<p>In this thesis, a practical superposition coding scheme based on multilevel low-density parity-check (LDPC) codes is proposed for discrete memoryless broadcast channels. The simulation results show that the performance of the proposed scheme approaches the information-theoretic limits. We also propose a method for optimizing the degree distribution of multilevel LDPC codes based on the analysis of EXIT functions.</p> / Master of Applied Science (MASc)

A converse method is developed for the source broadcast problem. Specifically, it is shown that the separation architecture is optimal for a variant of the source broadcast problem and the associated source-channel separation theorem can be leveraged, via a reduction argument, to establish a necessary condition for the original problem, which uni es several existing results in the literature. Somewhat surprisingly, this method, albeit based on the source-channel separation theorem, can be used to prove the optimality of non-separation based schemes and determine the performance limits in certain scenarios where the separation architecture is suboptimal. / Thesis / Master of Applied Science (MASc)

This research examines the relationship between online and offline sales in an omnichannel sales environment centered around the selling of parking spaces. This dissertation consists of a pilot study followed by an expanded study. The studies delved into the effects of e-commerce additions upon traditional brick and mortar revenue channels. The parking industry was selected as the backdrop, given the high degree of current relevant concerns in this space around internet sales-related cannibalization concerns against physical stores, and given the author’s substantial access to relevant research data. Data was collected for an intervention group and a control group from a leading parking management firm with thousands of parking garages located across North America. In the pilot study, and using panel data gathered from the firm, we sought to examine the effects of an online intervention to existing aggregate revenues through the implementation of a new 3rd party e-commerce sales channel (Parkwhiz.com). Under the intervention group, data was collected on 1.7 million revenue transactions over an approximately two-year period, from 2016 through 2018 across 15 parking properties in New York City. The control group consisted of 493,950 revenue transaction entries, also spanning a roughly two-year period from 2016 through 2018, and across 28 different parking properties throughout the City of New York. A fixed-effect model was used for analyzing the data, which came with unforeseen challenges of balance, outlier concerns, and sample size. Ultimately, insignificant results were observed, but these were attributed mainly to difficulties in data structure and sample size (N = 386) of daily revenue observations. Despite those challenges, individual summary statistics showed potential strength in the primary hypothesis, and this motivated further examination. In the expanded study, an adapted approach from the pilot was used to correct for a majority of its shortcomings in the data structure, sample size, balance, and modeling. Further, several moderating components were incorporated to test practice relevant relationships between revenue, the competitive landscape, and online search sessions. Using the same primary hypothesis from the pilot study, the expanded work provided for 15 intervention group properties and 15 control group properties in New York City, with a balanced dataset of 90 days pre-intervention and 90 days post-intervention for each property examined in the year 2018 or 2019. The original hypothesis (H1A) evaluates whether or not an online intervention increases total revenue at a given location. Additional hypotheses (H1B) evaluating whether offline revenue sources are affected by the online intervention, (H2) moderation of revenue by the volume of competition using the same online channel, (H3) moderation of revenue by the volume of parking locations in the marketplace (zip code area) regardless of selling online or offline, and (H4) revenue predicted by the volume of online searches for parking occurring in the marketplace. Sample sizes ranged from N = 3,491 to 5,098 across our various regression models. Our overall H1 outcomes (across four different regression models) showed strong statistical significance with p-values less than 0.001, and moderate R^2 scores between 37%-47% for the online ParkWhiz intervention. Online intervention increases revenue per parking space in the range of $1.171 to $1.196 in the experiment. The results provide support for the proposition that adding an online sales channel to an existing body of physical parking facilities is additive, non-cannibalistic and overall productive for the business. Our H2 and H3 study outcomes were inconclusive, as the moderators were not significant. The tests of the moderating effects in H2 and H3 provided no practical results, other than perhaps anecdotal perception to supplement the other findings. The testing of H4 did show significance in the importance of the assessment of online search demand in a given zip code as an amplifier of the effect of online intervention on parking revenue. Search volume is positively related to a change in the net new revenues. Overall, the analysis generated learnings valuable for future researchers to expand upon through better data gathering, statistical models, and analysis. In totality, the desired contribution of this body of research is to provide today’s brick and mortar business manager with strategic insights into the conditions needed to make healthy e-commerce decisions, based on observable market conditions, in an omnichannel environment that combines online and offline models for maximum aggregate revenue growth. Avoidance or minimization of cannibalization between existing channels and new channels can ensure success. Our work demonstrates several critical aspects of the phenomena of successful online and offline channel cohabitation with practical conclusions for the strategic decision-maker to use in reaching that equilibrium, and leaves a discernible path for future researchers to supplement our efforts with additional moderating variables. Keywords: Omnichannel, cannibalization; externality; brick and mortar; platform; two-sided marketplace; e-commerce; parking; retail; online/offline; distribution; multi-channel; cross-channel; offline-to-online service platform, channel addition, mobile apps. / Business Administration/Strategic Management

