295 research outputs found
Irregular Variable Length Coding
No full textIn this thesis, we introduce Irregular Variable Length Coding (IrVLC) and investigate its applications, characteristics and performance in the context of digital multimedia broadcast telecommunications. During IrVLC encoding, the multimedia signal is represented using a sequence of concatenated binary codewords. These are selected from a codebook, comprising a number of codewords, which, in turn, comprise various numbers of bits. However, during IrVLC encoding, the multimedia signal is decomposed into particular fractions, each of which is represented using a different codebook. This is in contrast to regular Variable Length Coding (VLC), in which the entire multimedia signal is encoded using the same codebook. The application of IrVLCs to joint source and channel coding is investigated in the context of a video transmission scheme. Our novel video codec represents the video signal using tessellations of Variable-Dimension Vector Quantisation (VDVQ) tiles. These are selected from a codebook, comprising a number of tiles having various dimensions. The selected tessellation of VDVQ tiles is signalled using a corresponding sequence of concatenated codewords from a Variable Length Error Correction (VLEC) codebook. This VLEC codebook represents a specific joint source and channel coding case of VLCs, which facilitates both compression and error correction. However, during video encoding, only particular combinations of the VDVQ tiles will perfectly tessellate, owing to their various dimensions. As a result, only particular sub-sets of the VDVQ codebook and, hence, of the VLEC codebook may be employed to convey particular fractions of the video signal. Therefore, our novel video codec can be said to employ IrVLCs. The employment of IrVLCs to facilitate Unequal Error Protection (UEP) is also demonstrated. This may be applied when various fractions of the source signal have different error sensitivities, as is typical in audio, speech, image and video signals, for example. Here, different VLEC codebooks having appropriately selected error correction capabilities may be employed to encode the particular fractions of the source signal. This approach may be expected to yield a higher reconstruction quality than equal protection in cases where the various fractions of the source signal have different error sensitivities. Finally, this thesis investigates the application of IrVLCs to near-capacity operation using EXtrinsic Information Transfer (EXIT) chart analysis. Here, a number of component VLEC codebooks having different inverted EXIT functions are employed to encode particular fractions of the source symbol frame. We show that the composite inverted IrVLC EXIT function may be obtained as a weighted average of the inverted component VLC EXIT functions. Additionally, EXIT chart matching is employed to shape the inverted IrVLC EXIT function to match the EXIT function of a serially concatenated inner channel code, creating a narrow but still open EXIT chart tunnel. In this way, iterative decoding convergence to an infinitesimally low probability of error is facilitated at near-capacity channel SNRs
Iterative decoding convergence and termination of serially concatenated codes
No full textIn this paper we demonstrate that previously proposed serially concatenated codes only facilitate iterative decoding convergence towards points that are near but not at the top-right hand corner of the EXIT chart, which typically results in an error floor. Furthermore, we propose a novel method for approaching the (1,1) point of the EXIT chart, where the Maximum Likelihood (ML) Bit Error Ratio (BER) performance is attained. Our method employs specifically designed termination sequences having a free distance of at least two to terminate an inner recursive code. Additionally, we provide optimal termination sequences for a range of inner code designs. Finally, we demonstrate that our novel approach facilitates useful BER reductions in the challenging application scenario when employing short frame lengths of the order of 100 bits, which are typical in wireless sensor networks, for example
A Scalable Turbo Decoding Algorithm for High-Throughput Network-on-Chip Implementation
No full textMatlab codes relating to the article Al-Dujaily, Ra'ed, Li, An, Maunder, Robert G, Mak, Terrence, Al-Hashimi, Bashir M. and Hanzo, Lajos (2016) A Scalable Turbo Decoding Algorithm for High-Throughput Network-on-Chip Implementation. IEEE Access.</span
From nominal to true a posteriori probabilities: an exact Bayesian theorem based probabilistic data association approach for iterative MIMO detection and decoding
No full textIt was conventionally regarded that the existing probabilistic data association (PDA) algorithms output the estimated symbol-wise a posteriori probabilities (APPs) as soft information. In this paper, however, we demonstrate that these probabilities are not the true APPs in the rigorous mathematicasense, but a type of nominal APPs, which are unsuitable for the classic architecture of iterative detection and decoding (IDD) aided receivers. To circumvent this predicament, we propose an exact Bayesian theorem based logarithmic domain PDA (EB-Log-PDA) method, whose output has similar characteristics to the true APPs, and hence it is readily applicable to the classic IDD architecture of multiple-input multiple-output (MIMO) systems using the general M-ary modulation. Furthermore, we investigate the impact of the PDA algorithms' inner iteration on the design of PDA-aided IDD receivers. We demonstrate that introducing inner iterations into PDAs, which is common practice in PDA-aided uncoded MIMO systems, would actually degrade the IDD receiver's performance, despite significantly increasing the overall computational complexity of the IDD receiver. Finally, we investigate the relationship between the extrinsic log-likelihood ratio (LLRs) of the proposed EB-Log-PDA and of the approximate Bayesian theorem based logarithmic domain PDA (AB-Log-PDA) reported in our previous work. We also show that the IDD scheme employing the EB-Log-PDA without incorporating any inner PDA iterations has an achievable performance close to that of the optimal maximum a posteriori (MAP) detector based IDD receiver, while imposing a significantly lower computational complexity in the scenarios considered
A unary error correction code for the near-capacity joint source and channel coding of symbol values from an infinite set
No full textA novel Joint Source and Channel Code (JSCC) is proposed, which we refer to as the Unary Error Correction (UEC) code. Unlike existing JSCCs, our UEC facilitates the practical encoding of symbol values that are selected from a set having an infinite cardinality. Conventionally, these symbols are conveyed using Separate Source and Channel Codes (SSCCs), but we demonstrate that the residual redundancy that is retained following source coding results in a capacity loss, which is found to have a value of 1.11 dB in a particular practical scenario. By contrast, the proposed UEC code can eliminate this capacity loss, or reduce it to an infinitesimally small value. Furthermore, the UEC code has only a moderate complexity, facilitating its employment in practical low-complexity applications
Survey of women with diminished ovarian reserve (DOR)
No full textWomen with diminished ovarian reserve (DOR) have fewer eggs than would be expected at their age. It is estimated that 10% of women seeking fertility treatment are diagnosed with DOR. This survey explored the health needs of women with DOR, treatment options and experience of treatment including traditional complementary integrative medicine.
