defined packet error rate.

2. The method according to claim 1, wherein in the method a target value is determined to the packet error rate, that the packet error rate is aimed to be kept substantially the same as the target value, and that the difference between the packet error rate and the target value is also used as a variable in the method.

3. The method according to claim 2, wherein for performing fuzzy control a first set of control values is formed, in which the packet error rate is used as a variable, a second set of control values is formed, in which the change rate of the packet error rate is used as a variable, and a set of fuzzy rules is arranged, which are used for determining the effect of the control values to the modulation mode used as a controllable value.

4. The method according to claim 3, wherein said control value sets are formed of the values:

positive large, positive medium, positive small, negligible, not small, not medium, and not large.

5. The method according to claim 4, wherein said set of fuzzy rules is determined on the basis of the following table:

6. The method according to claim 5, wherein said first set of control values comprised the following values:

7. The method according to claim 6, wherein in the method a set of modulation modes is defined, wherein for each modulation mode an individualizing index is defined, and in the method at least the following steps are taken:

an initialisation phase, wherein one of said indexes is selected in order to select the modulation mode used in the communication connection,

a computing phase, in which the difference of the packet error rate from the target value, and the change rate of the packet error rate are calculated, and

a fuzzy control phase, in which fuzzy control is used for defining the index change of the modulation mode, wherein the modulation mode according to the calculated new index is selected for the communication connection.

8. The method according to claim 7, wherein said calculating phase and the fuzzy control phase are repeated.

9. The method according to claim 1, wherein the transmission power is also controlled in the method.

10. The method according to claim 9, wherein in the method the modulation mode is adjusted until a such modulation mode is obtained, by which the packet error rate (PER) is substantially the same as said target value of the packet error rate, whereafter the transmission power is adjusted by using fuzzy control.

11. The method according to claim 9, wherein the modulation method and the transmission power are selected substantially simultaneously.

13. The communication system according to claim 12, wherein a target value is defined for the packet error rate, that the means for the link adaptation comprise means for adjusting the packet error rate to substantially the same as said target value, and that the difference between the packet error rate and the result value is additionally arranged to be used as a fuzzy control variable.

14. The communication system according to claim 13, wherein for performing fuzzy control a first set of control values is formed, in which the packet error rate has been used as a variable, and a second set of control values, in which the change rate of the packet error rate has been used as a variable, and that a set of fuzzy rules has been formed for defining the influence of the control values of said variables to the modulation mode used as a controllable value.

12. A communication system, comprising means for arranging two communication devices to communicate with each other in order to transfer packet-form information at least partly wirelessly, means for determining a packet error rate, and means for selecting for the connection a modulation mode from at least two modulation modes, wherein the communication system comprises means for using fuzzy control in the selection of the modulation mode, and that at least one variable arranged to be used in fuzzy control is the packet error rate.

15. An access point controller comprising means for arranging the access point controller and at least one wireless terminal to communicate with each other in order to transmit packet-form information at least partly in a wireless manner, means for defining the packet error rate, and means for selecting for the connection a modulation mode from at least two modulation modes, wherein the access point controller comprises means for using fuzzy control in the selection of the modulation mode, and that in fuzzy control at least one variable that is arranged to be used is said defined packet error rate.

16. A wireless terminal, comprising means for transmitting packet-form information at least partly wirelessly in a communication connection arranged between the wireless terminal and a second communication device, means for defining the packet error rate, and means for selecting for the connection a modulation mode from at least two modulation modes, wherein the wireless terminal comprises means for using fuzzy control in the selection of the modulation mode, and that in fuzzy control at least one variable that is arranged to be used is said defined packet error rate.