Showing papers by "Ravi Sankar published in 2011"

An Efficient Mutual Authentication and Access Control Scheme for Wireless Sensor Networks in Healthcare

Abstract: Wireless sensor networks (WSNs) will play an active role in the 21th Century Healthcare IT to reduce the healthcare cost and improve the quality of care. The protection of data confidentiality and patient privacy are the most critical requirements for the ubiquitous use of WSNs in healthcare environments. This requires a secure and lightweight user authentication and access control. Symmetric key - based access control is not suitable for WSNs in healthcare due to dynamic network topology, mobility, and stringent resource constraints. In this paper, we propose a secure, lightweight public key - based security scheme, Mutual Authentication and Access Control based on Elliptic curve cryptography (MAACE). MAACE is a mutual authentication protocol where a healthcare professional can authenticate to an accessed node (a PDA or medical sensor) and vice versa. This is to ensure that medical data is not exposed to an unauthorized person. On the other hand, it ensures that medical data sent to healthcare professionals did not originate from a malicious node. MAACE is more scalable and requires less memory compared to symmetric key-based schemes. Furthermore, it is much more lightweight than other public key-based schemes. Security analysis and performance evaluation results are presented and compared to existing schemes to show advantages of the proposed scheme.

Two-Relay-Based Cooperative MAC Protocol for Wireless Ad hoc Networks

Abstract: The cooperative communication approach promises improved throughput and delay performance by effective use of spatial diversity in wireless ad hoc networks. The CoopMAC I protocol proposed by Liu picks either a direct path or a relay path based on rate comparison to enhance average throughput and delay performances. However, its performance deteriorates under fading conditions due to lower direct path or relay path reliability. UtdMAC, which was proposed by Agarwal , performs better than CoopMAC I in terms of average throughput and delay performances due to improved transmission reliability provided by the backup relay path. Although it is better than CoopMAC I, UtdMAC does not fully benefit from higher throughput relay path (compared with the direct path) since it uses relay path only as a secondary backup path. In this paper, a new cooperative medium access control (MAC) protocol, which is termed the 2rcMAC protocol, is proposed for a small-sized network. The protocol makes use of two cooperating nodes to achieve superior throughput and delay performances, compared with the existing cooperative MAC protocols. The secondary relay path is invoked as a backup path for better transmission reliability and higher throughput through the relay path. Moreover, handshaking and single-bit feedbacks resolve contentions among relay nodes in proximity at the time and further provide the source node with rate information on source-to-destination, source-to-relay, and relay-to-destination links. Performance gains achieved by the 2rcMAC protocol under fast-fading conditions over the existing cooperative MAC protocols are compared and discussed. Simulation results clearly show an average throughput improvement of 7% and 25% and an average delay improvement of 94.8% and 98.9%, compared with UtdMAC and CoopMAC I, respectively.

Delay-Throughput Trade-Off with Opportunistic Relaying in Wireless Networks

Abstract: In this paper, we study the delay/throughput trade-off with opportunistic relaying over channels with random connections, in which the channel connections are independent and identically distributed (i.i.d.). Previous work~\cite{CA:07} which proposed an opportunistic relaying scheme has focused on the throughput analysis only, we show that the opportunistic relaying scheme provides an upper bound of $O(n)$ delay, including full effects of queueing in the network model. In addition, we use the redundant scheduling algorithm to reduce the upper bound of delay scaling to $O(n/\sqrt{\log n})$. Furthermore, we prove two key inequalities that capture the various tradeoffs inherent in the broad class of opportunistic relaying protocols, which indicate the tradeoff of $delay/throughput \geq O(n/\log n)$, illustrating that no scheduling and routing algorithm can simultaneously yield lower delay and higher throughput.

A brief survey of access control in Wireless Sensor Networks

Abstract: In this paper, we investigate applications of access control to Wireless Sensor Networks (WSNs). Although access control was well established for traditional computer systems, it has not been studied thoroughly in WSN environments. We briefly provide the WSN specifications and then stress the constraints of the WSNs that would affect the access control implementation. We also provide a literature overview and discuss further possible solutions.

Advanced two tier User Authentication scheme for heterogeneous Wireless Sensor Networks

Abstract: In this paper, we propose a novel User Authentication (UA) scheme for heterogeneous Wireless Sensor Networks (WSNs), which employs both Public Key Cryptography (PKC) and Symmetric Key Cryptography (SKC) approaches, such that it takes advantage of both schemes. Our analysis results have shown that, our scheme is not only more secure and scalable than existing SKC based schemes, but also requires lesser processing power and provides higher energy efficiency than existing PKC based schemes.

