Patent ID: 8223897

Claim:
A method for use in a communications receiver that is adapted to process a received communication signal, wherein the received communication signal provides a channel-distorted version of a communication signal that has been encoded in accordance with at least an in-phase component signal (x I (t) signal), wherein x I ⁡ ( t ) = ∑ j = 1 L + 1 ⁢ p Q ( k - j + 1 ) ⁢ Q ( k - j + 2 ) ⁡ ( t - kT + jT - T ) , for at least two discrete sample times, t, in each of a plurality of symbol intervals, including a k th symbol interval (kT≦t<(k+1)T), where L is a positive integer and L≦7, T is a symbol interval duration, k and j are integer counting variables, p Q (k−j+1), Q (k−j+2) (t)=m Q (k−j+1), Q (k−j+2) (t) h(t) is a compact pulse shape whose length is no longer than (L+1)T, h(t) is a finite impulse response filter whose impulse response has a length no longer than LT, m Q (k−j+1), Q (k−j+2) (t) is a state transition signal of a first real-valued baseband message signal (m I (t) signal) from a state Q(k−j+1) to a state Q(k−j+2), the m 1 (t) signal follows a first trajectory through an amplitude trellis in accordance with a binary data sequence that has been trellis encoded therein, and the first trajectory passes through a first particular sequence of trellis states, Q 0 , Q 1 , . . . Q k , at discrete times, kT, the method comprising: receiving the received communication signal from a channel, extracting at least an in-phase baseband component signal (Z I (t) signal) therefrom, lowpass filtering the Z I (t) signal, and oversampling the output of the lowpass filtering with an analog-to-digital converter (ADC) at an oversampling rate F s =OS/T, where 2≦OS≦8 is an oversampling factor, and the ADC provides OS voltage samples for the k th symbol interval; computing, for the k th symbol interval, using a k th set of the oversampled data samples that correspond to samples of the Z I (t) signal sampled during the k th symbol interval, a k th set of branch metrics, wherein each branch metric provides a measure of a respective distance between the k th set of the oversampled data samples and a respective one of a set of template state transition signals (x Template (t, S k , S k+1 ) signals) representative of each possible state transition from each possible first state S k =(Q k−1 , Q k−2 , . . . Q k−L ), to each second state S k+1 (Q k , Q k−1 , . . . Q k−L+1 ) for each next permissible state Q k that can be transitioned to from the state Q k−1 ; and implementing a trellis decoding algorithm using at least the k th set of branch metrics to determine a trellis decoded sequence and deriving an estimate of the binary data sequence based upon the trellis decoded sequence.