Methods for optimizing time variant communication channels

• US 7,200,178 B2
• Filed: 05/16/2003
• Issued: 04/03/2007
• Est. Priority Date: 06/12/2002
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Shoemake, Matthew B., Ahmed, Nasir
• Primary Examiner(s): PHU, PHUONG M
• Application Number:
  US10/439,770
• Publication Number:
  US 20030231715A1
• Time in Patent Office: 1,418 Days
• Field of Search: 375/260, 375/267, 375/227, 375/225, 375/299, 370/210, 370/330, 370/208
• US Class Current: 375/260
• CPC Class Codes: H04L 1/06 using space diversity
• CPC Class Codes: H04L 1/1671 the supervisory signal being transmitted together with control information
• CPC Class Codes: H04L 1/1809 Selective-repeat protocols
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/0028 Variable division signaling therefor H04L5/0092
• CPC Class Codes: H04L 5/0044 allocation of payload
• CPC Class Codes: H04W 52/24 using SIR [Signal to Interference Ratio] or other wireless path parameters
• CPC Class Codes: H04W 52/32 TPC of broadcast or control channels

Abstract

Methods and apparatus for optimizing wireless communications channels by employing multi-channel modulation techniques in wireless communication systems is disclosed. The wireless communications channel may comprise tones, and data may be allocated differently among the different tones according to the channel characterization measurements. In one embodiment, a method may include: transmitting data over a wireless channel using a first station (e.g., an access point), receiving the data using a second station, performing calculations on the received data, and allocating subsequent data transmissions among the tones according to the calculations. Other embodiments may utilize superfluous data transmissions—for example, data coming from the access point that is intended for other stations—in order to calculate channel characterization. Preferably, any portion of the transmitted data (e.g., preamble, header, data, etc.) may be used to calculate channel characterization.

Claims

1. A method of communication, comprising:

transmitting data over a wireless channel using a first station, wherein the channel comprises tones;

receiving the data using a second station;

estimating the wireless channel using at least information digitally encoded into the received data indicating a transmit power level used on the received data;

allocating subsequently transmitted data among the tones according to the channel estimation; and

transmitting the allocated data.

2. The method of claim 1, wherein the transmitted and the allocated data include training sequences used for the estimation.

3. The method of claim 2, wherein estimating the wireless channel comprises calculating signal-to-noise ratio.

4. The method of claim 3, wherein allocating subsequently transmitted data includes assigning the allocated data to the tones having higher signal-to-noise ratios.

5. The method of claim 2, wherein the transmitted data and the allocated data represent data frames and the training sequences are included within a preamble in the data frames.

6. The method of claim 5, wherein estimating the wireless channel includes computing a cumulative average of channel estimation over multiple frames of data.

7. The method of claim 6, wherein estimating the wireless channel includes calculating signal-to-noise ratio.

8. The method of claim 1, wherein the transmitted data and the allocated data include the power levels of each transmission.

9. The method of claim 1, wherein the allocated data includes the manner in which data was allocated among the tones.

10. The method of claim 9, wherein allocating subsequently transmitted data includes uniform allocations among the tones.

11. The method of claim 10, wherein the allocated data includes a single bit to indicate that uniform allocations have been performed.

12. The method of claim 9, wherein allocating subsequently transmitted data includes compressing data among the tones.

13. The method of claim 1, wherein the calculations are valid for a predetermined period of time.

14. The method of claim 13, wherein the allocated data is not allocated among the tones if the channel estimation are invalid.

15. The method of claim 13, wherein the allocated data is allocated equally among the tones prior to reaching the predetermined period of time.

16. The method of claim 1, wherein the first and second stations include a plurality of antennas and the data includes the antenna configuration information to designate which antennas are being used for transmission and reception of data.

32. The method of claim 1, wherein the allocated data includes at least one bit indicating whether a present allocation of data has been changed from a previous allocation.

17. A wireless network, comprising:

a first station that transmits data over a wireless channel, wherein the channel comprises tones; and

a second station that receives said data, performs calculations on said data to characterize the channel, and allocates subsequent data transmissions among the tones according to the calculations, wherein channel characterization is based at least in part on information digitally encoded into the received data indicating a transmit power level used on the data transmitted by the first station.

18. The wireless network of claim 17, wherein transmitted data includes training sequences used for calculations.

19. The wireless network of claim 17, wherein the calculations include computing a cumulative average over multiple frames of data.

20. The wireless network of claim 17, wherein transmitted data includes the power level of each transmission.

21. The wireless network of claim 17, wherein subsequent data transmissions include the manner in which data was allocated among the tones.

22. The wireless network of claim 17, wherein the calculations are valid for a predetermined period of time.

23. The wireless network of claim 17, wherein the first and second stations include a plurality of antennas and transmitted data includes antenna configuration information to designate which antennas are being used for transmission and reception of data.

24. A wireless network, comprising:

an access point;

a plurality of stations coupled to the access point using a wireless channel, wherein coordination data is exchanged between the access point and the plurality of stations to coordinate which station has control of the channel; and

wherein the coordination data is also used to obtain channel characteristics, wherein an indication of transmit power level used on the coordination data is digitally encoded into said coordination data.

25. The wireless network of claim 24, wherein the channel characteristics include signal-to-noise ratio.

26. The wireless network of claim 24, wherein the channel further comprises tones, and the channel characteristics are utilized to allocate data among the tones.

27. The wireless network of claim 26, wherein transmission of data between the access point and the station controlling the channel does not occur until the configuration data has been used to allocate data among the tones.

28. The wireless network of claim 26, wherein the subsequent transmissions include a single bit to indicate that similar allocations have been utilized.

29. The wireless network of claim 24, wherein a station utilizes coordination data intended for another station to obtain measurements of the channel characteristics.

30. The wireless network of claim 29, wherein the station examines a header of the configuration data to determine if it came from the access point and if so then the station estimates the channel characteristics using the configuration data.

31. The wireless network of claim 30, wherein the channel further comprises tones, and the channel characteristics are utilized to allocate data among the tones.