Patent ID: 7492839

Claim:
A method of estimating at least one transmitted MSK symbol by a Viterbi equalizer at a wireless receiver, the transmitted MSK symbols being alternately real and imaginary, the Viterbi states possible at the stages corresponding to real symbols constituting a first set of states, the Viterbi states possible at the stages corresponding to imaginary symbols constituting a second set of states, the method comprising the steps of: a. obtaining only the imaginary parts of the autocorrelation values of the channel impulse response corresponding to a time delay of odd number of stages; b. obtaining only the real parts of the autocorrelation values of the channel impulse response corresponding to a time delay of even number of stages; c. pre-computing an estimated ISI term for all Viterbi states using the real and imaginary parts obtained at steps (a) and (b); d. advancing the Viterbi trellis by a stage comprising the steps of: i. if the transmitted MSK symbol corresponding to the stage is real then performing steps of: 1. pre-processing the received symbol at the stage to obtain a real component representing the received symbol corresponding to the stage; and 2. determining the surviving path for only the first set of states at the stage, using the estimated ISI terms corresponding to the first set of states, the real component representing the received symbol corresponding to the stage and the path metrics of the surviving paths at the previous stage; else performing the steps of: 1. pre-processing the received symbol at the stage to obtain an imaginary component representing the received symbol corresponding to the stage; and 2. determining the surviving path for only the second set of states at the stage, using the estimated ISI terms corresponding to the second set of states, the imaginary component representing the received symbol corresponding to the stage and the path metrics of the surviving paths at the previous stage; ii. determining whether at least one transmitted MSK symbol can be estimated at the stage; and iii. estimating at least one transmitted MSK symbol using the surviving paths at the stage if it is determined that at least one transmitted MSK symbol can be estimated at the stage.