Mobile communication systems have continued to evolve beyond the currently deployed Third Generation (3G) systems with the main goal of providing higher capacity. Systems beyond 3G are expected to cater for a wide variety of services such as speech, data, image transmission, video, as well as multimedia services consisting of a combination of these. With the air interface being the bottleneck in mobile networks, recent enhancing technologies such as the High Speed Downlink Packet Access (HSDPA), incorporate major changes to the radio access segment of 3G Universal Mobile Telecommunications System (UMTS). HSDPA introduces new features such as fast link adaptation mechanisms, fast packet scheduling, and physical layer retransmissions in the base stations, necessitating buffering of data at the air interface which presents a bottleneck to end-to-end communication. Hence, in order to provide end-to-end Quality of Service (QoS) guarantees to multimedia services in wireless networks such as HSDPA, efficient buffer management schemes are required at the air interface. The main objective of this thesis is to propose and evaluate solutions that will address the QoS optimization of multimedia traffic at the radio link interface of HSDPA systems. In the thesis, a novel queuing system known as the Time-Space Priority (TSP) scheme is proposed for multimedia traffic QoS control. TSP provides customized preferential treatment to the constituent flows in the multimedia traffic to suit their diverse QoS requirements. With TSP queuing, the real-time component of the multimedia traffic, being delay sensitive and loss tolerant, is given transmission priority; while the non-real-time component, being loss sensitive and delay tolerant, enjoys space priority. Hence, based on the TSP queuing paradigm, new buffer managementalgorithms are designed for joint QoS control of the diverse components in a multimedia session of the same HSDPA user. In the thesis, a TSP based buffer management algorithm known as the Enhanced Time Space Priority (E-TSP) is proposed for HSDPA. E-TSP incorporates flow control mechanisms to mitigate congestion in the air interface buffer of a user with multimedia session comprising real-time and non-real-time flows. Thus, E-TSP is designed to provide efficient network and radio resource utilization to improve end-to-end multimedia traffic performance. In order to allow real-time optimization of the QoS control between the real-time and non-real-time flows of the HSDPA multimedia session, another TSP based buffer management algorithm known as the Dynamic Time Space Priority (D-TSP) is proposed. D-TSP incorporates dynamic priority switching between the real-time and non-real-time flows. D-TSP is designed to allow optimum QoS trade-off between the flows whilst still guaranteeing the stringent real-time component’s QoS requirements. The thesis presents results of extensive performance studies undertaken via analytical modelling and dynamic network-level HSDPA simulations demonstrating the effectiveness of the proposed TSP queuing system and the TSP based buffer management schemes.

M.Ing. / In general, error control coding is absolutely necessary for reliable data transmission. However, the performance of error control codes depends on the statistical structure of the error process on the communication channel. The mobile radio channel, which has been investigated, is subject to path loss effects, a variety of noise effects and interferences and various types of scattering and multipath fading. All these effects contribute to the error processes on the radio channel when transmitting data over it. Any meaningful analytical description of the error process in terms of the characteristics of the individual physical causes of errors are difficult to undertake. Consequently, alternative ways of modelling real communication. channels are being presented. It is more convenient to include the above mentioned perturbations in a discrete inner communication channel consisting of the modem, radio equipment and the mobile radio medium, which are then modelled with a discrete partitioned Markov chain. The partitioned Markov chain inner channel models also give a more accurate description of a real communication channel than does a binary symmetric channel model. However, in order to model a communication channel, the complete statistical structure of the bit error sequence on the channel must be known. In the first instance the memory effective recording of the error sequence of discrete inner communications channels has been considered. This has led to an implementation, where a portable recording system has been developed for mobile .radio channels or any other communication channel with a data rate of up to 4800 bits per second. Programs have been developed to determine all the important statistical distributions which are necessary to be able to model the channel. A channel modelling system has been developed, which fits a channel model to the real channel and then determines the important statistical distributions of the channel model to enable comparison with the real channel. The channel modelling system is versatile and can be used with any future communication system. A number of different mobile VHF and UHF inner channels have been investigated experimentally and the associated discrete models have been developed. In addition to the above mentioned discrete inner communications channels, some "outer channels" have been developed. The "outer channels" comprise of an inner channel and the block error detection, correction and misdetection events, associated with the code words of an error control system. It has been shown that the underlying statistical structure of these events on a discrete renewal inner channel can be represented with outer channel models, i.e. simple partitioned Markov processes, similar to the inner channel models. Analytical procedures to determine the parameters of these outer channel models are being presented. The inner channel parameters and the characteristics of the error control event have been used to develop the outer channel models, i.e. the simple partitioned Markov chains, representing the underlying statistical structure of the block error detection, decoding error in error correction and misdetection (undetected error) events of a block code on the discrete renewal inner channel. Finally it is shown that these outer channel models can be used to evaluate error control codes and systems. Forward-error control and automatic-repeat-request systems have been evaluated and compared with each other.

