Systems and methods for acquiring channel synchronization in time division multiple access communications systems using dual detection thresholds

A method for locating a known multi-symbol syncword in a received signal, the method comprising the steps of:

• locating a potential syncword in a first batch of samples of the received signal having a correlation energy with the known syncword which exceeds a first detection threshold;
• determining a correlation energy for a group of samples in a second batch of samples of the received signal with the known syncword, wherein the group of samples in the second batch of samples are selected based on the location of the potential syncword within the first batch of samples;
• comparing the correlation energy associated with the group of samples in the second batch of samples with a second detection threshold that is higher than the first detection threshold;
• and
• identifying the location of the known syncword based upon the comparison of the correlation energy associated with the group of samples in the second batch of samples with the second detection threshold and rejecting the location of the known syncword as a false positive if the correlation energy associated with the group of samples in the second batch of samples does not exceed the second detection threshold;
• and
• wherein the first batch of samples are obtained by sampling the received signal at a first sampling rate and wherein the second batch of samples are obtained by sampling the received signal at a second sampling rate that is higher than the first sampling rate.

A method for locating a known multi-symbol syncword in a received signal, the method comprising the steps of:

• locating a potential syncword in a first batch of samples of the received signal having a correlation energy with the known syncword which exceeds a first detection threshold;
• determining a correlation energy for a group of samples in a second batch of samples of the received signal with the known syncword, wherein the group of samples in the second batch of samples are selected based on the location of the potential syncword within the first batch of samples;
• comparing the correlation energy associated with the group of samples in the second batch of samples with a second detection threshold that is higher than the first detection threshold;
• and
• identifying the location of the known syncword based upon the comparison of the correlation energy associated with the group of samples in the second batch of samples with the second detection threshold and rejecting the location of the known syncword as a false positive if the correlation energy associated with the group of samples in the second batch of samples does not exceed the second detection threshold;
• and
• wherein the first batch of samples are obtained by sampling the received signal at one sample per symbol and wherein the second batch of samples are obtained by sampling the received signal at eight samples per symbol.

A system for locating a known multi-symbol syncword in a received signal, comprising:

• means for locating a potential syncword in a first batch of samples of the received signal having a correlation energy with the known syncword which exceeds a first predefined detection threshold;
• means for determining a correlation energy for a group of samples in a second batch of samples of the received signal with the known syncword, wherein the group of samples in the second batch of samples are selected based on the location of the potential syncword within the first batch of samples;
• means for comparing the correlation energy associated with the group of samples in the second batch of samples with a second predefined detection threshold that is higher than the first predefined detection threshold;
• and
• means for identifying the location of the known syncword based upon the comparison of the correlation energy associated with the group of samples in the second batch of samples with the second predefined detection threshold so as to only identify locations which have a correlation energy which exceeds both the first predefined threshold and the second predefined threshold.

A system for locating a known multi-symbol syncword in a received signal, comprising:

• means for locating a potential syncword in a first batch of samples of the received signal having a correlation energy with the known syncword which exceeds a first detection threshold;
• means for determining a correlation energy for a group of samples in a second batch of samples of the received signal with the known syncword, wherein the group of samples in the second batch of samples are selected based on the location of the potential syncword within the first batch of samples;
• means for comparing the correlation energy associated with the group of samples in the second batch of samples with a second detection threshold that is higher than the first detection threshold;
• and
• means for identifying the location of the known syncword based upon the comparison of the correlation energy associated with the group of samples in the second batch of samples with the second detection threshold;
• means for sampling the received signal at a first sampling rate to provide the first batch of samples and means for sampling the received signal at a second sampling rate, that is higher than the first sampling rate, for providing the second batch of samples;
• and
• wherein the means for locating the potential syncword comprises:
• means for identifying a group of consecutive samples within the first batch of samples which has the highest correlation energy with the known syncword;
• and
• means for comparing the coreelation energy associated with the identified group of consecutive samples with a first detection threshold.

