PhD Dissertation Defense

Physical- and MAC-Layer Mechanisms for Increasing
Base-Station Anonymity in Wireless Ad-hoc Networks

John Ward

10:00am Monday, 13 April 2015, ITE 325b, UMBC

Wireless ad hoc networks have become valuable assets to both the commercial and military communities with applications ranging from industrial control on a factory floor to reconnaissance of a hostile border. In most applications, data sources forward information over multi-hop paths to a base station (BS). The BS not only serves as the data sink, but also provides other basic control and management features such as protocol synchronization, a gateway to other networks, and operator failure notifications, without which the network becomes dysfunctional. The critical role of the BS makes it a natural target for an adversary that desires to achieve the most impactful attack on the network. Even if an ad-hoc network employs conventional security mechanisms such as encryption and authentication, an adversary may apply traffic analysis techniques to identify the BS. This motivates a significant need for achieving improved BS anonymity to conceal its identity, role, and location. Traffic analysis countermeasures found in the literature have focused on the link and network layers and little attention has been given to the physical-layer (PHY) approaches.

In this dissertation, we address the challenges of BS anonymity by developing PHY and Medium Access Control (MAC) traffic analysis countermeasures. We first consider the limitations associated with evidence theory, the adversary’s primary traffic analysis attack model. We analyze the susceptibility of evidence theory to imperfect received signal strength (RSS) measurements. Next we extend the standard evidence theory approach to consider the contribution of acknowledgements to BS anonymity. We call this approach Acknowledgement Aware Evidence Theory (AAET) and describe the adversary’s initial survey phase which is based on a novel message correlation approach. Accurate synchronization is required by an ad-hoc network to employ PHY countermeasures; however, synchronization represents a fundamental design tradeoff, since the low-cost nodes and conservation of energy limit the achievable accuracy of synchronization within the network. We consider the impact of two popular synchronization protocols, Reference Broadcast Synchronization (RBS) and Timing-Synch Protocol for Sensor Networks (TPSN) on BS anonymity.

We develop a novel PHY BS anonymity-boosting approach based on distributed beamforming, which we call Distributed Beamforming protocol for increased BS ANonymity (DiBAN). DiBAN is a protocol that includes a cross-layer relay selection algorithm that a node employs to determine the most appropriate number of helper relays to participate in distributed beamforming at each hop. While effective at increasing BS anonymity, the overhead associated with DiBAN is in addition to any overhead already associated with existing ad hoc network protocols. We refine DiBAN using cross-layer design methodology to create an integrated distributed beamforming protocol called Link and Physical Cross-layer design for increased Anonymity (LiPCA) that increases BS anonymity with minor additional overhead by taking advantage of the underlying services that the MAC already provides. We use simulation to demonstrate the anonymity performance and energy-efficiency of our approaches and use the popular Sensor MAC (S-MAC) protocol as an exemplar MAC protocol. Results show that the cross-layer design of our LiPCA protocol achieves equivalent anonymity performance to DiBAN, but with an energy savings of approximately 35 percent.

Committee: Drs. Mohamed Younis (Chair), Charles Nicholas, Richard Forno, Ryan Robucci and Pedro Rodriguez (JHU/APL)

This weekend, I used UMBC’s Bike Share for the first time- I don’t have a car and needed to do some nearby errands that were not on UMBC Transit’s bus routes.

It was super easy: I showed my red ID to the RAC front desk, signed a waiver, and was issued a bike, helmet, and lock to use until the RAC closed that night. The bikes are hybrid so they can ride on and off road surfaces. 

I was soon on my way, enjoying my bike ride, and spending less time doing errands because biking is certainly faster than walking!

If you need a way to get around the area, check out the bike share program at the RAC.  You can borrow a bike any time the RAC is open."