Advances and challenges in signal analysis for single trial P300-BCI

Abstract: In this paper a brief introduction to some of the goals, recent developments, and open problems in BCI research are given. We mainly focus on presenting our research work in signal processing for single-trial P300-BCI and discuss our current plans for improving the BCI method.

Coherence time-based cooperative MAC protocol 1 for wireless ad hoc networks

Abstract: In this article, we address the goal of achieving performance gains under heavy-load and fast fading conditions. CoopMACI protocol proposed in Proceedings of the IEEE International Conference on Communications (ICC), Seoul, Korea, picks either direct path or relay path based on rate comparison to enhance average throughput and delay performances. However, CoopMACI performance deteriorates under fading conditions because of lower direct path or relay path reliability compared to UtdMAC (Agarwal et al. LNCS, 4479, 415-426, 2007). UtdMAC was shown to perform better than CoopMACI in terms of average throughput and delay performances because of improved transmission reliability provided by the backup relay path. Although better than CoopMACI, UtdMAC does not fully benefit from higher throughput relay path (compared to the direct path), since it uses relay path only as a secondary backup path. In this article, we develop a cooperative MAC protocol (termed as instantaneous relay-based cooperative MAC--IrcMAC) that uses channel coherence time and estimates signal-to-noise ratio (SNR) of source-to-relay, relay-to-destination, and source-to-destination links, to reliably choose between relay path or direct path for enhanced throughput and delay performances. Unique handshaking is used to estimate SNR and single bit feedbacks resolve contentions among relay nodes, which further provides source node with rate (based on SNR) information on source-to-destination, source-to-relay, and relay-to-destination links. Simulation results clearly show that IrcMAC significantly outperforms the existing CoopMACI and the UtdMAC protocols in wireless ad hoc network. Results show average throughput improvements of 41% and 64% and average delay improvementd of 98.5% and 99.7% compared with UtdMAC and CoopMACI, respectively.

Throughput analysis in Aeronautical Data Networks

Abstract: The advances in signal processing, rapid-prototyping and an insatiable consumer demand for wireless connectivity is opening a new paradigm of data service, “Aeronautical Data Networks (ADN)”. The desire is to provide low delay and cost effective data network not only for an aeronautical platform, but also terrestrial networks by using aeronautical platforms as a backbone. An aeronautical station could be a commercial plane, a helicopter or any other very low orbit station i.e., Unmanned Air Vehicle (UAV), High Altitude Platform (HAP). In this paper, we investigate aeronautical broadband wireless access scheme to provide a ADN capacity analysis. First the geometry and connectivity of an ADN is investigated to present the parameters that effects the throughput of an ADN. Then the network throughput analysis based on finding the maximum number of concurrent successful transmissions method is done to provide an upper bound for the throughput of ADN. Simulation results are presented and it is shown that the analytically derived upper bound is tight under the condition that the aeronautical stations are independent and identically distributed (i.i.d.) over the ADN. Numerical results for various possible scenarios depending on ADN geometry are also presented.

Atrial fibrillation source identification

Abstract: Atrial Fibrillation, a common arrhythmia accompanied by an increased morbidity and mortality remains difficult to treat either with medications or invasive procedures. Targeted destruction of atrial fibrillation triggers offers the best hope for permanent resolution of the arrhythmia. In this work, identification of atrial triggers is based on the analysis of complex endocardial recordings. Here, we propose a novel algorithm to detect the source of atrial fibrillation by classifying the signals originating from the four pulmonary veins in the left atrium.

Feasibility study of pico cellular-relaying system in urban outdoor environment

Abstract: Heterogeneous networks, in particular cellular-relaying networks, have the potential to provide high data-rate services at low infrastructure costs. Macro and micro base stations have traditionally been used to provide coverage and capacity, respectively. In this paper, we analyze a new approach in which coverage is provided by means of inband relays. We show that compared with a traditional network based on macro base stations, a good outdoor coverage for a target data rate could be provided in a more cost efficient way by deploying a network based on pico base stations and relays. However, this is valid only for low data-rate because part of the spectrum is allocated to the backhaul and therefore the capacity of cellular-relaying networks is typically limited. Moreover, this break-even point depends on how the networks are deployed.