Channel estimation for OFDM communication systems

• US 7,463,576 B2
• Filed: 04/07/2005
• Issued: 12/09/2008
• Est. Priority Date: 10/29/2002
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Krishnan, Ranganathan, Kadous, Tamer
• Primary Examiner(s): Milord; Marceau
• Application Number:
  US11/101,908
• Publication Number:
  US 20050170783A1
• Time in Patent Office: 1,342 Days
• Field of Search: 370/203, 370/210, 370/342, 370/347, 370/348, 370/480, 370/335, 370/208, 370/329, 370/340, 370/344, 455/450, 455/452.1, 375/340, 375/346, 375/347
• US Class Current: 370/203
• CPC Class Codes: H04L 25/0212 of impulse response
• CPC Class Codes: H04L 25/022 of frequency response
• CPC Class Codes: H04L 25/023 with extension to other symbols
• CPC Class Codes: H04W 52/24 using SIR [Signal to Interference Ratio] or other wireless path parameters
• CPC Class Codes: H04W 52/325 Power control of control or pilot channels
• CPC Class Codes: H04W 52/34 TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

Techniques to estimate the frequency response of a wireless channel in an OFDM system. In one method, an initial estimate of the frequency response of the wireless channel is obtained for a first group of subbands based on a pilot transmission received via the subbands in the first group. An estimate of the impulse response of the wireless channel is then derived based on the initial frequency response estimate. An enhanced estimate of the frequency response of the wireless channel is then derived for a second group of subbands based on the impulse response estimate. The first and second groups may each include all or only a subset of the usable subbands. Subband multiplexing may be used to allow simultaneous pilot transmissions by multiple terminals on their associated groups of subbands.

Claims

1. A method for estimating a frequency response of a wireless communication channel, the method comprising:

estimating the frequency response of the wireless communication channel based on a subset of a plurality of available tones, wherein the subset comprises a plurality of equally spaced tones, the equally spaced tones being equally spaced by a spacing number of the plurality of available tones between the equally spaced tones,

wherein the estimating comprises;

using a received power equal to P*N/S, where P is an average received power for the plurality of available tones, N is a total available tone number and S is a subset number indicating the subset number of tones in the subset.

2. A method for estimating a frequency response of a wireless communication channel, the method comprising:

estimating the frequency response of the wireless communication channel based on a subset of a plurality of available tones, wherein the subset comprises a plurality of equally spaced tones, the equally spaced tones being equally spaced by a spacing number of the plurality of available tones between the equally spaced tones,

wherein the subset comprises a subset number S of the plurality of available tones, wherein S=2^r, wherein r is an integer.

3. A wireless communication access point comprising:

a receiver configured to receive a wireless communication signal in a wireless communication channel; and

a processor coupled to the receiver and configured to estimate a frequency response of the wireless communication channel based on a subset of a plurality of available tones, wherein the subset comprises a plurality of equally spaced tones, the equally spaced tones being equally spaced by a spacing number of the plurality of available tones between the equally spaced tones,

wherein the processor is further configured to use a received power equal to P*N/S for estimating the frequency response, where P is an average received power for the plurality of available tones, N is a total available tone number and S is a subset number indicating the subset number of tones in the subset.

4. A wireless communication access point comprising:

a receiver configured to receive a wireless communication signal in a wireless communication channel; and

a processor coupled to the receiver and configured to estimate a frequency response of the wireless communication channel based on a subset of a plurality of available tones, wherein the subset comprises a plurality of equally spaced tones, the equally spaced tones being equally spaced by a spacing number of the plurality of available tones between the equally spaced tones,

wherein the subset comprises a subset number S of the plurality of available tones, wherein S=2^r, wherein r is an integer.

5. A wireless communication access point comprising:

a receiving means for receiving a wireless communication signal in a wireless communication channel; and

a processing means for estimating a frequency response of the wireless communication channel based on a subset of a plurality of available tones, wherein the subset comprises a plurality of equally spaced tones, the equally spaced tones being equally spaced by a spacing number of the plurality of available tones between the equally spaced tones, the processing means coupled to the receiving means,

wherein the processing means is further configured to use a received power equal to P*N/S, where P is an average received power for the plurality of available tones, N is a total available tone number and S is a subset number indicating the subset number of tones in the subset for estimating the frequency response.

6. A wireless communication access point comprising:

a receiving means for receiving a wireless communication signal in a wireless communication channel; and

a processing means for estimating a frequency response of the wireless communication channel based on a subset of a plurality of available tones, wherein the subset comprises a plurality of equally spaced tones, the equally spaced tones being equally spaced by a spacing number of the plurality of available tones between the equally spaced tones the processing means coupled to the receiving means,

wherein the subset comprises a subset number S of the plurality of available tones, wherein S=2^r, wherein r is an integer.

