Our thoughts are fleeting and immaterial, this mysterious stuff that’s locked away in our heads. Painstakingly, we collect our thoughts and transform them into words and documents. This transformation from thought into action is time-consuming and expensive. Thinking is a decidedly “offline” and manual process. What would happen if you could instead make your thoughts tangible and concrete? What if you could collect your thoughts as readily as you can search online? What if your thoughts could self-organize around your tasks while you’re off doing other things? Thought networking is the idea that’s driving our efforts at Primal Fusion to explore these big questions. In this demonstration Primal Fusion will show the thought networking platform and its applications. This will be an interactive demonstration, where users are invited to try out their own thoughts and actions on the platform. A poster will provide a high-level technical description of the semantic platform components.

Cross-entropy (CE) in information theory is introduced as a method to analyse iterative decoding. The maximum a posteriori probability decoding algorithm is shown to minimise the CE between the a priori and the extrinsic information under given code constraints. The error-correcting ability of the constituent decoders is evaluated in terms of CE. Analysis on turbo decoding is carried out based on theoretical findings from several aspects, including analysis of convergence rate, derivation of the E-b/N-0 threshold for convergence, evaluation of error performance in the 'error-floor' region and a design example of asymmetric turbo codes. Compared with conventional methods, the new technique provides stricter prediction on the E-b/N-0 threshold for convergence and quicker error performance evaluation. An asymmetric turbo code designed with the guidance of our new method exhibits more than 0.1 dB of gain over that guided by classical bounding techniques in both high and low bit error rate regions. Particularly, since no information on the source is required and the density of the a priori/extrinsic information can be arbitrary, the new technique is valuable for both offline design and online evaluation in practical systems.

In this paper, a new approximation of the check node rule algorithm is proposed for updating the check nodes messages in LDPC decoding. The new technique evaluates the check node min-sum magnitude algorithm using the Taylor series and results in reduced computational complexity and hardware implementation. The architecture of a check node processing unit, implementing the new alternative approximation of the check node, is also presented. The proposed method can achieve the same BER performance with a reduction of ~20% hardware complexity in the LDPE decoder. The simulation results obtained shows that the packet error rate performance of 10-7, which is the DVB-S2 requirement for MPEG packets transmitted, can be achieved with this new method.

Novel soft-input soft-output (SISO) decoding algorithms suitable for turbo codes are proposed with good compromise between complexity and bit error rate (BER) performance. The algorithms are based on the application of the max/max* (i.e. Jacobian logarithm) operations at different levels when computing the decoder soft-output value. It is observed that some decoding schemes from the authors' previously published work fall into the family of methods described here. The effect is to provide a range of possibilities allowing system designers to make their own choices for turbo code BER performance against complexity.

The authors deal with the sum-product algorithm (SPA) based on the hyperbolic tangent (tanh) rule when it is applied for decoding low-density parity-check (LDPC) codes. Motivated by the finding that, because of the large number of multiplications required by the algorithm, an overflow in the decoder may occur, two novel modifications of the tanh function (and its inverse) are proposed. By means of computer simulations, both methods are evaluated using random-based LDPC codes with binary phase shift keying (BPSK) signals transmitted over the additive white Gaussian noise (AWGN) channel. It is shown that the proposed modifications improve the bit error rate (BER) performance up to 1 dB with respect to the conventional SPA. These results have also shown that the error floor is removed at BER lower than 10 -6 . Furthermore, two novel approximations are presented to reduce the computational complexity of the tanh function (and its inverse), based on either a piecewise linear function or a quantisation table. It is shown that the proposed approximations can slightly improve the BER performance (up to 0.13 dB) in the former case, whereas small BER performance degradation is observed (<0.25 dB) in the latter case. In both cases, however, the decoding complexity is reduced significantly

The constant log-MAP decoding algorithm suitable for duo-binary turbo codes. Motivated by an existing algorithm approach, an efficient algorithm is presented which is superior in terms of frame/bit error rate performance and has approximately the same computational complexity. Compared with log-MAP decoding, the proposed algorithm has negligible performance degradation, exactly as for binary turbo codes.

A novel approach for improving the performance of the soft-output Viterbi algorithm (SOVA) when applied to turbo decoding is proposed. Based upon a modified two-step scaling factor approach for the decoder's extrinsic information, it is shown that the proposed technique reduces significantly the error floor present in previous SOVA-based turbo decoding techniques. Various computer simulated bit error rate (BER) performance evaluation results for binary phase shift keying (BPSK) signals transmitted over the additive white Gaussian noise (AWGN) and flat Rician fading channels clearly indicate that for large interleaver sizes and high numbers of decoding iterations no error floor is observed for BERs as low as 10-6

The use of cross-entropy to analyse the convergence behaviour of a turbo decoder is proposed. Based on the new method, E-b/N-0 thresholds are predicted and compared with those predicted by existing techniques. Simulation results show that the new technique is effective and advantageous in practical applications.

This paper describes the performance of sequential decoding as applied to a subcode of Reed Solomon (RS) codes. As an efficient soft decision decoding technique sequential decoding using a modified Fano algorithm has been attempted. An encoding technique for generating subcode is designed to enhance the performance and the computational efficiency of the decoder. The performance has been estimated on an AWGN channel. Sequential decoding performance of the subcode of (15,11) RS code could produce a comparable performance as well as computational efficiency to Viterbi decoding of rate 1/2 convolutional code with constraint length 7.

