Venkatesh Sarangan

PMAC: an adaptive energy-efficient MAC protocol for wireless sensor networks

We propose a novel adaptive MAC protocol for wireless sensor networks. In existing protocols such as SMAC, the sensor nodes are put to sleep periodically to save energy. As the duty cycle is fixed in such protocols, the network throughput can degrade under heavy traffic, while under light loads, unwanted energy consumption can occur. In the proposed pattern-MAC (PMAC) protocol, instead of having fixed sleep-wakeups, the sleep-wakeup schedules of the sensor nodes are adaptively determined. The schedules are decided based on a nodes own traffic and that of its neighbors. Our analytical and experimental results show that in comparison to SMAC, PMAC achieves more power savings under light loads, and higher throughput under heavier traffic loads. Furthermore, unlike SMAC, only the sensor nodes involved in communication wake up frequently in PMAC and hence energy is conserved in other sensor nodes.

A framework for fast RFID tag reading in static and mobile environments

A framework for reducing the average reading time of passive RFID tags in dense environments is introduced. The proposed framework termed Accelerated Frame Slotted ALOHA (AFSA) can be used in conjunction with almost all RFID tag reading protocols that are based on frame slotted ALOHA. It is shown that AFSA reduces the tag reading time by avoiding the wastage in bit times due to collisions and idle slots. The implementation of AFSA in conjunction with two different ALOHA protocols - one with unlimited frame sizes and the other with limited frame sizes is discussed. For both these protocols, extensions of AFSA to read passive tags in a mobile setting are described. Simulation results show that AFSA reduces the average tag reading time by up to 40% with respect to the stand alone ALOHA protocols under both static and mobile settings.

Comparative study of protocols for dynamic service negotiation in the next-generation Internet

This article presents a survey of the protocols that have been proposed for facilitating dynamic service negotiation in the next-generation Internet. We begin by illustrating the terms service level agreement and service level specification defined by the IETF. We then discuss the working of the existing service negotiation protocols with respect to generic network architecture. Following that, we enumerate a list of characteristics desired in an ideal service negotiation protocol and draw a comparison between the various protocols based on this list. We conclude the article by discussing possible future research directions in this area.

Dynamic service negotiation protocol (DSNP) and wireless DiffServ

This paper presents the design principles of dynamic service negotiation protocol (DSNP). DSNP is a protocol to negotiate the SLS (service level specification) in the IP layer. It can be used for service negotiation from host to network, network to host, and network to network. The automated negotiation makes service negotiation efficient in terms of time, cost, and correctness. The dynamic negotiation not only allows users to adapt their needs dynamically, but also lets providers utilize the network better. DSNP can be used in both wireline and wireless networks. It is, however, particularly useful in the mobile environment. To demonstrate the usefulness of DSNP, a reference wireless QoS architecture based on DiffServ is presented. Example applications and experimental results are illustrated.

Online energy aware routing in wireless networks

Online energy aware routing in wireless networks is the problem of finding energy efficient routes that maximize the network lifetime without the knowledge of future message flows. To maximize network lifetime, the paths for message flows are chosen in such a way that the total energy consumed along the path is minimized while avoiding energy depleted nodes. Finding paths which consume minimum energy and finding paths which do not use energy depleted nodes lead to conflicting objectives. In this paper, we propose two-phased energy aware routing strategies that balance these two conflicting objectives by transforming the routing problem into a multi-metric widest path problem. We find that the proposed approaches outperform the best-known algorithms in the literature. We also demonstrate a simple but insightful relationship between the total energy required along a path and the minimum remaining energy of a node along the path. We further exploit this relationship to show that staying within the solution space of paths with high residual energy and low total energy provides much improved lifetimes in general.

Quality-of-service routing in IP networks

Multimedia applications such as video-conferencing, telemedicine, HDTV, etc. have very stringent quality-of-service (QoS) demands and require a connection-oriented service. For these applications, a path satisfying their requirements in terms of bandwidth, delay buffer, etc. needs to be found. As conventional IP routing is based only on hop counts, it is not suitable for multimedia applications. It is clear that, to route requests that have QoS requirements, existing routers should be made QoS aware and the packet forwarding should be based on QoS parameters. Also, routing protocols like OSPF and RIP must be extended suitably to facilitate QoS routing. The goal of QoS routing algorithms is to find a loop-less path satisfying a given set of constraints on parameters like bandwidth, delay, etc. The path selection process could return either the entire path to the destination or the best next hop for the request. The first case is called source routing and the second is referred to as distributed routing. In this paper, we propose a new distributed QoS routing algorithm for unicast flows, which has a very low call establishment overhead. Our algorithm makes use of existing IP routing protocols such as OSPF and RIP with minimal modifications.

