Pico-Cellular architecture fully reuses frequency to increase network capacity. However, it will increase the occurance of Handoff due to the small range of cell. Previous works in channel allocations can reduce blocking probability of handoff call, but it may increase blocking probability of new call. As a result, channel utilization is decreased because they can not adapt to network changes. In this thesis, we present a Dynamic Channel Allocation Mechanism with priority support. All channels and calls are divided into high and low priority. If there is no high_priority channel for high_priority call, high_priority call may downgrade its priority by sacrificing some QoS to utilize low_priority channels. We define two new array for network information status, one is next_cell state, and the other is the transition probability. Next_cell state is used to save prior M Cell_Ids where handoff calls may move to. Transition probability is used to save the probabilities for active calls moving to other neighboring cells. According to next_cell state and transition probability, we can accurately predict the probabilities for mobile hosts moving to other neighboring cells. Therefore, we can dynamically adjust bandwidth reservation requests sending to neighboring cells by the latest transition probability and the number of active calls in this cell. We analyze the proposed mechanism through a mathematical model. In the model, we build a four-dimension Markov Chain and use MATLAB[41] tool to evaluate blocking probability, channel throughput and utilization. We found out that blocking probability of handoff call can be decreased and channel utilization can be increased through the proposed channel allocation mechanisms with high and low priority support.

The lack of a real English environment in Taiwan and big class teaching had long limited the opportunities for Taiwanese English learners to use English. Due to thriving development of internet technology in recent years, the predicament has been broken through. Internet not only opens a new communicational channel for teachers and students, but also creates an authentic environment for English learners. As the new curriculum policy ¡§coherence curriculum of civil education¡¨, which emphasizes on setting information instruction into each subjects, is taken into practice, learning English with internet tools must will become a trend in the future. Therefore, this research examines the distance between the ideal and the reality using an internet-based English teaching project, and probe into some feasible ways to conduct similar program in the future. There were four purposes of this research: 1. To find out the key factors of success in internet-based English teaching from relative theories and former researches. 2. To understand the teacher¡¦s and students¡¦ performances and the students¡¦ reflections during the first half year joining an internet-based English teaching project. 3. To probe into the merits and defects of the internet-based English teaching project, AJET. 4. To discover the difficulties and feasible ways for senior high schools to carry out internet-based English teaching. The subjects of this research were a senior high school class and their teacher who first joined an internet-based English teaching project named ¡§Advanced Joint English Teaching¡¨ (AJET) in Kaohsiung. All 44 students were male. During the research period, they participated in six internet-based teaching activities, which were ¡§group e-mailing,¡¨ ¡§web-based course,¡¨ ¡§e-mail writing program,¡¨ ¡§English homepage design,¡¨ ¡§video conference¡¨ and ¡§chatroom discussion.¡¨ The researcher traced the students¡¦ performances and collected their work pieces mainly through e-mail, AJET homepage and telephone during the research period. A questionnaire was given to elicit relevant information on the participants¡¦ perception of, and attitudes towards, using the internet technology to complete their Internet-based English projects. Follow-up interview with 10 students and 2 teachers were also collected at the end of the research to understand their reflections on the project. In addition, the students¡¦ performances at the second homepage contest were also recorded. After data collection, the quantitative and qualitative methods were performed. The quantitative statistic analysis was employed using descriptive analysis to investigate the learners¡¦ perceptions towards the Web-based project. The qualitative analysis made from the student responses to the open-ended questions and the researcher¡¦s observation, provided the opportunity to uncover deeper issues than might have been apparent in a quantitative study. Students¡¦ responses to the open-ended questions were broken down into excerpts, where each excerpt represented one complete answer to a question, including any follow-up questions or clarification by student interviews. The main findings and conclusions of this research are as follows: 1. The students¡¦ participation and interaction were not good, and need the teacher¡¦s supervision to help them to form active learning habits. 2. The teacher was overloaded in the project and found it difficult to do both administration and teaching. There is a need of others¡¦ coordination. 3. The students liked and approved of English learning through internet, but differed in their opinions about its benefits to English learning. 4. The project provided the students an opportunity to experience new technologies, felt the pleasure of learning and increased their learning possibilities. 5. To carry out an internet-based English project, the project must spread relative concepts, consider the teacher¡¦s and students¡¦ loads, design each activity with proper number of participants, conduct relative training, and enhance the equipment and communicational efficiency. To sum up, although there is a distance between the ideal and the reality in the internet-based English teaching project, this way of English teaching is worth developing and expanding. Finally, according to the findings of this research, the researcher provides some suggestions for future organizations, teachers and researchers who are interested in this field.

