Method and an apparatus for estimating residual noise in a signal and an apparatus utilizing the method

• US 6,871,066 B1
• Filed: 09/14/2000
• Issued: 03/22/2005
• Est. Priority Date: 09/17/1999
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Lindoff, Bengt, Khullar, Anders, Stenström, Niklas
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): RAMPURIA, SHARAD K
• Application Number:
  US09/661,677
• Time in Patent Office: 1,650 Days
• Field of Search: 455423-425, 4552261-2263, 455/67.1, 455/67.3, 455/67.6, 455/570, 379/22.08, 379/406.08, 375/296
• US Class Current: 455/423
• CPC Class Codes: H04L 1/0002 by adapting the transmission rate
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/20 using signal quality detector

Abstract

The invention relates to: A method for estimating residual noise in the frequency range (271) of a desired part (240) of a signal to a corresponding apparatus and to a mobile telephone utilizing the method.

The object of the present invention is to generate a measure for the residual noise in a signal.

The problem is solved in that the amplitude of the signal (114) comprising the noise is modified, and the signal (114) is combined with the modified signal (115) to create a noise estimation measure (116).

The invention may e.g. be used in digital radio communications systems to contribute to the monitoring of link quality and therefore to improve payload throughput. One of the advantages of the invention is that an indication of link quality at an early stage in the receiver is provided.

Claims

1. A method for estimating residual noise in a frequency range of a desired part of a signal received in a mobile receiver via a digital cellular radio system, the desired part of the received signal representing a selected channel of the digital cellular radio system, the method comprising:

modifying the amplitude of the received signal, the received signal including the residual noise;

combining the received signal with the modified received signal to create a noise estimation measure; and

transmitting, uplink from the mobile receiver and via the digital cellular radio system, the noise estimation measure or a post-processed version of the noise estimation measure to a link quality control system of the digital cellular radio system.

2. The method according to claim 1, wherein the noise estimation measure is based on an average power content of the signal and the modified signal over their frequency spectra.

3. The method according to claim 2, wherein the noise estimation measure is based on the average power content of the signal and the modified signal over one or more common ranges of their frequency spectra.

4. The method according to any one of claims 1 to 3, wherein the signal is attenuated primarily outside a frequency range of the desired part of the signal.

5. The method according to claim 2 or 3, wherein the noise estimation measure is based on a difference in average power content between the signal and the modified signal.

6. The method according to any one of claims 1 to 3, wherein the signal is a digital signal.

7. The method according to claim 4, wherein the signal is attenuated primarily outside the frequency range of the desired part of the signal via a digital filter.

8. The method according to any one of claims 1 to 3, wherein the noise estimation measure is quantized in a number of different levels each indicating different levels of noise present.

9. The method according to claim 1, wherein a noise estimation measurement is performed during each of the basic time units of a channel of the digital cellular radio system, and the result is communicated to the link quality control system of the digital cellular radio system as an estimator of current link quality.

10. The method according to claim 1, wherein several noise estimation measurements are performed, the results are stored, and the results are evaluated, and a derived trend is communicated to the link quality control system of a digital cellular radio system as an estimator of current link quality.

11. The method according to claim 1, wherein the noise estimation measure transferred to the link quality control system is used by the digital cellular radio system to optimize user information channel throughput by adjusting at least one of the data transmission rate, the error correction depth, and a type of modulation.

12. The method according to claim 1, wherein the noise estimation measure is transferred to a digital demodulator and used to adjust a receiver algorithm.

13. An apparatus for estimating residual noise in a frequency range of a desired part of a signal received in a mobile receiver via a digital cellular radio system, the desired part of the received signal representing a selected channel of the digital cellular radio system, the apparatus comprising:

means for modifying an amplitude of the received signal, the received signal comprising the residual noise;

means for combining the received signal with the modified signal to create a noise estimation measure;

means for transferring the noise estimation measure to a processing unit;

means for storing consecutive values of the noise estimation measure;

means for processing the consecutive values to extract a trend;

means for transmitting, uplink from the mobile receiver and via the digital cellular radio system, the stored consecutive values, the extracted trend, a post-processed version of the stored consecutive values, or a post-processed version of the extracted trend to a quality control system of the digital cellular radio system.

14. The apparatus according to claim 13, wherein the means modified for combining the signal with the signal to create a noise estimation measure comprise a power meter for measuring average power content of the signal and the modified signal over at least one of a plurality of common ranges of their frequency spectra.

15. The apparatus according to claim 13 or 14, wherein the means for modifying the amplitude of the signal comprising the noise include means for attenuating the signal primarily outside the frequency range of the desired part of the signal.

16. The apparatus according to claim 14, wherein the means for combining the signal with the modified signal to create a noise estimation measure comprise means for computing a difference in average power content between the signal and the modified signal.

17. The apparatus according to claim 13 or 14, wherein the apparatus is adapted to handle digital signals.

18. The apparatus according to claim 17, wherein the means for attenuating the signal primarily outside the frequency range of the desired part of the signal comprise a digital filter.

19. A mobile telephone comprising:

means for estimating residual noise in a frequency range of a desired part of a signal received in the mobile telephone via a digital cellular radio system, the desired part of the received signal representing a selected channel of the digital cellular radio system

wherein the amplitude of the received signal is modified, the received signal comprising the residual noise;

wherein the received signal is combined with the modified received signal to create a noise estimation measure;

means for estimating residual noise in the frequency range of the desired part of the received signal;

means for storing, evaluating, and transmitting, uplink from the mobile telephone and via the digital cellular radio system, at least one of resulting noise estimation measurements and post-processed versions of the resulting noise estimation measurements to a link quality control system of the digital cellular radio system.

20. The mobile telephone according to claim 19, wherein the mobile telephone is adapted to perform a noise estimation measurement during each of a plurality of basic time units of a channel of the digital cellular radio system.