To discuss this project, please contact the Author Alison Maunder <[email protected]> ORCID 0000-0003-3564-930
EXIT-chart Aided Joint Source-Coding, Channel-Coding and Modulation Design for Two-Way Relaying
No full textIn this contribution, we have proposed and investigated an attractive Joint Source-coding, Channel coding and Modulation (JSCM) scheme for a two-way relaying system. We commence by quantifying the achievable capacity of the corresponding two-way relay channel, before proposing low-complexity source coding schemes for concatenation with bandwidth-and power-efficient coded modulation schemes. Extrinsic Information Transfer (EXIT) charts is used to investigate the decoding convergence of the joint source and channel decoder as well as for the overall system design. The quality of the decoded source signals is quantified using the Bit-Error Ratio (BER) metric. It is found that the two-way relay based JSCM scheme is capable of attaining a combined coding and relaying gain of 5.7 dB over the conventional non-cooperative JSCM scheme, when communicating over uncorrelated Rayleigh fading channels in an outdoor environment
A low-complexity turbo decoder architecture for energy-efficient wireless sensor networks
No full textTurbo codes have recently been considered for energy-constrained wireless communication applications, since they facilitate a low transmission energy consumption. However, in order to reduce the overall energy consumption, Look-Up- Table-Log-BCJR (LUT-Log-BCJR) architectures having a low processing energy consumption are required. In this paper, we decompose the LUT-Log-BCJR architecture into its most fundamental Add Compare Select (ACS) operations and perform them using a novel low-complexity ACS unit. We demonstrate that our architecture employs an order of magnitude fewer gates than the most recent LUT-Log-BCJR architectures, facilitating a 71% energy consumption reduction. Compared to state-of- the-art Maximum Logarithmic Bahl-Cocke-Jelinek-Raviv (Max- Log-BCJR) implementations, our approach facilitates a 10% reduction in the overall energy consumption at ranges above 58 m
Naturopaths approach to care of women with infertility
No full textMany women use traditional, complementary and integrative medicine to improve their chances of conceiving. While there is evidence of the use of naturopathy by women attempting to conceive, there is no evidence of the way that naturopaths approach and manage their treatment. This study aims to describe how naturopaths manage female infertility, including their approaches, clinical decisions, knowledge sources, and safety considerations in providing naturopathic care.
<p>To discuss this project, please contact the Author Alison Maunder [email protected] ORCID 0000-0003-3564-930
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The Maunder minimum (1645-1715) was indeed a grand minimum: a reassessment of multiple datasets
No full textAims.
Although the time of the Maunder minimum (1645–1715) is widely known as a period of extremely low solar activity, it is still being debated whether solar activity during that period might have been moderate or even higher than the current solar cycle (number 24). We have revisited all existing evidence and datasets, both direct and indirect, to assess the level of solar activity during the Maunder minimum.
Methods.
We discuss the East Asian naked-eye sunspot observations, the telescopic solar observations, the fraction of sunspot active days, the latitudinal extent of sunspot positions, auroral sightings at high latitudes, cosmogenic radionuclide data as well as solar eclipse observations for that period. We also consider peculiar features of the Sun (very strong hemispheric asymmetry of the sunspot location, unusual differential rotation and the lack of the K-corona) that imply a special mode of solar activity during the Maunder minimum.
Results.
The level of solar activity during the Maunder minimum is reassessed on the basis of all available datasets.
Conclusions.
We conclude that solar activity was indeed at an exceptionally low level during the Maunder minimum. Although the exact level is still unclear, it was definitely lower than during the Dalton minimum of around 1800 and significantly below that of the current solar cycle #24. Claims of a moderate-to-high level of solar activity during the Maunder minimum are rejected with a high confidence level
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