The wide application of analog and mixed-signal (AMS) designs makes the verification of AMS circuits an important task. However, verification of AMS circuits remains as a significant challenge even though verification techniques for digital circuits design have been successfully applied in the semiconductor industry. In this thesis, we propose two techniques for AMS verification targeting DC and transient verifications, respectively. The proposed techniques leverage a combination of circuit modeling, satisfiability (SAT) and circuit simulation techniques. For DC verification, we first build bounded device models for transistors. The bounded models are conservative approximations to the accurate BSIM3/4 models. Then we formulate a circuit verification problem by gathering the circuit's KCL/KVL equations and the I-V characteristics which are constrained by the bounded models. A nonlinear SAT solver is then recursively applied to the problem formula to locate a candidate region which is guaranteed to enclose the actual DC equilibrium of the original circuit. In the end, a refinement technique is applied to reduce the size of candidate region to a desired resolution. To demonstrate the application of the proposed DC verification technique, we apply it to locate the DC equilibrium points for a set of ring oscillators. The experimental results show that the proposed DC verification technique is efficient in terms of runtime. For transient verification, we perform reachability analysis to verify the dynamic property of a circuit. Our method combines circuit simulation SAT to take advantage of the efficiency of simulation and the soundness of SAT. The novelty of the proposed transient verification lies in the fact that a significant part of the reachable state space is discovered via fast simulation while the full coverage of the reachable state space is guaranteed by the invoking of a few SAT runs. Furthermore, a box merging algorithm is presented to efficiently represent the reachable state space using grid boxes. The proposed technique is used to verify the startup condition of a tunnel diode oscillator and the phase-locking of a phase-locked loop (PLL). The experimental results demonstrate that the proposed transient verification technique can perform reachability analysis for reasonable complex circuits over a great number of time steps.

The ever-increasing number of devices capable of, not only connecting to existing communication networks, but also, independently creating new ones is defining a new communication network, in which the Internet is only one of the substrate networks pro- viding connectivity between diverse devices. This is a network with many interconnected mobile devices connecting to infrastructure networks and creating their own dynamic substrate networks. We present a novel routing scheme for diverse collections of substrate networks with a mix of mobile and static nodes. A key element of the routing scheme is to utilize the exiting routing paths in substrate networks, and set up routing paths between substrate networks. We use sets of nodes as landmarks and define locators that describe node position in the network relative to landmarks. This allows our routing scheme to scale to a large number of nodes, as only information about landmarks needs to be propagated throughout the network.

The ever-increasing number of devices capable of, not only connecting to existing communication networks, but also, independently creating new ones is defining a new communication network, in which the Internet is only one of the substrate networks pro- viding connectivity between diverse devices. This is a network with many interconnected mobile devices connecting to infrastructure networks and creating their own dynamic substrate networks. We present a novel routing scheme for diverse collections of substrate networks with a mix of mobile and static nodes. A key element of the routing scheme is to utilize the exiting routing paths in substrate networks, and set up routing paths between substrate networks. We use sets of nodes as landmarks and define locators that describe node position in the network relative to landmarks. This allows our routing scheme to scale to a large number of nodes, as only information about landmarks needs to be propagated throughout the network.

Integrated circuits have traveled a long way from being a general purpose microprocessor to an application specific circuit. It has become an integral part of the modern era of technology that we live in. As the applications and their complexities are increasing rapidly every day, so are the sizes of these circuits. With the increase in the design size, the associated testing effort to verify these designs is also increased. The goal of this thesis is to leverage some of the static analysis techniques to reduce the effort of testing and verification at the register transfer level. Studying a design at register transfer level gives exposure to the relational information for the design which is inaccessible at the structural level. In this thesis, we present a way to generate a Data Dependency Graph and a Control Flow Graph out of a register transfer level description of a circuit description. Next, the generated graphs are used to perform relation mining to improve the test generation process in terms of speed, branch coverage and number of test vectors generated. The generated control flow graph gives valuable information about the flow of information through the circuit design. We are using this information to create a framework to improve the branch reachability analysis mainly in terms of the speed. We show the efficiency of our methods by running them through a suite of ITC'99 benchmark circuits. / Master of Science

Reachability routing is a newly emerging paradigm in networking, where the goal is to determine all paths between a sender and a receiver. It is becoming relevant with the changing dynamics of the Internet and the emergence of low-bandwidth wireless/ad hoc networks. This thesis presents the case for reinforcement learning (RL) as the framework of choice to realize reachability routing, within the confines of the current Internet backbone infrastructure. The setting of the reinforcement learning problem offers several advantages, including loop resolution, multi-path forwarding capability, cost-sensitive routing, and minimizing state overhead, while maintaining the incremental spirit of the current backbone routing algorithms. We present the design and implementation of a new reachability algorithm that uses a model-based approach to achieve cost-sensitive multi-path forwarding. Performance assessment of the algorithm in various troublesome topologies shows consistently superior performance over classical reinforcement learning algorithms. Evaluations of the algorithm based on different criteria on many types of randomly generated networks as well as realistic topologies are presented. / Master of Science

No description available.

