Patent ID: 7394875

Claim:
A method of radio frequency message preamble detection comprising the steps of: receiving in-phase and quadrature input samples of a radio frequency message; coherently accumulating a first predetermined number of said in-phase and quadrature input samples; forming an absolute value of the coherently accumulated input samples; non-coherently combining a second predetermined number of said absolute values of said coherently accumulated input samples; selecting a preamble detection threshold τ according to the equation: τ = 1 16 ⁢ N B ⁢ ∑ j = 1 N B ⁢ ∑ i = 1 16 ⁢ C N ^ nca , W ^ ⁡ ( Z n , nca ) j , i ξ i , W , N nca where: N B is a number of preamble detection attempts; C {circumflex over (N)} nca ,Ŵ is a fixed constant depending on {circumflex over (N)} nca and Ŵ; {circumflex over (N)} nca is an equivalent number of coherent packets; Ŵ is an equivalent search window; (Z n,nca ) j,i is a non-coherently combined values; and ξ i,W,N nca is an expected value of (Z n,nca ) j,i ; and detecting a preamble in the radio frequency message employing said selected preamble detection threshold τ.