We propose a novel call admission control which makes use of ratio-based traffic measurement to estimate the required bandwidth when a new call is issued. Existing approaches fail to estimate properly the required bandwidth. To alleviate the problem, we calculate the ratio between the measured mean rate and the mean rate declared by UPC parameters. The ratio and the target cell loss rate are used to estimate the required bandwidth to make decision if a new call is accepted or rejected. Because of more accurate estimation of required bandwidth, our method can provide a better control on quality of service.

ATM (Asynchronous Transfer Mode) networks were deemed the best choice for multimedia communication. The traditional mode was replaced because ATM can provide varied traffic types and QoS (quality of service). Maintaining QoS, however, requires a flexible traffic control, including call admission control and congestion control. Traditional approaches fail to estimate the required bandwidth and cell loss rate precisely. To alleviate these problems, we employ AI methods to improve the capability of estimated bandwidth and predicted cell loss rate. This thesis aims to apply neural network techniques to ATM traffic control and consists of two parts. The first part concerns a neural-based call admission control, while the second part presents an intelligent congestion control for ATM networks. In the first part, we focus on the improvement of RBF (Radial basis function) networks and the design of a neural-based call admission control. RBF networks have been widely used for modeling a function from given input-output patterns. However, two difficulties are encountered with traditional RBF networks. One is that the initial configuration of a RBF network needs to be determined by a trial-and-error method. The other is that the performance suffers from some difficulties when the desired output has abrupt changes or constant values in certain intervals. We propose a novel approach to overcome these difficulties. New kernel functions are used for hidden nodes, and the number of nodes is determined automatically by an ART-like algorithm. Parameters and weights are initialized appropriately, and then tuned and adjusted by the gradient descent method to improve the performance of the network. Then, we employ ART-RBF networks to design and implement a call admission control. Traditional approaches fail to estimate appropriately the required bandwidth, leading to a waste of bandwidth or a high cell loss rate. To alleviate the problem, we employ ART-RBF networks to estimate the required bandwidth, and thus a new connection request can then be accepted or rejected. Because of the more accurate estimation on the required bandwidth, the proposed method can provide a better control on quality of service for ATM networks. In the second part, we propose a neural-fuzzy rate-based feedback congestion control for ATM networks. Traditional methods perform congestion control by monitoring the queue length. The source rate is decreased by a fixed rate when the queue length is greater than a predefined threshold. However, it is difficult to get a suitable rate according to the degree of traffic congestion. We employ a neural-fuzzy mechanism to control the source rate. Through learning, cell loss can be predicted from the current value and the derivative of the queue length. Then an explicit rate is calculated and the source rate is controlled appropriately. In summary, we have proposed improvements on architecture and performance of neural networks, and applied neural networks to traffic control for ATM networks. We have developed some control mechanisms which, through simulations, have been shown to be more effective than traditional methods.

The emerging popularity and interest in Voice-over-IP (VoIP) has been accompanied by customer concerns about voice quality over these networks. The lack of an appropriate real-time capable infrastructure in packet networks along with the threats of denial-of service (DoS) attacks can deteriorate the service that these voice calls receive. And these conditions contribute to the decline in call quality in VoIP applications; therefore, error-correcting/concealing techniques remain the only alternative to provide a reasonable protection for VoIP calls against packet losses. Traditionally, each voice call employs its own end-to-end forward-error-correction (FEC) mechanisms. In this paper, we show that when VoIP calls are aggregated over a provider's link, with a suitable linear-time encoding for the aggregated voice traffic, considerable quality improvement can be achieved with little redundancy. We show that it is possible to achieve rates closer to channel capacity as more calls are combined with very small output loss rates even in the presence of significant packet loss rates in the network. The advantages of the proposed scheme far exceed similar or other coding techniques applied to individual voice calls.

