This thesis studies the impact of mobility and wireless channel characteristics, i. e. , variability and high bit-error-rate, on the performance of integrated voice and data wireless systems from network, transport protocol and application perspectives. <br /><br /> From the network perspective, we study the impact of user mobility on radio resource allocation. The goal is to design resource allocation mechanisms that provide seamless mobility for voice calls while being fair to data calls. In particular, we develop a distributed admission control for a general integrated voice and data wireless system. We model the number of active calls in a cell of the network as a Gaussian process with time-dependent mean and variance. The Gaussian model is updated periodically using the information obtained from neighboring cells about their load conditions. We show that the proposed scheme guarantees a prespecified dropping probability for voice calls while being fair to data calls. Furthermore, the scheme is stable, insensitive to user mobility process and robust to load variations. <br /><br /> From the transport protocol perspective, we study the impact of wireless channel variations and rate scheduling on the performance of elastic data traffic carried by TCP. We explore cross-layer optimization of the rate adaptation feature of cellular networks to optimize TCP throughput. We propose a TCP-aware scheduler that switches between two rates as a function of TCP sending rate. We develop a fluid model of the steady-state TCP behavior for such a system and derive analytical expressions for TCP throughput that explicitly account for rate variability as well as the dependency between the scheduler and TCP. The model is used to choose RF layer parameters that, in conjunction with the TCP-aware scheduler, improve long-term TCP throughput in wireless networks. A distinctive feature of our model is its ability to capture variability of round-trip-time, channel rate and packet error probability inherent to wireless communications. <br /><br /> From the application perspective, we study the performance of wireless messaging systems. Two popular wireless applications, the short messaging service and multimedia messaging service are considered. We develop a mathematical model to evaluate the performance of these systems taking into consideration the fact that each message tolerates only a limited amount of waiting time in the system. Using the model, closed-form expressions for critical performance parameters such as message loss, message delay and expiry probability are derived. Furthermore, a simple algorithm is presented to find the optimal temporary storage size that minimizes message delay for a given set of system parameters.

This thesis studies the impact of mobility and wireless channel characteristics, i. e. , variability and high bit-error-rate, on the performance of integrated voice and data wireless systems from network, transport protocol and application perspectives. <br /><br /> From the network perspective, we study the impact of user mobility on radio resource allocation. The goal is to design resource allocation mechanisms that provide seamless mobility for voice calls while being fair to data calls. In particular, we develop a distributed admission control for a general integrated voice and data wireless system. We model the number of active calls in a cell of the network as a Gaussian process with time-dependent mean and variance. The Gaussian model is updated periodically using the information obtained from neighboring cells about their load conditions. We show that the proposed scheme guarantees a prespecified dropping probability for voice calls while being fair to data calls. Furthermore, the scheme is stable, insensitive to user mobility process and robust to load variations. <br /><br /> From the transport protocol perspective, we study the impact of wireless channel variations and rate scheduling on the performance of elastic data traffic carried by TCP. We explore cross-layer optimization of the rate adaptation feature of cellular networks to optimize TCP throughput. We propose a TCP-aware scheduler that switches between two rates as a function of TCP sending rate. We develop a fluid model of the steady-state TCP behavior for such a system and derive analytical expressions for TCP throughput that explicitly account for rate variability as well as the dependency between the scheduler and TCP. The model is used to choose RF layer parameters that, in conjunction with the TCP-aware scheduler, improve long-term TCP throughput in wireless networks. A distinctive feature of our model is its ability to capture variability of round-trip-time, channel rate and packet error probability inherent to wireless communications. <br /><br /> From the application perspective, we study the performance of wireless messaging systems. Two popular wireless applications, the short messaging service and multimedia messaging service are considered. We develop a mathematical model to evaluate the performance of these systems taking into consideration the fact that each message tolerates only a limited amount of waiting time in the system. Using the model, closed-form expressions for critical performance parameters such as message loss, message delay and expiry probability are derived. Furthermore, a simple algorithm is presented to find the optimal temporary storage size that minimizes message delay for a given set of system parameters.

