On robust and secure wireless communication system design using software-defined radios

This dissertation is composed of three parts: airborne multi input multi output (MIMO) communications, physical layer authentication, and software radio design for DARPA Spectrum Challenge. A common theme for the three distinct problems is the system perspective that we have adopted throughout this dissertation. Instead of considering isolated issues within these problems, we have provided a holistic design approach to the three problems and have implemented all three systems using the GNU Radio/USRP (Universal Software Radio Peripheral) platform. In the first part, we develop a MIMO communication system for airborne platforms. MIMO communication has long been considered to be suitable only for environment that is rich in scatterers. This, unfortunately is not the case for airborne platforms. However, this lack of scattering can be compensated by the large aperture of the airborne MIMO platform; this is corroborated by our careful analysis using real measurement data. Our analysis of the airborne MIMO channels leads to the development of a variable rate MIMO transceiver architecture. This architecture is numerically shown to improve the bit error rate (BER) over conventional transceiver architectures that are developed for rich scattering environments. A software radio based MIMO system is then implemented to demonstrate experimentally the efficacy of the developed architecture. In the second part, we develop a physical layer authentication scheme as a counter measure to primary user emulation attack (PUEA) in cognitive radio (CR) networks. In this attack, a malicious user emulates the signal characteristics of the primary user (PU) when it is silent which prevents unsuspecting secondary user (SU) from utilizing the network. The developed physical layer authentication is based on embedding cryptographic hash signatures, referred to as authentication tags, within PU\u27s signal constellations. The embedding is performed such that the legacy receivers are not affected. We analyze the scheme using the fast fading Rayleigh channel model and present an optimal scheme to embed signals in PU\u27s constellations which minimizes the tag BER. Experimental results are obtained that corroborate our theoretical claims, thereby establish that reliable authentication can be achieved without sacrificing signal quality at the primary receivers. In the final part, we describe in detail our design of software radios developed as part of the DARPA Spectrum Challenge (DSC), a year long competition that started in January 2013 and concluded in March 2014 with the final tournament held in Arlington, VA at the DARPA headquarter. DSC was comprised of two tournaments, competitive and cooperative. In the competitive mode two radio pairs, each composed of a transmitter and a receiver, are pitted against each other to transmit the most amount of data error-free while operating concurrently in the same frequency band. In the cooperative mode, three radio pairs have to share a frequency band in a cooperative manner wherein the goal is to maximize the throughput of all the three pairs. We describe the design of our software radio system that integrates some key technologies crucial in operating in an environment that does not allow user coordination and spectrum pre-planning, including: spectrum sensing, adaptive transmission both in spectrum utilization and transmission rate, opportunistic jamming, and sliding window feedback. The developed radio is robust in the presence of unknown interference and achieves the desired balance between throughput and reliability in an uncoordinated transmission environment

Efficient Channel Modeling Methods for Mobile Communication Systems

Siirretty Doriast

Formally-Based Testing of Radiotherapy Accelerators

The paper presents the aims and research plan of the CONFORMED project (Conformance Of Radiological/Medical Devices). This three-year project will develop tools and techniques for modelling and testing radiotherapy equipment. Formal specifications in LOTOS (Language Of Temporal Ordering Specification) will be used to model accelerators formally and to derive tests rigorously based on these specifications

Formal Methods for Communication Services

We survey formal methods as they are applied to the development of communication services. We report on industrial and academic projects, consider different communication architectures and work related to the feature interaction problem. Based on our survey, the results reported in the literature and most importantly, on extensive discussions with industry, we investigate important industrial concerns and criticisms about the use of formal methods for the development of communication services. We report on a collaborative project between the Swiss Federal Institute of Technology in Lausanne, Swisscom, Alcatel and Thomson in which these industrial concerns have been taken into account from the very beginning. The results of this project are currently being integrated into an industrial software development platform

A conformance test framework for the DeviceNet fieldbus

The DeviceNet fieldbus technology is introduced and discussed. DeviceNet is an open standard fieldbus which uses the proven Controller Area Network technology. As an open standard fieldbus, the device conformance is extremely important to ensure smooth operation. The error management in DeviceNet protocol is highlighted and an error injection technique is devised to test the implementation under test for the correct error-recovery conformance. The designed Error Frame Generator prototype allows the error management and recovery of DeviceNet implementations to be conformance tested. The Error Frame Generator can also be used in other Controller Area Network based protocols. In addition, an automated Conformance Test Engine framework has been defined for realising the conformance testing of DeviceNet implementations. Automated conformance test is used to achieve consistent and reliable test results, apart from the benefits in time and personnel savings. This involves the investigations and feasibility studies in adapting the ISO 9646 conformance test standards for use in DeviceNet fieldbus. The Unique Input/Output sequences method is used for the generation of DeviceNet conformance tests. The Unique Input/Output method does not require a fully specified protocol specification and gives shorter test sequences, since only specific state information is needed. As conformance testing addresses only the protocol verification, it is foreseen that formal method validation of the DeviceNet protocol must be performed at some stage to validate the DeviceNet specification

Test case verification by model checking

Verification of a test case for testing the conformance of protocol implementations against the formal description of the protocol involves verifying three aspects of the test case: expected input/output test behavior, test verdicts, and the test purpose. We model the safety and liveness properties of a test case using branching time temporal logic. There are four types of safety properties: transmission safety, reception safety, synchronization safety, and verdict safety. We model a test purpose as a liveness property and give a set of notations to formally specify a test purpose. All these properties expressed as temporal formulas are verified using model checking on an extended state machine graph representing the composed behavior of a test case and protocol specification. This methodology is shown to be effective in finding errors in manually developed conformance test suites. © 1993 Kluwer Academic Publishers

Design and implementation of a TTCN to C translator

The conformance testing of a protocol implementation, may be logically divided into, the specification of the abstract test suite (ATS) from a formal descnption of the protocol, and the subsequent derivation of the executable test suite (ETS) from the ATS specification. Our concern here is with the latter step, in particular, the automatic derivation of an ATS expressed in the Tree and Tabular Combined Notation (TTCN) to an executable C language equivalent. This process is currently a manual one, and as a consequence is error prone, time consuming, often repetitive and not necessarily consistent. To overcome these problems, there exists the real need for a computer aided, and if possible, fully automatic solution. This study descnbes the design and implementation of a fully working TTCN subset to C language translator, which takes a TTCN ATS and produces an equivalent ETS, with a minimal amount of manual intervention. The methodology used is logically divided into three stages direct TTCN to C language mappings, implementation issues, including the generation of additional code to drive the above mappings, and test system implementation issues. The system was tested using parts of an ETSI ISDN LAPD ATS and the results showed considerable time savings against a similar manual implementation. In conclusion, suggestions are provided to the further development of the TTCN to C translator system, and discussion is given to the apphcation of this tool to a complete conformance testing system