Preamble detection with multiple receive antennas

A system comprising:

• a differential demodulation module that (i) receives modulated signals from R antennas and (ii) differentially demodulates said modulated signals to generate differentially demodulated signals, where R is an integer greater than 1;
• a first summing module that sums said differentially demodulated signals to generate a combined signal;
• a state detection module that detects states of X symbols in said combined signal, where X is an integer greater than 1, and where each of said X symbols has one of a first state and a second state;
• a second summing module that (i) receives Y preamble sequences each comprising X predetermined symbols and (ii) generates X sums for each of said Y preamble sequences by adding each of said states of said X symbols with corresponding states of said X predetermined symbols of each of Y preamble sequences, where Y is an integer greater than 1, wherein said second summing module generates cross-correlation values by adding said X sums generated for each of said Y preamble sequences;
• a control module in communication with said differential demodulation module and said second summing module, wherein said control module (i) selects a largest one of said cross-correlation values, and (ii) detects one of said Y preamble sequences in said modulated signals when said largest one of said cross-correlation values is greater than or equal to a predetermined threshold;
• and
• a correlation module in communication with said differential demodulation module and said control module, wherein said correlation module generates correlation values by correlating (i) at least one of said differentially demodulated signals and (ii) at least one of derived preamble sequences that generate at least two of said cross-correlation values, wherein said cross-correlation values are greater than said predetermined threshold and are substantially the same.

A method comprising:

• receiving modulated signals from R antennas, where R is an integer greater than 1;
• differentially demodulating said modulated signals to generate differentially demodulated signals;
• summing said differentially demodulated signals to generate a combined signal;
• detecting states of X symbols in said combined signal, where X is an integer greater than 1, and where each of said X symbols has one of a first state and a second state;
• receiving Y preamble sequences each comprising X predetermined symbols;
• generating X sums for each of said Y preamble sequences by adding each of said states of said X symbols with corresponding states of said X predetermined symbols of each of Y preamble sequences, where Y is an integer greater than 1;
• and
• generating said states of said X predetermined symbols by inverting states of derived symbols in derived preamble sequences,
• wherein said derived preamble sequences are derived from said Y preamble sequences,
• wherein each of said Y preamble sequences is different from others of said Y preamble sequences, and
• wherein each of said derived symbols of one of said derived preamble sequences has a first binary value when a corresponding symbol and a symbol adjacent to said corresponding symbol in a corresponding one of said Y preamble sequences have opposite binary values, and said each of said derived symbols has a second binary value that is opposite to said first binary value when said corresponding symbol and said symbol adjacent to said corresponding symbol have the same binary value.

A method comprising:

• receiving modulated signals from R antennas, where R is an integer greater than 1;
• differentially demodulating said modulated signals to generate differentially demodulated signals;
• summing said differentially demodulated signals to generate a combined signal;
• detecting states of X symbols in said combined signal, where X is an integer greater than 1, and where each of said X symbols has one of a first state and a second state;
• receiving Y preamble sequences each comprising X predetermined symbols;
• generating X sums for each of said Y preamble sequences by adding each of said states of said X symbols with corresponding states of said X predetermined symbols of each of Y preamble sequences, where Y is an integer greater than 1;
• generating cross-correlation values by adding said X sums generated for each of said Y preamble sequences;
• selecting a largest one of said cross-correlation values and detecting one of said Y preamble sequences in said modulated signals when said largest one of said cross-correlation values is greater than or equal to a predetermined threshold;
• and
• generating correlation values by correlating at least one of said differentially demodulated signals and at least one of derived preamble sequences that generate at least two of said cross-correlation values, wherein said cross-correlation values are greater than said predetermined threshold and are substantially the same.