<p> In this thesis, we present a novel signalling scheme for blind channel identification of Alamouti space-time coded (STBC) channel and a space-time coded multiple-input single-output (MISO) system under flat fading environment. By using p-ary and q-ary PSK signals (where p and q are co-prime integers), we prove that a) under a noise-free environment, only two distinct pairs of symbols are needed to uniquely decode the signal and identify the channel, and b) under complex Gaussian noise, if the pth and qth order statistics of the received signals are available, the channel coefficients can also be uniquely determined. In both cases, simple closed-form solutions are derived by exploiting specific properties of the Alamouti STBC code and linear Diophantine equation theory.</p> <p> When only a limited number of received data are available, under Gaussian noise environment, we suggest the use of the semi-definite relaxation method and/or the sphere decoding method to implement blind ML detection so that the joint estimation of the channel and the transmitted symbols can be efficiently facilitated. Simulation results show that blind ML detection methods with our signalling scheme provide superior normalized mean square error in channel estimation compared to the method using only one constellation and that the average symbol error rate is close to that of the coherent detector (which necessitates perfect channel knowledge at the receiver), particularly when the SNR is high.</p> / Thesis / Master of Applied Science (MASc)

no / Peer-to-Peer (P2P) has become a popular live streaming delivery technology owing to its scalability and low cost. P2P streaming systems often employ multi-channels to deliver streaming to users simultaneously, which leads to a great challenge of allocating server resources among these channels appropriately. Most existing P2P systems resort to over-allocating server resources to different channels, which results in low-efficiency and high-cost. To allocate server resources to different channels efficiently, we propose a dynamic resource allocation algorithm based on a streaming quality model for P2P live streaming systems. This algorithm can improve the channel streaming quality for multi-channel P2P live streaming system and also guarantees the streaming quality of the channels under extreme Internet conditions. In an experiment, the proposed algorithm is validated by the trace data.

This dissertation addresses the problem of channel assignment in multi-hop, multi-transceiver wireless networks. We investigate (1) how channels can be assigned throughout the network to ensure that the network is connected and (2) how the channel assignment can be adapted to suit the current traffic demands. We analyze a traffic-aware method for channel assignment that addresses both maintaining network connectivity and adapting the topology based on dynamic traffic demands. The traffic-aware approach has one component that assigns channels independently of traffic conditions and a second component that assigns channels in response to traffic conditions. The traffic-independent (TI) component is designed to allocate as few transceivers or radios as possible in order to maintain network connectivity, while limiting the aggregate interference induced by the topology. The traffic-driven (TD) component is then designed to maximize end-to-end flow rate using the resources remaining after the TI assignment is complete. By minimizing resources in the TI component, the TD component has more resources to adapt the topology to suit the traffic demands and support higher end-to-end flow rate. We investigate the fundamental tradeoff between how many resources are allocated to maintaining network connectivity versus how many resources are allocated to maximize flow rate. We show that the traffic-aware approach achieves an appropriately balanced resource allocation, maintaining a baseline network connectivity and adapting to achieve near the maximum theoretical flow rate in the scenarios evaluated. We develop a set of greedy, heuristic algorithms that address the problem of resource- minimized TI assignment, the first component of the traffic-aware assignment. We develop centralized and distributed schemes for nodes to assign channels to their transceivers. These schemes perform well as compared to the optimal approach in the evaluation. We show that both of these schemes perform within 2% of the optimum in terms of the maximum achievable flow rate. We develop a set of techniques for adapting the network's channel assignment based on traffic demands, the second component of the traffic-aware assignment. In our approach, nodes sense traffic conditions and adapt their own channel assignment independently to support a high flow rate and adapt when network demand changes. We demonstrate how our distributed TI and TD approaches complement each other in an event-driven simulation. / Ph. D.

