This thesis examines the mechanisms improving user terminal mobility in a wireless cellular network. It addresses the problem of the lack of self-organisation in the cell reselection algorithms used in the mobile radio access networks. This mechanism is an autonomous terminal mobility procedure used when moving between cells. This work refers to the practical examples of the evolution of cellular teclmologies specified by 3rd G~neration Partnership Project (3 GPP). FUlthermore, this thesis is based on the detailed system analysis of the cell reselection procedure, aiming to identifY areas where the system could be improved by the application of the self-organising design approach. It studies how the performance of the cell measurements mechanism, allowing a tenninal mobility in the network could be increased by using the self-organising concept, in terms of the better cell reselection performance and the terminal energy efficiency trade-off. The main goal of these improvements is providing better quality of service, enhanced user experience and increased network operational performance while minimising maintenance costs. The main contributions of this thesis can be summarised as follows. Firstly, it investigates the autonomously controlled user terniimil mobility, its drawbacks, and limitations during the mobility between macro cells. Then, techniques increasing the energy efficiency of the terminal, without compromising the system performance during the cell reselection, are identified. Also, signalling protocol aspects during the cell reselection algorithm are studied and performance improvements are proposed. Furthermore, an evaluation and optimization of the cell reselection performance is undeltaken, considering different system level and user experience criteria. It draws on simulation results to analyse the serving cell quality, mobility measurements effOli impacting terminal energy efficiency and the related performance trade-offs. Finally, a selforganising approach based framework, with a practical example of the possible mechanism allowing a cost efficient self-optimization ofthe autonomously controlled mobility is proposed. Key words: Cell Reselection, Energy Efficiency, Land Mobile Radio Cellular Systems, Neighbour Cells Measurements, Radio Access Network, Radio Resource Control Protocol, SelfOrganising Networks

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The aim of this project is to investigate the attenuation due to clouds at 20- 50GHz; to develop an accurate long-term prediction model of cloud attenuation applicable to slant-path links and evaluate the impact of cloud attenuation dynamics on the design of future portable EHF earth-space systems. Higher frequencies offer several advantages, for example, greater bandwidth and immunity to ionospheric effects. The EHF band is being targeted for the launch of earth-space communication systems to provide global delivery of bandwidthintensive services (e.g. interactive HDTV, broadband internet access and multimedia services, television receive-only, etc.) to portable terminal units. Since spectrum shortage and terminal bulk currently preclude the realization of these breakthrough-broadband wireless communication services at lower frequencies, a better understanding is needed in order to optimize their usage. One major obstacle in the design of EHF earth-space communication systems is the large and variable signal attenuation in the lower atmosphere, due to a range of mechanisms including attenuation (and scattering) due to clouds and rain, tropospheric scintillation caused by atmospheric turbulence and variable attenuation by atmospheric gasses. In particular, cloud attenuation becomes very significant at EHF. In this thesis, we start with an overview of literature review in the first chapter. Followed next by the theory and description of accepted-up to date- cloud attenuation models in the field (chapter 2). Then followed up by a description of the pre-processing, validations, sources and assumptions made in order to conduct the analysis of the cloud attenuation in this work (chapter 3). Afterwards, a comprehensive analysis of Meteorological and local tropospheric degradation was carried out (chapter 4). That was followed by an overview of cloud fade statistics and suggested methods to counter their effects (chapter 5). And finally the improved cloud attenuation model and the enhancement of the currently accepted cloud attenuation model (ITU-R 840.4) by terms of validating the effective temperature concept and ways of acquiring it (chapter 6).

Today, more than 90% of Britons own a mobile phone handset. Yet, the popularity of mobile telephony is a fairly recent phenomenon, with the first mobile phone call in the UK made only 21 years ago. Mobile technology has come a long way since the first mobile call that was made from St Katherine's dock to Vodafone's head office in Newbury. Many interesting mobile computing technologies have surfaced, including pagers, laptop computers, tablet PCs and Blackberries, constantly offering altogether new communicative acts to mobile workers. Innovation of mobile information systems, too, has changed quite dramatically over this time period. What was once an industry marked by low competition and high profit margins for devices developed purely by Research and Development departments now increasingly involves, even requires, the interaction with users for the innovation of new mobile devices in highly competitive environments. Despite the increasing popularity of mobile technologies, the concept of mobility and the innovation of mobile information systems remain largely unexplored. This study takes up the challenge to examine how innovation of mobile technology unfolds today. With this focus, this research explores the relationships between innovators of technology for mobile work and its users. It departs from the prevalent product- oriented view of innovation and treats technology in the making as a conscious human activity, made possible through the trinity of innovator companies, their organisational clients as innovation partners and their particular mobile workers as end users of the technology. This study examines the complex interaction and coalescence of these parties as shaped by their respective organisational activities, their unique motives for cooperation with one another, their use of technology and their relationship to the geographical mobility and distribution of work. From the outset, this study was committed to providing a rigorous examination grounded in actual work. As an Action Researcher, I was very fortunate to be invited to follow the innovation and development of a fundamentally new mobile information system, based on the convergence of mobile telephony and Radio Frequency Identification (RFID) technology. The empirical work and theoretical analysis emphasised the epistemological differences among innovation participants and unearthed many complications that shape how interactive innovation of technology for mobile work unfolds. Moreover, the analysis of the empirical work led to the conceptual difference between mobility and pervasiveness of work as it pertains to innovation. It revealed Individual Pervasiveness, or the extent to which an individual's technology is aware of its immediate context and communicates details of its bearer and his behaviour. It also uncovered a Pervasive Order, imposed from superior to mobile worker and made possible in this case through mobile RFID. Together, these two concepts fundamentally change the information flow within mobile work activities. The trajectory from mobility to pervasiveness dramatically reshapes the activities of mobile workers and their superiors and, thus, the activity of interactive innovation of technology for mobile work.

