Vineet Khandelwal

A New Approximation for Average Symbol Error Probability over Log-Normal Channels

The average symbol error probability(ASEP) is an important measure to evaluate the performance of different modulation techniques over fading channels. The phenomenon of both shadowing and slow fading in wireless communication system is generally characterized by log-normal probability distribution. Approximating log-normal integrals by constructing Taylor series expansion of second order, a simple tight closed-form approximation for ASEP over log-normal fading channel is derived. This expression facilitates the computation of average symbol error rate for a broader class of coherent digital modulation schemes. The efficiency of the expression is numerically examined and comparison of the results is carried out in relation to the existing approximate expressions.

On the Applicability of Average Channel Capacity in Log-Normal Fading Environment

The statistical characterization of channel capacity in slow fading environment modeled by log-normal probability density function is considered. The probability density function of channel capacity is found to be positively skewed and significantly departs from bell shaped curve for higher values of σdB. The computation of first two moments of channel capacity provides a measure for relative fluctuation in terms of coefficient of variation (CV). It is noted that the value of CV is quite high in lower range of SNR and starts declining with increasing SNR. This may question the applicability of average channel capacity as a performance measure in slow fading scenario and accordingly a more appropriate measure is based on outage capacity. A simple procedure based on three-point estimate is outlined to obtain the approximate expression for higher order moments of channel capacity and they are found to be in excellent agreement with exact results.

A novel approach to video matting using automated scribbling by motion analysis

Video matting can be described as a method of extracting the foreground object from each frame of a video and composite (or transfer) it to a different background or a different video. An automatic scribbling approach based on the motion of the foreground object in a video is introduced. Probability maps (PMs) are computed by analysing the motion of object in the video. In the proposed technique the corrupted PMs are refined and reconstructed using morphological techniques. The frames are scribbled with reference to the reconstructed PMs. Closed form solution based matting technique uses the scribbled frame to yield the matte and the foreground.

Video matting by automatic scribbling using Quadra directional filling of segmented frames

Video matting is defined as the process of changing the background of the video by extracting the foreground image from each frame of a video. In this paper, we propose a video matting technique which uses Ncut segmentation technique to segment the frames. Further, Sobel edge detection technique is used on the segmented frames for detecting edges. Afterwards, Edge thickening process fills up all the gaps in between the edges and Quadra directional filling method generates the probability maps (PMs). The frames are scribbled with reference to the constructed PMs. Scribbled frame and the original frame along with a new background image are then fed to closed form matting technique which gives the frame with the changed background.

A novel approach to fetal ECG extraction and enhancement using blind source separation (BSS-ICA) and adaptive fetal ECG enhancer (AFE)

Eight out of one thousand born live infants have some form of heart defect, making it the single most common class of congenital abnormalities. Identification of these cases during early pregnancy reduces risks by timely treatment or planned delivery. The non-invasive fetal ECG (FECG) monitoring by means of abdominal surface electrodes provides valuable information about the cardiac electrical activity of fetus. In this paper, analysis and comparative study of four channel adaptive maternal ECG canceller-adaptive fetal ECG enhancer (FAMC-AFE) and blind source separation (BSS-ICA) methods are presented. These methods have been applied to real multichannel ECG recordings obtained from a pregnant womans skin and synthetic biomedical signals. After investigation of the results the BSS-ICA AFE approach, proposed by us, has been shown to be superior for extraction and enhancement of fetal ECG compared to other BSS scheme.

Automated segmentation of gallstones in ultrasound images

Gallstones are solid particles formed from bile in the gall bladder. In this paper, we propose a technique to automatically detect Gallstones in ultrasound images, christened as, Automated Gallstone Segmentation (AGS) Technique. Speckle Noise in the ultrasound image is first suppressed using Anisotropic Diffusion Technique. The edges are then enhanced using Unsharp Filtering. NCUT Segmentation Technique is then put to use to segment the image. Afterwards, edges are detected using Sobel Edge Detection. Further, Edge Thickening Process is used to smoothen the edges and probability maps are generated using Floodfill Technique. Then, the image is scribbled using Automatic Scribbling Technique. Finally, we get the segmented gallstone within the gallbladder using the Closed Form Matting Technique.

A Simple Closed form Approximation of Average Channel Capacity for Weakly Turbulent Optical Wireless Links

Performance of optical wireless link is degraded by the presence of atmospheric turbulence induced fading. In this paper, a simple tight closed form expression for average channel capacity of optical wireless communication (OWC) system in weak atmospheric turbulence is given. The channel capacity of OWC systems employing spatial diversity reception with maximum ratio combining and equal gain combining over independent and identical turbulence induced fading channels is also computed using proposed expression. Results computed by employing our expressions are in excellent agreement with results based on numerical Monte Carlo simulations over permissible turbulence strength for a wide range of signal to noise ratio.

Effect of aperture averaging and spatial diversity on capacity of optical wireless communication systems over lognormal channels

In this paper it is evaluated average channel capacity of an optical wireless communication system with aperture averaging and diversity reception over lognormal channels using a simple approximate closed form expression. The qualitative improvement in channel capacity is compared and investigated for various turbulence mitigation techniques: namely aperture averaging, diversity techniques such as maximal ratio combining and equal gain combining. Based on our study it is found that aperture averaging gives reasonably improved performance as compared to both types of diversity reception beyond certain turbulence strength. However, irrespective of turbulence strength, substantial improvement in capacity may be achieved with an array of direct detection receivers. Results obtained using the proposed expressions are in excellent agreement with those based on Monte Carlo simulations.

Channel Capacity Analysis over Slow Fading Environment: Unified Truncated Moment Generating Function Approach

A unified approach based on truncated moment generating function (TMGF) is employed to derive the explicit expressions for channel capacity of log-normal channel under different adaptive transmission policy. The analysis is carried out assuming channel state information known to both transmitter and receiver. The efficacy of the approach is based on the fact it yields computationally convenient and efficient results in log-normal fading environment. Based on TMGF, a simple closed form expression for higher order moments of channel capacity for log-normal channels is obtained when channel state information is only known to receiver. Numerical computation in relation to simulation results for varying value of