A dynamic network scenario emulation tool

Comparative performance measurements of distributed applications and network protocols require the availability of appropriate network environments. Network emulation approaches offer a flexible way to mimic the properties of a variety of networks. Existing emulation tools work either with centralized real-time simulation components, limiting the scenario size and maximum traffic, or focus on the emulation of some network properties at a single point. We propose a tool for the realistic emulation of network links, and show how several emulated links can be combined to reproduce a comprehensive network model. In addition to that, the model can include changing network properties, e.g. emerging from mobile communication partners. This facilitates the distributed emulation of a comprehensive, dynamic network scenario to support repeatable performance measurements

They Can Hear Your Heartbeats: Non-Invasive Security for Implantable Medical Devices

Wireless communication has become an intrinsic part of modern implantable medical devices (IMDs). Recent work, however, has demonstrated that wireless connectivity can be exploited to compromise the confidentiality of IMDs' transmitted data or to send unauthorized commands to IMDs---even commands that cause the device to deliver an electric shock to the patient. The key challenge in addressing these attacks stems from the difficulty of modifying or replacing already-implanted IMDs. Thus, in this paper, we explore the feasibility of protecting an implantable device from such attacks without modifying the device itself. We present a physical-layer solution that delegates the security of an IMD to a personal base station called the shield. The shield uses a novel radio design that can act as a jammer-cum-receiver. This design allows it to jam the IMD's messages, preventing others from decoding them while being able to decode them itself. It also allows the shield to jam unauthorized commands---even those that try to alter the shield's own transmissions. We implement our design in a software radio and evaluate it with commercial IMDs. We find that it effectively provides confidentiality for private data and protects the IMD from unauthorized commands.National Science Foundation (U.S.). (Grant number CNS-0831244)National Science Foundation (U.S.). Graduate Research Fellowship ProgramAlfred P. Sloan Foundation. FellowshipUnited States. Dept. of Health and Human Services. Cooperative Agreement (90TR0003/01

Energy-efficient wireless communication

In this chapter we present an energy-efficient highly adaptive network interface architecture and a novel data link layer protocol for wireless networks that provides Quality of Service (QoS) support for diverse traffic types. Due to the dynamic nature of wireless networks, adaptations in bandwidth scheduling and error control are necessary to achieve energy efficiency and an acceptable quality of service. In our approach we apply adaptability through all layers of the protocol stack, and provide feedback to the applications. In this way the applications can adapt the data streams, and the network protocols can adapt the communication parameters

Characterization of Network Inaccessibility in IEEE 802.15.4 Wireless Networks

Wireless communications are vulnerable to the presence of errors during the network operation. These errors may be originated from different sources such as external electromagnetic interferences, obstacles in communication path, or even glitches in the communication circuitry. Such origins may lead the medium access control (MAC) layer to deviate from its normal operation (without presence of errors), forcing the execution of additional actions to maintain the network operational. The execution of such actions may imply the occurrence of periods of "communication silence", where the network, although not being failed, is not performing communications. These periods of ``communication silence" are dubbed network inaccessibility, which may induce inaccurate fault detections and deadline misses. Additionally, the occurrence of network inaccessibility may compromise network properties such as predictability, dependability, and timeliness. Thus, this report presents an exhaustive study about network inaccessibility, using the 802.15.4 standard as a case study. All network inaccessibility scenarios are presented, discussing important steps to achieve predictability, dependability, and timeliness in wireless communications.This work was partially supported by EC, through project IST-STREP-288195 (KARYON) and by FCT through the Multiannual Funding and CMU-Portugal Programs and the Individual Doctoral Grant SFRH/BD/45270/2008

Tactics-Based Remote Execution for Mobile Computing

into a computing giant able to run resource-intensive applications such as natural language translation, speech recognition, face recognition, and augmented reality. However, easily partitioning these applications for remote execution while retaining application-specific information has proven to be a difficult challenge. In this paper, we show that automated dynamic repartitioning of mobile applications can be reconciled with the need to exploit application-specific knowledge. We show that the useful knowledge about an application relevant to remote execution can be captured in a compact declarative form called tactics. Tactics capture the full range of meaningful partitions of an application and are very small relative to code size. We present the design of a tactics-based remote execution system, Chroma, that performs comparably to a runtime system that makes perfect partitioning decisions. Furthermore, we show that Chroma can automatically use extra resources in an overprovisioned environment to improve application performance

Encryption on the air : non-Invasive security for implantable medical devices

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 73-78).Modern implantable medical devices (IMDs) including pacemakers, cardiac defibrillators and nerve stimulators feature wireless connectivity that enables remote monitoring and post-implantation adjustment. However, recent work has demonstrated that flawed security tempers these medical benefits. In particular, an understandable lack of cryptographic mechanisms results in the IMD disclosing private data and being unable to distinguish authorized from unauthorized commands. In this thesis, we present IMD-Shield; a prototype defenses against a previously proposed suite of attacks on IMDs. IMD-Shield is an external entity that uses a new full dulpex radio design to secure transmissions to and from the IMD on the air wihtout incorporating the IMD itself. Because replacing the install base of wireless-enabled IMDs is infeasible, our system non-invasively enhances the security of unmodified IMDs. We implement and evaluate our mechanism against modern IMDs in a variety of attack scenarios and find that it effectively provides confidentiality for private data and shields the IMD from unauthorized commands.by Haitham Al-Hassanieh.S.M

Measurement and analysis of real-world 802.11 mesh networks

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.Includes bibliographical references (p. 63-65).Despite many years of work in wireless mesh networks built using 802.11 radios, the performance and behavior of these networks in the wild is not well understood. This is primarily due to a lack of access to data from a wide range of these networks; most researchers have access to only one or two testbeds at any time. In recent years, however, these networks have been deployed commercially and have real users who use the networks in a wide range of conditions. This thesis analyzes data collected from 1407 access points in 110 different commercially deployed Meraki wireless mesh networks, constituting perhaps the largest study of real-world 802.11 mesh networks to date. After analyzing a 24-hour snapshot of data collected from these networks, we answer questions from a variety of active research topics, including the accuracy of SNR-based bit rate adaptation, the impact of opportunistic routing, and the prevalence of hidden terminals. The size and diversity of our data set allow us to analyze claims previously only made in small-scale studies. In particular, we find that the SNR of a link is a good indicator of the optimal bit rate for that link, but that one could not make an SNR-to-bit-rate look-up table that was accurate for an entire network. We also find that an ideal opportunistic routing protocol provides little to no benefit on most paths, and that "hidden triples"-network topologies that can lead to hidden terminals-are more common than suggested in previous work, and increase in proportion as the bit rate increases.by Katrina L. LaCurts.S.M