This thesis analyses how and why culture and geography influence the allocation and licensing of the radio frequency (RF) spectrum in different nations. Based on a broad study of 235 countries, an inter-disciplinary approach is used to explore regulatory frameworks and attitudes toward risk. In addition, detailed case studies of the UK, France, the US and Ecuador provide deeper insights into the main contrasting regulatory styles. Three alternative sociological theories are used to analyse and explain the results for both the in-depth and broad brush studies. The Cultural Theory of Mary Douglas and co-workers is first used to categorise countries in terms of perceptual filters. The empirical findings indicate some countries to be apparently exceptional in their behaviour. The theory of Bounded Rationality is used to investigate and explain these apparent irrationalities. Finally, Rational Field Theory shows how beliefs and values guide administrations in their RF regulation. A number of key factors are found to dominate and patterns emerge. The European RF harmonisation is unique. Following European unification, wireless regulation is divided into two major camps (the EU and the US), which differ in their risk concerns, approach to top-down mandated standards, allocation of RF spectrum to licence-exempt bands and type approval process. The adoption of cellular and TV standards around the world reflects geopolitical and colonial influence. The language of a country is a significant indicator of its analogue TV standard. Interestingly, the longitude of a country to a fair extent defines RF allocation: Africa and West Asia follow Europe, whereas the Americas approximate the US. RF regulation and risk tolerability differ between tropical and non-tropical climates. The collectivised/centralised versus the individualised/market-based rationalities result in different regulatory frameworks and contrasting societal and risk concerns. The success of the top-down European GSM and the bottom-up Wi-Fi standards reveal how the central- planning and market-based approaches have thrived. Attitudes to RF human hazards and spurious emissions levels reveal that the US, Canada and Japan are more tolerant of these risks than Europe. Australia, Canada, New Zealand, UK and USA encourage technological innovation. A practical benefit of this study is that it will give regulators more freedom to choose a rational RF licensing protocol, by better understanding the possibly self-imposed boundaries of cultural and geographical factors which are currently shaping allocation. Academically, there is utility in undertaking a cultural and geographic analysis of a topic that is mostly the domain of engineering, economic and legal analysts.

Direct satellite broadcasting is considered to be a very important stage in mass media development. It is a way of sending television programmes from the earth to orbiting satellites, which then directly transfer these programmes by their converters to small dishes fixed to the roofs and outside walls of domestic buildings. Television sets inside the buildings are linked to these dishes and their owners can, thus, watch an almost unlimited number of programmes from all over the world. The only apparatus needed to do this is a receiver, a satellite dish and a television set. Libya's location in North Africa, and its proximity to southern Europe, makes it easy for Libyan audiences to receive satellite channels from many satellites in orbit. A visitor to any Libyan city, town, or village would notice the various types of satellite dishes, of different sizes and shapes, dominating the skyline above private and public buildings. The satellite channels started to spread in Libya at the beginning of the 1990s, increasing after the prices of the apparatus fell, especially after 1997. The introduction and spread of satellite broadcasting in Libya have, as a result, changed local television viewing habits. This study seeks to examine the response of Libyan audiences to direct satellite broadcasting. The effect the viewing of satellite channels has had on the viewing of local television channels is examined in this thesis. In addition, the effects of the spread of satellite channels on the Libyan television services are also considered. At the outset of this research, the researcher posed a number of questions to which he hoped to find answers. In order to address these questions, he adopted a survey study method incorporating a structured questionnaire and a series of interviews, to provide information about viewers' opinions on satellite television. The interviews were conducted with Libyan experts and specialists in the field of mass media. The respondents to the Questionnaire were 256 media students and 256 members of the general viewing public. The field study was conducted in Tripoli during the months of March, April, May and June, 2000. Some of the interviews with the media experts and specialists were conducted at the same time. The Questionnaire consisted of 36 questions designed to elicit information about satellite-channel viewing habits and other related points. The SPSS method was used to analyse the data. The results revealed the most popular days for viewing and the most popular viewing times of the sample groups; the most frequently watched programmes and the reasons for watching television in general. The satellite-channel viewing habit is widespread among Libyan audiences, which the results of this study have confirmed, with more than three-quarters of the sample groups possessing satellite dishes. The ten most frequently watched satellite channels are MBC, Aljazeera, Egyptian Channel, Dubai, Lebanese Future, Abu Dhabi, LBC, ART Channels, Nile Channel, and ANN.