We propose a modified hyperbolic tangent (tanh) function that is used in the sum-product algorithm (SPA). This is done in order to approximate the infinite argument of the tanh function, when decoding low-density parity-check (LDPC) codes. As shown by computer simulation results, the proposed modification has a significant impact on the error floor reduction of the code and to the coding gain improvement with respect to the SPA with no modification. Computer simulation results with approximations using both piecewise linear function and coarse quantization are also presented.

Digital watermarking is the art of hiding information in digital contents such as images, audio clips, and videos. We can take advantage of this technique by adding author information as well as buying information for a digital purchase. In this paper we propose a protocol for secure anonymous digital purchase to deter buyers from executing illegal redistribution of digital contents. We propose a protocol to allow merchants to obtain a proof of treachery from dishonest buyers

This paper describes and evaluates implementations of the Dorsch algorithm for RS codes. This algorithm has previously been applied only to binary codes and requires adaptation for application to multilevel codes. The Dorsch algorithm has also been applied to some Reed Solomon codes which can also be formulated as binary codes in order to compare the two approaches. On the AWGN channel, the binary approach shows better performance for the same complexity than the multilevel approach and it appears that the Dorsch algorithm is not well suited to multilevel codes.

New soft-input soft-output (SISO) decoding algorithms are proposed that combine both the max operation of the Max-Log-MAP algorithm and the max* operation (Jacobian logarithm) of the Log-MAP algorithm. This combination is restricted not only to the reliability estimation, as in one previous publication, but is also expanded to include the case of the forward and backward metrics computation in the turbo decoding process.

In this paper, a dual level access scheme is proposed to provide two levels of access to the broadcast data; one to video signals protected for authorized users, another to extra information e.g. advertisements provided for the remaining users in the network. In the scheme, video signals in MPEG format are considered. The video contents are protected from unauthorized viewing by encrypting the DC coefficients of the luminance component in I-frames, which are extracted from the MPEG bit-stream. An improved direct sequence spread spectrum technique is used to add extra information to non-zero AC coefficients, extracted from the same MPEG bit-stream. The resultant MPEG bit-stream still occupies the same existing bandwidth allocated for a broadcast channel. At the receiver, the extra information is recovered and subtracted from the altered AC coefficients. The result is then combined with the decrypted DC coefficients to restore the original MPEG bit-stream. The experimental results show that less than 2.9% of the size of MPEG bit-stream was required to be encrypted in order to efficiently reduce its commercial value. Also, on average, with a 1.125 Mbps MPEG bit-stream, an amount of extra information up to 1.4kbps could be successfully transmitted, while the video quality (PSNR) was unnoticeably degraded by 2.81 dB.

This paper describes a mechanism for secure online user authentication and document signature with a cryptogram Java card in an insecure environment. The mechanism requires possession of both the card and some secrets, known as Concepts, to authenticate the user. The concepts are represented in image form. A method of secure document signing with the concept-based images is also outlined. Possible security weakness and attack methods are analysed in the paper. An implementation of the mechanism is also described in brief. It is anticipated that the mechanism would provide security and non-repudiation for e-Commerce customers in an insecure operating

We propose several bandwidth efficient HARQ schemes based on multilevel coded modulation in this paper. These schemes combine the bandwidth efficiency of coded modulation with power efficiency of forward error control to provide a high efficient transmission. Simulations are carried out over the wireless channels. Both throughput and reliability are found to be improved by employing the HARQ schemes based on the multilevel coded modulation instead of the conventional trellis coded modulation. Simulation and performance analysis on code combining in multilevel HARQ is also presented. Code combining in the different multilevel HARQ schemes is found to influence the multistage decoding differently. Suggestion on scheme choosing for various requirements is presented at the end.

A new method of video scene content characteristic detection is proposed. This method can be applied in conjunction with digital watermarking schemes in order to improve the transparency. In addition, new methods of video watermarking are also proposed. Three related original aspects are reported. First, the authors' previous robust image watermarking methods, which consider the block texture are extended into video. In the detection process, watermark extraction with or without the original frame is provided. Secondly, a method is proposed to improve imperceptibility by reducing the flickering effect. Finally, a method is introduced to detect video scene characteristics in order to suit the particular embedding scheme. By doing so, the embedding method can be chosen adaptively in accordance with the video scene. The subjective tests illustrate an imperceptibility improvement and experiments with various attacks show the watermarking robustness.

The iterative soft output Viterbi algorithm (SOVA) is a sub-optimum algorithm when it is used to decode turbo codes. By normalizing its extrinsic information we get a performance improvement compared to the standard SOVA. In particular, if the extrinsic information is increased in the last decoding iteration, an additional coding gain improvement is noticed. For example, this is 0.25 dB for a frame length of 1000 bits in the additive white Gaussian noise (AWGN) channel as well as in an uncorrelated Rician fading channel at bit error rate (BER) of 10/sup -6/. Also, this normalized SOVA is only about 0.25 dB worse than a turbo decoder using the log-MAP algorithm, both in the AWGN channel and in an uncorrelated Rayleigh fading channel at BER of around 10/sup -6/. Furthermore, with an 8-state component code, a frame length of 500 bits performs 0.125 dB better than a 16-state bidirectional (bi)-SOVA turbo decoder at BER of 10/sup -5/ in the AWGN channel.

It is known that the performance of a SOVA (soft output Viterbi algorithm) turbo decoder can be improved, as the extrinsic information that is produced at its output is over-optimistic. A new parameter associated with the branch metrics calculation in the standard Viterbi algorithm is introduced that affects the turbo code performance. Different parameter values show a simulation improvement in the AWGN channel as well as in an uncorrelated Rayleigh fading channel. By choosing the best value of this parameter, a coding gain improvement of 0.25 dB at BER of 10(-5) is achieved compared to existing schemes.