Call centers have become a preferred and prevalent means for companies to communicate with their customers. As a consequence of this, the call center industry has seen a huge growth in both volume and scope in the last couple of decades. Operations managers are challenged with the fact that personnel costs, especially staffing, account for over 65% of the cost of running the typical call center. The trade-off between service quality (marketing) and efficiency (operations), thus naturally arises, and a central goal of ours is to contribute to its understanding. We present here a server switching policy for routing of calls to Customer Service Representatives (CSR) in a multi-skilled inbound call center utilizing skill-based routing (SBR). We model the system as a queueing network and propose stochastic Petri net based models for the design and performance analysis of call centers. Our models and experimentations help in identifying practices that result in efficient usage of existing personnel in a call center. In our work, we have considered two types of scenarios in which a multi-skilled SBR call center handling inbound calls can function - (i) with specialist agents only, and (ii) with a mix of specialist and flexible agents. We have developed both these models and compared the rewards obtained from each of them. This analysis helped us answer important issues regarding the routing decision of calls to CSRs, identify the hedging point where one obtains the highest rewards and the impact of varying the strategic and tactical level decisions on the overall call center performance.

Thesis (MTech (Business Administration))--Cape Peninsula University of Technology, 2009. / Includes bibliographical references (leaves 57-59). Also available online.

In a standard tennis match each player has an unlimited opportunity to challenge an umpire’s call, but if three incorrect challenges are made in a set he is not allowed to challenge anymore in that set. If the set goes into a tie break the limit on incorrect challenges increases by one. These limited incorrect challenges are not carried over from one set to another. So this is kind of a limited resource available to the player and if he knows how to use this resource in a best possible way, there is a scope for increasing his overall chances of winning a match. With the motive of gaining insight on when to challenge a call, we have modeled a single game in a tennis match as a Markov decision process. We have also studied the impact of variables like player’s probability of winning a point, the player’s perception of the challengability of a call and proportion of challengable calls on the decision making process. / text

This paper measures the channels by which private information is incorporated in prices in the equity and option markets. Using a mispricing events approach and conditioning on the option market being the cause of the mispricing event, I analyse the subsequent behaviour of both the options and equity markets and I find that options markets play an important role in the price discovery process. When conditioning on option caused mispricing events, the equity price adjusts towards the options price to reconcile the prices. I find that around 40% of the option caused mispricing events contain information, and the equity prices adjust 35-40%, depending on the exchange, of the maximum discrepancy before prices reconcile. When the equity market causes the mispricing, the option market follows due to the autoquote mechanism. Additionally, I use Monte Carlo to assess the suitability of the Hasbrouck (1995) Information Share and Gonzalo-Granger (1995) Component Share measures in the option-equity context. I find that neither metric is suitable, however the Putnins (2013) Information Leadership metric is and the options market has on average a 35% information leadership share.

Computer-assisted language learning (CALL) allows designers to control for rate of speech and the amount and kinds of control learners have over playback in listening comprehension exercises for second language (L2) learners. Research shows that slower rates of speech can improve listening comprehension (Chaudron, 1988; Zhao, 1997), as can pausing (Zhao, 1997). Jensen and Vinther's (2003) work suggests that, in listening comprehension training, slower speeds can help improve L2 learners' comprehension of grammatical structures.This study examined the influence of different rates of speech and learner controls in a CALL environment. The study used a pretest--training--posttest design. All subjects were pre-tested on listening comprehension on both slow (135 words per minute) and fast (180 words per minute) dialogues. They also performed a maze task as a pretest. Then the participants were randomly assigned to one of four conditions for ten training sessions: A) trained on only fast dialogues, B) trained on only slow dialogues, C) given a choice of speed for the second playback during the lessons, and D) given an option to pause playback when listening the second time. Posttests followed training. Data were also collected through surveys and interviews, allowing the issues of CALL design and communication and learning strategy use to be investigated as well.The data support the previous research but also suggest that design features can affect L2 learners either positively or negatively. This study, which was done with Chilean, college-level students of English as a foreign language (EFL), has implications for CALL design and classroom teaching, as well as language testing. These are discussed, as are suggestions for future research.