System and method for automated link quality measurement for adaptive modulation systems using noise level estimates

• US 7,499,515 B1
• Filed: 08/27/2007
• Issued: 03/03/2009
• Est. Priority Date: 08/27/2007
• Status: Active Grant

• Current Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Beadle, Edward R.
• Primary Examiner(s): Bocure, Tesfaldet
• Application Number:
  US11/845,160
• Publication Number:
  US 20090060014A1
• Time in Patent Office: 554 Days
• Field of Search: 375/295, 375/316, 375/340, 375/377, 375/140, 375/343, 375362-368, 370504-515
• US Class Current: 375/358
• 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 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/0036 arrangements specific to the receiver

Abstract

A communications system includes a transmitter that transmits a modulated signal having encoded communications data over a communications channel. The transmitter adjusts one of at least modulation and coding at the transmitter based on the received channel state information of the transmitted signal. A receiver determines received signal metrics from the modulated signal. A noise power estimator estimates the noise power of the received communications signal by collecting N data samples from the communications signals, forming a covariance matrix of the N data samples based on a model order estimate, computing the eigenvalue decomposition of the covariance matrix and ranking resultant eigenvalues from the minimum to the maximum for determining the noise power of the received signal. At least one of modulation and coding are adjusted based on the monitored link quality of the communications channel to enhance use of the available channel capacity.

Claims

1. A communications system, comprising:

a transmitter that transmits a modulated signal having encoded communications data over a communications channel, and comprising link resource allocator that adjusts one of at least modulation and coding at the transmitter based on received channel state information of the transmitted signal;

a receiver that receives the transmitted signal, and comprising a

demodulator that determines received signal metrics from the modulated signal;

a noise power estimator that estimates the noise power of the received communications signal by collecting N data samples from the communications signals, forming a covariance matrix of the N data samples based on a model order estimate, computing the eigenvalue decomposition of the covariance matrix and ranking resultant eigenvalues from the minimum to the maximum for determining the noise power of the received signal; and

a link quality generator that determines the link quality of the communications channel and generates channel state information based on the estimated noise power and received signal metrics and transmits the channel state information to said link resource allocator within said transmitter, wherein at least one of modulation and coding are adjusted based on monitored link quality of the communications channel to enhance use of the available channel capacity.

2. The communications system according to claim 1, wherein the signal metrics comprise the signal-to-noise ratio.

3. The communications system according to claim 1, wherein said communications channel comprises a scalar, multi-signal communications channel.

4. The communications system according to claim 1, wherein said noise power estimator is operative for estimating the model order based on a number to over bound a maximum possible number of possible individual signals from the transmitter.

5. The communications system according to claim 1, wherein said noise power estimator is operative for estimating the model order based on one of at least a Multiple Signal Classifier, Pisarenko Harmonic Decomposition, Auto-regression, Pade Approximation, Bayesian Information Criterion, Akaike'"'"'s Information Criterion and Minimum Description Length algorithm.

6. The communications system according to claim 1, wherein said noise power estimator is operative with a block adaptation size based on an estimated margin, noise dimension and expected signal-to-noise ratio used for averaging the smallest eigenvalue.

7. The communications system according to claim 1, wherein said communications channel between said transmitter and receiver comprises a control channel and data channel, wherein link quality of the communications channel is monitored at the receiver based on the data channel.

8. The communications system according to claim 1, wherein said link resource allocator is operable for allocating bit rate/source by policy.

9. A receiver comprising:

a signal input for receiving a modulated signal having encoded communications data that has been transmitted over a communications channel;

a demodulator that determines received signal metrics from the modulated signal;

a noise power estimator that estimates the noise power of the received communications signal by collecting N data samples from the communications signals, forming a covariance matrix of the N data samples based on a model order estimate, computing the eigenvalue decomposition of the covariance matrix and ranking resultant eigenvalues from the minimum to the maximum for determining the noise power of the received signal; and

a link quality generator operative with the demodulator and noise power estimator that determines the link quality of the communications channel and generates channel state information based on the estimated noise power and received signal metrics and transmits the channel state information to a transmitter where at least one of modulation and coding are adjusted based on monitored link quality of the communications channel to enhance use of the available channel capacity.

10. The receiver according to claim 9, wherein the signal metrics comprise the signal-to-noise ratio.

11. The receiver according to claim 9, wherein said communications channel comprises a scalar, multi-signal communications channel.

12. The receiver according to claim 9, wherein said noise power estimator is operative for estimating model order based on a number to over bound a maximum possible number of possible individual signals from the transmitter.

13. The receiver according to claim 9, wherein said noise power estimator is operative for estimating the model order based on one of at least a Multiple Signal Classifier, Pisarenko Harmonic Decomposition, Auto-regression, Pade Approximation, Bayesian Information Criterion, Akaike'"'"'s Information Criterion and Minimum Description Length algorithm.

14. The receiver according to claim 9, wherein said noise power estimator is operative with a block adaptation size based on an estimated margin, noise dimension and expected signal-to-noise ratio used for averaging the smallest eigenvalue.

15. The receiver according to claim 9, wherein said modulated signal comprises data and synchronization pulses and said receiver comprises a first filter matched to a synchronization pulse, a second filter inversely matched to the synchronization pulse, a detector that determines the synchronization pulse based on outputs from the first and second filters, wherein said noise power estimator is coupled to the detector and estimates the noise power and sets a noise threshold based on the input signal using a covariance matrix that is formed of the N data samples based on the model order estimate.

16. A method of communicating, comprising:

transmitting from a transmitter a modulated signal having encoded communications data over a communications channel;

receiving the modulated signal within a receiver;

demodulating the received signal while determining the received signal metrics from the modulated signal;

estimating the noise power of the received communications signal by collecting N data samples from the communications signals, forming a covariance matrix of the N data samples based on a model order estimate, computing the eigenvalue decomposition of the covariance matrix and ranking resultant eigenvalues from the minimum to the maximum for determining the noise power of the received signal;

determining the link quality of the communications channel and generating channel state information based on the estimated noise power and received signal metrics;

transmitting the channel state information to the transmitter adjusting at least one of the coding and modulating based on monitored link quality of the communications channel to enhance use of the available channel capacity.

17. The method according to claim 16, wherein the signal metrics comprise the signal-to-noise ratio.

18. The method according to claim 16, wherein the communications channel comprises a scalar, multi-signal communications channel.