The role of adaptive evolution of phenotypic plasticity and historical population genetic processes in purple loosestrife (Lythrum salicaria L.) invasion in North America

The introduction and spread of non-native species has become a global ecological and environmental problem. We will be able to develop a deeper understanding on the background of invasiveness from the studies of evolutionary changes that invasive species undergo from their introduction to the establishment and aggressive spread. The ultimate goal of this dissertation is to contribute a deeper knowledge on the ability of invasive species to respond to the novel environment and prevail via evolutionary changes, using purple loosestrife (Lythrum salicaria L. Lythraceae) as a model system.;The dissertation is composed of several journal papers. Chapter 1 is a general introduction and Chapter 2 is a review paper summarizing recent studies on the leading hypotheses on the mechanisms for invasiveness: EICA (Evolution of Increased Competitive Ability), the evolution of phenotypic plasticity, local adaptation, allelopathy, hybridization/polyploidization. Chapter 3 tests the evolution of phenotypic plasticity hypothesis with an empirical study on the phenotypic plasticity in native vs. invasive populations subject to experimentally manipulated water and nutrient environments. This study has been published in Ecology and expanded into a larger international collaborative project that aims to detect the genetic difference in demography and phenotypic plasticity between native and invasive populations. Essentially this is a reciprocal transplant study with multiple common gardens involving collaborators from New Jersey and Germany. The results from the Iowa common garden have been presented in Chapter 4, employing structural equation modeling approach (path analysis) to describe causal relationships between fitness and traits that contribute to fitness (fitness-related traits) considering the ontogeny of purple loosestrife. Chapter 5 is a technical note on the development of a genomic DNA extraction protocol for plants that have a large amount of secondary metabolites including polysaccharides and polyphenols. Chapter 6 is a population genetic study on the same populations used in Chapter 3, to examine the effect of major evolutionary forces on invasive populations - whether the formation of invasive populations is purely due to stochastic events such as genetic drift and migration, or instead by disruptive and/or stabilizing selection leading to locally adapted populations in the North America

Data mixing at the source, relay, and in the air in multiple-access relay networks

The concept of cooperative relay is an essential technique for future cellular networks such as wireless mesh networking or wireless ad-hoc networking. In a practical relay network, channel coding, network coding, and antenna arrays, will coexist and yet the joint optimization of these conventional coding schemes and cooperative relay is not well understood. To build a design guideline for relay network, this dissertation develop a joint optimization methodology for multiple coding schemes in multiple access relay network. There are four major contributions in this thesis: First, we jointly optimize conventional coding schemes and radio resources of multiple access relay network with multiple antennas. The combined design of MIMO transmission modes, channel coding at the source, network coding at the relay have been investigated. We develop optimal design rule that minimize the end-to-end error probability. Second, we derive the fundamental tradeoff between achievable rate and reliability of multiple access relay network with multiple antennas. We consider three MIMO transmission modes, spatial multiplexing (SM), Alamouti coding as transmit diversity (TD), and Golden Coding, and random linear network coding at the relay. We compare the average decoding error probability of each transmission mode. Third, we present an interference cancellation scheme for multi-user MIMO. The proposed Log-likelihood-ratio (LLR) ordered successive interference cancellation (SIC) scheme provides 1 ~ 3 dB gain over the conventional SNR-ordered SIC and the gain increases with increasing number of users. Finally, we present a new architecture for MIMO receivers that cancel the co-channel interference (CCI) using a single radio frequency (RF) and baseband (BB) chain, while still achieving nearly the same bit error rate that can be provided by the conventional receiver requiring multiple RF/BB chains

Improving public spaces in Helsinki during wintertime

This thesis is about public spaces in Helsinki, focusing on cultivating urban life during the winter months. Unlike the vibrant public life present during the summer, public spaces in winter are mostly unavailable and consequently, public life is highly limited. Through a literature review, the study of public life is explained, and its historical background, methods, and primary focus are elaborated. Through observational research, how public spaces in winter Helsinki, particularly around the Helsinki central railway station, are used by the public is described. The research findings revealed that the streets and commercial places are the most frequently used public spaces in winter. The key argument is that because of the long wintertime, it needs to be considered thoughtfully how public life in winter has developed and how it can be improved. Through further discussion of these aspects, design ideas to help promote public life on the street and in commercial areas are suggested.Chun, Ji

