Nikil Jayant

Delivering diagnostic quality video over mobile wireless networks for telemedicine

In real-time remote diagnosis of emergency medical events, mobility can be enabled by wireless video communications. However, clinical use of this potential advance will depend on definitive and compelling demonstrations of the reliability of diagnostic quality video. Because the medical domain has its own fidelity criteria, it is important to incorporate diagnostic video quality criteria into any video compression system design. To this end, we used flexible algorithms for region-of-interest (ROI) video compression and obtained feedback from medical experts to develop criteria for diagnostically lossless (DL) quality. The design of the system occurred in three steps-measurement of bit rate at which DL quality is achieved through evaluation of videos by medical experts, incorporation of that information into a flexible video encoder through the notion of encoder states, and an encoder state update option based on a built-in quality criterion. Medical experts then evaluated our system for the diagnostic quality of the video, allowing us to verify that it is possible to realize DL quality in the ROI at practical communication data transfer rates, enabling mobile medical assessment over bit-rate limited wireless channels. This work lays the scientific foundation for additional validation through prototyped technology, field testing, and clinical trials.

Home gateway for three-screen TV using H.264 SVC and raptor FEC

This paper describes the design and implementation of a multimedia home gateway for threescreen television (3STV) service. The proposed in-home wireless network uses scalable video coding (SVC) and unequal error protection with Raptor forward error correction (FEC) for maximizing the quality of experience (QoE) over the variable-bandwidth, error-prone wireless network. The gateway incorporates (a) dynamic SVC layerswitching, which enables the server to perform selecting appropriate layers from SVC bitstreams, (b) adaptive Raptor FEC, which controls the overhead of Raptor FEC according to packet loss rate (PLR), (c) an efficient combination of (a) and (b), and (d) slice group-based selective streaming in the overall gateway architecture. The paper explains the home gateway architecture as well as experiments for performance evaluation as compared to that of traditional SVC streaming. In the experiments conducted, gains in video quality vary from 2 to 5dB in peak signal-to-noise ratio (PSNR), with corresponding subjective improvements. Overall reductions of bit rate at the input to the home gateway vary from 28% to 36%1.

Wireless communication of vital signs using the Georgia Tech Wearable Motherboard

The Georgia Tech Wearable Motherboard/sup TM/ (GTWM) provides a versatile framework for incorporation of sensing, monitoring and information processing devices. It has opened up new frontiers in telemedicine, infant care, military, space exploration and athletics. We have developed a working prototype of wireless communication between the GTWM and the outside world. The overall system consists of data acquisition, data transmission, computation and data storage, and user interface. It can serve as a full wearable computer, providing functionalities for tracking the physiological conditions of the user as well as sensory information from the environment and other peripherals. The system performs well in indoor wireless environments with signal to noise ratio as low as 5 dB. This prototype opens up many research opportunities in the fields of affective computing, human-computer interaction, and mobile information processing.

A low-power, fixed-point, front-end feature extraction for a distributed speech recognition system

This work describes the optimization of a signal processing front-end for a distributed speech recognition system with the goal of reducing power consumption. Two categories of source code optimizations were used, architectural and algorithmic. Architectural optimizations reduce the power consumption for a particular system, in this case, the HP Labs Smartbadge IV prototype portable system. Algorithmic optimizations are more general and involve changes in the algorithmic implementation of the source code to run faster and consume less power. A cycle accurate energy simulation shows a reduction in power usage by 83.5% with these optimizations. The optimized source code runs 34 times faster than the original code, therefore it can run at lower processor clock speeds and voltages for further reductions in power consumption. This technique, known as dynamic voltage scaling, was implemented on the Smartbadge IV hardware for an overall reduction in power usage of 89.2%.

