This paper proposes an efficient method to estimate the point spread function (PSF) of a blurred image using image gradients spatial correlation. A patch-based image degradation model is proposed for estimating the sample covariance matrix of the gradient domain natural image. Based on the fact that the gradients of clean natural images are approximately uncorrelated […]
Archives for January 2012
Cooperative Channelization in Wireless Networks with Network Coding
we address congestion of multicast traffic in multihop wireless networks through a combination of network coding and resource reservation. Network coding reduces the number of transmissions required in multicast flows, thus allowing a network to approach its multicast capacity. In addition, it efficiently repairs errors in multicast flows by combining packets lost at different destinations. […]
load shedding in mobile systems with mobiqual
In location-based, mobile continual query (CQ) systems, two key measures of quality-of-service (QoS) are: freshness and accuracy. To achieve freshness, the CQ server must perform frequent query reevaluations. To attain accuracy, the CQ server must receive and process frequent position updates from the mobile nodes. However, it is often difficult to obtain fresh and accurate […]
Localization of Mobile Nodes in Wireless Networks with Correlated in Time Measurement Noise
Wireless sensor networks are an inherent part of decision making, object tracking, and location awareness systems. This work is focused on simultaneous localization of mobile nodes based on received signal strength indicators (RSSIs) with correlated in time measurement noises. Two approaches to deal with the correlated measurement noises are proposed in the framework of auxiliary […]
An Optimal Algorithm for Relay Node Assignment in Cooperative Ad Hoc Networks
Recently, cooperative communications, in the form of having each node equipped with a single antenna and exploit spatial diversity via some relay node’s antenna, is shown to be a promising approach to increase data rates in wireless networks. Under this communication paradigm, the choice of a relay node (among a set of available relay nodes) […]
An Adaptive Network Coded Retransmission Scheme for Single-Hop Wireless Multicast Broadcast Services
Network coding has recently attracted attention as a substantial improvement to packet retransmission schemes in wireless multicast broadcast services (MBS). Since the problem of finding the optimal network code maximizing the bandwidth efficiency is hard to solve and hard to approximate, two main network coding heuristic schemes, namely opportunistic and full network coding, were suggested […]
Call Admission Control Performance Analysis in Mobile Networks Using Stochastic Well-Formed Petri Nets
(This work is an extension of our conference paper at Valuetools 2006 [18].) Stochastic Well-formed Petri Nets (SWNs) are a powerful tool for modeling complex systems with concurrency, synchronization, and cooperation. Call Admission Control (CAC) is an important mechanism for mobile networks. While several studies have been done on GSM/GPRS and on UMTS system with […]
Missing Value Estimation for Mixed-Attribute Data Sets
Missing data imputation is a key issue in learning from incomplete data. Various techniques have been developed with great successes on dealing with missing values in data sets with homogeneous attributes (their independent attributes are all either continuous or discrete). This paper studies a new setting of missing data imputation, i.e., imputing missing data in […]
Authenticated Multistep Nearest Neighbor Search
Multistep processing is commonly used for nearest neighbor (NN) and similarity search in applications involving high-dimensional data and/or costly distance computations. Today, many such applications require a proof of result correctness. In this setting, clients issue NN queries to a server that maintains a database signed by a trusted authority. The server returns the NN […]
On Computing Farthest Dominated Locations
In reality, spatial objects (e.g., hotels) not only have spatial locations but also have quality attributes (e.g., price, star). An object p is said to dominate another one p’, if p is no worse than p’ with respect to every quality attribute and p is better on at least one quality attribute. Traditional spatial queries […]