On Modeling Heterogeneous Wireless Networks Using Non-Poisson Point Processes

Future wireless networks are required to support 1000 times higher data rate, than the current LTE standard. In order to meet the ever increasing demand, it is inevitable that, future wireless networks will have to develop seamless interconnection between multiple technologies. A manifestation of this idea is the collaboration among different types of network tiers such as macro and small cells, leading to the so-called heterogeneous networks (HetNets). Researchers have used stochastic geometry to analyze such networks and understand their real potential. Unsurprisingly, it has been revealed that interference has a detrimental effect on performance, especially if not modeled properly. Interference can be correlated in space and/or time, which has been overlooked in the past. For instance, it is normally assumed that the nodes are located completely independent of each other and follow a homogeneous Poisson point process (PPP), which is not necessarily true in real networks since the node locations are spatially dependent. In addition, the interference correlation created by correlated stochastic processes has mostly been ignored. To this end, we take a different approach in modeling the interference where we use non-PPP, as well as we study the impact of spatial and temporal correlation on the performance of HetNets. To illustrate the impact of correlation on performance, we consider three case studies from real-life scenarios. Specifically, we use massive multiple-input multiple-output (MIMO) to understand the impact of spatial correlation; we use the random medium access protocol to examine the temporal correlation; and we use cooperative relay networks to illustrate the spatial-temporal correlation. We present several numerical examples through which we demonstrate the impact of various correlation types on the performance of HetNets.Comment: Submitted to IEEE Communications Magazin

Active-IRS Aided Wireless Network: System Modeling and Performance Analysis

Active intelligent reflecting surface (IRS) enables flexible signal reflection control with \emph{power amplification}, thus effectively compensating the product-distance path-loss in conventional passive-IRS aided systems. In this letter, we characterize the communication performance of an active-IRS aided single-cell wireless network. To this end, we first propose a \emph{customized} IRS deployment strategy, where the active IRSs are uniformly deployed within a ring concentric with the cell to serve the users far from the base station. Next, given the Nakagami-$m$ fading channel, we characterize the cascaded active-IRS channel by using the \emph{mixture Gamma distribution} approximation and derive a closed-form expression for the mean signal-to-noise ratio (SNR) at the user averaged over channel fading. Moreover, we numerically show that to maximize the system performance, it is necessary to choose a proper active-IRS density given a fixed number of total reflecting elements, which significantly differs from the passive-IRS case for which the centralized IRS deployment scheme is better. Furthermore, the active-IRS aided wireless network achieves higher spatial throughput than the passive-IRS counterpart when the total number of reflecting elements is small

A Stochastic Geometric Analysis of Device-to-Device Communications Operating over Generalized Fading Channels

Device-to-device (D2D) communications are now considered as an integral part of future 5G networks which will enable direct communication between user equipment (UE) without unnecessary routing via the network infrastructure. This architecture will result in higher throughputs than conventional cellular networks, but with the increased potential for co-channel interference induced by randomly located cellular and D2D UEs. The physical channels which constitute D2D communications can be expected to be complex in nature, experiencing both line-of-sight (LOS) and non-LOS (NLOS) conditions across closely located D2D pairs. As well as this, given the diverse range of operating environments, they may also be subject to clustering of the scattered multipath contribution, i.e., propagation characteristics which are quite dissimilar to conventional Rayeligh fading environments. To address these challenges, we consider two recently proposed generalized fading models, namely $\kappa-\mu$ and $\eta-\mu$, to characterize the fading behavior in D2D communications. Together, these models encompass many of the most widely encountered and utilized fading models in the literature such as Rayleigh, Rice (Nakagami-$n$), Nakagami-$m$, Hoyt (Nakagami-$q$) and One-Sided Gaussian. Using stochastic geometry we evaluate the rate and bit error probability of D2D networks under generalized fading conditions. Based on the analytical results, we present new insights into the trade-offs between the reliability, rate, and mode selection under realistic operating conditions. Our results suggest that D2D mode achieves higher rates over cellular link at the expense of a higher bit error probability. Through numerical evaluations, we also investigate the performance gains of D2D networks and demonstrate their superiority over traditional cellular networks.Comment: Submitted to IEEE Transactions on Wireless Communication