Method of, and receiver for, estimating the bit rate of data

• US 6,898,237 B2
• Filed: 05/22/2001
• Issued: 05/24/2005
• Est. Priority Date: 05/31/2000
• Status: Expired due to Term

• Current Assignee: ST-Ericcson SA (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Porcino, Domenico G.
• Primary Examiner(s): Le, Amanda T.
• Application Number:
  US09/862,281
• Publication Number:
  US 20020001341A1
• Time in Patent Office: 1,463 Days
• Field of Search: 375/224, 375/225, 370/252, 455/226.1
• US Class Current: 375/225
• CPC Class Codes: H04L 25/0262 Arrangements for detecting the data rate of an incoming signal

Abstract

A bit rate detector for detecting the speed of transmission of a data signal having one of at least two alternative bit rates, comprises a differential decoder (28) for differentially decoding received digitally modulated signals into oversampled complex signals, a summing stage (38, 40 and 42) for forming a running sum of successive groups of samples, and a bit rate detector (58). The bit rate detector (58) having a stage (62, 66 (FIG. 5)) for determining if the running sum represents a signal as opposed to interference, and if the running sum represents a signal, determining the sign of the running sum, a stage (74 (FIG. 5)) for assigning one of two binary values dependent on whether the sign is positive or negative, a shift register (82 (FIG. 5)) for storing successive binary values, a comparator (88 (FIG. 5)) for comparing the content of the shift register with a threshold value related to one of the at least two alternative bit rates, and if the threshold value is exceeded concluding that the data signal is at said one bit rate, but if not repeating the method with the threshold value being related to the other or another of the bit rates.

Claims

1. A method of detecting the presence of a data signal having one of at least two alternative bit rates, the method comprising differentially decoding the digitally modulated signals into oversampled complex signals, forming a running sum of successive groups of samples, determining if the running sum represents a signal as opposed to interference, if the running sum represents a signal, determining the sign of the running sum, assigning one of two binary values dependent on whether the sign is positive or negative, storing successive binary values in a shift register, comparing the content of the shift register with a threshold value related to one of the at least two alternative bit rates, and if the threshold value is exceeded concluding that the data signal is at said one bit rate, but if not repeating the method with the threshold value being related to the other or another of the bit rates.

2. A method as claimed in claim 1, characterised by determining the nature of the running sum by comparing the most significant bit with another threshold value and if it is exceeded treating the running sum as representing a signal.

3. A method as claimed in claim 1, characterised in that the running sum is weighted in favour of the presence of a signal.

4. A method as claimed in claim 3, characterised in that the running sum is weighted by deriving the absolute value of successive running sums, comparing the absolute value with a plurality of threshold values of different magnitudes, the difference between threshold values of successive magnitudes comprising a window having a weighting value assigned to it, and in that the running sum is multiplied by the weighting value determined.

5. A method as claimed claim 1, wherein the data signal comprises a 2-FSK signal, characterised in that a constellation containing differentially decoded imaginary values is used to form the running sum.

6. A receiver comprising means for receiving a data signal, means for forming the data signal into oversampled differentially decoded complex signals, means for forming a running sum of successive groups of samples, means for determining if the running sum represents a signal as opposed to interference, and, in response to determining that the running sum represents a signal, for determining the sign of the running sum, means for assigning one of two binary values dependent on whether the sign is positive or negative, a shift register for storing successive binary values, and comparing means for comparing the content of the shift register with a threshold value related to one of the at least two alternative bit rates, the comparing means having an output for a signal representing the bit rate has been detected.

7. A receiver as claimed in claim 6, characterised in that the means for determining the nature of the running sum comprises a comparator having a first input for the most significant bit of the running sum, a second input for another threshold value, and an output for a decision that the running sum represent an acceptable signal.

8. A receiver as claimed in claim 6, characterised by means for further weighting the sum according to known statistics of expected results.

9. A receiver as claimed in claim 6, characterised by means for weighting the running sum in favour of the presence of a signal.

10. A receiver as claimed in claim 9, characterised in that the means for weighting the running sum comprises means for deriving the absolute value of successive running sums, means for deriving a plurality of threshold values of different magnitudes, a comparator for comparing the absolute value with the plurality of threshold values of different magnitudes, the difference between threshold values of successive magnitudes comprising a window having a weighting value assigned to it, and multiplying means for multiplying the running sum by the weighting value determined.

11. A receiver as claimed in claim 6, characterised in that when the data signal comprises a 2-FSK signal, means are provided for supplying a constellation containing differentially decoded imaginary values to the means for forming the running sum.