When internet-mediated messaging and social networking applications were introduced in mobile phones, mobile messaging entered a new paradigm. Users can easily create profiles and communicate with other users instantly at anytime of day and anywhere in the world. This paradigm however, has brought forward new privacy issues. Over the course of this exegesis I aimed to explore different aspects of privacy issues related to mobile messaging, including users' awareness and the control of the privacy issues when using social networking messaging. This was demonstrated by conducting a project, which involved development of a mobile phone application and a role-playing game. The project created a frictional scenario of users communicating via mobile messaging. My research revealed that the participants lacked awareness of privacy violations when using mobile messaging, and tended not to modify their behaviours immediately when privacy breaches arose. This research contributes to the existing body of research in the area of mobile messaging privacy, and advocated user awareness of privacy issues in this domain. It could potentially be used as a base for future research.

近年來網路的快速發展與普及，而由於使用網路的人口快速增加，資訊傳遞日益頻繁，使用網際網路來做為傳遞訊息工具，有逐漸上升趨勢。本研究的主要目的是利用行動代理人技術發展一於應用於網際網路上的傳訊機制，這個機制稱之為行動傳訊代理人(Mobile-Messaging Agent)，主要是讓訊息、郵件可以跟著使用者所在位置而傳送，並且建構一個使用者專屬的信差。而這樣的傳訊機制包含了四個元件：(1)Messenger，即為信差代理人，負責幫使用者接收郵件、訊息﹔(2)AgentFinder，為負責接受使用者的要求來搜尋Messenger﹔(3)MessengerFinder，為行動傳訊代理人系統與使用者溝通的介面，是負責幫助使用者呼叫Messenger﹔(4)Register，為MessengerFinder啟動時，幫助尋找AgentFinder。而根據本研究實作行動傳訊代理人系統結果發現，行動傳訊代理人應用於網際網路之傳訊機制，具有降低伺服主機負載、增加網路連線品質、訊息有效管理、資料隱私性及安全性高、訊息自主性、易跨平台等優點。 　而以行動傳訊代理人建置傳訊機制，使得訊息物件具有行動力、自主性、延展性，未來，期望行動傳訊代理人可以整合至可攜性較高的行動設備，例如膝上型電腦、數位個人助理(PDA)或是行動電話，最後，透過此系統行動傳訊代理人的自主性與行動性，讓使用者無論走到那裡，都可以即時收取訊息、郵件。

Increased globalization and the thought of converging values has lead marketing practitioners and academics to consider more standardized approaches to marketing and advertising strategies. Even though cultures seem to evolve closer to each other, cultural diversity still exists. Advertising reflects and influences our cultural values and therefore it cannot be ignored when building effective advertising. Results show that culture impacts execution more than creative strategy (Wei &amp; Jiang, 2005) and therefor execution is seen as an important element of cross-cultural marketing and advertising. The emergence of new social media channels is raising the question whether previous execution styles are suitable for these marketing channels and whether similar connection with the culture exists. This thesis examines how cultural characteristics are reflected in advertising execution and draws special attention to the marketing communication through mobile messaging applications. However, this study takes new approach for viewing culture’s influence on advertising executions by exploring the preferences of audience. This research aims to shed light on the under researched area of cross-cultural advertising in Asian region in terms of two culturally similar countries. This study examines Chinese and South Korean preferences and perceptions of execution styles and explores to what extent similarities and differences occur. These similarities and differences are analyzed in terms of culture and whether these findings can be attributed to the nations' cultural characteristics. To address the topic holistically in its cultural context, a qualitative mixed-methods research approach was adopted for this research. This present study combines cultural and advertising theories to produce a theoretical frame for data collection and further analysis. Findings indicate that culture does influence execution preferences even in rather similar cultures. Although advertising reflects nations’ cultural values, it does not directly translate into the preferences of that audience. This study indicated that the channel of marketing communication influences execution preferences. Mobile messaging application as a marketing channel was seen affecting the preferences of Chinese and Koreans towards more direct and informational communication which have been considered untypical for East Asian cultures. However, overall changes in the preferences appeared indicating value shift, changes in the expressions of culture, or paradoxal values. Results suggest that cross-cultural marketers and advertisers should recognize the importance of cultural characteristics when planning and designing execution strategies.