Wireless Universal Serial Bus (W-USB) has been proposed to offer a mechanism in short range and high speed Wireless Personal Area Networks (WPAN). Wireless USB has now been standardized by utilizing the common WiMedia Ultra Wideband (UWB) radio platform to use the services of Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) as the transport mechanism. With regards to the high data rate mode using DCM modulation scheme, different DCM demapping methods resulting in different system performance are presented, which include soft bit demapping, Maximum Likelihood (ML) soft bit demapping and I Log Likelihood Ratio (LLR) demapping. The proposed Channel State Information (CSl) aided scheme coupled with the band hopping information is used as the further technique to improve the DCM demapping performance.

Considering that efficient use of the available radio spectrum is an important require- ment for future wireless communication, designing a multiple access technique which can support higher loaded conditions with affordable complexity and near single user performance is a challenge, This thesis aims to address this challenge by propos- ing an efficient multiple access technique called low density signature OFDMA (LDS- OFDMA), LDS-OFDMA is a special case of the multi-carrier CDMA (MC-CDMA) system where its spreading sequences have low density, This technique benefits horn an iterative near to optimum MUD and is able to support overloaded conditions under multipath fading channel. The BER results show LDS-:9FDMA gains a performance near to single user bound under 200% load condition, Also, for load of 1QO%, LDS- OFDM outperforms MC-CDMA with MMSE detector 'by 8,1 dB at BER= 10-3 which is a considerable gain, Comparing the BER performance with OFDMA, it is shown that, the BPSK coded LDS-OFDMA system with 400% loading offers 6,65 dB gain over 16 QAM coded OFDMA at BER of 10-3, Furthermore, in terms of complexity Also it is shown that for LDS-OFDMA the raise in the complexity as the number of users increase is much less than similar techniques with optimum ¥UDs, Based on the iterative nature of the MUD, we also proposed a suitable design and analy- . sis tool to obtain an efficient detection/decoding algorithm, Therefore, by applying the extrinsic information transfer (EXIT) chart, the convergence behaviour of the iterative detector is analysed, Evaluating the effect of different factors on the performance of MUD could help us find design guidelines for improving the LDS structure, Moreover, a tuned turbo multiuser detector/decoder (MUDD) for LDS-OFDMA is proposed, Us- ing the EXIT chart analysis wc were able to tunc the receiver in a way that the turbo MUDD elm approach its final performance using a smaller number of inner iterations, 2,21 dB gain at BER=1O-4 is achieved by turbo MUDD with 3 turbo iterations over conventional LDS-OFDMA receiver. In order to gain insights on the performance of LDS schemes, an analytical model for the capacity of LDS based schemes for the uplink of multipath fading channels is proposed, The proposed model is then improved to take into account realistic assumptions, which arc more suitable for practical systems. :Nlonte- Carlo. simulation results are used to validate the proposed model by comparing the results with the sum rate of conventional multiple access channel. The simulation results show that there is Cl, 2 dB ga.p between the sum rate of conventional LDS scheme and the one for multiple access channel which is the cost for complexity reduction. Also it is shown that for practical LDS schemes with modulation and convolutional coding the gap increases to 4.8 dB. However using capacity approach codes such as LDPC eo des the gap can be reduced significantly. Key words: Low Density Signature Structures, Chip Level Iterated Multiuser Detec- tion, Overloaded Conditions, Turbo Multiuser Detection/Decoding.

Cognitive radio (CR) technology offers an innovative solution to improve spectrum efficiency, thus satisfying the greater demand to be placed on the electromagnetic spectrum by future wireless networks and communications. In this sense, the ulti- mate purpose of the spectrum sensing feature in cognitive radio is to determine the absence or presence of licensed users' signals in a frequency band of interest. More- over, due to the wide variety of scenarios in which cognitive radios may operate and the random nature of wireless channels, spectrum sensing algorithms are expected to perform well at a very low signal-to-noise-ratio (SNR), thus playing not only an important but also a very challenging role in CR. In this thesis, locally optimum (LO) detection, (known to be optimum at low SNR), is adopted in the design of blind and semi-blind detection algorithms by fo- cusing on linear modulation in the presence of an unknown phase shift and additive white Gaussian noise. The proposed LO detectors are shown to significantly out- perform the energy detector in the case of BPSK signals and to be less sensitive to noise power mismatch whilst their complexity is only slightly higher than that of the energy detector. Furthermore, the spectrum sensing performance is improved by taking advantage of the spatial diversity gained through cooperation. In addition, next generation wireless networks will need higher data rates to meet the requirements of the expected customers and services. The spectrum sen- sing duration and the secondary user's achievable throughput trade-off problem is addressed here by allowing the constraint on the probability of detection to be in outage with a specified percentage, taking into account the detrimental effect of unknown channel gains over different fading conditions in centralised cooperative networks, which is a more realistic scenario. The spectrum sensing time/secondary user's achievable throughput trade-off is then formulated and optimised accordingly.