On the structure and performance of a novel blind source separation based carrier phase synchronization error compensator

In this paper we carry out a detailed performance analysis of a novel blind-source-seperation (BSS) based DSP algorithm that tackles the carrier phase synchronization error problem. The results indicate that the mismatch can be effectively compensated during the normal operation as well as in the rapidly changing environments. Since the compensation is carried out before any modulation specific processing, the proposed method works with all standard modulation formats and lends itself to efficient real-time custom integrated hardware or software implementations.

The modified Max-Log-MAP turbo decoding algorithm by extrinsic information scaling for wireless applications

The iterative nature of turbo-decoding algorithms increases their complexity compare to conventional FEC decoding algorithms. Two iterative decoding algorithms, Soft-Output-Viterbi Algorithm (SOVA) and Maximum A posteriori Probability (MAP) Algorithm require complex decoding operations over several iteration cycles. So, for real-time implementation of turbo codes, reducing the decoder complexity while preserving bit-error-rate (BER) performance is an important design consideration. In this chapter, a modification to the Max-Log-MAP algorithm is presented. This modification is to scale the extrinsic information exchange between the constituent decoders. The remainder of this chapter is organized as follows: An overview of the turbo encoding and decoding processes, the MAP algorithm and its simplified versions the Log-MAP and Max-Log-MAP algorithms are presented in section 1. The extrinsic information scaling is introduced, simulation results are presented, and the performance of different methods to choose the best scaling factor is discussed in Section 2. Section 3 discusses trends and applications of turbo coding from the perspective of wireless applications.

Children's television: the soft underbelly of public service broadcasting

The provision of children's content should be a key constituent of the public service brand, but has often been viewed as a programme category at risk. Certainly in many countries children's television has moved from the 'scarcity' associated with terrestrial provision, to the 'plenty' of digital (see Ellis 2000). However in spite of a range of dedicated public service children's channels in Europe (CBeebies, Kika, Z@ppelin), domestically produced children's television in Europe is notoriously under-resourced if not marginalised. There is a pronounced reliance on imports (particularly on commercial television) notwithstanding the launch by US-owned multinationals (Disney, Nickelodeon, Cartoon Network) of localised versions of their children's television channels in many European countries. Within the broader context of global developments in children's media, this paper starts by outlining the recent and rapid crisis in British children's television and the factors that caused it. This was a crisis, which caught broadcasters and producers by surprise in the middle of 2006, but reflects many of the challenges faced by the children's television sector in other countries. It clearly demonstrated how a combination of the lack of regulatory protection, a change in commercial priorities among broadcasters, advertising restrictions, budgetary pressures and the competitive environment at home and abroad all combined to reinforce the trend towards a contraction of domestic production. The crisis also served to underline the dominance of the BBC - both as a representative of public service principles, and as the dominant producer and commissioner in the market. With the reasons underpinning the crisis explained, the paper will then analyse how the children's television community responded to the crisis and with what effect. Based on interviews, contemporary accounts and documentary evidence the paper will chart the converging and diverging views of broadcasters, producers, regulatory authority Ofcom, and a range of advocacy groups which represent children's interests and the industry. What arguments were elaborated in favour of protecting children's television as an integral part of the public service media brand? Can lessons be learned about how best to ensure the origination of children's media within a public service environment? Can developments in the UK be used to provide insight into how children's media might develop further?

Increasing the speed of parallel decoding of turbo codes

Turbo codes experience a significant decoding delay because of the iterative nature of the decoding algorithms, the high number of metric computations and the complexity added by the (de)interleaver. The extrinsic information is exchanged sequentially between two Soft-Input Soft-Output (SISO) decoders. Instead of this sequential process, a received frame can be divided into smaller windows to be processed in parallel. In this paper, a novel parallel processing methodology is proposed based on the previous parallel decoding techniques. A novel Contention-Free (CF) interleaver is proposed as part of the decoding architecture which allows using extrinsic Log-Likelihood Ratios (LLRs) immediately as a-priori LLRs to start the second half of the iterative turbo decoding. The simulation case studies performed in this paper show that our parallel decoding method can provide %80 time saving compared to the standard decoding and %30 time saving compared to the previous parallel decoding methods at the expense of 0.3 dB Bit Error Rate (BER) performance degradation.

The Impact of Uncertainty Shocks under Measurement Error: A Proxy SVAR approach

A growing literature considers the impact of uncertainty using SVAR models that include proxies for uncertainty shocks as endogenous variables. In this paper we consider the impact of measurement error in these proxies on the estimated impulse responses. We show via a Monte-Carlo experiment that measurement error can result in attenuation bias in impulse responses. In contrast, the proxy SVAR that uses the uncertainty shock proxy as an instrument does not su¤er from this bias. Applying this latter method to the Bloom (2009) data-set results in impulse responses to uncertainty shocks that are larger in magnitude and more persistent than those obtained from a recursive SVAR.