Amal Punchihewa

Markov Chain-based analytical model of Opportunistic Routing protocol for wireless sensor networks

In a resource constrained wireless sensor network (WSN), communication tasks can be expensive in terms of power consumption. Thus, when good communication is required, a mechanism that can maximize the chances of a successful transmission of information via wireless network is very desirable. The Opportunistic Routing (OR) protocol [1, 2] has been proposed as an alternative and efficient method for exploiting the spatial and temporal characteristics of a wireless network. In this paper, we propose an analytical framework model based on Markov Chain of OR and M/D/l/K queue to measure its performance in term of end-to-end delay and reliability in wireless sensor network. The performance predicted by the proposed framework is validated through simulation and is in very good agreement. We also discuss the enhancement strategy on OR to achieve better QoS guarantee in term of delay constraint.

Adaptive Simplification of Prediction Modes for H.264 Intra-Picture Coding

In an H.264 coding system, an intra prediction method that uses neighbor pixels within the current picture has been adopted for improving coding efficiency. However the large number of intra prediction modes that must be searched significantly increases the number of operations at the encoder. In this paper, we first investigate the usage distribution of intra prediction modes. Then for the focus region of the picture being coded, all of prediction modes are applied. For the other regions, only the important modes are utilized. Important modes are determined from the usage distribution in the previous coded picture; prediction modes that are utilized more than 10% of the time are considered important. From the simulation results, we can verify that the H.264 encoding time may be reduced by approximately 28% for I-picture only and 7% for I, P-pictures without significant loss in the subjective picture quality.

Distributed Video Coding Based on Compressed Sensing

Compressed Sensing (CS) is a new approach to signal acquisition that can potentially allow us to design very simple video encoders that can be implemented on mobile devices with limited resources. However, previously proposed CS based video codec either require a conventional video codec or a feedback channel for effective operation, thus increasing the complexity. In this paper, a distributed Compressed Video Sensing codec is proposed that only makes use of CS at the encoder. A novel Side Information generation scheme is incorporated in the decoder which exploits the correlation between CS measurements of nearby frames. It is much simpler than other schemes found in the literature and yet effective. Simulation results demonstrate that effective video coding can be achieved using this codec.

Dynamic Time Warping based speech recognition for isolated sinhala words

Currently there is a considerable tendency in developing Automatic Speech Recognition (ASR) systems which are capable of tracking the human speech done in local specific languages and identifying them because the people prefer to work with computers using their native language. In Sri Lanka, a sizable portion of the population is discouraged to use computers simply because of the language barrier and difficulty of using the conventional interfaces. Consequently there is a great demand for a computer interface which enables the communication in Sinhala. This paper presents an approach to identify Sinhala speech based on Dynamic Time Warping (DTW) and the Mel Frequency Cepstral Coefficients (MFCC). The correct recognition was achieved in several phases and each phase is described in detail.

The Development of a Novel Image Quality Metric and a Synthetic Colour Test Image for Objective Quality Assessment of Digital Codecs

This paper proposes a novel image quality metric for colour codecs and a novel colour test image. The degree of colour error (bleeding) due to image compression is evaluated with a special colour test image designed to emphasise colour artefacts. The known reference approach, which is used in this research, offers swift and accurate measurements. The proposed test image replaces the full field static colour bar test signal used in analogue television and video engineering. The proposed test image can be used to evaluate the performance of digital video and television broadcasting facilities. The objective quality measure can also be used in the codec development process and in benchmarking codec performance. The efficacy of the new metric and test image is assessed using a JPEG codec at a range of compression levels.

Exploring the implementation of JPEG compression on FPGA

This paper presents the implementation of the JPEG compression on a field programmable gate array as the data are streamed from the camera. The goal was to minimise the logic resources of the FPGA and the latency at each stage of compression. The modules of these architectures are fully pipelined to enable continuous operation on streamed data. The designed architectures are detailed in this paper and they were described in Handel-C. The compliance of each JPEG module was validated using MATLAB. The resulting JPEG compressor has a latency of 8 rows of image readout plus 154 clock cycles.

Radio Resource Allocation in Multi-User Cooperative Relaying Networks with Resource Block Pairing and Fairness Constraints

In this paper we address the problem of radio resource allocation in cooperative relaying networks. We focus on the resource block and power allocations for the downlink of OFDM-based relaying multi-user network. The resource allocation is investigated for both amplify and forward and decode and forward protocols under the constraints of power, resource block pairing and data rate fairness. To reduce complexity, the optimization problem is solved in two steps. In the first step, resource block pairing and allocation are conducted jointly with equal transmission power for both the base station and the relay. In the second step, transmission power is further optimized to maximize the system throughput. Our analysis is focused on the total achievable system throughput and the achievable individual throughput for each user.

Tutorial on IPTV and its latest developments

This tutorial presents on IPTV technology. Internet Protocol television (IPTV) is a system through which television services are delivered using the architecture and networking methods of the Internet Protocol suite over a packet-switched network infrastructure. IPTV services may be classified into three main groups: live television, time-shifted programming, and video on demand. IPTV can be viewed on a display with a set-top box that accesses channels, subscription services, on demand and other interactive multimedia services over a secure, end-to-end operator managed broadband IP data network with desired QoS to the public with a broadband Internet connection. This tutorial also discusses the IPTV architecture, network technologies, implementation of IPTV, different types of STBs that are being used with in New Zealand, the standards, different business models, hardware and software of IPTV.

Performance analysis of implicit acknowledgement coordination scheme for opportunistic routing in wireless sensor networks

The Opportunistic Routing (OR) protocol provides an alternative and efficient method for exploiting the spatial and temporal characteristics of wireless networks. In addition to prioritisation and selection of relay nodes, another important aspects of the OR protocol is its ability to coordinate between potential relays node. A common approach for coordination is based on a mechanism known as the slotted time and priority-based acknowledgement scheme which relies on the use of control packets. In resource-constrained wireless sensor networks (WSN) with limited amount of energy, an excessive number of transmissions involved in the scheme may not be favourable. In addition, the coordination time overhead for this scheme can also potentially increase the end-to-end delay which can be critical for the WSN applications with delay-constraint requirement. In this paper, we propose a coordination scheme that achieves better energy efficiency with shorter end-to-end delay for WSNs. Through simulation analysis, we show the advantage of the proposed scheme in terms of the average packets end-to-end delay and energy efficiency.

Test pattern based evaluation of ringing and blur in JPEG and JPEG2000 compressed images

In this paper we present main parameters of the ringing artefact and demonstrate their influence on image fidelity of lossy compressed images. We apply variations of these parameters to create a specific set of test images to highlight the ringing artefact and to be able to evaluate the behaviour of ringing along edges. Therefore we introduce a new ringing metric, that analyzes image profiles of compressed images in terms of global luminance shift, blur and ringing.