M.Ing. (Electrical and Electronic Engineering) / Please refer to full text to view abstract

M.B.A. / The first mobile cellular telephone was established In St. louis (Missouri. USA) in 1946. In a few years time Europe followed with a similar service. These systems were based on technology developed during the World War 2 (Vodacom Corporate Profile:1999/2000:1). Between 1950 and 1960, cellular radio evolved to become automatic and Its costs dropped due to the Introduction of transistor technology. During the 1970's large scale integration and development of micro-processors enabled more complex systems development (Vodacom Corporate Profile :1999/2000:1 ). In 1988 the European Telecommunications Standard Institute (ETSI) was created. This Institute enabled network operators and telecommunications equipment manufacturers to become Involved In the specification of Global System for Mobile Communications (GSM) (Vodacom Corporate Profile :199~/2000:1 ). The GSM standard of communication was launched In Europe in 1992. This standard Is widelyused In European and African countries...

The frequency spectrum allocated to cellular mobile telephone systems is very limited. Efficient channel assignment schemes can significantly increase the utilization of the available frequency channels. Virtually Fixed Channel Assignment (VFCA) is a dynamic channel assignment method. The idea behind it is simple: each cell is allocated a set of nominal channels. A call request generated in a cell is assigned a nominal channel if one is available. Otherwise, a channel from an adjacent cell is borrowed to serve this call as long as frequency interference constraints are satisfied. VFCA is a promising method because (i) it is efficient in channel assignment, and (ii) it is relatively easy to implement compared to other dynamic channel assignment methods. VFCA has been analyzed based primarily on simulation studies in the past twenty years. In this thesis, we focus our study on development of new channel borrowing strategies and analytical models for VFCA. The contribution of this work is summarized as follows. (1) Development of an queuing model for performance analysis of VFCA. This model may also be used to conduct sensitivity analysis on some system parameters when VFCA is used. (2) Proposed a new channel reservation scheme for handoffs. (In a cellular system, when a call using a channel crosses a cell boundary, it needs to be handed off to a new channel in the new cell. This is called a handoff.) An optimization model for this channel reservation scheme is developed. (3) Applied the fluid-flow approach to modeling an integrated mobile cellular system that uses VFCA to estimate the distribution of data queue length in a cell of the system. These results are useful in the design, performance analysis and optimization of VFCA schemes.

Thesis (Ph. D.)--Faculty of Science, University of Oulo, Finland, 2006. / Includes bibliographical references (p. 218-236).

