Back to results
US 7,606,139 B2Granted
Preamble detection using frequency based correlation
AssigneeIntel Corporation
InventorsEyal Bick, Uri Perlmutter, Yuval Lomnitz
Life of this patent
Estimating the term…
Abstract
A method for detecting a preamble location in a multiple preamble OFDM (Orthogonal Frequency Division Multiplexing) system is disclosed. An OFDM signal is generated with a plurality of frames, and each of the frames includes symbols and a predetermined preamble symbol. A maximum FDDC (Frequency Domain Differential Correlator) value is computed for each of the symbols in some of the frames. The preamble location in a frame is determined by summing the maximum FDDC value for each symbol at a same frame location in consecutive frames of the OFDM signal.
Claims14
A method comprising:
- storing, in a memory, instructions for performing the method;
- executing the instructions on a processor;
- according to the instructions being executed;
- receiving a multiple preamble Orthogonal Frequency Division Multiplexing (OFDM) signal comprising a plurality of frames, the frames comprising symbols and a preamble with a plurality of predetermined preamble symbols;
- computing a maximum Frequency Domain Differential Correlator (FDDC) value for each of the symbols in the frames;
- and
- determining a location of the preamble in one of the plurality of frames by summing the maximum FDDC value for each symbol at a same frame location in consecutive frames of the OFDM signal, wherein said determining the location of the preamble further comprises comparing the summed maximum FDDC values for each symbol at a same frame location in consecutive frames with a summed maximum FDDC values for each symbol at an adjacent frame location in consecutive frames, wherein said determining the preamble location further comprises identifying the preamble location of the symbols at the same frame location in consecutive frames as having a summed maximum FDDC value lamer than the summed maximum FDDC value for each symbol in the adjacent frame locations in consecutive frames.
4 more elements
An apparatus comprising:
- a first circuit to compute a maximum Frequency Domain Differential Correlator (FDDC) value for each of a plurality symbols disposed within frames of a multiple preamble Orthogonal Frequency Division Multiplexing (OFDM) signal, each of the frames including a predetermined preamble symbol;
- and
- a second circuit to determine a preamble time location in the frames by summing the maximum FDDC value for each symbol at a same frame location in consecutive frames of the OFDM signal, wherein the second circuit to determine the preamble time location further comprises:
- a comparator circuit to compare the summed maximum FDDC values for each symbol at a same frame location in consecutive frames with a summed maximum FDDC values for each symbol at an adjacent frame location in consecutive frames;
- an identification circuit to identify the preamble time location of the symbols at the same frame location in consecutive frames as having a summed maximum FDDC value lamer than the summed maximum FDDC value for each symbol in the adjacent frame locations in consecutive frames.
2 more elements
A system comprising:
- an antenna to receive a multiple preamble Orthogonal Frequency Division Multiplexing (OFDM) signal including a plurality of frames, said frames including symbols and a predetermined preamble symbol;
- a receiver coupled with the antenna to receive the OFDM signal;
- a translation circuit to filter the OFDM signal;
- a Fast Fourier Transform (FFT) circuit coupled with the translation circuit to generate a discrete FFT signal from the OFDM signal;
- a first circuit coupled with the FFT circuit to compute a maximum Frequency Domain Differential Correlator (FDDC) value for each of the symbols in some of the frames;
- and
- a second circuit to determine a time location of the predetermined preamble symbol in a frame by summing the maximum FDDC value for each symbol at a same frame location in consecutive frames of the OFDM signal, wherein the second circuit that determines the time location of the preamble further comprises:
- a comparator circuit to compare the summed maximum FDDC values for each symbol at a same frame location in consecutive frames with a summed maximum FDDC values for each symbol at an adjacent frame location in consecutive frames;
- and
- an identification circuit to identify the preamble time location of the symbols at the same frame location in consecutive frames as having a summed maximum FDDC value larger than the summed maximum FDDC value for each symbol in the adjacent frame locations in consecutive frames.
7 more elements
A computer readable medium comprising:
- computer executable instructions which, when executed by a processor, causes the processor to:
- i. receive a plurality of frames derived from an Orthogonal Frequency Division Multiplexing (OFDM) signal, the frames comprising symbols and a preamble including a predetermined preamble symbol;
- ii. compute a maximum Frequency Domain Differential Correlator (FDDC) value for each of the symbols in the frames, wherein the FDDC value (FDDC(x, y, z)) for a preamble x having a frequency offset y at a symbol location z within one of the frames is computed from
- FDDC
-
- (
- x
- ,
- y
- ,
- z
- )
- =
- ∑
- k
- =
- 0
- Plen
- -
- 1
-
- FftOut
-
- (
- z
- ,
- Y
- 0
- +
- y
- +
- StepSize
- ×
- k
- )
- ×
- conj
-
- {
- FftOut
-
- (
- z
- ,
- Y
- 0
- +
- y
- +
- StepSize
- ×
- (
- k
- +
- 1
- )
- )
- }
- ×
- DP
-
- (
- x
- ,
- k
- )
- wherein Plen is a length of the predetermined preamble symbol in bits. StepSize is a difference in Fast Fourier Transform (FFT) bins between consecutive bits of the preamble symbol, Y0 is a frequency offset of an FFT bin where a first bit of a symbol is transmitted, and function DP(x, k) includes a bit k of a preamble sequence x in differential form having an output selected from a group consisting of −1 or +1;
- and
- iii. determine a location of the preamble in one of the plurality of frames by summing the maximum FDDC value for each symbol at a same frame location in consecutive frames of the OFDM signal.
66 more elements
Dependencies are inferred from the claim text.