8751830
Power-Modulated Challenge-Response Schemes for Verifying Location Claims
Location information should be verifiable in order to support new computing and information services. In this paper, we adapt the classical challenge-response method for authentication to the task of verifying an entity's location. Our scheme utilizes a collection of transmitters, and adapts their power allocations to verify a user's claimed location. This strategy, which we call power-modulated challenge response, is able to be used with existing wireless sensor networks, and we present three variations. First, we propose a direct method, where some transmitters are selected to send "challenges" that the claimant node should be able to witness based on its claimed location, and for which the claimant node must correctly respond in order to prove its location. Second, we reverse the strategy by presenting an indirect method, where some transmitters send challenges that the claimant node should not be able to witness. Finally, we present a signal strength based method, where the node responds with its received signal strength and thereby provides improved location verification. To evaluate our schemes, we examine different adversarial models for the claimant, and characterize the performance of our power-modulated challenge response schemes under these adversarial models.
17443935
Facilitating an Active Transmit-only RFID System Through Receiver-based Processing
Many asset tracking applications demand long-lived, low-cost, and continuous monitoring of a large number of items, which has posed a significant challenge to today's RFID design. In order to satisfy these requirements, we propose to adopt transmit-only tags without a receiver, which can offer both low power and low cost. In spite of their great potential, such a platform faces many challenges since it cannot sense the channel, causing the collisions among tag transmissions to be high. It is thus crucial to employ effective multi-user detection schemes at the tag reader to extract valid information from collided signals. Traditional detection schemes, such as successive cancellation, cannot be directly applied to the targeted system. Firstly, due to the simplicity of receiver-less transmit-only tags, there is no mechanism for feedback to the tags that is traditionally needed for accurate multi-user detection. More importantly, these schemes impose serious processing and memory requirements on the underlying system, which makes real-time tracking impossible. In this study, we address these challenges by performing a statistical estimation of the signal amplitude, and by dividing the received signal sequence (from all the tags) and assigning each block to one reader. We also adopt an online learning mechanism so that readers can anticipate the tags that belong to them. We show that the proposed detection algorithm can achieve low detection error under realistic system conditions.
37152915
Image Disorientation Auto-Recovery
Automatically detecting and correcting disoriented image frames in a content-related image sequence is a problem that must be addressed in many image and video applications. In this paper, we give a robust feature-based algorithm to efficiently detect and adjust the disorientation of images. Keyword image orientation, crop, Robert edge detection, line feature, Hough transformation.
18837154
Inverting sensor networks and actuating the environment for spatio-temporal access control
Wireless sensor networks are typically deployed to measure the information field, rather than create an information field. However, by utilizing the radio on sensor nodes, it is possible to invert the role of sensor networks, and allow sensor nodes to actuate the environment. Such actuation can facilitate new forms of access control that are based on whether a user is located at the right place at the right time. In this paper, we explore the challenges of supporting spatio-temporal access control, where access to an object or service is based on the user's spatio-temporal context. Specifically, we focus on supporting spatio-temporal access control through the specification of access control policies, and show how complex spatio-temporal policies can be specified using automata. We outline a challenge-response mechanism for verifying user location in a centralized spatio-temporal access control mechanism. We utilize sensor networks in an inverted fashion to support spatio-temporal access control. Sensor nodes announce keys according to a time-varying schedule, and users may access restricted files/resources only if they are in the neighborhood of the correct sensor node and witness the appropriate cryptographic key.
17429523
A Novel Trust-based Cooperative Node Selection Scheme in Wireless Sensor Networks
For communication between the cluster head node (CHN) and the distant data fusion center (DFC) with the cooperation of intra-cluster nodes in wireless sensor networks (WSNs), reliable handling of packets by the cooperative node (CN) is difficult to ensure. In this paper, we propose a novel CN selection scheme based on trust for WSNs. This scheme can choose one of high trust nodes to assist in the transmission of CHN, which aims to improve the transmission performance over cooperative communication in the presence of potential malicious nodes. First, we establish a trust model to improve the reliability of transmission by CN in WSNs, which is based on both the direct trust and the indirect trust of nodes. Then the CHN selects a node based on the proposed trust model to aid the CHN in transmission. Simulation results show that the proposed scheme can mitigate the impact of the potential malicious nodes on transmission performance and the simulation results also demonstrate the efficiency of the proposed scheme.
14270166
A Role-Based Approach in Dynamic Task Delegation in Agent Teamwork
This paper presents a role-based agent teamwork language called RoB-MALLET (Role-Based Multi-Agent Logic Language for Encoding Teamwork). Roles have been used to form multi-agent theories and guide the construction of multi-agent architectures and systems. Different from the most existing agent teamwork models that emphasize practical reasoning based on beliefs, desires and intentions (BDI), a role-based teamwork language stresses the concept of organization and thereby cooperation. RoB-MALLET is able to handle unexpected uncertainties and allow for the conceptual specification of teamwork knowledge for reuse. Finally, we present several experiments that explore plan reusability of RoB-MALLET, show that it is flexible in supporting simultaneity of invocation and evaluate its efficiency in supporting teamwork.
44610157
A New Robust Bandpass Sampling Scheme for Multiple RF Signals in SDR System
Software defined radio (SDR) technology has been widely applied for its powerful universality and flexibility in the past decade. To address the issue of bandpass sampling of multiband signals, a novel and efficient method of finding the minimum valid sampling frequency is proposed. Since there are frequency deviations due to the channel effect and hardware instability in actual systems, we also consider the guard-bands between downconverted signal spectra in determining the minimum sampling frequency. In addition, the case that the spectra within the sampled bandwidth are located in inverse placement can be avoided by our proposed method, which will reduce the complexity of the succeeding digital signal process significantly. Simulation results illustrate that the proper minimum sampling frequency can be determined rapidly and accurately.
5679790
Proactive Information Exchange During Team Cooperation
We are concerned, ultimately, with multi-agent teams involving both software and human agents in which the software agents assist in training the humans, e.g., as virtual team members. The software agents must be capable of utilizing the teamwork mechanisms used by humans. In this paper, we describe how to give agents the same implicit communication capabilities, i.e., observation, that humans use. We show how agents can use observations of the environment and teammates' actions to estimate other agents beliefs without bothering them with unnecessary messages; we also show how agents can anticipate information needs among the team and proactively exchange information, reducing the total communication volume. To achieve these goals, we add sensing capabilities to agents and present algorithms that infer teammates' mental state from the observation. Experimental data is presented that shows that the advantage of observation in proactive information exchange as well as enhanced team performance.
8300404
Modeling Internet Link Delay Based on Measurement
Understanding Internet link delay is an important key of taking full advantage of Internet resources. In this paper, we find that the link delay follows Gammadistribution using Maximum Likelihood Estimation based on data measured in a large-scale network. The correlations between the link delay and the edge load, the node degree, and the betweenness are analyzed respectively. The link delay distribution parameters for different ranges of edge load are calculated. We findthat the edge load is correlated positively with the shape parameter of link delay Gamma distribution and negatively with the scale parameter.