A system for locating a known multi-symbol syncword in a received signal, comprising:

• a receiver subsystem for receiving a signal at a selected frequency and for sampling the signal at a sampling rate at least equal to the symbol rate of the received signal so as to provide first and second batches of samples;
• a processor for:
• locating a potential syncword in the first batch of samples having a correlation energy with the known syncword which exceeds a first predetermined detection threshold;
• determining a correlation energy for a group of samples in the second batch of samples with the known syncword, wherein the group of samples in the second batch of samples are selected based on the location of the potential syncword within the first batch of samples;
• comparing the correlation energy associated with the group of samples in the second batch of samples with a second predefined detection threshold that is higher than the first predefined detection threshold;
• and
• identifying the location of the known syncword based upon the comparison of the correlation energy associated with the group of samples in the second batch of samples with the second predefined detection threshold so as to only identify locations which have a correlation energy which exceeds both the first predefined threshold and the second predefined threshold.

A system for locating a known multi-symbol syncword in a received signal, comprising:

• a receiver subsystem for receiving a signal at a selected frequency and for sampling the signal at a sampling rate at least equal to the symbol rate of the received signal so as to provide first and second batches of samples;
• a processor for:
• locating a potential syncword in the first batch of samples having a correlation energy with the known syncword which exceeds a first detection threshold;
• determining a correlation energy for a group of samples in the second batch of samples with the known syncword, wherein the group of samples in the second batch of samples are selected based on the location of the potential syncword within the first batch of samples;
• comparing the correlation energy associated with the group of samples in the second batch of samples with a second detection threshold that is higher than the first detection threshold;
• and
• identifying the location of the known syncword based upon the comparison of the correlation energy associated with the group of samples in the second batch of samples with the second detection threshold and rejecting the location of the known syncword as a false positive if the correlation energy associated with the group of samples in the second batch of samples does not exceed the second detection threshold;
• and
• wherein the receiver subsystem obtains the first batch of samples by sampling the received signal at a first sampling rate and wherein the receiver subsystem obtains the second batch of samples by sampling the received signal at a second sampling rate that is higher than the first sampling rate.

A method for locating one of a plurality of known multi-symbol syncwords in a received signal, the method comprising the steps of:

• locating a potential syncword in a first batch of samples of the received signal having a correlation energy with one of the plurality of known syncwords which exceeds a first detection threshold by identifying a group of consecutive samples within the first batch of samples which has the highest correlation energy with any one of the plurality of known syncwords and comparing the correlation energy associated with the identified group of consecutive samples with a first detection threshold;
• determining a correlation energy for at least one group of samples in a second batch of samples of the received signal with the one of a plurality of known syncwords, wherein the at least one group of samples in the second batch of samples are selected based on the location of the potential syncword within the first batch of samples;
• comparing the correlation energy associated with each of the at least one group of samples in the second batch of samples with a second detection threshold that is higher than the first detection threshold;
• and
• identifying the location of the one of a plurality of known syncwords based upon the comparison of the correlation energy associated with each of the at least one group of samples in the second batch of samples with the second detection threshold;
• wherein the first batch of samples are obtained by sampling the received signal at a first sampling rate and wherein the second batch of samples are obtained by sampling the received signal at a second sampling rate that is higher than the first sampling rate.

A method for locating a known syncword in a received signal, the method comprising:

• locating a first portion of the received signal having a correlation with the known syncword which exceeds a first predefined detection threshold;
• selecting a second portion of the received signal based on the location of the first portion of the received signal;
• determining a correlation value representing the correlation between the second portion of the received signal and the known syncword;
• comparing the determined correlation value with a second predefined detection threshold that is higher than the first detection threshold;
• and
• identifying the location of the known syncword based upon the comparison of the determined correlation value with the second predefined detection threshold so as to only identify locations which have a correlation energy which exceeds both the first predefined threshold and the second predefined threshold.