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   Computation of Moments in the Trellis; ; Sorger, Ulrich  in Proceedings of IEEE International Symposium on Information Theory (2008) Decisions on sources with memory transmitted over independent channels can be taken by employing trellis calculations. In this paper, it is shown that for a certain class of functions their moments can be ... [more ▼] Decisions on sources with memory transmitted over independent channels can be taken by employing trellis calculations. In this paper, it is shown that for a certain class of functions their moments can be computed in the trellis, too. This is done by generalizing the forward/backward recursion known from the BCJR algorithm [1]. In analogy to the symbol probabilities, by introducing a constraint at a certain depth in the trellis we obtain symbol moments. These moments are required for an ef?cient implementation of the discriminated belief propagation algorithm in [2], and can furthermore be utilized to compute conditional entropies in the trellis. The moment computation algorithm has the same asymptotic complexity as the BCJR algorithm. It is applicable to any commutative semi-ring, thus also providing a generalization of the Viterbi algorithm [3]. [less ▲] Detailed reference viewed: 142 (3 UL)Doppler-Variant Modeling of the Vocal Tract; Sorger, Ulrich ; in Proceedings of IEEE International Conference on Acoustics, Speech, and Signal Processing (2008) A common technique to deploy linear prediction to non-stationary signals is time segmentation and local analysis. Variations of a process within such a segment cause inaccuracies. In this paper, we model ... [more ▼] A common technique to deploy linear prediction to non-stationary signals is time segmentation and local analysis. Variations of a process within such a segment cause inaccuracies. In this paper, we model the temporal changes of linear prediction coef?cients (LPCs) as a Fourier series. We obtain a compact description of the vocal tract model limited by the predictor order and the maximum Doppler frequency. Filter stability is guaranteed by all-pass ?ltering, deploying the human ear?s insensitivity to absolute phase. The periodicity constraint induced by the Fourier series is counteracted by oversampling in the Doppler domain. With this approach, the number of coef?cients required for the vocal tract modeling is signi?cantly reduced compared to a LPC system with block-wise adaptation while exceeding its prediction gain. As a by-product it is found that the Doppler frequency of the vocal tract is in the order of 10 Hz. A generalization of the algorithm to an auto-regressive moving average model with time-correlated ?lter coef?cients is straight forward. [less ▲] Detailed reference viewed: 141 (1 UL)Doppler-variant Modeling of the Vocal Tract: Stability Considerations; Sorger, Ulrich in Proceedings of 8th ITG Conference on Speech Communication (2008) A common technique to deploy linear prediction to non-stationary signals is time segmentation and local analy-sis. In [1], the temporal changes of linear prediction coef?cients (LPCs) are modeled as a ... [more ▼] A common technique to deploy linear prediction to non-stationary signals is time segmentation and local analy-sis. In [1], the temporal changes of linear prediction coef?cients (LPCs) are modeled as a Fourier series. This allows analysis and optimization of larger speech segments, i.e., virtually global analysis. Possibly resulting non-minimum-phase prediction error polynomials are subject to all-pass ?ltering. We show that introducing the stabilizing ?lter does not deteriorate the overall predictor performance. [less ▲] Detailed reference viewed: 68 (2 UL)Turbo Decoding: Why Stopping Criteria do Work; Sorger, Ulrich in Proceedings of 5th International Symposium on Turbo Codes & Related Topics (2008) The convergence of iterative decoding schemes is considered. The class of dually coupled codes is recalled, being a super class to both Turbo and LDPC codes. It is proven that the output L-values of a ... [more ▼] The convergence of iterative decoding schemes is considered. The class of dually coupled codes is recalled, being a super class to both Turbo and LDPC codes. It is proven that the output L-values of a Turbo decoder cannot grow to in?nity, while those of an LDPC decoder can. Finally, a new decoder parameter is introduced by which the convergence behavior can be controlled. [less ▲] Detailed reference viewed: 151 (1 UL)Computation of distributions and their moments in the trellis; ; Sorger, Ulrich in Advances in Mathematics of Communications (2008), 2(4), 373391 Consider a function whose set of vector arguments with known distribution is described by a trellis. For a certain class of functions, the distribution of the function values can be calculated in the ... [more ▼] Consider a function whose set of vector arguments with known distribution is described by a trellis. For a certain class of functions, the distribution of the function values can be calculated in the trellis. The forward/backward recursion known from the BCJR algorithm [2] is generalized to compute the moments of these distributions. In analogy to the symbol probabilities, by introducing a constraint at a certain depth in the trellis we obtain symbol distributions and symbol moments, respectively. These moments are required for an efficient implementation of the discriminated belief propagation algorithm in [8], and can furthermore be utilized to compute conditional entropies in the trellis. The moment computation algorithm has the same asymptotic complexity as the BCJR algorithm. It is applicable to any commutative semi-ring, thus actually providing a generalization of the Viterbi algorithm [10]. [less ▲] Detailed reference viewed: 141 (4 UL) |
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