7. A computer readable medium embodying instructions for performing a method for estimating a frequency response of a wireless communication channel, the method comprising:

estimating the frequency response of the wireless communication channel based on a subset of a plurality of available tones, wherein the subset comprises a plurality of equally spaced tones, the equally spaced tones being equally spaced by a spacing number of the plurality of available tones between the equally spaced tones,

wherein the estimating comprises;

using a received power equal to P*N/S, where P is an average received power for the plurality of available tones, N is a total available tone number and S is a subset number indicating the subset number of tones in the subset.

8. A computer readable medium embodying instructions for performing a method for estimating a frequency response of a wireless communication channel, the method comprising:

estimating the frequency response of the wireless communication channel based on a subset of a plurality of available tones, wherein the subset comprises a plurality of equally spaced tones, the equally spaced tones being equally spaced by a spacing number of the plurality of available tones between the equally spaced tones,

wherein the subset comprises a subset number S of the plurality of available tones, wherein S=2^r, wherein r is an integer.

9. A method of selecting a pilot signal for a pilot transmission from a wireless communication terminal, the method comprising:

selecting for the pilot transmission a subset of a plurality of available tones, wherein the subset comprises a plurality of equally spaced tones, the equally spaced tones being equally spaced by a spacing number of the plurality of available tones between the equally spaced tones; and

selecting a transmit power P equal to T*N/S, where T is an average power for the plurality of available tones, N is a total available tone number and S is a subset number indicating the subset number of tones in the subset.

10. A method of selecting a pilot signal for a pilot transmission from a wireless communication terminal, the method comprising:

selecting for the pilot transmission a subset of a plurality of available tones, wherein the subset comprises a plurality of equally spaced tones, the equally spaced tones being equally spaced by a spacing number of the plurality of available tones between the equally spaced tones,

wherein the subset comprises a subset number S of the plurality of available tones, wherein S=2^r, wherein r is an integer.

11. A wireless communication terminal comprising:

a processor configured to select for a pilot transmission a subset of a plurality of available tones, wherein the subset comprises a plurality of equally spaced tones, the equally spaced tones being equally spaced by a spacing number of the plurality of available tones between the equally spaced tones; and

a transmitter coupled to the processor, the transmitter configured to transmit the pilot transmission over the air,

wherein the processor is further configured to select a transmit power P equal to T*N/S, where T is an average power for the plurality of available tones, N is a total available tone number and S is a subset number indicating the subset number of tones in the subset.

12. A wireless communication terminal comprising:

a processor configured to select for a pilot transmission a subset of a plurality of available tones, wherein the subset comprises a plurality of equally spaced tones, the equally spaced tones being equally spaced by a spacing number of the plurality of available tones between the equally spaced tones; and

a transmitter coupled to the processor the transmitter configured to transmit the pilot transmission over the air,

wherein the subset comprises a subset number S of the plurality of available tones, wherein S=2^r, wherein r is an integer.

13. A wireless communication terminal comprising:

a processing means for selecting for a pilot transmission a subset of a plurality of available tones, wherein the subset comprises a plurality of equally spaced tones, the equally spaced tones being equally spaced by a spacing number of the plurality of available tones between the equally spaced tones; and

a transmitting means for transmitting the pilot transmission over the air, the transmitting means coupled to the processing means,

wherein the processing means is further configured to select a transmit power P equal to T*N/S, where T is an average power for the plurality of available tones, N is a total available tone number and S is a subset number indicating the subset number of tones in the subset.

14. A wireless communication terminal comprising:

a processing means for selecting for a pilot transmission a subset of a plurality of available tones, wherein the subset comprises a plurality of equally spaced tones, the equally spaced tones being equally spaced by a spacing number of the plurality of available tones between the equally spaced tones; and

a transmitting means for transmitting the pilot transmission over the air, the transmitting means coupled to the processing means,

wherein the subset comprises a subset number S of the plurality of available tones, wherein S=2^r, wherein r is an integer.

15. A computer readable medium embodying instructions for performing a method for selecting a pilot signal for a pilot transmission from a wireless communication terminal, the method comprising:

selecting for the pilot transmission a subset of a plurality of available tones, wherein the subset comprises a plurality of equally spaced tones, the equally spaced tones being equally spaced by a spacing number of the plurality of available tones between the equally spaced tones; and

selecting a transmit power P equal to T*N/S, where T is an average power for the plurality of available tones, N is a total available tone number and S is a subset number indicating the subset number of tones in the subset.

16. A computer readable medium embodying instructions for performing a method for selecting a pilot signal for a pilot transmission from a wireless communication terminal, the method comprising:

selecting for the pilot transmission a subset of a plurality of available tones, wherein the subset comprises a plurality of equally spaced tones, the equally spaced tones being equally spaced by a spacing number of the plurality of available tones between the equally spaced tones,

wherein the subset comprises a subset number S of the plurality of available tones, wherein S=2^r, wherein r is an integer.