Robert Simon

A multi-channel defense against jamming attacks in wireless sensor networks

Radio jamming in wireless sensor networks is an effective means by which an attacker can disrupt communication between sensor nodes. The purpose of such an attack can be to delay or prevent nodes from reporting their readings to the basestation, to deplete vital network resources such as energy, or both. This paper presents MULEPRO (MULti-channel Exfiltration PROtocol), a fully distributed network based protocol designed to rapidly exfiltrate data from a jammed area. MULEPRO targets sensor network applications that require an immediate and robust response to radio jamming denial-of-service (DoS) attacks. It works by automatically and efficiently assigning nodes to different channels in the jammed area in order to defeat an attacker. We have extensively evaluated MULEPRO under avariety of attack configurations. These tests show that even when the attacker uses a channel hopping strategy MULEPRO can effectively exfiltrate data.

A bandwidth-reservation mechanism for on-demand ad hoc path finding

One of the major challenges faced by designers of ad hoc network systems is the deployment of end-to-end quality-of-service support mechanisms. This paper describes QoS-AODV, an integrated route discovery and bandwidth reservation protocol. QoS-AODV is designed to operate within a TDMA network. Unlike other path finding and route discovery protocols that ignore the impact of the data link layer, QoS-AODV incorporates slot scheduling information to ensure that end-to-end bandwidth is actually reserved. Further, QoS-AODV is an enhanced version of the Ad hoc On-demand Distance Vector routing protocol, and is therefore compatible with proposed route discovery and maintenance techniques. In order to test the effectiveness of our protocol we implemented a version of QoS-AODV, along with two similar protocols, in the ns-2 simulator. Our experiments showed the QoS-AODV significantly improved the probability of being able to find an end-to-end QoS path.

Performance analysis for ad hoc QoS routing protocols

One of the major challenges faced by designers of ad hoc network systems is the deployment of end-to-end quality-of-service support mechanisms. The paper presents a comprehensive performance analysis and comparison of two QoS-enhanced ad hoc network protocols. We assume that the underlying network uses a time slotted data link layer such as TDMA. We developed integrated, QoS-aware versions of AODV (ad-hoc on-demand distance vector) and TORA (temporally ordered routing algorithm), two well-known ad hoc routing protocols. Using the ns-2 simulator, we have conducted an extensive set of performance experiments for these protocols with a wide variety of mobility patterns and reservation strategies. Our experiments show that by using the relatively minor modifications we suggest, both routing methods can significantly improve the probability of being able to find an end-to-end QoS path.

Harvesting-Aware Energy Management for Time-Critical Wireless Sensor Networks With Joint Voltage and Modulation Scaling

As Cyber-Physical-Systems (CPSs) evolve they will be increasingly relied on to support time-critical and performance-intensive monitoring and control activities. Further, many CPSs that utilize Wireless Sensor Networking (WSN) technologies will require the use of energy harvesting methods to extend their lifetimes. For this application class, there are currently few algorithmic techniques that combine performance sensitive processing and communication with efficient management techniques for energy harvesting. Our paper addresses this problem. We first propose a general purpose, multihop WSN architecture capable of supporting time-critical CPS systems using energy harvesting. We then present a set of Harvesting Aware Speed Selection (HASS) algorithms. Our technique maximizes the minimum energy reserve for all the nodes in the network, thus ensuring highly resilient performance under emergency or fault-driven situations. We present an optimal centralized solution, along with an efficient, distributed solution. We propose a CPS-specific experimental methodology, enabling us to evaluate our approach. Our experiments show that our algorithms yield significantly higher energy reserves than baseline methods.

Maximum utility rate allocation for energy harvesting wireless sensor networks

There is currently tremendous interest in deploying energy harvesting wireless sensor networks. Engineering such systems requires striking a careful balance between sensing performance and energy management. Our work addresses this problem through the design and analysis of a harvesting aware utility-based sensing rate allocation algorithm. Based on a network utility formulation, we show that our algorithm is optimal in terms of assigning rates to individual nodes to maximize overall utility, while ensuring energy-neutral operation. To our knowledge, our work is the first optimal solution that maximizes network utility through rate assignments for tree-structured energy harvesting sensor networks. Our algorithm is fast and efficient with running time O(N3), where N is the number of nodes. We evaluate the performance, scalability, and overhead of our algorithm for various utility functions and network sizes, underlining its significant advantages.

