Real-Time Radio Spectrum Assessment Engine

Patent metadata

Field	Value
Publication number	US-2016337891-A1
Application number	US-201615222519-A
Country	US
Kind code	A1
Filing date	Jul 28, 2016
Priority date	Feb 25, 2013
Publication date	Nov 17, 2016
Grant date	—

Abstract

A decoder for a modulation scheme is configured to operate close to the radio noise floor. A correlation value may be constantly updated, in an effort to match to a signature to a preamble of a packet. A low clamp value may act as a floor to which a calculated correlation value is set, if it is less than the low clamp value. If a correlation threshold is exceeded, then the correlation value is examined to determine it is a peak value. If the peak is found, power of the preamble is compared to a power threshold that is relative to the radio noise floor. If the power threshold is exceeded, positive correlation is detected. A channel optimizer is used to remove the frequency misalignment. This enables the use of a filter that is approximately equal to the occupied bandwidth of the incoming signal, further rejecting noise and interference.

First claim

What is claimed is:

1 . A decoder, comprising:
a correlator to:
calculate a correlation value between incoming samples and a signature of a preamble of a packet;
iteratively compare the correlation value to a correlation value threshold to find a peak correlation value, and
upon finding the peak correlation value, compare a preamble power to a power threshold to determine if a valid preamble has been detected;
a bit constructor to construct bits from a payload of the packet having the preamble; and a channel optimizer configured to:
estimate frequency misalignment;
tune to remove the estimated frequency misalignment; and
filter at a location indicated by the tuning.

2 . The decoder as recited in claim 1 , wherein calculation by the correlator comprises:
setting a low clamp value at a level such that if a valid packet arrives, then a low value of the calculated correlation value will not prevent correlation.

3 . The decoder as recited in claim 1 , additionally comprising:
resetting the calculated correlation value if a preamble power value is less than a power threshold.

4 . The decoder as recited in claim 1 , wherein the power threshold is based in part on a radio noise floor level.

5 . The decoder as recited in claim 1 , wherein:
a correlation value threshold is set to indicate correlation between the calculated correlation value of the samples and the signature of the preamble; and the power threshold is based in part on a radio noise floor.

6 . The decoder as recited in claim 5 , additionally comprising:
tracking a noise floor to determine a level of the noise floor; and using the noise floor to set the power threshold.

8 . The decoder as recited in claim 1 , wherein:
the filter is set to a width of approximately an occupied band width (OBW) of an incoming signal.

9 . The decoder as recited in claim 1 , wherein calculation by the correlator comprises:
using the peak correlation value to synchronize to a beginning of the payload of the packet.

10 . A decoder, comprising:
a correlator to calculate a correlation value between incoming samples and a signature of a preamble of a packet; a bit constructor to construct bits from a payload of the packet having the preamble; and a channel optimizer configured to:
estimate frequency misalignment based at least in part on measurement of rotational frequency error of incoming samples, and based at least in part on detecting a valid preamble, wherein the estimating of the frequency misalignment is performed over a full length of the preamble;
tune to remove the estimated frequency misalignment using a complex mixer; and
filter in the time domain at a location indicated by the tuning, wherein the filter is set to approximately an occupied bandwidth (OBW) of an incoming signal.

11 . A decoder to decode a modulation scheme, comprising:
a correlator to calculate a correlation value between incoming samples and a signature, wherein calculating the correlation value is based at least in part on comparing power of a sample from among the incoming samples to a power threshold, and if the power threshold is exceeded, finding the correlation value to be positive; a channel optimizer configured to:
estimate frequency misalignment of the incoming samples from an intended frequency; and
tune according to the estimated frequency misalignment; and
a bit constructor to construct bits from a payload of a packet having a preamble indicated by the calculated correlation value.

12 . The decoder as recited in claim 11 , wherein the correlator comprises:
a correlation value threshold set to indicate correlation between the calculated correlation value of the samples and the signature; and a power threshold to compare to a preamble power value, wherein:
the preamble power value is based at least in part on the incoming samples; and
the power threshold is based in part on a noise floor.

13 . The decoder as recited in claim 11 , wherein the correlator is configured to:
restrict the calculated correlation value to a region above a low clamp value.

14 . The decoder as recited in claim 11 , wherein the correlator is configured to:
determine a level of a noise floor; and use the noise floor to set a power threshold.

15 . The decoder as recited in claim 11 , additionally comprising:
a filter set at a width of approximately an occupied band width (OBW) of an incoming signal.

16 . The decoder as recited in claim 11 , wherein the channel optimizer is additionally configured to:
sum a plurality of terms; and divide by a number of samples in the preamble of a packet; wherein the summing of the plurality of terms ends when a correlation is found with a preamble.

17 . A method of decoding a modulation scheme, comprising:
correlating incoming samples to a signature, wherein the correlating comprises:
comparing power of a preamble of a packet to a power threshold; and
if the power threshold is exceeded, finding a correlation value to be positive;
estimating frequency misalignment, between a transmitter and a receiver, based at least in part on a point of correlation to the preamble of the packet; and tuning according to the estimated frequency misalignment.

18 . The method as recited in claim 17 , additionally comprising:
calculating a correlation value of sample bits to a signature of a preamble; requiring the correlation value to be greater than or equal to a low clamp value; and finding correlation when:
the correlation value exceeds a correlation value threshold; and
a correlation power value exceeds a power threshold.

19 . The method as recited in claim 17 , additionally comprising:
detecting a peak in the correlation value; and using the detected peak to synchronize to a beginning of a payload of the packet.

20 . The method as recited in claim 17 , wherein:
estimating frequency misalignment is performed using adders and shifters; tuning according to the estimated frequency misalignment is performed using a complex mixer; and filtering at a location indicated by the tuning is performed by use of a filter set to approximately an occupied bandwidth of an incoming signal.

Assignees

• Itron Inc

Inventors

• Seely Danny Ray

Classifications

• H04W24/04

  Arrangements for maintaining operational condition · CPC title

• H04W24/08 Primary

  Testing, {supervising or monitoring} using real traffic · CPC title