An adaptive FEC with QoS provisioning for real-time traffic in LEO satellite networks

This paper presents an adaptive forward error correction (AFEC) protocol that provides a reliable communication service for real-time traffic over low-earth orbit (LEO) satellite networks. In time-varying wireless links, such as LEO satellite networks. A reliable channel estimation scheme with an appropriate code selection technique is essential for adaptive error-control systems. This paper proposes a new channel estimation scheme that uses receiver-initiated messages (ACKs, NAKs, and INCs). These messages feed back to the transmitter which then selects the code rate for sending packets. In addition, the scheme uses the concept of a dynamic transmittable code set by adjusting the maximum code rate in the set of possible codes from which the transmitter can select. In terms of throughput (from network providers viewpoint) and packet error rate (from subscribers viewpoint), performance results show that the proposed scheme guarantees the quality of service (QoS) requirements of real-time applications.

Energy-aware distributed speech recognition for wireless mobile devices

Severe limitations in computational, memory, and energy resources make implementing high-quality speech recognition in embedded devices a difficult challenge. In this article, the authors investigate the energy consumption of computation and communication in an embedded distributed speech recognition system and propose optimizations that reduce overall energy consumption while maintaining adequate quality of service for the end user. This article considers the application of DSR traffic to both Bluetooth and 802.11b networks.

Angle clustering in indoor space-time channels based on ray tracing

Clustering of paths in angle in RF multipath scenarios has been observed in measured data, explicitly used in stochastic propagation models, and shown to have a significant impact on the capacity of MIMO links. A 3D ray tracing is used to characterize the path delays and angles in a rectangular building in which all interior walls are parallel and perpendicular to the exterior walls. Path delays and angles are recorded for 200 random transmitter and receiver locations, maintaining constant range and throughout a particular building model. The main contribution of this paper is the observation that when all of the path angles from all 200 trials are measured relative to one building wall and collectively analyzed in a histogram, clustering is clearly apparent. Furthermore, the mean angles of the clusters are a function of the range between the transmitter and receiver. While this angle clustering in the ensemble of channels is not the same as clustering in a single channel trial, it may partially account for the clusters observed in single trials. As a practical matter, these results may impact the use and placement of directional antennas for wireless LANs in buildings of this type. By simply measuring the angles relative to the line-of-sight (LOS) path rather than the building wall, the data is shown to be consistent with the joint probability density function (PDF) of delay and angle based on the geometrically based elliptical model (GBEM).

Relevance feedback for semantics based image retrieval

Content based image retrieval is one of the most active research areas in the field of multimedia technology. Currently, the relevance feedback approach has attracted great attention since it can bridge the gap between low-level features and the semantics of images. We propose a new relevance feedback technique, which uses the normal mixture model for the high-level similarity metric of the users intention and estimates the unknown parameters from the users feedback. Our approach is based on a novel hybrid algorithm where the criterion for the selection of the display image set is evolved from the most informative to the most probable as the retrieval process progresses. Experiments on the Corel image set show that the proposed algorithm outperforms MindReader at the semantics based search.

`Mean Time Between Failures': A Subjectively Meaningful Video Quality Metric

As digital communication of television content becomes more pervasive, the long-standing problem of assessing video quality becomes particularly important. This work describes some innovative guidelines for easy and reliable determination of a quality metric that is subjectively meaningful: mean time between failures (MTBF), representing how often a typical viewer observes a noticeable visual error and a related instantaneous metric relating to the fraction of viewers that find a given video portion to be within acceptable quality levels. The value of MTBF is addressed in the context of video quality, and objective measurements that correlate well with subjective evaluations of MTBF are investigated for different video clips at bit rates in the range of 1.5 - 5 Mbps. The full-reference objective metrics of PSNR and JND are found to have correlation coefficients of 0.69 and 0.88 respectively. In contrast, a reduced-reference objective metric, spatial temporal join metric (S. Wolf and M.H. Pinson, 1999) (STJM) is found to have a correlation coefficient of 0.84. A method for estimating the MTBF of a video sequence from objective measurements is also described

Next-generation E-health communication infrastructure using converged super-broadband optical and wireless access system

Delivering affordable high-quality E-health care services requires effective telecommunication and multimedia technologies in conjunction with medical expertise. In this paper, we propose and demonstrate a telecommunication and networking architecture for implementing next generation Telemedicine and Telehealth systems. Our integrated optical-wireless based network provides super broadband, ultra low-latency connectivity for voice, video, image and data across various telemedicine modalities to facilitate real-time and near real-time communication of remote health care information.