The worldwide demand for personal communication system (PCS) devices is motivating the development of compact, high-performance antennas. It is also prompting a better understanding of the effects of the user and the mobile communication environment on the antenna performance. The objective of this dissertation is to add to the current knowledge in both areas. Using the Finite-Difference Time-Domain (FDTD) technique, a monopole antenna and a diversity antenna were modeled for PCS applications. Also, techniques were developed and applied to facilitate the accurate numerical analysis of PCS antennas and to investigate the electromagnetic interaction between PCS antennas and the mobile communication environment. A monopole antenna and a polarization diversity antenna (PDA) were investigated at frequencies near 900 MHz. Antenna performance was evaluated in terms of the far-field radiation patterns, the mean effective gain (MEG), the radiation efficiency and the specific absorption rate (SAR) of energy in the user's body. For the diversity antenna, the statistical independence of the two diversity branches was determined from the correlation coefficient. The antenna modeling incorporated the antenna, a cellular telephone handset, models of the user's head and hand, and a statistical model of the mobile environment. Two mobile environments, an urban outdoor environment and a suburban outdoor environment, were modeled. The results show that (i) changing the antenna configuration from the monopole antenna to the PDA significantly affects the antenna efficiency and SAR in the user’s body; (ii) the type of mobile communication environment chosen (urban or suburban) has a pronounced effect on the correlation coefficient of the PDA and on the MEGs of the PDA and the monopole antenna; (iii) in terms of the MEG, the PDA is more sensitive than the monopole antenna to the presence of the user’s body; and (iv) overall, the PDA performs better than the monopole antenna in terms of antenna efficiency, peak averaged SAR in the head, and MEG. The accurate FDTD modeling of wires is crucial to the FDTD analysis of PCS antennas, particularly as monopole antennas and other linear wire antennas are often used with PCS devices. A study of the FDTD modeling of thin wires is included in this dissertation. The accuracy of the wire models was determined by calculating the input impedance of a dipole antenna over a broad range of dipole radii and comparing with the results of a Method of Moments formulation. Two existing thin wire models were analyzed and found to be inaccurate for some purposes. This finding led to the development of a new model, which includes a special treatment of the field components at the wire ends and a model of the source region. The proposed wire model is more accurate than the two existing wire models for a given spatial resolution. Thus, this new wire model facilitates accurate computations of input impedance and resonant frequency for linear wire antennas. The stability of the wire model was addressed, and a formulation for the maximum stability coefficient to be used with the proposed thin wire model was developed. / Graduate

University of Macau / Faculty of Science and Technology. / Department of Electrical and Computer Engineering

by Shu-chuen Lee. / "Revised : September 1994." / Thesis (M.Phil.)--Chinese University of Hong Kong, 1994. / Includes bibliographical references (leaves 61-62). / Acknowledgment --- p.i / Lists of Illustration --- p.ii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- References --- p.4 / Chapter Chapter 2 --- The Meandering Inverted-F Antenna --- p.5 / Chapter 2.1 --- Evolution of the antenna --- p.6 / Chapter 2.2 --- The first prototype --- p.10 / Chapter 2.2.1 --- Geometry of the first prototype --- p.10 / Chapter 2.2.2 --- Resonant frequency --- p.12 / Chapter 2.2.3 --- Bandwidth --- p.16 / Chapter 2.3 --- Antenna with longer meandering line --- p.17 / Chapter 2.4 --- Antenna loaded with dielectric substrate --- p.20 / Chapter 2.4.1 --- Frequency characteristics --- p.21 / Chapter 2.4.2 --- Radiation pattern measurements --- p.22 / Chapter 2.4.3 --- Radiation patterns --- p.26 / Chapter 2.5 --- The 1.9GHz antenna --- p.34 / Chapter 2.6 --- Summary --- p.36 / Chapter 2.7 --- References --- p.37 / Chapter Chapter 3 --- The Meandering Posted Microstrip Antenna --- p.38 / Chapter 3.1 --- Introduction --- p.39 / Chapter 3.2 --- Theory --- p.40 / Chapter 3.3 --- Meandering Inverted-F antenna implemented on PCB --- p.44 / Chapter 3.3.1 --- Geometry for the antenna --- p.44 / Chapter 3.3.2 --- Microstrip bends --- p.45 / Chapter 3.3.3 --- Frequency characteristics --- p.47 / Chapter 3.3.4 --- Implementation of the microstrip antenna with different line width --- p.49 / Chapter 3.3.5 --- Radiation patterns --- p.51 / Chapter 3.4 --- Physical realization --- p.58 / Chapter 3.5 --- Summary --- p.60 / Chapter 3.6 --- References --- p.61 / Chapter Chapter 4 --- Conclusions --- p.63

Thesis (M.Eng.)(Electronic)--University of Pretoria, 2006. / Includes summary. Includes bibliographical references.