Carl James Debono

Cross-Layer Design for Optimized Region of Interest of Ultrasound Video Data Over Mobile WiMAX

The application of advanced error concealment techniques applied as a postprocess to conceal lost video information in error-prone channels, such as the wireless channel, demands additional processing at the receiver. This increases the delivery delay and needs more computational power. However, in general, only a small region within medical video is of interest to the physician and thus if only this area is considered, the number of computations can be curtailed. In this paper, we present a technique whereby the region of interest specified by the physician is used to delimit the area where the more complex concealment techniques are applied. A cross-layer design approach in mobile worldwide interoperability for microwave access wireless communication environment is adopted in this paper to provide an optimized quality of experience in the region that matters most to the mobile physician while relaxing the requirements in the background, ensuring real-time delivery. Results show that a diagnostically acceptable peak signal-to-noise-ratio of about 36 dB can still be achieved within reasonable decoding time.

Maximizing the Lifetime of Wireless Sensor Networks through Intelligent Clustering and Data Reduction Techniques

Wireless sensor networks are generally deployed in remote areas where no infrastructure is available. This imposes the use of battery operated devices which seriously limits the lifetime of the network. In this paper we present a cluster-based routing algorithm which is based on Fuzzy-ART neural networks to maximize the life span of such networks. Results show that the energy saving obtained improves the network lifetime by 79.6%, 17.1% and 22.4% (in terms of First Node Dies) when compared to LEACH, a centralised version of LEACH and a self-organizing map (SOM) neural network-based clustering algorithm respectively. Furthermore, this paper explores the use of a base station centric predictive filtering algorithm to reduce the amount of transmitted data leading to a further increase in network lifetime.

Increasing wireless sensor network lifetime through the application of SOM neural networks

Wireless sensor networks are an emerging technology that have garnered significant research attention due to their extensive ability to monitor the physical world and their applicability to an extensive range of applications. These networks are generally battery powered making the lifetime of the network a major concern. This energy consumption problem can be mitigated to some extent through the use of energy-aware cluster-based routing algorithms. This work presents a novel cluster-based routing algorithm based on self-organizing map (SOM) neural networks. This solution optimizes the network in clusters in an attempt to balance the energy and reduce the transmission power required by the nodes. Results show that through the application of this optimization technique the systems lifetime is increased by 57% (in terms of first node dies) when compared to LEACH.

A Robust Error Detection Mechanism for H.264/AVC Coded Video Sequences Based on Support Vector Machines

Current trends in wireless communications provide fast and location-independent access to multimedia services. Due to its high compression efficiency, H.264/AVC is expected to become the dominant underlying technology in the delivery of future wireless video applications. The error resilient mechanisms adopted by this standard alleviate the problem of spatio-temporal propagation of visual artifacts caused by transmission errors by dropping and concealing all macroblocks (MBs) contained within corrupted segments, including uncorrupted MBs. Concealing these uncorrupted MBs generally causes a reduction in quality of the reconstructed video sequence.

An analysis on the effect of transmission errors in real-time H.264-MVC Bit-streams

This paper studies the quality of transmitted multi-view video when the corrupted packets are not discarded by the underlying protocols of the decoder. It assumes a wireless channel where the errors can be significant and implements solutions within the current H.264-MVC to reduce their impact on the video quality perceived by the user. The results show that transmission errors drastically reduce the quality of the reconstructed 3D video and confirm that a new type of error propagation between views exists. Furthermore, employing the Context Adaptive Variable Length Coding (CAVLC) entropy encoder, coding and transmitting the video streams in smaller packets, and having a small cyclic-Intra coded period, all improve the error resilience of the system.

Exploiting depth information for fast multi-view video coding

Multi-view video coding exploits inter-view redundancies to compress the video streams and their associated depth information. These techniques utilize disparity estimation techniques to obtain disparity vectors (DVs) across different views. However, these methods contribute to the majority of the computational power needed for multi-view video encoding. This paper proposes a solution for fast disparity estimation based on multi-view geometry and depth information. A DV predictor is first calculated followed by an iterative or a fast search estimation process which finds the optimal DV in the search area dictated by the predictor. Simulation results demonstrate that this predictor is reliable enough to determine the area of the optimal DVs to allow a smaller search range. Furthermore, results show that the proposed approach achieves a speedup of 2.5 while still preserving the original rate-distortion performance.

