Preamble sequence detection of direct sequence spread spectrum (DSSS) signals

Patent metadata

Field	Value
Publication number	US-9935681-B2
Application number	US-201615071998-A
Country	US
Kind code	B2
Filing date	Mar 16, 2016
Priority date	Mar 16, 2016
Publication date	Apr 3, 2018
Grant date	Apr 3, 2018

Abstract

A direct sequence spread spectrum (DSSS) receiver includes an antenna, signal-to-noise ratio (SNR) estimation logic, and preamble detection logic. The antenna is configured to receive a DSSS signal. The SNR estimation logic is configured to estimate SNR of the received DSSS signal. The preamble detection logic is configured to, in response to the SNR estimate exceeding a SNR threshold value, detect a preamble sequence in the DSSS signal based on an absolute value of a sequence of correlation values. The sequence of correlation values is a complex quantity.

First claim

What is claimed is:

1. A direct sequence spread spectrum (DSSS) receiver, comprising:
an antenna wherein the antenna receives a DSSS signal;
signal-to-noise ratio (SNR) estimation logic wherein the SNR estimation logic is coupled to the antenna;
preamble detection logic coupled to the SNR estimation logic; and
a sampler coupled to the antenna, SNR estimation logic, and preamble detection logic;
wherein the preamble detection logic comprises:
difference logic;
accumulation logic coupled to the difference logic; and
correlation logic coupled to the accumulation logic;

wherein the correlation logic further comprises a offset quadrature phase shift keying ( 0 -QPSK) demodulator.

2. A method of detecting a preamble sequence in a direct sequence spread spectrum (DSSS) signal comprising:
receiving a DSSS signal;
generating a digital sequence of samples representative of the DSSS signal;
calculating differential chip values between pairs of samples of the digital sequence of samples to form a sequence of differential values;
correlating a known preamble differential value sequence with the sequence of differential values to form a sequence of correlation values;

estimating a signal-to-noise ratio (SNR) of the received DSSS signal;
comparing the estimated SNR to a SNR threshold value; and

in response to the estimated SNR being less than the SNR threshold value, comparing an imaginary value of the sequence of correlation values with a preamble threshold to detect a location of the preamble in the digital sequence of samples.

3. The method of claim 2 , wherein, in response to the estimated SNR being less than the SNR threshold value, the detecting the location of the preamble sequence in the digital sequence of samples comprises identifying a peak in the imaginary value of the sequence of correlation values exceeding the preamble threshold.

4. The method of claim 2 , wherein, in response to the estimated SNR exceeding the SNR threshold value, comparing an absolute value of the sequence of correlation values with the preamble threshold to detect the location of the preamble in the digital sequence of samples.

5. The method of claim 4 , wherein, in response to the estimated SNR exceeding the SNR threshold value, the detecting the location of the preamble sequence in the digital sequence of samples comprises identifying a peak in the absolute value of the sequence of correlation values exceeding the preamble threshold.

6. The method of claim 2 , wherein the correlating the known preamble differential value sequence with the sequence of differential values comprises:
accumulating an extended sequence of differential chip values;
calculating a first complex fast Fourier transform (FFT) of the extended sequence of differential chip values;
multiplying the first complex FFT by a second complex FFT of the known preamble differential value sequence to form a product; and
calculating an inverse FFT (IFFT) of the product.

7. The method of claim 6 , wherein the preamble sequence is 32 bits.

Assignees

• Texas Instruments Inc

Inventors

• Lingam Srinivas
• Schmidl Timothy Mark

Classifications

• H04B1/709

  Correlator structure · CPC title

• H04B1/7097 Primary

  Interference-related aspects · CPC title

• H04B1/707 Primary

  using direct sequence modulation · CPC title

• H04L1/1671

  the supervisory signal being transmitted together with control information · CPC title

• H04L1/20

  using signal quality detector · CPC title