Embedded devices almost involve every part of our lives, such as health condition monitoring, communicating with other people, traveling, financial transactions, etc. Within the embedded devices, our private information is utilized, collected and stored. Cryptography is the security mechanism within the embedded devices for protecting this secret information. However, cryptography algorithms can still be analyzed and attacked by malicious adversaries to steal secret data. There are different categories of attacks towards embedded devices, and the side-channel attack is one of the powerful attacks. Unlike analyzing the vulnerabilities within the cryptography algorithm itself in traditional attacks, the side-channel attack observes the physical effect signals while the cryptography algorithm runs on the device. These physical effects include the power consumption of the devices, timing, electromagnetic radiations, etc., and we call these physical effects that carry secret information side-channel leakage. By statistically analyzing these side-channel leakages, an attacker can reconstruct the secret information. The manifestation of side-channel leakage happens at the hardware level. Therefore, the designer has to ensure that the hardware design of the embedded system is secure against side-channel attacks. However, it is very arduous work. An embedded systems design including a large number of electronic components makes it very difficult to comprehensively capture every side-channel vulnerability, locate the root cause of the side-channel leakage, and efficiently fix the vulnerabilities. In this dissertation, we developed methodologies that can help designers detect and fix side-channel vulnerabilities within the embedded system design at low cost and early design stage. / Doctor of Philosophy / Side-channel leakage, which reveals the secret information from the physical effects of computing secret variables, has become a serious vulnerability in secure hardware and software implementations. In side-channel attacks, adversaries passively exploit variations such as power consumption, timing, and electromagnetic emission during the computation with secret variables to retrieve sensitive information. The side-channel attack poses a practical threat to embedded devices, an embedded device's cryptosystem without adequate protection against side-channel leakage can be easily broken by the side-channel attack. In this dissertation, we investigate methodologies to build up comprehensive side-channel resistant embedded systems. However, this is challenging because of the complexity of the embedded system. First, an embedded system integrates a large number of components. Even if the designer can make sure that each component is protected within the system, the integration of the components will possibly introduce new vulnerabilities. Second, the existing side-channel leakage evaluation of embedded system design happens post-silicon and utilizes the measurement on the prototype of the taped-out chip. This is too late for mitigating the vulnerability in the design. Third, due to the complexity of the embedded system, even though the side-channel leakage is detected, it is very hard to precisely locate the root cause within the design. Existing side-channel attack countermeasures are very costly in terms of design overhead. Without a method that can precisely identify the side-channel leakage source within the design, huge overhead will be introduced by blindly add the side-channel countermeasure to the whole design. To make the challenge even harder, the Power Distribution Network (PDN) where the hardware design locates is also vulnerable to side-channel attacks. It has been continuously demonstrated by researchers that attackers can place malicious circuits on a shared PDN with victim design and open the opportunities for the attackers to inject faults or monitoring power changes of the victim circuit. In this dissertation, we address the challenges mentioned above in designing a side-channel-resistant embedded system. We categorize our contributions into three major aspects—first, we investigating the effects of integration of security components and developing corresponding countermeasures. We analyze the vulnerability in a widely used countermeasure - masking, and identify that the random number transfer procedure is a weak link in the integration which can be bypassed by the attacker. We further propose a lightweight protection scheme to protect function calls from instruction skip fault attacks. Second, we developed a novel analysis methodology for pre-silicon side-channel leakage evaluation and root cause analysis. The methodology we developed enables the designer to detect the side-channel leakage at the early pre-silicon design stage, locate the leakage source in the design precisely to the individual gate and apply highly targeted countermeasure with low overhead. Third, we developed a multipurpose on-chip side-channel and fault monitoring extension - Programmable Ring Oscillator (PRO), to further guarantee the security of PDN. PRO can provide on-chip side-channel resistance, power monitoring, and fault detection capabilities to the secure design. We show that PRO as application-independent integrated primitives can provide side-channel and fault countermeasure to the design at a low cost.

Space Time Trellis Coding (STTC) is a unique technique that combines the use of multiple transmit antennas with channel coding. This scheme provides capacity benefits in fading channels, and helps in improving the data rate and reliability of wireless communication. STTC schemes have been primarily designed assuming perfect channel estimates to be available at the receiver. However, in practical wireless systems, this is never the case. The noisy wireless channel precludes an exact characterization of channel coefficients. Even near-perfect channel estimates can necessitate huge overhead in terms of processing or spectral efficiency. This practical concern motivates the study of the impact of channel estimation errors on the design and performance of STTC. The design criteria for STTC are validated in the absence of perfect channel estimates at the receiver. Analytical results are presented that model the performance of STTC systems in the presence of channel estimation errors. Training based channel estimation schemes are the most popular choice for STTC systems. The amount of training however, increases with the number of transmit antennas used, the number of multi-path components in the channel and a decrease in the channel coherence time. This dependence is shown to decrease the performance gain obtained when increasing the number of transmit antennas in STTC systems, especially in channels with a large Doppler spread (low channel coherence time). In frequency selective channels, the training overhead associated with increasing the number of antennas can be so large that no benefit is shown to be obtained by using STTC. The amount of performance degradation due to channel estimation errors is shown to be influenced by system parameters such as the specific STTC code employed and the number of transmit and receive antennas in the system in addition to the magnitude of the estimation error. Hence inappropriate choice of system parameters is shown to significantly alter the performance pattern of STTC. The viability of STTC in practical wireless systems is thus addressed and it is shown that that channel estimation could offset benefits derived from this scheme. / Master of Science