The Impact of the Mobility Model on Delay Tolerant Networking Performance Analysis

Delay tolerant networks (DTNs) are a class of networks that experience frequent and long-duration partitions due to sparse distribution of nodes. The topological impairments experienced within a DTN pose unique challenges for designing effective DTN routing protocols. For an important class of DTNs nodes depend on their mobility to carry message to the destination. It is therefore essential to understand the impact of commonly-used mobility models on performance analysis of DTN routing schemes. This paper shows how the underlying statistical properties of a frequently used mobility model can be used to enhance our understanding of DTN simulation results. Using these results we also analyze several DTN routing techniques, including direct transmission, Spray and Wait, and a novel core-assisted routing schemes

Class-based access control for distributed video-on-demand systems

The focus of this paper is the analysis of threshold-based admission control policies for distributed video-on-demand (VoD) systems. Traditionally, admission control methods control access to a resource based on the resource capacity. We have extended that concept to include the significance of an arriving request to the VoD system by enforcing additional threshold restrictions in the admission control process on request classes deemed less significant. We present an analytical model for computing blocking performance of the VoD system under threshold-based admission control. Extending the same methodology to a distributed VoD architecture we show through simulation that the threshold performance conforms to the analytical model. We also show that threshold-based analysis can work in conjunction with other request handling policies and are useful for manipulating the VoD performance since we are able to distinguish between different request classes based on their merit. Enforcing threshold restrictions with the option of downgrading blocked requests in a multirate service environment results in improved performance at the same time providing different levels of quality of service (QoS). In fact, we show that the downgrade option combined with threshold restrictions is a powerful tool for manipulating an incoming request mix over which we have no control into a workload that the VoD system can handle.

End-to-end analysis of distributed video-on-demand systems

The focus of the research presented in this paper is the end-to-end analysis of a distributed Video-on-Demand (VoD) system. We analyze the distributed architecture of a VoD system to design global request handling and admission control strategies and evaluate them using global metrics. The performance evaluation methodology developed in this paper helps in determining efficient ways of using all resources in the VoD architecture within the constraints of providing guaranteed high quality service to each request. For instance, our simulation results show that request handling policies based on limited redirection of blocked requests to other resources perform better than load sharing policies. We also show that request handling policies based on redirection have simpler connection establishment semantics than load sharing policies and, therefore, are easily incorporated into reservation or signaling protocols.

Characteristics of common mobility models for opportunistic networks

Understanding the characteristics of synthetic mobility models is important for the design and analysisof routing schemes for mobile ad hoc networks (MANETs). This is especially true for mobile opportunistic networks where node mobility is utilized to achieve message delivery. In this paper, we study the properties of common mobility models. Specifically, we analytically show that inter-contact times of mobile nodes can be closely approximated as exponentially distributed in Random Waypoint and Random Direction mobility models under typical opportunistic network settings. Analytical and experimental results are presented.

Using multiple communication channels for efficient data dissemination in wireless sensor networks

This paper presents McTorrent and McSynch, two multichannel sensor network protocols for data dissemination. Both protocols are designed to take advantage of the spatial multiplexing properties of the half-duplex radio transceivers available on the current generation of sensor nodes. McTorrent is used for reliable end-to-end dissemination of a large data object. Compared to existing protocols, we show that McTorrent significantly reduces the amount of time required to propagate a large data object throughout a sensor network. McSynch is used to achieve data object synchronization within a local cluster of nodes. By using a scheduled channel access approach and an appropriate number of transmission channels, McSynch can significantly reduce the amount of time required to update a local cluster. We also describe our experiences implementing a multichannel system, and report on lessons learned for channel and frequency settings