1,720,973 research outputs found
A fully-parallel turbo decoding algorithm
Get PDFThis paper proposes a novel alternative to the Log-BCJR algorithm for turbo decoding, yielding significantly improved processing throughput and latency. While the Log-BCJR processes turbo-encoded bits in a serial forwards-backwards manner, the proposed algorithm operates in a fully-parallel manner, processing all bits in both components of the turbo code at the same time. The proposed algorithm is compatible with all turbo codes, including those of the LTE and WiMAX standards. These standardized codes employ odd-even interleavers, facilitating a novel technique for reducing the complexity of the proposed algorithm by 50%. More specifically, odd-even interleavers allow the proposed algorithm to alternate between processing the odd-indexed bits of the first component code at the same time as the even-indexed bits of the second component, and vice-versa. Furthermore, the proposed fully-parallel algorithm is shown to converge to the same error correction performance as the state-of-the-art turbo decoding algorithm. Owing to its significantly increased parallelism, the proposed algorithm facilitates throughputs and latencies that are up to 6.86 times superior to those of the state-of-the art algorithm, when employed for the LTE and WiMAX turbo codes. However, this is achieved at the cost of a moderately increased computational complexity and resource requirement
A unary error correction code for the near-capacity joint source and channel coding of symbol values from an infinite set
Get PDFA 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
Near-capacity joint source and channel coding of symbol values from an infinite source set using Elias Gamma Error correction codes
Get PDFIn this paper we propose a novel low-complexity Joint Source and Channel Code (JSCC), which we refer to as the Elias Gamma Error Correction (EGEC) code. Like the recently-proposed Unary Error Correction (UEC) code, this facilitates the practical near-capacity transmission of symbol values that are randomly selected from a set having an infinite cardinality, such as the set of all positive integers. However, in contrast to the UEC code, our EGEC code is a universal code, facilitating the transmission of symbol values that are randomly selected using any monotonic probability distribution. When the source symbols obey a particular zeta probability distribution, our EGEC scheme is shown to offer a 3.4 dB gain over a UEC benchmarker, when Quaternary Phase Shift Keying (QPSK) modulation is employed for transmission over an uncorrelated narrowband Rayleigh fading channel. In the case of another zeta probability distribution, our EGEC scheme offers a 1.9 dB gain over a Separate Source and Channel Coding (SSCC) benchmarker
On the complexity of unary error correction codes for the near-capacity transmission of symbol values from an infinite set
Get PDFUnary Error Correction (UEC) codes have recently been proposed for the near-capacity Joint Source and Channel Coding (JSCC) of symbol values that are selected from a set having an infinite cardinality. In this paper, we characterize the computational complexity of UEC decoders and use complexity analysis for striking a desirable trade-off between the contradictory requirements of low complexity and near-capacity operation. We investigate a wide range of application scenarios and offer a deep insight into their beneficial parameterizations. In particular, we introduce puncturing for controlling the scheme’s throughput and for facilitating fair comparisons with a Separate Source and Channel Coding (SSCC) benchmarker. The UEC scheme is found to offer almost 1.3 dB gain, when operating within 1.6 dB of the capacity bound. This is achieved without any increase in transmission energy, bandwidth, transmit duration or decoding complexity
Energy-conscious turbo decoder design: a joint signal processing and transmit energy reduction approach
No full textConventionally, the decoding energy consumption Epr of turbo codes were not a significant contribution to the overall energy consumption of a system, since the popular applications of turbo codes were focused on long-range communication systems, such as mobile phone networks or deep space communications. However, with advances in IC fabrication, sophisticated Error-Correcting Codes (ECCs), such as turbo codes, may be embedded into low-cost Wireless Sensor Networks (WSNs). In this paper, it is demonstrated that to design a turbo code for WSNs, the processing energy must be considered as an important factor during the early design stage. However, conventionally, the processing energy has not been considered in the design process, since no technique has been available for estimating it using conventional designs. Hence, we proposed a processing energy estimation framework for minimising the overall energy consumption of a turbo coded scheme at the code design stage
Analysis of voltage- and clock-scaling-induced timing errors in stochastic LDPC decoders
No full textLow Density Parity Check (LDPC) decoders have an inherent capability of correcting the transmission errors that occur, when communicating over a hostile wireless channel. This capability allows LDPC-coded schemes to employ lower transmission energies than uncoded schemes, at the cost of introducing a significant processing energy consumption during LDPC decoding. Traditional energy-reduction techniques, such as voltage and clock scaling can be employed for reducing the LDPC decoder’s energy consumption. However, these techniques may induce timing errors, which can degrade the LDPC decoder’s error correction capability. Our previous work has demonstrated that in contrast to other types of LDPC decoders, stochastic decoders have an inherent tolerance to timing errors, allowing them to maintain a high error correction capability in clock- scaling scenarios. In this paper, we investigate this timing error tolerance in voltage-scaling scenarios, by extending our previous model of timing errors using extensive SPICE simulations. Furthermore, we use these SPICE simulations to characterize the processing energy consumption of stochastic LDPC decoders for the first time. We demonstrate that a modified stochastic LDPC decoder can operate at 0.8 V and a clock period of 915.11 ps, while maintaining the error correction capability of a conventional stochastic decoder operating at 1 V and a clock period of 1019.2 ps, offering a 36.7% reduction in processing energy consumption
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
On the performance and complexity of irregular variable length codes for near-capacity joint source and channel coding
No full textIn this paper we propose a novel Irregular Variable Length Coding (IrVLC) scheme for near-capacity joint source and channel coding. We employ a number of component Variable Length Coding (VLC) codebooks having different coding rates for encoding particular fractions of the input source symbol stream. These fractions may be chosen with the aid of EXtrinsic Information Transfer (EXIT) charts in order to shape the inverted EXIT curve of the IrVLC codec for ensuring that it does not cross the EXIT curve of a serially concatenated channel codec. In this way, an open EXIT chart tunnel may be created even at low SNR values that are close to the capacity bound of the channel. We propose iteratively decoded serially concatenated IrVLC designs amalgamated with Trellis Coded Modulation (TCM). These schemes are shown to be capable of operating within 0.6 dB of the uncorrelated narrowband Rayleigh fading channel's capacity bound using an average interleaver length of 217,500 bits and an effective bandwidth efficiency of 1.56 bit/s/Hz, assuming ideal Nyquist filtering. By contrast, the equivalent-rate regular VLC-based bench-marker schemes were found to be capable of operating at a higher distance of 1.1 dB from the capacity bound, which is nearly twice that of the proposed IrVLC-TCM scheme. Additionally, an Irregular Convolutional Coding (IrCC) based bench-marker was found to be capable of operating at 0.8 dB from the capacity bound, owing to its slightly eroded performance when operating with the considered interleaver lengt
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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