Gain control metric computation in a wireless repeater

• US 8,867,987 B2
• Filed: 03/12/2010
• Issued: 10/21/2014
• Est. Priority Date: 05/11/2009
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Wang, Michael Mao, Gore, Dhananjay Ashok, Jarosinski, Tadeusz
• Primary Examiner(s): TRINH, TAN H
• Application Number:
  US12/722,733
• Publication Number:
  US 20100285744A1
• Time in Patent Office: 1,684 Days
• Field of Search: 455/24, 455/7, 455/9, 455/10, 455/11.1, 455/13.1, 455/13.4, 455/16, 455/67.16, 455/67.13, 455/67.11, 455/63.1, 455/69, 455/115.1, 455/115.3, 455/135, 455/136, 455/138, 455/213, 455/464, 455/522, 455/570, 455/571, 455/513, 370/241, 370/252, 370/315, 370/335, 370/342, 370/234, 370/246, 370/274, 370/286, 370/289, 375/142, 375/211, 375/213, 375/267
• US Class Current: 455/24
• CPC Class Codes: H04B 7/15578 by gain adjustment

Abstract

A method for computing a gain control metric used in controlling gain in a wireless repeater operates to store correlation and normalization values associated with the gain control metric for the previous N samples in registers. For each new sample of the gain control input signal, the correlation and normalization values are computed by discarding the multiplication terms of the obsolete sample and adding the multiplication terms of the new sample to the stored correlation and normalization values. In this manner, the complexity of the computation is greatly reduced and the complexity of the computation does not increase with the integration length.

Claims

1. A method for computing a gain control metric used in controlling gain in a wireless repeater, the wireless repeater receiving an input signal at a receiving antenna and transmitting an output signal on the transmitting antenna, the input signal being a sum of a remote signal to be repeated and a feedback signal resulting from a feedback channel between the receiving antenna and a transmitting antenna, the feedback channel thus forming a feedback loop between the transmitting antenna and the receiving antenna, the method comprising:

providing a tap-specific gain control metric indicative of a loop gain of the repeater, the tap-specific gain control metric at a given channel tap being computed from a gain control input signal and being a square of a correlation term divided by a normalization term, the correlation term and the normalization term having an integration length of N, the correlation term being indicative of a correlation of the gain control input signal and a delayed version of the gain control input signal and the normalization term being indicative of a power of the gain control input signal that is not delayed, the gain control input signal being taken from any point in the feedback loop of the repeater;

providing a first register for storing a stored correlation value, the stored correlation value being the correlation term computed over a previous N samples;

providing a second register for storing a stored normalization value, the stored normalization value being the normalization term computed over a previous N samples;

receiving a new sample of the gain control input signal;

computing an updated correlation value by performing a first multiplication using an obsolete sample of the gain control input signal, the obsolete sample being the (N+1)th previous sample, and a second multiplication using the new sample of the gain control input signal, the updated correlation value being computed by adding the product from the second multiplication and subtracting the product from the first multiplication;

computing an updated normalization value by performing a third multiplication using an obsolete sample of the gain control input signal, the obsolete sample being the (N+1)th previous sample, and a fourth multiplication using the new sample of the gain control input signal, the updated normalization value being computed by adding the product from the fourth multiplication and subtracting the product from the third multiplication; and

computing the tap-specific gain control metric using the updated correlation value and the updated normalization value.

2. The method of claim 1, further comprising:

computing the tap-specific gain control metric over each channel tap using the updated correlation value and the updated normalization value; and

computing a gain control metric based on a combination of the computed tap-specific gain control metric over all channel taps.

3. The method of claim 2, wherein computing a gain control metric based on a combination of the computed tap-specific gain control metric over all channel taps comprises computing a gain control metric based on a linear combination of the computed tap-specific gain control metrics over all channel taps.

4. The method of claim 2, wherein computing a gain control metric based on a combination of the computed tap-specific gain control metric over all channel taps comprises computing a gain control metric based on a non-linear combination of the computed tap-specific gain control metrics over all channel taps.

5. The method of claim 1, wherein the tap-specific gain control metric at a given channel tap τ

is g_i[τ

]=(R[τ

]/S)², where R[τ

] is the correlation term and S is the normalization term.