I found information about the bikeshare here: http://ies.umbc.edu/files/2014/03/Retrieverfleet.pdf

Molissa Udevitz 

UMBC Eco-Ambassador

President of Geography and Environmental Systems Council of Majors

GES and Dance double major '15

March 31 marked the end of the PMP rating period (April 1, 2014 through March 31, 2015). UMBC requires supervisors to evaluate the performance of all regular/grant-funded exempt and non-exempt employees. The deadline for submission of the PMP forms to the Department of Human Resources is Friday, May 1, 2015.

For additional information, visit http://hr.umbc.edu/pmp/. If you have any questions, please contact Elmer Falconer at ext. 5-3645 or Shobhna Arora at ext. 5-1638.

Ph.D. Dissertation Defense
Electrical Engineering

Simultaneous Polarization-Insensitive Phase-space
Trans-multiplexingand Wavelength Multicasting via
Cross-phase Modulation in a Photonic Crystal Fiber at 10 GBd

Brice Cannon

2:00pm Monday, 6 April 2015, ITE325b, UMBC

This thesis investigates the all-optical combination of amplitude and phase modulated signals into one unified multi-level phase modulated signal, utilizing the Kerr nonlinearity of cross-phase modulation (XPM). Predominantly, the first experimental demonstration of simultaneous polarization-insensitive phase-transmultiplexing and multicasting (PI-PTMM) will be discussed. The PI-PTMM operation combines the data of a single 10-Gbaud carrier-suppressed return-to-zero (CSRZ) on-off keyed (OOK) pump signal and 4×10-Gbaud return-to-zero (RZ) binary phase-shift keyed (BPSK) probe signals to generate 4×10-GBd RZ-quadrature phase-shift keyed (QPSK) signals utilizing a highly nonlinear, birefringent photonic crystal fiber (PCF). Since XPM is a highly polarization dependent nonlinearity, a polarization sensitivity reduction technique was used to alleviate the fluctuations due to the remotely generated signals’ unpredictable states of polarization (SOP). The measured amplified spontaneous emission (ASE) limited receiver sensitivity optical signal-to-noise ratio (OSNR) penalty of the PI-PTMM signal relative to the field-programmable gate array (FPGA) pre-coded RZ-DQPSK baseline at a forward-error correction (FEC) limit of 10-3 BER was ≈ 0.3 dB. In addition, the OSNR of the remotely generated CSRZ-OOK signal could be degraded to ≈ 29 dB/0.1nm, before the bit error rate (BER) performance of the PI-PTMM operation began to exponentially degrade. A 138-km dispersion-managed recirculating loop system with a 100-GHz, 13-channel mixed-format dense-wavelength-division multiplexed (DWDM) transmitter was constructed to investigate the effect of metro/long-haul transmission impairments. The PI-PTMM DQPSK and the FPGA pre-coded RZ-DQPSK baseline signals were transmitted 1,900 km and 2,400 km in the nonlinearity-limited transmission regime before reaching the 10-3 BER FEC limit. The relative reduction in transmission distance for the PI-PTMM signal was due to the additional transmitter impairments in the PCF that interact negatively with the transmission fiber.

Committee: Drs. Professor Gary M. Carter (Chair), William Astar, Anthony M. Johnson, Tinoosh Mohsenin, Thomas E. Murphy, Terrance L. Worchesky

Ph.D. Dissertation Defense
Computer Engineering

PSANDE: A Framework for Accurate Dynamic
Power Supply Analysis and Delay Estimation

Sushmita K. Rao

11:30am Friday, 3 April 2015, ITE 325b, UMBC

Power-supply noise is a major contributing factor for yield loss in sub-micron designs. Excessive switching in test mode causes supply voltage to droop more than in functional mode, leading to failures in delay tests that would not occur otherwise under normal operation. There exists a need to accurately estimate on-chip supply noise early in the design phase to meet power requirements in normal mode and during test to prevent over-stimulation during testing and avoid false failures. Simultaneous switching activity (SSA) of several logic components is one of the main sources of power-supply noise (PSN) which results in reduction of supply voltages at the power-supplies of the logic gates. Current research concentrates on static IR-drop, which accounts for only part of the total voltage drop on the power grid and therefore is insufficient for nanometer designs. Inductive drop is not included in current noise analysis techniques for simplification.

