Patent ID: 8687672

Claim:
An apparatus comprising: a despreader comprising: a first storage element including a received signal; a second storage element including an interference-rejecting direct-sequence despreading code; and a computational device configured to apply the interference-rejecting direct-sequence despreading code to the received signal, wherein the despreader is configured to despread a received signal and introduce a notch into a power spectrum of the received signal by applying the interference-rejecting direct-sequence despreading code to the received symbol, wherein the interference-rejecting direct-sequence despreading code is based on a gradient vector of an objective function J(c) having a jth element represented as âˆ‡ â¢ J â¡ ( c _ ) j = âŒŠ âˆ‘ f âˆˆ Î² â¢ âˆ‘ l = 0 - , l â‰ j N - 1 â¢ c l â¢ cos â¡ ( 2 â¢ Ï€ â¢ â¢ fT s â¡ ( l - j ) / N ) âŒ‹ [ âˆ‘ f â¢ âˆ‘ l 1 , l 2 = 0 N - 1 â¢ c l 1 â¢ c l 2 â¢ cos â¡ ( 2 â¢ Ï€ â¢ â¢ fT s â¡ ( l 1 - l 2 ) / N ) ] - [ âˆ‘ f âˆˆ Î² â¢ âˆ‘ l 1 , l 2 = 0 N - 1 â¢ c l 1 â¢ c l 2 â¢ cos â¡ ( 2 â¢ Ï€ â¢ â¢ fT s â¡ ( l 1 - l 2 ) / N ) ] [ âˆ‘ f â¢ âˆ‘ l = 0 , l â‰ j N - 1 â¢ c l â¢ cos â¡ ( 2 â¢ Ï€ â¢ â¢ fT s â¡ ( l - j ) ) / N ] [ âˆ‘ f â¢ âˆ‘ l 1 , l 2 = 0 N - 1 â¢ c l 1 â¢ c l 2 â¢ cos â¡ ( 2 â¢ Ï€ â¢ â¢ fT s â¡ ( l 1 - l 2 ) / N ) ] 2 where c l is an element of a despreading code c, N is a spreading factor, and T s is a symbol interval.