Patent ID: 7529323

Claim:
A receiver for demodulating a received signal generated by a modulator providing quaternary precoding and quaternary continuous phase modulation of a binary bit sequence, the receiver for providing an estimate of the bit sequence, the receiver comprises a demodulator comprising, a bank of filters for providing a matched filter response of pulse-amplitude modulation components of the received signal, the received signal being a quaternary continuous phase modulation signal, a sampler for sampling the matched filter response for providing samples, and a generator for generating log-likelihood-ratio-based soft bit metrics ρ 1 and ρ 2 from the samples using maximum likelihood sequence estimation Viterbi algorithm forming the estimate of the bit sequence, the received signal being a waveform indicating a sequence of quaternary symbols with each pair of bits in the bit sequence forming a quaternary symbol, wherein, the generator outputs ρ 1 and ρ 2 are respectively, ρ 1 , k = ∫ 0 NT ⁢ r ⁡ ( t ) ⁢ s ⁡ ( t , u _ ( i 1 ) , u k = 1 ⁢ a 2 , k ( i 1 ) ) ⁢ ⁢ ⅆ t - ∫ 0 NT ⁢ r ⁡ ( t ) ⁢ s ⁡ ( t , u _ ( j 1 ) , u k = 0 ⁢ a 2 , k ( j 1 ) ) ⁢ ⁢ ⅆ t and ρ 2 , k = ∫ 0 NT ⁢ r ⁡ ( t ) ⁢ s ⁡ ( t , u _ ( i 2 ) , u k = a 1 , k ( i 2 ) ⁢ ⁢ 1 ) ⁢ ⅆ t - ∫ 0 NT ⁢ r ⁡ ( t ) ⁢ s ⁡ ( t , u _ ( j 2 ) , u k = a 1 , k ( j 2 ) ⁢ 0 ) ⁢ ⁢ ⅆ t where u (i) for i∈{i 1 , i 2 , j 1 , j 2 } are quaternary data sequences achieving the respective maximums and {a (i) 1,k , a (i) 2,k } are bit values associated with the quaternary data sequences for an index k, NT being an observation window where N is a number of symbols and T is a symbol time, r(t) being the received signal, S( ) being a waveform corresponding to a path in a constraint trellis.