| 1. |
- Anderson, John B, et al.
(författare)
-
An optimal circular Viterbi decoder for the bounded distance criterion
- 2002
-
Ingår i: IEEE Transactions on Communications. - 0090-6778. ; 50:11, s. 1736-1742
-
Tidskriftsartikel (refereegranskat)abstract
- We propose a Viterbi-type decoder for tailbiting trellis codes that works by traversing the tailbiting circle somewhat more than once. The traversal is the least possible for any bounded distance Viterbi decoder. Procedures are given that compute this minimum. Unlike previous decoders of the type, the new scheme does not suffer limit cycles or from pseudocodewords. The bit-error rate is compared to that of Bahl-Cocke-Jelinek-Raviv and maximum-likelihood decoding.
|
|
| 2. |
- Anderson, John B
(författare)
-
Coded modulation by outright filtering
- 2002
-
Ingår i: Proceedings 2002 IEEE International Symposium on Information Theory (Cat. No.02CH37371). - 0780375017 ; , s. 471-471
-
Konferensbidrag (refereegranskat)abstract
- We investigate the bandwidth and distance of codes created by ordinary lowpass filtering of a pulse stream. The encoder is thus a convolution, but over the reals. Performance of these codes is compared to the TCM and PRS code families; despite their simplicity, the new codes perform equally well. Since a simple decoder exists, these are attractive codes.
|
|
| 3. |
- Anderson, John B, et al.
(författare)
-
Coded Modulation Systems
- 2003
-
Ingår i: Kluwer Academic / Plenum Publishers. - 0306472791
-
Bok (övrigt vetenskapligt/konstnärligt)abstract
- This textbook studies the 3 main types of coded modulation: trellis-coded modulation (TCM), continuous-phase modulation (CPM) codes, and linear modulation codes like those that arise from filtering and intersymbol interference. In 2 final chapters, code-division multiple-access receivers are discussed. The book begins with a review of coding, modulation and information theory.
|
|
| 4. |
- Anderson, John B, et al.
(författare)
-
New Trellis source codes based on linear congruential recursions
- 2003
-
Ingår i: Proc., 2003 IEEE International Symposium on Information Theory, Yokohama. - 0780377281 ; , s. 170-170
-
Konferensbidrag (refereegranskat)abstract
- We evaluate a new class of rate-distortion codes based on simple linear congruential recursions. Codes are demonstrated for the uniform and Gaussian sources, whose performance exceeds that so far reported in the literature, including that reported for TCQ codes. The results also point to a new correlation relationship that apparently must exist for trellis codes.
|
|
| 5. |
- Anderson, John B
(författare)
-
On the complexity of bounded distance decoding for the AWGN channel
- 2002
-
Ingår i: IEEE Transactions on Information Theory. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9448. ; 48:5, s. 1046-1060
-
Tidskriftsartikel (refereegranskat)abstract
- Earlier work has derived the storage complexity of the bounded distance decoder (BDD) for binary-channel convolutional codes. We extend this work to the Gaussian noise channel and to partial-response codes. We show that the storage requirement similar to(2(1-R) - 1)(-t) paths for rate-R convolutional codes over the binary channel becomes similar to2(2Rt) over the Gaussian channel, where the decoder must correct t errors. Thus, convolutional coding over the Gaussian channel is not only 3 dB more energy efficient, but its decoding is simpler as well. Next, we estimate the path storage for partial-response codes, i.e., real-number convolutional codes, over the Gaussian channel. The growth rate depends primarily on the bandwidth of the code. A new optimization procedure is devised to measure the maximum storage requirement in Gaussian noise for these two code types. An analysis based on difference equations predicts the asymptotic storage growth for partial response codes.
