Method and apparatus for determining channel quality and performing adaptive modulation/coding within a multicarrier communication system

• US 20060008020A1
• Filed: 07/07/2004
• Published: 01/12/2006
• Est. Priority Date: 07/07/2004
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Classon, Brian K., Blankenship, Yufei W., Sartori, Philippe J.
• Granted Patent: US 7,272,190 B2
• Time in Patent Office: Days
• US Class Current: 375/261
• 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 1/0019 in which mode-switching is based on a statistical approach
• CPC Class Codes: H04L 27/0008 arrangements for allowing a transmitter or receiver to use more than one type of modulation negotiating modulation type for two-way transmission paths H04L5/1453
• CPC Class Codes: H04L 27/0012 arrangements for identifying the type of modulation
• CPC Class Codes: H04L 27/34 Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0016 Time-frequency-code
• CPC Class Codes: H04L 5/0044 allocation of payload
• CPC Class Codes: H04L 5/006 Quality of the received signal, e.g. BER, SNR, water filling
• CPC Class Codes: H04L 5/0064 Rate requirement of the data, e.g. scalable bandwidth, data priority
• CPC Class Codes: H04L 5/0085 when channel conditions change
• CPC Class Codes: Y02D 30/50 in wire-line communication networks, e.g. low power modes or reduced link rate

Abstract

In a multi-carrier communication system employing adaptive modulation and coding, a receiver feeds back channel quality information for a “binned” group of subcarriers instead of sending an individual quality report for each subcarrier. A transmitter will utilize the channel quality information for the bin to determine a set of γ_eff values corresponding to a set of modulation and coding scheme candidates, where γ_eff is an effective SNR that would yield a same FER in an AWGN channel. The transmitter utilizes the set of γ_eff values to aid in determining a modulation and coding scheme, and determine a single modulation and coding scheme for all subcarriers within the channel.

Claims

1. A method for performing adaptive modulation and coding of a data stream in a multi-carrier communication system employing a plurality of subcarriers, wherein the plurality of subcarriers are divided into bins of subcarriers, the method comprising the steps of:

receiving a channel-quality report comprising a value related to a mean in channel quality for at least one bin of subcarriers;

determining an expected FER_AWGN(γ

_eff) for a set of modulation and coding scheme candidates based on the channel-quality report, where γ

_eff is an effective SNR that would yield a same FER in an AWGN channel;

determining a modulation and coding scheme for the data stream based on the the expected FER_AWGN(γ

_eff); and

utilizing the modulation and coding scheme to transmit the data stream over the multi-carrier communication system.

2. The method of claim 1 further comprising the step of receiving the channel-quality report comprises the step of receiving a channel-quality report comprising a value related to a mean in channel quality for at least one bin of OFDM subcarriers.

3. The method of claim 1 wherein the step of receiving the channel-quality report comprises the step of receiving a channel-quality report comprising a value related to a mean and a value related to a variance in channel magnitude for the at least one bin of subcarriers.

4. The method of claim 1 wherein the step of receiving the channel-quality report comprises the step of receiving a set of γ

_eff values corresponding to a set of modulation and coding scheme candidates, where γ

_eff is an effective SNR that would yield a same FER in an AWGN channel.

5. The method of claim 1 wherein the step of receiving the channel-quality report comprises the step of receiving a channel-quality report comprising a value related to a mean and a value related to a variance in signal-to-noise ratio (SNR) for the at least one bin of subcarriers.

6. The method of claim 1 wherein the step of determining the modulation and coding scheme comprises the steps of:

determining an expected frame error rate (FER) for all modulation and coding scheme candidates that can be assigned; and

choosing the modulation and coding scheme that has a highest possible throughput with an expected FER lower than a target value.

7. The method of claim 6 wherein the step of determining the expected FER comprises the step of determining FER_AWGN(γ

_eff), where γ

_eff is the effective SNR that would yield a same FER in an AWGN channel, and

8. The method of claim 7 wherein

9. The method of claim 1 wherein the step of determining the modulation and coding scheme comprises the step of determining the modulation from the group consisting of QPSK and 16-QAM.

10. The method of claim 1 wherein the step of determining the modulation and coding scheme comprises the step of determining the coding from the group consisting of ¼

, ½

, and ¾

rate coding.

11. A method for receiving adaptively modulated and coded data in a multi-carrier communication system employing a plurality of subcarriers, wherein the plurality of subcarriers are divided into bins of subcarriers, the method comprising the steps of:

determining channel quality for at least one bin of subcarriers;

reporting to a transmitter, a set of γ

_eff values corresponding to a set of modulation and coding scheme candidates, where γ

_eff is an effective SNR that would yield a same FER in an AWGN channel; and

receiving data modulated and coded via a modulation and coding scheme based on the set of γ

_eff values.

12. An apparatus for performing adaptive modulation and coding of a data stream in a multi-carrier communication system employing a plurality of subcarriers, wherein the plurality of subcarriers are divided into bins of subcarriers, the apparatus comprising:

a MCS selector receiving a channel-quality report comprising a value related to a mean in channel quality for the at least one bin of subcarriers, the MCS selector outputting a modulation and coding scheme for the data stream based on the received channel-quality report and an effective SNR that would yield a same FER in an AWGN channel; and

a modulator/coder receiving the MCS and outputting modulated and coded data based on the modulation and coding scheme.

13. The apparatus of claim 12 further comprising:

a transmitter for transmitting the modulated and coded data over the plurality of subcarriers.

14. The apparatus of claim 12 wherein the channel-quality report additionally comprises a value related to the standard deviation in channel quality for the at least one bin of subcarriers.

15. The apparatus of claim 12 wherein the channel-quality report comprises a mean and a standard deviation in SNR for the at least one bin of subcarriers.

16. The apparatus of claim 12 wherein the modulation and coding scheme comprises a modulation from the group consisting of QPSK and 16-QAM.

17. An apparatus for receiving adaptively modulated and coded data in a multi-carrier communication system employing a plurality of subcarriers, wherein the plurality of subcarriers are divided into bins of subcarriers, the apparatus comprising:

a bin quality determiner analyzing a received signal and determining a set of γ

_eff values corresponding to a set of modulation and coding scheme candidates, where γ

_eff is an effective SNR that would yield a same FER in an AWGN channel; and

a receiver for receiving adaptively modulated and coded data that was modulated and coded via the modulation and coding scheme chosen based on the set of γ

_eff values.