Wireless propagation modelling inside a business jet

Wireless communication on-board aircraft has recently received increased attention as passengers are demanding for seamless office-like communication environments during their flight. Aircraft manufacturers are also interested in this technology to reduce cable complexity and provide new in-flight services. Various technologies are being considered for this purpose, such as IEEE802.11a/b/g. A radio propagation map is necessary to determine the received signal strengths inside the environment and can be obtained either through accurate modelling or through a measurement campaign. A simulation model is more attractive as it can be used to identify ideal antenna locations that maximize coverage at the design stage. Since the business jet market necessitates customized cabin configurations for each customer this will avoid costly measurement campaigns. This work presents a novel simulation model which has been used to characterize propagation characteristics inside a Dassault Aviation business jet. The developed package is based on geometric optics (GO) and adopts ray tracing techniques. Simulation results were compared with actual measurements performed on-board the aircraft with a good correlation between the two. This study takes into account only a static channel whereby all passengers are seated.

The Implementation of an Adaptive Data Reduction Technique for Wireless Sensor Networks

Wireless sensor networks (WSN) have gained significant attention due to their ability to monitor physical phenomena within a wide range of applications. These networks are generally deployed in remote areas and are battery powered. This means that the lifetime of the network depends on the energy consumption, thus necessitating careful hardware and software design to sustain the long period of operation without human intervention. One way of reducing the energy required is to minimize the number of data transmissions. A prediction-based data reduction algorithm based on the least-mean-square (LMS) algorithm was implemented on a field programmable gate array (FPGA) to reduce the communication between the sensor nodes and the base station. Measurement results show that communication can be reduced by as much as 90% in a temperature monitoring application if an error of 0.5 degree is acceptable. This has a large impact on the lifetime of the wireless sensor network since the transceiver can be switched off during non-communication periods saving precious energy.

Robust decoder-based error control strategy for recovery of H.264/AVC video content

Real-time wireless conversational and broadcasting multimedia applications offer particular transmission challenges as reliable content delivery cannot be guaranteed. The undelivered and erroneous content causes significant degradation in quality of experience. The H.264/AVC standard includes several error resilient tools to mitigate this effect on video quality. However, the methods implemented by the standard are based on a packet-loss scenario, where corrupted slices are dropped and the lost information concealed. Partially damaged slices still contain valuable information that can be used to enhance the quality of the recovered video. This study presents a novel error recovery solution that relies on a joint source-channel decoder to recover only feasible slices. A major advantage of this decoder-based strategy is that it grants additional robustness while keeping the same transmission data rate. Simulation results show that the proposed approach manages to completely recover 30.79% of the corrupted slices. This provides frame-by-frame peak signal-to-noise ratio (PSNR) gains of up to 18.1 dB, a result which, to the knowledge of the authors, is superior to all other joint source-channel decoding methods found in literature. Furthermore, this error resilient strategy can be combined with other error resilient tools adopted by the standard to enhance their performance.

Error concealment techniques for multi-view video

The H.264/AVC multi-view extension provides for high compression ratios of multi-view sequences. The coding scheme used exploits spatial, temporal and inter-view dependability for this scope. However, in the event of transmission errors, this leads to the propagation of the distorted macroblocks, degrading the quality of the video perceived by the user. In this paper we introduce error resilient coding and error concealment techniques in Multi-view Video Coding to reduce this effect. The results obtained demonstrate that better multiview video reconstruction is obtained when Intra-coded frames are spatially concealed while Inter-coded frames are concealed using motion compensation techniques, within the multi-view prediction structure. Furthermore, additional gain in quality can be achieved when Anchor frames are concealed using a combination of spatial and motion compensation techniques.