Adaptive modulation and coding

• US 20050025254A1
• Filed: 07/29/2004
• Published: 02/03/2005
• Est. Priority Date: 07/31/2003
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Awad, Yassin Aden, Vadgama, Sunil Keshavji
• Granted Patent: US 7,590,181 B2
• Time in Patent Office: Days
• US Class Current: 375/295
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0021 in which the algorithm uses adaptive thresholds
• CPC Class Codes: H04L 1/203 Details of error rate determination, e.g. BER, FER or WER

Abstract

In an adaptive modulation and coding method one or more adjustable values are created (S1), each corresponding to at least one of a plurality of available modulation and coding levels applicable to a signal transmitted from a transmitter to a receiver, and each representing a change to the level(s) to which it corresponds. One or more of said adjustable values is/are adjusted in dependence upon whether or not the signal is received successfully by the receiver (S2-S5). One of said available modulation and coding levels is selected (S6-S8) to apply to the signal based on such an adjustable value. Such a method can enable the appropriate modulation and coding level to be selected even when the path and channel conditions vary. The method is applicable to selecting modulation and coding levels in a high-speed downlink packet access system of a wireless communication network.

Claims

1. An adaptive modulation and coding method comprising:

holding one or more adjustable values, each corresponding to at least one of a plurality of available modulation and coding levels applicable to a signal transmitted from a transmitter to a receiver, and each representing a change to the or each said level to which it corresponds;

adjusting one or more of said adjustable values in dependence upon whether or not the signal is received successfully by the receiver; and

selecting one of said available modulation and coding levels to apply to said signal based on such an adjustable value.

2. A method as claimed in claim 1, wherein the holding, adjusting and selecting steps are carried out by the transmitter.

3. A method as claimed in claim 1, wherein the receiver transmits to the transmitter an indication of whether or not the signal was received successfully, and the transmitter adjusts one or more of the adjustable values in dependence upon the received indication.

4. A method as claimed in claim 1, wherein the adjusting step comprises increasing one or more of the adjustable values when the signal is received successfully and decreasing one or more of said adjustable values when the signal is not received successfully.

5. A method as claimed in claim 1, wherein there are at least two said adjustable values and said adjusting step comprises adjusting one said adjustable value by an amount different from an amount by which another said adjustable value is adjusted.

6. A method as claimed in claim 1, wherein an amount by which the or one said adjustable value is adjusted is dependent upon a target error rate.

7. A method as claimed in claim 1, wherein the or each said adjustable value is a non-integer value and in the selecting step a rounded version of the or one said adjustable value is employed to select said modulation and coding level to apply to said signal, said rounded version representing the nearest integer value to said non-integer adjustable value.

8. A method as claimed in claim 1, further comprising:

proposing one of the available modulation and coding levels based on a signal transmission quality; and

selecting said modulation and coding level based on the adjustable value corresponding to the proposed modulation and coding level.

9. A method as claimed in claim 8, wherein the receiver produces a measure of said signal transmission quality, and the method further comprises employing a fixed mapping to map said measure to the proposed modulation and coding level.

10. A method as claimed in claim 8, wherein the proposing step is carried out by the receiver which transmits information specifying the proposed modulation and coding level to the transmitter.

11. A method as claimed in claim 1, wherein one or said transmitter and said receiver is a base station of a wireless communication system, and the other of said transmitter and said receiver is a user equipment of said system.

12. A method as claimed in claim 11, wherein said signal is a packet access signal.

13. Adaptive modulation and coding apparatus comprising:

an adjustable value holding unit which holds one or more adjustable values, each corresponding to at least one of a plurality of available modulation and coding levels applicable to a signal transmitted from a transmitter to a receiver, and each representing a change to the or each said level to which it corresponds;

an adjusting unit which adjusts one or more of said adjustable values in dependence upon whether or not the signal is received successfully by the receiver; and

a selecting unit which selects one of said available modulation and coding levels to apply to said signal based on such an adjustable value.