Side Channel Attacks (SCA) are a class of passive attacks on cryptosystems that exploit implementation characteristics of the system. Currently, a lot of research is focussed towards developing countermeasures to side channel attacks. In this thesis, we address two challenges that are an inherent part of the efficient implementation of SCA countermeasures. While designing a system, design choices made for enhancing the efficiency or performance of the system can also affect the side channel security of the system. The first challenge is that the effect of different design choices on the side channel resistance of a system is currently not well understood. It is important to understand these effects in order to develop systems that are both secure and efficient. A second problem with incorporating SCA countermeasures is the increased design complexity. It is often difficult and time consuming to integrate an SCA countermeasure in a larger system. In this thesis, we explore that above mentioned problems from the point of view of developing embedded software that is resistant to power based side channel attacks. Our first work is an evaluation of different software AES implementations, from the perspective of side channel resistance, that shows the effect of design choices on the security and performance of the implementation. Next we present work that identifies the problems that arise while designing software for a particular type of SCA resistant architecture - the Virtual Secure Circuit. We provide a solution in terms of a methodology that can be used for developing software for such a system - and also demonstrate that this methodology can be conveniently automated - leading to swifter and easier software development for side channel resistant designs. / Master of Science

Vehicular communications are a major subject of research and policy activity in industry, government, and academia. Dedicated Short-Range Communications (DSRC) is currently the main protocol used for vehicular communications, and it operates in the 5.9 GHz band. In addition to DSRC radios, other potential uses of this band include Wi-Fi, LTE-V, and communication among unlicensed devices. This dissertation presents an architecture and a feasibility analysis including field measurements and analysis for vehicle-to-train (V2T) communications, a safety-critical vehicular communication application. The dissertation also presents a survey of research relevant to each of several possible combinations of radio-spectrum and vehicular-safety regulations that would affect use of the 5.9 GHz band, identifies the most challenging of the possible resulting technical challenges, and presents initial measurements to assess feasibility of sharing the band by DSRC radios and other devices that operate on adjacent frequencies using different wireless communication standards. Although wireless technology is available for safety-critical communications, few applications have been developed to improve railroad crossing safety. A V2T communication system for a safety warning application with DSRC radios can address the need to prevent collisions between trains and vehicles. The dissertation presents a V2T early warning application architecture with a safety notification time and distance. We conducted channel measurements at a 5.86–5.91-GHz frequency and 5.9-GHz DSRC performance measurements at railroad crossings in open spaces, shadowed environments, and rural and suburban environments related to the presented V2T architecture. Our measurements and analyses show that the DSRC protocol can be adapted to serve the purpose of a V2T safety warning system. The 5.9 GHz band has been sought after by several stakeholders, including traditional mobile operators, DSRC proponents, unlicensed Wi-Fi proponents and Cellular-Vehicle-to-Everything (C-V2X) proponents. The FCC and National Highway Traffic Safety Administration (NHTSA), the two major organizations that are responsible for regulations related to vehicular communications, have not finalized rules regarding this band. The relative merits of the above mentioned wireless communication standards and coexistence issues between these standards are complex. There has been considerable research devoted to understanding the performance of these standards, but in some instances there are gaps in needed research. We have analyzed regulation scenarios that FCC and NHTSA are likely to consider and have identified the technical challenges associated with these potential regulatory scenarios. The technical challenges are presented and for each a survey of relevant technical literature is presented. In our opinion for the most challenging technical requirements that could be mandated by new regulations are interoperability between DSRC and C-V2X and the ability to detect either adjacent channel or co-channel coexisting interference. We conducted initial measurements to evaluate the feasibility of adjacent channel coexistence between DSRC, Wi-Fi, and C-V2X, which is one of the possible regulatory scenarios. We set DSRC at Channel 172, Wi-Fi at Channel 169 for 20 MHz bandwidth and at Channel 167 for 40 MHz, and C-V2X at Channel 174 with almost 100% spectrum capacity. From the measurements, we observed almost no effects on DSRC performance due to adjacent channel interference. Based on our results, we concluded that adjacent channel coexistence between DSRC, C-V2X, and Wi-Fi is possible. DSRC systems can provide good communication range; however, the range is likely to be reduced in the presence of interference and / or Non-Line-of-Sight (NLoS) conditions. Such environmental factors are the major influence on DSRC performance. By knowing the relationship between DSRC and environmental factors, DSRC radios can be set up in a way that promotes good performance in an environment of interest. We chose propagation channel characteristics to generate DSRC performance modelling by using estimation methods. The conducted DSRC performance measurements and propagation channel characteristics are independent; however, they share the same distance parameters. Results of linear regression to analyze the relationship between DSRC performance and propagation channel characteristics indicate that additional V2T measurements are required to provide data for more precise modeling. / PHD / Researchers and regulators in industry, government, and academic institutions are interested in vehicular communications. Dedicated Short-Range Communications (DSRC) is currently the standard protocol for communication between vehicles, including for safety applications, and operates in the band of radio frequencies near 5.9 GHz. In addition to operators of DSRC radios, other potential users are interested in using the 5.9 GHz band. This dissertation presents an architecture and a feasibility analysis including field measurements for vehicle-to-train (V2T) communications, a safety-critical vehicular communication application. The dissertation also identifies major technical challenges that could become important in the future for users of the 5.9 GHz band. The challenges will be different depending on what decisions government regulators make about the types of radios and communication protocols that are allowed in the 5.9 GHz band and about which types of radios should be used for vehicular safety. Although wireless technology is available for safety-critical communications, few applications have been developed to improve railroad crossing safety. To prevent collisions between trains and vehicles, we present a vehicle-to-train (V2T) communication system that uses DSRC radios to provide safety warnings to motorists. Although the term V2T is used, the emphasis is on communication from the train to vehicles. We present a high-level design, or architecture, of the warning system that includes goals for safety notification time and vi distance. We conducted measurements of radio channels near 5.9 GHz as well as measurements of 5.9 GHz DSRC radio link performance at the same locations (railroad crossings in open spaces, shadowed or obstructed environments, and rural and suburban environments). The measurements were performed to help decide whether the V2T warning system architecture would work. A DSRC system can provide good communication range; however, that range could be reduced if the DSRC system experiences interference from other radios or if the signal is partially blocked due to objects between the DSRC radios. The environmental factors are the most important influence on DSRC performance. By knowing the relationship between DSRC and environmental factors, manufacturers and operators can set up the radios to perform well in environments of interest. Although DSRC performance and radio channel characteristics were measured separately, they were measured in the same locations near railroad crossings. This made it possible to perform a statistical analysis of the relationship between DSRC performance and propagation channel characteristics. This analysis indicated that additional measurements will be required to collect enough data to develop robust statistical models that relate DSRC performance directly to measured channel characteristics. However, the results of the V2T measurements that we conducted near rural and suburban railroad crossings with varying numbers and types of obstacles to the radio signals provide a strong indication that DSRC can be used for to provide V2T safety warnings. The 5.9 GHz band has been sought after by several stakeholders, including traditional mobile operators and others who support use of the band for DSRC, unlicensed Wi-Fi, and CellularVehicle-to-Everything (C-V2X) communication. The FCC and National Highway Traffic Safety Administration (NHTSA), the two major organizations that are responsible for vii regulations related to vehicular communications, have not finalized the rules regarding this band. The relative merits of the above mentioned communication standards and coexistence issues between these standards are complex. There has been considerable research devoted to understanding the performance of these standards, but in some instances there are gaps in needed research. We have analyzed regulation scenarios that FCC and NHTSA are likely to consider and have identified the technical challenges associated with these potential regulatory scenarios. The technical challenges are presented and for each a survey of relevant technical literature is presented. In our opinion for the most challenging technical requirements that could result from new regulations are interoperability between DSRC and C-V2X and the ability to detect either adjacent channel or co-channel coexisting interference. We conducted initial measurements to evaluate the feasibility of adjacent channel coexistence between DSRC, Wi-Fi, and C-V2X, which is one of the possible regulatory scenarios. From the measurements, we observed almost no effect on DSRC performance when other types of radios used frequencies adjacent to the frequencies used by the DSRC radios. Based on our results, we concluded that adjacent channel coexistence between DSRC, C-V2X, and Wi-Fi is possible.