Jerker Björkqvist

Expanding Window Fountain coded scalable video in broadcasting

The Expanding Window Fountain (EWF) codes are a new class of rateless codes, providing Unequal Error Protection (UEP). These codes are especially suitable for Scalable Video Coding (SVC) having unequally important data layers. In this paper, we show that EWF codes are usable for transmitting scalable video in mobile channels. We characterize the channel by field measurements in a DVB-H network. We tune the EWF code parameters to achieve real-time transmissions of SVC video. Moreover, we use a code symbol header for the EWF codes, which is also used in the IPDC over DVB-H standard, such that the codes can be efficiently used without the need for excessive packet header redundancy. We show that if some latency in the video is acceptable, then EWF codes can be used for real-time transmissions.

System architecture and interactivity model for mobile TV applications

Interactive services and applications for Mobile TV are considered to be one of the promising concepts that offer new opportunities for mass media, mobile and broadcast industry. This article explores the concepts of interactivity, interactive applications and system architecture aspects in interactive mobile TV. It investigates demands and constraints for the software platform of mobile TV, suggests possible solutions for them and proposes prototype software architecture for mobile TV based on this investigation and proposed solutions. Interactivity model for the interactive mobile TV applications is proposed that facilitate the evaluation of these applications to prospect the terminal and server sides requirements. This model has significance because it specifies the overall image of mobile interactive system that will be helpful for defining common application framework based on the users perception.

Convergence of Hardware and Software in Platforms for Radio Technologies

Technologies used in wireless broadband systems are typically data-driven and require a very high processing speed. In this article we discuss technological issues that could be utilized in designing converged hardware/software platforms for future radio technologies in both civilian and military communications. We focus on current and future radio applications as well as hardware and software technologies, and discuss issues in integrating these technologies into converged single-processor radio platforms that can switch dynamically from one radio standard to another with intelligent application software, and that can also be taken advantage of as parts of complex systems and networks-on-chips

Distributed Spectrum Sensing Using Low Cost Hardware

A distributed spectrum sensing network is prototyped using off the shelf hardware consisting of Raspberry Pi mini-computers and DVB-T receivers with software defined radio capabilities. Using the prototype network, coordinated, distributed wideband spectrum sensing is performed in a geographical area. The spectrum sensing data from the nodes is collected in a database. Well established low-complexity algorithms for distributed spectrum sensing are applied, and the results are compared against a professional spectrum sensing system. We show that with this simple low-cost setup, the decisions made on the availability of spectrum using the distributed sensing data correspond well with the decisions made on the reference data.

Sparse-graph AL-FEC solutions for IP datacasting in DVB-H

DVB-H is an IP-based wireless broadcast technology in which users are offered, among other services, the IP datacast (IPDC) service for downloading broadcasted files to their mobile terminals. In this paper, we explore different AL-FEC solutions providing simple and efficient file delivery. Our investigation is focused on recently popular classes and design methods of sparse-graph codes decoded using the iterative decoding algorithm. We provide performance comparisons of various possible AL-FEC schemes in a simulated DVB-H environment. The benefits and drawbacks of different sparse-graph AL-FEC solutions are discussed.

Designing Tornado Codes as Hyper Codes for Improved Error Correcting Performance

Digital services are increasingly being delivered to user terminals over wireless multicast networks. When the target service requires uncorrupted data delivery, there is an increasing need for developing techniques for reliable content delivery. In multicast networks, the typical way of providing reliable content delivery is to apply forward error correcting techniques (FEC). In this paper, we introduce a modification to the Tornado code, where we combine the structures of Tornado codes and Hyper codes. Standard Tornado codes have the drawback that they are dependent on the error distribution on the data path. By combining the Tornado code with a Hyper code, we decrease the probability of the Tornado decoder failing due to inopportune error distribution in the source data. We demonstrate, based on a simulated transmission channel, that the error correcting performance is improved, at the cost of slightly longer decoding times, by using a combination of Hyper codes and Tornado codes, compared to the standard Tornado codes.

Receiver Coding Gain in DVB-H Terminals Using Application Layer FEC Codes

DVB-H is targeted for broadcasting digital content to handheld devices. The content is generally divided into streaming media or file downloading. In file downloading scenarios there is typically a requirement on a zero error ratio which can be met using either a data carousel or additional forward error correction codes. Both methods however induce a higher energy consumption in the receiver. This paper analyses the energy consumption needed for two different forward error correction codes based on emulator results for typical hardware in a handheld device. The energy used for error correction is compared to the energy used when receiving more carousel rounds in order to meet the zero error ratio requirement. This difference is denoted as receiver coding gain. Additionally, error correction also leads to a reduction in the reception time.

Improving Object Delivery Using Application Layer Tornado Codes in DVB-H Systems

This paper analyzes the effects of applying application layer forward error correcting (FEC) coding to a wireless filecasting system, here represented by DVB-H. We show the benefit of moving error correcting coding to higher levels in the data transmission protocol stack. The data is delivered using a data carousel and the FEC code utilized is a hyper-Tornado code for which the main characteristics are long codewords and near linear complexity. Because the hyper-Tornado code provides internal data interleaving and supports long code lengths, we can observe a significantly decreased number of mean data carousel iterations before an error-free carousel object is received compared to the basic DVB-H system. This reduction is for the user observed as decreased download-time, but also provides energy saving in the receiver due to shorter receiver on-times

Detecting design flaws in control systems using optimisation methods

Complicated control systems are used in many safety-critical applications, such as in cars and airplanes. Due to the nature of these systems, verification can be very difficult to do analytically or algorithmically. The only feasible analysis and verification method is often simulation. The generation of good test cases that can expose flaws in the controller design is therefore of great importance. In this paper we investigate the use of optimisation methods for finding such test cases automatically. For this purpose we give a language to express assertions in control systems, as well as a translation of the assertions to a form suitable for optimisation. We also discuss different ways to generate the input signals for the systems to maximise performance of the optimisation. To evaluate if optimisation is a feasible approach, we provide a case study demonstrating that optimisation methods are beneficial for investigating properties of control system designs.

Power Balancing of Internal Combustion Engines – A Time and Frequency Domain Analysis

Abstract Power balancing of internal combustion engines is studied in time and frequency domains. Speed measurements at the flywheel and the load side are used to estimated the torque applied to the flywheel. The power contributions during the cylinder-wise work phases are estimated by integrating the reconstructed torque, and a controller which adjusts the fuel injections to reduce power unbalances is applied. A convergent power balancing algorithm is presented for multi-cylinder engines, where the work phases of the individual cylinders may overlap. This time-domain method is verified against previous frequency-domain approaches. The analysis shows that for engines with flexible crankshafts, the time-domain method performs in general differently from frequency-domain cylinder balancing approaches. The feasibility of the power balancing algorithm is investigated by simulations and full-scale tests on a large diesel power plant engine.