Broadcasting is an essential and effective data propagation mechanism with several important applications, such as route discovery, address resolution and many other network services. Though data broadcasting has many advantages, it can also cause a high degree of contention, collision and congestion, leading to what is known as 'broadcast storm problems'. Broadcasting has traditionally been based on the flooding protocol, which simply overflows the network with a high number of rebroadcast messages until these reach all the network nodes. A good probabilistic broadcast protocol can achieve high saved rebroadcast (SRB), low collision and a lower number of relays. When a node is in a sparse region of the network, rebroadcasting is relatively more important while the potential redundancy of rebroadcast is low because there are few neighbours which might rebroadcast the packet unnecessarily. Further, in such a situation, contention over the wireless medium resulting from Redundant broadcasts is not as serious as in scenarios with medium or high density node populations. This research proposes a dynamic probabilistic approach that dynamically fine-tunes the rebroadcast probability according to the number of neighbouring nodes distributed in the ad-hoc network for routing request packets (RREQs) without requiring the assistance of distance measurements or location-determination devices. The main goal of this approach is to reduce the number of rebroadcast packets and collisions in the network. The performance of the proposed approach is investigated and compared with simple AODV, fixed-probabilistic and adjusted-probabilistic flooding [1] schemes using the GloMoSim network simulator and a number of important MANET parameters, including node speed, traffic load and node density under a Random Waypoint (RWP) mobility model. Performance results reveal that the proposed approach is able to achieve higher SRB and less collision as well as a lower number of relays than fixed probabilistic, simple AODV and adjusted-probabilistic flooding. In this research, extensive simulation experiments have been conducted in order to study and analyse the proposed dynamic probabilistic approach under different mobility models. The mobility model is designed to describe the movement pattern of mobile customers, and how their position, velocity and acceleration change over time. In this study, a new enhanced dynamic probabilistic flooding scheme is presented. The rebroadcast probability p will be calculated dynamically and the rebroadcasting decision will be based on the average number of nodes in the ad-hoc networks. The performance of the new enhanced algorithm is evaluated and compared to the simple AODV, fixed-probabilistic, adjusted-probabilistic and dynamic-probabilistic flooding schemes. It is demonstrated that the new algorithm has superior performance characteristics in terms of collision, relays and SRB. Finally, the proposed schemes are tested and evaluated through a set of experiments under different mobility models to demonstrate the relative merits and capabilities of these schemes.

Mining spatio-temporal reachable regions aims to find a set of road segments from massive trajectory data, that are reachable from a user-specified location and within a given temporal period. Accurately extracting such spatio-temporal reachable area is vital in many urban applications, e.g., (i) location-based recommendation, (ii) location-based advertising, and (iii) business coverage analysis. The traditional approach of answering such queries essentially performs a distance-based range query over the given road network, which have two main drawbacks: (i) it only works with the physical travel distances, where the users usually care more about dynamic traveling time, and (ii) it gives the same result regardless of the querying time, where the reachable area could vary significantly with different traffic conditions. Motivated by these observations, in this thesis, we propose a data- driven approach to formulate the problem as mining actual reachable region based on real historical trajectory dataset. The main challenge in our approach is the system efficiency, as verifying the reachability over the massive trajectories involves huge amount of disk I/Os. In this thesis, we develop two indexing structures: 1) spatio-temporal index (ST-Index) and 2) connection index (Con-Index) to reduce redundant trajectory data access operations. We also propose a novel query processing algorithm with: 1) maximum bounding region search, which directly extracts a small searching region from the index structure and 2) trace back search, which refines the search results from the previous step to find the final query result. Moreover, our system can also efficiently answer the spatio-temporal reachability query with multiple query locations by skipping the overlapped area search. We evaluate our system extensively using a large-scale real taxi trajectory data in Shenzhen, China, where results demonstrate that the proposed algorithms can reduce 50%-90% running time over baseline algorithms.

<p>Friction Stir Welding (FSW) is a new technology which joins materials by using frictional heat. Inthe first part of this thesis, a profound literature study is performed. The basic principles, therobotic implementation and possibilities to use FSW for high strength titanium alloys areexamined. In the next phase, a FSW-tool is modelled and implemented on an industrial robot in arobot simulation program. Reachability tests are carried out on car body parts and jet engineparts. By using a simulation program with embedded collision detection, all possible weldinglocations are determined on the provided parts. Adaptations like a longer FSW-tool and amodified design are suggested in order to get a better reachability. In different case studies, thenumber of required robots and the reduction of weight and time are investigated and comparedto the current spot welding process.</p>

Friction Stir Welding (FSW) is a new technology which joins materials by using frictional heat. Inthe first part of this thesis, a profound literature study is performed. The basic principles, therobotic implementation and possibilities to use FSW for high strength titanium alloys areexamined. In the next phase, a FSW-tool is modelled and implemented on an industrial robot in arobot simulation program. Reachability tests are carried out on car body parts and jet engineparts. By using a simulation program with embedded collision detection, all possible weldinglocations are determined on the provided parts. Adaptations like a longer FSW-tool and amodified design are suggested in order to get a better reachability. In different case studies, thenumber of required robots and the reduction of weight and time are investigated and comparedto the current spot welding process.