Delay-Constrained, Energy-Efficient Routing in Wireless Sensor Networks Through Topology Control

In this paper, we investigate the problem of finding energy-efficient paths for delay-constrained data in wireless sensor networks. This problem has been shown to be NP-complete and current solutions for this problem are inadequate, as they do not model the delays introduced by the channel access mechanisms. We present a heuristic solution for the aforesaid problem that employs topology control for sensor networks using 802.11 like channel access schemes. We propose a network architecture and a routing framework that enable us to model the access delays caused by the MAC layer. This in turn, allows us to obtain better estimates for the end-to-end delays along various paths. We identify a set of paths between the source and sink nodes, and index them in increasing order of their energy consumption. We then estimate the end-to-end delay along each of these ordered paths, and select the one with the lowest index that satisfies the delay constraint. Our studies show that the proposed framework achieves a good balance between latency introduced in the transfer and energy consumption, when compared with conventional solutions

Impact of mobility prediction on the temporal stability of MANET clustering algorithms

Scalability issues for routing in mobile ad hoc networks (MANETs) have been typically addressed using hybrid routing schemes operating in a hierarchical network architecture. Several clustering schemes have been proposed to dynamically identify and maintain hierarchy in MANETs. To achieve significant performance gains, it is important that the underlying clustering scheme is able to identify stable clusters such that the cost associated with maintaining the clustered architecture is minimized. In this paper, we study the impact of mobility prediction schemes on the temporal stability of the clusters obtained using a mobility-aware clustering framework. We investigate the performance of the prediction schemes with respect to Gauss-Markov, Random Waypoint, and Reference Point Group mobility models under varying network and mobility conditions. Our results indicate that while mobility prediction significantly improves temporal stability of the clusters, an accurate mobility tracking algorithm need not always lead to an accurate mobility prediction scheme.

A Mobility-Prediction-Based Relay Deployment Framework for Conserving Power in MANETs

There has been a growing interest in designing mobile systems consisting of special relay nodes whose mobility can be controlled by the underlying network. In this paper, we consider the design of a heterogeneous mobile ad hoc network (MANET) consisting of two kinds of mobile nodes-traditional nodes with limited energy and a few controllable mobile relay nodes with relatively abundant energy resources. We propose a novel relay deployment framework that utilizes mobility prediction and works in tandem with the underlying MANET routing protocol to optimally define the movement of the relay nodes. We present two instances of the relay deployment problem, together with the solutions, to achieve different goals. Instance 1, termed Min-Total, aims to minimize the total energy consumed across all the traditional nodes during data transmission, while instance 2, termed Min-Max, aims to minimize the maximum energy consumed by a traditional node during data transmission. Our solutions also enable the prioritization of individual nodes in the network based on residual energy profiles and contextual significance. We perform an extensive simulation study to understand the trade-offs involved in deploying an increasing fraction of such relay nodes in the network. We also investigate the performance of the proposed framework under different mobility prediction schemes. Results indicate that even when the relay nodes constitute a small fraction of the total nodes in the network, the proposed framework results in significant energy savings. Further, we observed that while both the schemes have their potential advantages, the differences between the two optimization schemes are clearly highlighted in a sparse network.

Interference aware multi-path routing in wireless networks

We can improve the end-to-end throughput between a sender and receiver in a wireless network using multiple paths which do not interfere with each other. Given that the problem of finding such paths is computationally hard, the paper focuses on finding multiple paths which may have interference between them, but still are able to obtain the maximum possible throughput. It is achieved by observing that the pattern of interference is more important than the number of interfering links. The nature of path sets with non-destructive interference is discussed and based on these observations, combinatorial techniques for finding interference aware disjoint paths in a wireless network are presented. Simulation results indicate that the proposed solutions achieve throughputs that are significantly higher than the established theoretical results.