Variable OFDM subchannel coding and modulation

• US 20070248179A1
• Filed: 04/25/2006
• Published: 10/25/2007
• Est. Priority Date: 04/25/2006
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Huitema, Christian, Wu, Deyun, Abhishek, Abhishek, Kuehnel, Thomas, Hassan, Amer
• Granted Patent: US 7,634,016 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 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 5/0046 Determination of how many bits are transmitted on different sub-channels
• CPC Class Codes: Y02D 30/50 in wire-line communication networks, e.g. low power modes or reduced link rate

Abstract

A system for selecting a modulation scheme and an error correction coding scheme for each subchannel in an OFDM system based on the energy detected on that subchannel.

Claims

1. A method of wireless communication between two or more devices at a minimum data rate, the method comprising the acts of:

a) detecting the energy level on one or more subchannels; and

b) selecting a modulation scheme for each of said subchannels based on the energy level detected for each of said subchannels.

2. The method of claim 1, further comprising selecting an error correction coding scheme for each of said subchannels based on the energy level detected for said subchannel.

3. The method of claim 2, further comprising:

c) calculating the total transmission rate based on the selected modulation scheme and the selected error correction coding scheme; and

d) selecting a higher order modulation scheme on one subchannel if the minimum data rate exceeds said total transmission rate.

4. The method of claim 2, further comprising:

c) calculating the total transmission rate based on the selected modulation scheme and the selected error correction coding scheme; and

d) selecting an error correction coding scheme with a higher error correction rate on one subchannel if the minimum data rate exceeds said total transmission rate.

5. The method of claim 1, wherein the modulation scheme is quadrature amplitude modulation.

6. The method of claim 3, wherein the modulation scheme for each of said subchannels is selected from 16-QAM, 64-QAM, 128-QAM, 256-QAM, 512-QAM, and 1024-QAM.

7. The method of claim 2, further comprising:

c) transmitting data over said subchannels using orthogonal frequency division multiplexing.

8. The method of claim 2, wherein the error correction coding scheme is a convolutional coding scheme.

9. The method of claim 2, wherein the error correction coding scheme is a block coding scheme.

10. The method of claim 2, wherein the error correction coding scheme is selected from a series of coding schemes, such that each coding scheme is punctured from a base coding scheme.

11. A wireless communication system for transmitting data at a requested rate including a plurality of communication devices, the system comprising:

a) an energy detection module to detect the noise level on one or more

OFDM subchannels; and

b) a modulation selection scheme module to select a modulation scheme for each OFDM subchannel based on the energy level detected for that subchannel.

12. The system of claim 11, wherein the system further comprises an error correction selection scheme module to select an error correction scheme for each OFDM subchannel based on the energy level detected for that subchannel.

13. The system of claim 11, wherein the modulation selection scheme module selects a quadrature amplitude modulation scheme.

14. The system of claim 11, wherein the quadrature amplitude modulation scheme is selected from 16-QAM, 64-QAM, 128-QAM, 256-QAM, 512-QAM, and 1024-QAM.

15. The system of claim 11, wherein the energy detection module is part of a transmitter.

16. The system of claim 15, wherein the energy detection module detects the noise level using feedback from a receiver.

18. The computer-readable medium of claim 15, wherein the method further comprises modulating a signal on each OFDM subchannel with a modulation scheme based on the signal-to-noise level measured for each said OFDM subchannel.

19. The computer-readable medium of claim 16, wherein the modulation scheme is selected from quadrature amplitude modulation, quadrature phase shift keying, and binary phase shift keying.

20. The computer-readable medium of claim 15, wherein the error correction coding scheme is selected from a convolutional coding scheme and a block coding scheme.

17. A computer-readable medium having computer-readable signals stored thereon that define instructions that, as a result of being executed by a computer, instruct the computer to perform a method of wireless communication at a requested data rate, the method comprising:

a) measuring the signal-to-noise level on each OFDM subchannel; and

b) coding a modulated signal on each OFDM subchannel using an error correction coding scheme based on the signal-to-noise level measured for each said OFDM subchannel.