Preamble detection in a multi-antenna MIMO 802.16e receiver
A preamble detector for a plurality of streams of baseband digitized signals has a plurality of preamble processors, each preamble processor coupled to an input and generating an output. Each preamble processor has an input coupled to a first delay, the output of the first delay coupled to a second delay generating an output. The first and second delay are substantially equal to a preamble part. A first multiplier generates an output from a conjugated output of the second delay output and a first delay output. A second multiplier generates an output from a conjugated first delay output and an input stream. The first and second multiplier outputs are accumulated over an interval, and the complex output of the accumulator is formed into a magnitude, thereby generating the output of each preamble processor. The outputs of the preamble processors are summed and compared to a threshold to generate a preamble detect.
1. A preamble detector having:
a plurality of preamble processors, each preamble processor having:
a preamble processor input coupled to a first delay and producing an output;
a second delay generating an output and having an input coupled to said first delay output;
a first multiplier coupled to a conjugated output of said second delay and to said first delay output, thereby generating a first multiplier output;
a second multiplier coupled to a conjugated output of said first delay and to said preamble processor input, thereby generating a second multiplier output;
a subtractor forming the difference between said first multiplier output and said second multiplier output, said subtractor thereby forming an output substantially equal to the sum of m previous first multiplier output values;
said subtractor coupled to a magnitude generator for producing a magnitude substantially equal to the magnitude of the real and imaginary parts of said accumulator output, thereby generating a preamble processor output;
a summer for accepting said preamble processor outputs and forming a preamble detector sum;
a comparator coupled to said summer and generating an output when said summer output exceeds a threshold value.
2. The preamble detector of claim 1 where said preamble processor input is coupled to a down-converted stream of digital samples which include a preamble.
3. The preamble detector of claim 2 where said preamble includes a preamble which conforms to IEEE 802.16e.
4. The preamble detector of claim 1 where said first said second delay are substantially equal to a preamble part duration.
5. The preamble detector of claim 1 where said conjugator reverses the sign of an imaginary part.
6. The preamble detector of claim 1 where said first and said second multiplier are complex multipliers.
7. The preamble detector of claim 1 where said magnitude generates an output by producing the square root of the sum of the squared real part and squared imaginary part.
8. The preamble detector of claim 1 where said threshold is determined from at least one preamble processor input stream.
9. The preamble detector of claim 1 where each said preamble processor is coupled to a stream of baseband signals which includes a preamble which satisfies IEEE 802.16e.
10. The preamble detector of claim 1 where the number of said preamble processors is two or three.
11. A preamble detection processor having:
a preamble detection processor input coupled to a first delay and producing an output;
a second delay generating an output and having an input coupled to said first delay output;
a first multiplier coupled to a conjugated output of said second delay and to said first delay output, thereby generating a first multiplier output;
a second multiplier coupled to a conjugated output of said first delay and to said preamble detection processor input, thereby generating a second multiplier output;
a subtractor forming the difference from said first multiplier output and said second multiplier output, said subtractor forming an output substantially equal to the sum of m previous first and second multiplier output results;
said subtractor coupled to a magnitude generator for producing a magnitude substantially equal to the magnitude of the real and imaginary parts of said accumulator output, thereby generating a preamble detection processor output.