The power delivery networks in today’s very deep-submicron chips are susceptible to slight variations and cause sudden large current spikes leading to higher Ldi/dt drop than resistive drop, necessitating the need to be accounted. Especially of concern is simultaneous switching in localized areas in a chip because it concentrates current drawn on a particular power bump further reducing supply voltage. Thus, there arises a growing need to accurately characterize the resistive and inductive voltage drop caused by simultaneous switching of multiple paths. Power-supply noise also impacts circuit operation, causing a significant increase in path delays. It is critical to account for this increase in delay during the ATPG process otherwise it can lead to overkill during transition and delay testing. However, it is infeasible to carry out full-chip SPICE-level simulations on a design to validate the large number of ATPG generated test patterns. Accurate and efficient techniques are required to quantify supply noise and its impact on path delays to ensure reliable operation in both mission mode and during test.

A scalable current-based dynamic method is presented to estimate both IR and Ldi/dt drop caused by simultaneous switching activity. Also presented is a technique to predict the increase in path delays caused by supply noise. The noise and delay estimation techniques use simulations of individual extracted switching logic in comparison to time-consuming full-chip simulations and thus it can be integrated with existing ATPG tools. A design partitioning technique is also presented that makes the framework feasible for larger designs. Supply noise estimation error is less than 12% of SPICE level full-chip results across all test cases in the combinational and sequential benchmark circuits. The effect of power supply noise on path delays is modeled effectively. Results from multiple designs show that using the convolution-based technique the increase in path delay can be accurately predicted with a worst case error of 4% as compared to full-chip simulation results demonstrating the effectiveness of the technique.

Committee: Drs. Chintan Patel (Chair), Dhananjay Phatak, Ryan Robucci, Nilanjan Banerjee and Ismed Hartanto (Xilinx)

On Wednesday, April 8th on the Commons Main Street AND the RAC from 10-4pm, the Women’s Center will be displaying the Clothesline Project in honor of Sexual Assault Awareness Month. This display includes t-shirts with messages from UMBC community members over the years related to their experiences of sexual assault or relationship violence. This can be a powerful experience for passersby.

The display in the RAC will be part of the Retriever Heath and Wellness Expo.

Opportunities to contribute a t-shirt to the Project will be available in the Women’s Center prior to the 8th. For more information on dates and times, visit the Women’s Center’s myUMBC group page.

The UMBC student community is invited to join the Women’s Center staff for a workshop from 12-1pm on the same day on how to support survivors of sexual violence and work together as a community to cultivate a survivor-responsive campus. For more details on this workshop, visit the myUMBC event page.

For additional information, feel free to contact the Women’s Center at 410.455.2714 or email womens.center@umbc.edu. Information regarding the event, including an event flyer, can be found on myUMBC.

In recognition of Sexual Assault Awareness Month, join the Women’s Center, UHS Health Education and Voices Against Violence on Commons Main Street on April 16th at 6pm and let’s take back the night!

Events and activities include:

• Community Resource Fair (beginning at 6pm)
• The Clothesline Project
• Survivor Speak Out Forum (begins at 6:30pm)
• March Against Sexual Violence (begins approx around 7:20pm)
• Art Activism and Community Building (post march)

Community members are encouraged to make rally signs prior to TBTN to show your solidarity with survivors. You can make signs in the Women’s Center between 12-3pm on April 13, 14 and 15.

#UMBCtbtn is the official Twitter event hashtag, so follow us there and post your pictures from the evening. Want to learn more about what Take Back The Night is? Visit www.takebackthenight.org for more information.

This event is co-sponsored by: The Women’s Center, UHS Health Education, and Voices Against Violence. For more information, contact the Women’s Center at womens.center@umbc.edu or 410-455-2714.