CURRENT RESEARCH PROJECTS
- Long-range Ocean Communication Links Powered by Energy Harvesting
- Preserving User Privacy in Server-driven Dynamic Spectrum Access System
- TWC:Medium:SDR Shield: A Hardware-based Security Solution for Software Defined Radio
- CAREER: Study of Coexistence Restrictions of Cross-layer Designs in Wireless Networks
Duration: Oct 2015-Sept 2017
Advancements in maritime communications are severely lagging behind its land counterpart. Existing marine communication technologies usually have very limited capacity and are extremely expensive to operate. Novel solutions are demanded to meet the imminent requirements for broadband marine mobile wireless access. The purpose of this project is to fill the void of marine broadband wireless communications by developing long-range self-powered ocean wireless communication links. The ocean wireless link is composed of compact, maintenance-free and low cost floating wireless base stations (BS) that can be simply dropped into the water. Once in the water, the BSs start to harvest energy from ocean waves and establish communication links with each other. Users' broadband traffic, then, can be delivered to the Internet through these links. This project will bring revolutionary change to the maritime communications. New maritime networked applications and operation scenarios that are infeasible but highly desirable in the past can be enabled by this technology. It can have significant impact on all aspect of ocean related industry, such as fishing, recreational boating, marine transportation, oil and gas industry, ocean scientific study, and national security and defense. The project will focus on two thrust areas: Thrust 1 is about ocean wave energy harvesting. For a BS to provide large coverage range and high capacity links to its users and other BSs, the BS must consume a large amount of energy. It is nontrivial to design such an energy-harvesting unit while staying low-cost, compact and maintenance-free. Existing technologies are too large in size and hence are expensive and hard to be stabilized in rough ocean states and require frequent maintenance. This project solves this critical challenge by a novel power takeoff mechanism. This design enables the researchers to build an ocean wave energy harvester that can effectively harvest tens watts of power on typical ocean states with a floating buoy of less than 1 meter diameter. Thrust 2 is about building the high capacity marine communication links. The constantly moving ocean waves can affect the capacity, stability and range of the backhaul links among BSs. In this project, we will study how to analyze and model the channel and design antenna and radio hardwares to handle the complex channel of ocean communication links. The researchers will also study the unique features of ocean communication links and their potential beneficial and/or harmful impact on network communications.
Duration: Jan 2016-Dec 2018
Dynamic spectrum access (DSA) technique enables wireless devices, which is called secondary users (SUs), to use spectrum that are allocated to licensed incumbent users (IUs) as long as they do not interfere with IUs' operation. It has been widely accepted as a crucial solution to mitigate the spectrum scarcity problem for wireless communications. As a key form of DSA, US government has proposed to release more Federal spectrum for sharing with commercial wireless users. It has also recommended a spectrum access system (SAS) database to govern the spectrum sharing between IUs and SUs. However, the flourish of SAS-driven Federal-Commercial sharing hinges upon how privacy issues are managed. In current SAS schemes, the operation data of both federal IUs and commercial SUs need to be shared with the SAS database for it to decide if sharing is permitted. Yet, operation data of federal IUs are often classified information and SU operation data may also be commercial secret. Since SAS is not necessarily operated by a trusted third party and can potentially be breached by attackers, these current schemes threaten the privacy of both IUs and SUs. To address this privacy issue, this project will develop a privacy-preserving SAS (P2-SAS), which ensures that the SAS system can still accurately decide whether spectrum sharing among IUs and SUs are permitted while it learns nothing about the operation data of IUs and SUs. This project is the first to be able to successfully realize privacy-preserving spectrum allocation in SAS. It will address regulators’ concerns with DSA’s privacy issue and hence greatly help the development of the entire nation's broadband networks. The project will also provide a blueprint on how privacy-preserving mechanisms can be integrated in many other communication systems beyond DSA. The project realizes its privacy preserving spectrum allocation using secure homomorphic computation. In P2-SAS, IUs and SUs share only ciphertexts of their operation data with the SAS Server. SAS Server then performs secure homomorphic computation directly over these ciphertexts, so that none of the IU/SU operation data would be exposed to any snooping party, including the SAS itself. The project is able to convert complex spectrum allocation computation and certification procedures into the limited homomorphic computation types provided by efficient Paillier cryptosystems. Leveraging the unique characteristics of spectrum allocation computation, various refining techniques are explored to significantly reduce the computation and communication overhead of P2-SAS and prevent potential attacks on the system.
Software Defined Radio (SDR) technology has the flexibility of implementing a large part of physical layer functions in software. It is one of the major technologies that will provide broadband services to millions of US residences. However, unlike conventional radio whose RF signals are tightly regulated by FCC-certified hardware, the software components of SDR can be easily exploited by hackers to create a wide range of unauthorized waveforms to launch attacks on many security-critical wireless systems. The existing preventive software-based security counter measures are not possible to prevent the myriad of potential software security loopholes and themselves often become targets of the malware. The objective of this project is to design an effective hardware-based SDR integrity assessment and behavior regulation device named SDR Shield. SDR Shield resides between the vulnerable SDR software and the security-critical SDR hardware to detect any malicious configuration of the RF device and prevent it from being used to attack wireless systems. The SDR Shield uses side channel and communication channel information from different SDR components to detect deviations from expected execution status. SDR shield also includes a regulation circuit to enforce safety-critical properties of SDR operation. A secure update process is developed to maintain SDR shield’s flexibility and its own security. The generality of SDR Shield’s design provides a unified security mechanism for SDR design and hence can ease the burden on FCC or any future SDR design verification institutes in certifying security measures of SDR products.
Of late, there has been an explosive growth of cross-layer designs proposed for wireless networks. These designs break the layered structure to actively exploit the dependence between protocol layers in wireless networks. However, the large number of cross-layer designs creates serious coexistence issues. The violation of layered structure may not comply with restrictions that constrain the coexistence among many cross-layer designs and other network systems, causing significant issues, such as degraded performance, inconsistent distributed decision making, network partition, and instability. The objective of this project is to systematically and rigorously categorize and analyze coexistence restrictions of cross-layer designs in wireless networks. In this project, coexistence restrictions of various cross-layer designs are theoretically modeled and analyzed. Different kinds of coexistence restrictions are defined, the conditions for their occurrences and their impact on network operations are revealed, and methods to check coexistence issues are developed. The project also seeks restriction-compliant protocol design techniques. This project serves as a major effort in the understandings of cross-layer designs in wireless networks and is the pioneer in providing systematic analysis of coexistence restrictions of cross-layer designs. The result of this project can be used to evaluate cross-layer designs’ limitations and potential problems. This will promote the acceptance of good cross-layer designs in real systems and prevent architecture failures in design integration. In addition, this project provides practical techniques for designing more compatible cross-layer systems. Ultimately, this will greatly enhance the flexibility and robustness of current and future wireless network systems.