14. A transmitter, for use in a wireless communication system, comprising:

an adjustable value holding unit which holds one or more adjustable values, each corresponding to at least one of a plurality of available modulation and coding levels applicable to a signal transmitted from the transmitter to a receiver of said system, and each representing a change to the or each said level to which it corresponds;

an adjusting unit which adjusts one or more of said adjustable values in dependence upon whether or not said signal is received successfully by said receiver; and

a selecting unit which selects one of said available modulation and coding levels to apply to said signal based on such an adjustable value.

15. A receiver, for use in a wireless communication system, comprising:

an adjustable value holding unit which holds one or more adjustable values, each corresponding to at least one of a plurality of available modulation and coding levels applicable to a signal transmitted from a transmitter of said system to said receiver, and each representing a change to the or each said level to which it corresponds;

an adjusting unit which adjusts one or more of said adjustable values in dependence upon whether or not said signal is received successfully by said receiver;

a selecting unit which selects one of said available modulation and coding levels based on such an adjustable value; and

a level informing unit which transmits to said transmitter information specifying said selected modulation and coding level.

16. A base station, for use in a wireless communication system, comprising:

an adjustable value holding unit which holds one or more adjustable values, each corresponding to at least one of a plurality of available modulation and coding levels applicable to a downlink signal transmitted from the base station to a user equipment of said system, and each representing a change to the or each said level to which it corresponds;

an adjusting unit which adjusts one or more of said adjustable values in dependence upon whether or not said downlink signal is received successfully by said user equipment; and

a selecting unit which selects one of said available modulation and coding levels to apply to said downlink signal based on such an adjustable value.

17. A base station, for use in a wireless communication system, comprising:

an adjustable value holding unit which holds one or more adjustable values, each corresponding to at least one of a plurality of available modulation and coding levels applicable to an uplink signal transmitted from a user equipment of said system to said base station, and each representing a change to the or each said level to which it corresponds;

an adjusting unit which adjusts one or more of said adjustable values in dependence upon whether or not said uplink signal is received successfully by said base station;

a selecting unit which selects one of said available modulation and coding levels based on such an adjustable value; and

a level informing unit which transmits to said user equipment information specifying said selected modulation and coding level.

18. A user equipment, for use in a wireless communication system, comprising:

an adjustable value holding unit which holds one or more adjustable values, each corresponding to at least one of a plurality of available modulation and coding levels applicable to an uplink signal transmitted from the user equipment to a base station of said system, and each representing a change to the or each said level to which it corresponds;

an adjusting unit which adjusts one or more of said adjustable values in dependence upon whether or not said uplink signal is received successfully by said base station; and

a selecting unit which selects one of said available modulation and coding levels to apply to said uplink signal based on such an adjustable value.

19. A user equipment, for use in a wireless communication system, comprising:

an adjustable value holding unit which holds one or more adjustable values, each corresponding to at least one of a plurality of available modulation and coding levels applicable to a downlink signal transmitted from a base station of said system to said user equipment, and each representing a change to the or each said level to which it corresponds;

an adjusting unit which adjusts one or more of said adjustable values in dependence upon whether or not said downlink signal is received successfully by said user equipment;

a selecting unit which selects one of said available modulation and coding levels based on such an adjustable value; and

a level informing unit which transmits to said base station information specifying said selected modulation and coding level.

20. A machine-readable recording medium having recorded thereon an operating program which, when run on a processor in a transmitter of a wireless communication system, causes the transmitter to carry out the steps of:

holding one or more adjustable values, each corresponding to at least one of a plurality of available modulation and coding levels applicable to a signal transmitted from said transmitter to a receiver of said system, and each representing a change to the or each said level to which it corresponds;

adjusting one or more of said adjustable values in dependence upon whether or not the signal is received successfully by said receiver; and

selecting one of said available modulation and coding levels to apply to said signal based on such an adjustable value.

21. A machine-readable recording medium having recorded thereon an operating program which, when run on a processor in a receiver of a wireless communication system, causes the receiver to carry out the steps of:

holding one or more adjustable values, each corresponding to at least one of a plurality of available modulation and coding levels applicable to a signal transmitted from a transmitter of said system to said receiver, and each representing a change to the or each said level to which it corresponds;

adjusting one or more of said adjustable values in dependence upon whether or not the signal is received successfully by said receiver;

selecting one of said available modulation and coding levels based on such an adjustable value; and

transmitting to said transmitter information specifying the selected modulation and coding level.