|
|
| 6. |
- Bigler, Christian, 1972-
(författare)
-
Diatoms as indicators of Holocene climate and environmental change in northern Sweden
- 2001
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The objective of the thesis was to explore the potential of diatoms (Bacillariophyceae) as indicators of Holocene climate and environmental change in northern Sweden (Abisko region, 68°21'N, 18°49'E). A modern surface-sediment calibration set including 100 lakes was developed and lake-water pH, sedimentary organic content (assessed by loss-on-ignition) and temperature were identified as most powerful environmental variables explaining the variance within the diatom assemblages. Transfer functions based on unimodal species response models (WA-PLS) were developed for lake-water pH and mean July air temperature (July T), yielding coefficients of determination of 0.77 and 0.70, and prediction errors based on leave-one-out cross-validation of 0.19 pH units and 0.96 °C for lake-water pH and July T, respectively. The transfer functions were validated with monitoring data covering two open-water seasons (lake-water pH) and meteorological records covering the 20th century (July T). The good agreement between diatom-based inferences and measured monitoring data confirmed the prediction ability of the developed transfer functions. Analysing a Holocene sediment core from a lake nearby Abisko (Vuoskkujávri), diatoms infer a linearly decreasing July T trend (1.5 °C) since 6,000 cal. BP, which compares well with inferences based on chironomids and pollen from the same sediment core. The lake-water pH inference shows a pattern of moderate natural acidification (c. 0.5 pH units) since the early Holocene, reaching present-day pH values at c. 5,000 cal. BP. By fitting fossil diatom samples to the modern calibration set by means of residual distance assessment within canonical correspondence analysis (CCA), the early Holocene (between 10,600 and 6,000 cal. BP) was identified as a problematic time-period for diatom-based inferences and, consequently, reconstructions during this period are tentative. Pollen-based inferences also show 'poor' fit between 10,600 and 7,500 cal. BP and chironomids probably provide the most reliable July T reconstruction at Vuoskkujávri, with 'poor' fit only during the initial part of the Holocene (between 10,600 and 10,250 cal. BP). Possible factors confounding diatom-based July T inferences were investigated. Using detrended CCA (DCCA), Holocene sediment sequences from five lakes indicate that during the early Holocene, mainly physical factors such as high minerogenic erosion rates, high temperature and low light availability may have regulated diatom assemblages, favouring Fragilaria species. In all five lakes, diatom assemblages developed in a directional manner, but timing and scale of development differed substantially between lakes. The differences are attributed primarily to the geological properties of the lake catchments (with strong effects on lake-water pH), but other factors such as climatic change, vegetation, hydrologic setting and in-lake processes appear to regulate diatom communities in each lake differently. The influence of long-term natural acidification on diatom assemblages progressively declined during the Holocene with corresponding increase of the influence of climatic factors.
|
|
| 7. |
- Eriksson, Tomas, et al.
(författare)
-
Good trellis source codes at fractional rates
- 2004
-
Ingår i: Proceedings. 2004 IEEE International Symposium on Information Theory. - 0780382803 ; , s. 496-496
-
Konferensbidrag (refereegranskat)abstract
- Two new kinds of fractional-rate trellis source codes based on linear congruential recursions are evaluated. Properties of good codes are given. Square error distortion is similar to or better than competing schemes
|
|
| 8. |
- Eriksson, Tomas, et al.
(författare)
-
Image coding with the MAP criterion
- 2002
-
Ingår i: Proceedings, IEEE 2002 Data Compression Conference. - 0769514774 ; , s. 453-453
-
Konferensbidrag (refereegranskat)abstract
- BCJR based source coding of image residuals is investigated. From a trellis representation of the residual, a joint source-channel coding system is formed. Then the BCJR algorithm is applied to find the MAP encoding. MAP and minimized squared error encoding are compared. The novelty of this work is the use of the BCJR algorithm and the MAP criterion in the source coding procedure. The source encoding system described preserves more features than an MSE based encoder. Also, blocking artifacts are reduced.
|
|
| 9. |
- Eriksson, Tomas, et al.
(författare)
-
MAP criterion image coding using the BCJR algorithm
- 2002
-
Ingår i: Proceedings 2002 IEEE International Symposium on Information Theory (Cat. No.02CH37371). - 0780375017 ; , s. 291-291
-
Konferensbidrag (refereegranskat)abstract
- BCJR based source coding of image residuals is explored. From a trellis representation of the residual, a joint source-channel coding system is formed. The use of the BCJR algorithm is possible due to a procedure which transforms the residuals to a representation with independent identically distributed components having unit variance
|
|
| 10. |
- Eriksson, Tomas, et al.
(författare)
-
MAP criterion trellis source coding for short data sequences
- 2003
-
Ingår i: Proc., IEEE Data Compression Conf., Snowbird, UT. - 0769518966 ; , s. 43-52
-
Konferensbidrag (refereegranskat)abstract
- New trellis constructions for compression of short data sequences are presented. Traditional low rate trellis source coding suffers from having a too small a reproduction alphabet. Governed by alphabet-constrained rate-distortion theory we propose a simple method which for a source coding rate of 1 bit per sample allows 2n reconstruction values for a trellis with 2n states. The proposed method is based on the maximum a posteriori probability criterion distortion measure and it employs tailbiting. Simulation results are compared to TCQ-like methods.
|
|