6. A wireless repeater having a receiving antenna for receiving an input signal and a transmitting antenna for transmitting an output signal, the input signal being a sum of a remote signal to be repeated and a feedback signal resulting from a feedback channel between the receiving antenna and the transmitting antenna, the feedback channel thus forming a feedback loop between the transmitting antenna and the receiving antenna, the repeater comprising:

a gain control block configured to control a gain of the repeater, the gain control block comprising a gain metric calculator configured to receive a gain control input signal and to compute a tap-specific gain control metric indicative of a loop gain of the repeater, the tap-specific gain control metric at a given channel tap being a square of a correlation term divided by a normalization term, the correlation term and the normalization term having an integration length of N, the correlation term being indicative of a correlation of the gain control input signal and a delayed version of the gain control input signal and the normalization term being indicative of a power of the gain control input signal that is not delayed, the gain metric calculator comprising;

a first register configured to store a stored correlation value, the stored correlation value being the correlation term computed over a previous N samples of the gain control input signal; and

a second register configured to store a stored normalization value, the stored normalization value being the normalization term computed over a previous N samples of the gain control input signal,

wherein the gain metric calculator block is configured to receive a new sample of the gain control input signal and the gain metric calculator is configured to compute an updated correlation value by performing a first multiplication using an obsolete sample of the gain control input signal, the obsolete sample being the (N+1)th previous sample, and a second multiplication using the new sample of the gain control input signal, the updated correlation value being computed by adding the product from the second multiplication and subtracting the product from the first multiplication; and

wherein the gain metric calculator is configured to compute an updated normalization value by performing a third multiplication using an obsolete sample of the gain control input signal, the obsolete sample being the (N+1)th previous sample, and a fourth multiplication using the new sample of the gain control input signal, the updated normalization value being computed by adding the product from the fourth multiplication and subtracting the product from the third multiplication, the gain metric calculator being configured to compute the tap-specific gain control metric using the updated correlation value and the updated normalization value.

7. The wireless repeater of claim 6, wherein the gain metric calculator is configured to compute the tap-specific gain control metric over each channel tap using the updated correlation value and the updated normalization value and a gain control metric is computed based on a combination of the computed tap-specific gain control metrics over all channel taps.

8. The wireless repeater of claim 7, wherein the gain control metric is computed based on a linear combination of the computed tap-specific gain control metrics over all channel taps.

9. The wireless repeater of claim 7, wherein the gain control metric is computed based on a non-linear combination of the computed tap-specific gain control metrics over all channel taps.

10. The wireless repeater of claim 6, wherein the tap-specific gain control metric at a given channel tap τ

is g_i[τ

]=(R[τ

]/S)², where R[τ

] is the correlation term and S is the normalization term.

11. The wireless repeater of claim 6, wherein the gain metric calculator is configured to take the gain control input signal from any point in the feedback loop of the repeater.

12. A wireless repeater having a receiving antenna for receiving an input signal and a transmitting antenna for transmitting an output signal, the input signal being a sum of a remote signal to be repeated and a feedback signal resulting from a feedback channel between the receiving antenna and the transmitting antenna, the feedback channel thus forming a feedback loop between the transmitting antenna and the receiving antenna, the repeater comprising:

means for controlling a gain of the repeater, the means comprising a first means for receiving a gain control input signal and computing a tap-specific gain control metric indicative of a loop gain of the repeater, the tap-specific gain control metric at a given channel tap being a square of a correlation term divided by a normalization term, the correlation term and the normalization term having an integration length of N, the correlation term being indicative of a correlation of the gain control input signal and a delayed version of the gain control input signal and the normalization term being indicative of a power of the gain control input signal that is not delayed, the first means comprising;

a second means for storing a stored correlation value, the stored correlation value being the correlation term computed over a previous N samples of the gain control input signal; and

a third means for storing a stored normalization value, the stored normalization value being the normalization term computed over a previous N samples of the gain control input signal,

wherein the first means is configured for receiving a new sample of the gain control input signal and computing an updated correlation value by performing a first multiplication using an obsolete sample of the gain control input signal, the obsolete sample being the (N+1)th previous sample, and a second multiplication using the new sample of the gain control input signal, the updated correlation value being computed by adding the product from the second multiplication and subtracting the product from the first multiplication; and

wherein the first means is configured for computing an updated normalization value by performing a third multiplication using an obsolete sample of the gain control input signal, the obsolete sample being the (N+1)th previous sample, and a fourth multiplication using the new sample of the gain control input signal, the updated normalization value being computed by adding the product from the fourth multiplication and subtracting the product from the third multiplication, the gain metric calculator being configured to compute the tap-specific gain control metric using the updated correlation value and the updated normalization value.