Patent ID: 7130339

Claim:
A spread spectrum receiver for receiving and decoding a data frame having one of a plurality of coding rates, the spread spectrum receiver comprising: a rate determination device coupled to receive a data frame coded at one of the plurality of coding rates and to receive symbol data from the receiver, the rate determination device being adapted to determine a probability based at least upon rate-based symbol repetition constraints within the data frame, wherein the probability is an indication of the rate at which the data frame is encoded, wherein the probability comprises a log likelihood ratio based at least upon the rate-based symbol repetition constraints within the data frame and wherein the log likelihood ratio indicative of the rate is the maximum of the group of log likelihood ratios comprising: log ⁢ p ⁡ ( { y i } | r 1 ) p ⁡ ( { y i } | r 1 ) = 0 log ⁢ p ⁡ ( { y i } | r 2 ) p ⁡ ( { y i } | r 1 ) ≈ 4 ⁢ ⁢ log ⁢ ⁢ 2 - 2 ⁢ γ ⁢ ⁢ Δ 1 log ⁢ p ⁡ ( { y i } | r 3 ) p ⁡ ( { y i } | r 1 ) ≈ 6 ⁢ ⁢ log ⁢ ⁢ 2 - 2 ⁢ γ ⁢ ⁢ ( Δ 1 + Δ 2 ) log ⁢ p ⁡ ( { y i } | r 4 ) p ⁡ ( { y i } | r 1 ) ≈ 7 ⁢ ⁢ log ⁢ ⁢ 2 - 2 ⁢ γ ⁢ ⁢ ( Δ 1 + Δ 2 + Δ 3 ) where y i represents a sequence of received symbols, r i represents the coding rates, Δ represents a reliability that pairs of symbols or partial sums have a same sign or opposite signs, and γ represents a ratio of mean and variance of v i a decoder, decoding the received data frame according to the determined frame rate.