In a context of energy saving and operational cost reduction, energy efficiency (EE) has emerged as an important performance metric in cellular networks. According to the famous Shannon’s capacity theorem, maximising the EE while maximising the spectral efficiency (SE) are conflicting objectives, hence, both metrics can be jointly studied via their trade-off, i.e. the EE-SE trade-off. In this context, the aim of this thesis is to investigate the fundamental trade-off between EE and SE in futuristic cellular networks where distributed multiple-input multiple output (DMIMO) or coordinated multi-point (CoMP) scheme is utilised for meeting the high data rate of the next generation wireless communication networks. Focusing on the DMIMO system, a novel tight closed-form approximation of its EE-SE trade-off is derived and its accuracy verified for both the uplink and downlink channels and for both the idealistic and realistic power consumption models (PCMs). In addition, the low and high-SE regime approximations of the DMIMO EE-SE trade-off are derived in the uplink and downlink channels. Furthermore, these approximations are utilised for assessing both the EE gain of the DMIMO over the co-located MIMO (CMIMO) and the incremental EE gain of DMIMO in the downlink channel. It is observed that DMIMO is more energy efficient than CMIMO for cell edge users in both PCMs; whereas the results for realistic incremental EE gain indicate that the optimal approach in terms of EE is to connect the user terminal to only one radio access unit. Focusing on the uplink of the CoMP system, a generic closed-form approximation of the EE-SE trade-off is derived and its accuracy is demonstrated for both the idealistic and realistic PCMs. Asymptotic approximations of this trade-off in both the low and high SE regimes are also presented. Furthermore, these approximations are utilised to compare the EE of the CoMP system with the EE of the traditional non-cooperative system with orthogonal multiple access scheme. It is observed that in the idealistic PCM, CoMP is more energy efficient than the non-cooperative system due to a reduction in power consumption; whereas in the realistic PCM, CoMP can also be more energy efficient but due to an improvement in SE and mainly for cell-edge communication and small cell deployment.

The growth of mobile communications systems over the past decade indicates a trend towards an always-on, ubiquitously networked society. This increase in communications availability leads to a corresponding increase in information gathered, processed, and transmitted over these networks. Some of this information is loosely considered by users of these systems to be private, and in some cases, even the general pattern of use of network services could be regarded as revealing personal information. Therefore, along with growth in communications comes growth in privacy concerns. One approach to protecting users' privacy is to offer anonymity: the ability to blend into a crowd, such that any communications cannot be attributed to a particular real identity. This research study investigates two aspects of providing anonymity in mobile networks: in services, and for network access. Anonymous mobile service provision is approached by analysing several fixed-network approaches to anonymous communications, and examining how they can be reapplied to mobile systems. A set of conclusions and recommendations for future implementations are contributed, along with a case study of providing anonymous location-based services for mobile systems. Being able to connect to a network while remaining truly anonymous is a novel concept, only made possible by the untethered nature of mobile communications. Analysis of the practical requirements for achieving such service is presented, and a solution is proposed, based on a new approach to mobile network service provision called the Digital Marketplace. To support this approach to network access, the fair and reliable operation of the market is ensured by securing its protocol operation. Further modifications to this scheme are proposed, in order to enable fully anonymous network access.

Over the past decades cellular technology has developed through user demand and influence into the Third Generation (3G) of mobile communication systems that are in use today. These networks have adopted a microcellular network approach in densely populated areas with cells only a few 100 meters wide resulting in users roaming between cells at a much higher rate due to the smaller cell sizes compared to legacy cellular networks. This places a fundamental challenge to the handover process, the most frequently requested, complex and time-critical function of a cellular network. As it ensures the continuity of a connection it has a direct impact on the quality perceived by users and is a key factor when measuring system performance and efficiency as well as Quality of Service provided to users. With a user base that is expected to continue rising an efficient and scalable handover scheme is therefore essential to ensure user satisfaction in Third Generation mobile communication systems now and in the future. One way to achieve this is to consider future user movement with the aim to predict the next visited cell to forward data destined for a mobile device and allocate resources prior to a hand over being initiated which is being considered in this thesis. Abstract Following a mathematical description of the problem to be solved to allow the implementation of scenarios for experimental analysis, this dissertation is focusing on the development of an adaptive learning based prediction scheme using Neural Networks (NN) to predict the future movement steps of mobile devices using historical movement information to support the handover process. The aim of the developed scheme is to improve system efficiency by supporting the delivery of a constant Quality of Service to mobile devices by facilitating resource reservation in the future visited cells prior to their arrival while at the same time keeping additional overhead and resource requirements low. The focus of this research undertaken within this thesis is different to previous work as it takes into consideration the changes to mobility behaviour of mobile devices over time. As part of this a detailed performance analysis of the developed system is conducted to study its behaviour in the presence of changing mobility patterns. This study resulted in the development of an adaptive Genetic Algorithm (GA) based retraining scheme tailored to the NN based prediction system to counteract the effects of changing mobility pattern and to add robustness. The NN based prediction system with GA based retraining is then further developed providing a description of a hierarchical implementation within a cellular communication system of the Third Generation. The concepts of the developed schemes have been investigated through experimental as well as simulation work within a framework developed in the simulation environment OPNET to study the behaviour and establish their efficiency. Obtained results confirm the success of the developed concepts with respect to their predictive properties and ability to retrain the NN based prediction system.

Location plays an important role in current mobile applications and services whether it is social applications, gaming, entertainment or mobile commerce, the global market for LBS is projected to reach £13.26 billion by 2015 and a subscriber base of 1.24 billion. It is the well proven winning combination of location awareness and ubiquitous nature of mobile phones that is responsible for a steady increase in mobile data usage and it is predicted that by 2013 mobile devices will overtake PC as the most common web access device. Applications and services utilising traditional location tracking approaches of GPS and Cell id fail to provide a good experience indoors so alternative location positioning schemes need to be utilised. These applications claim to be truly ubiquitous however whether they are social applications, commerce, advertising, gaming or entertainment applications they still tend to engulf the user in computing process, for example if we consider location based or mobile mixed reality gaming it becomes clear that although location plays a part in the game play actual user interaction with the localised environment is often limited. , The work presented in this thesis explores the utilisation of implied location technologies to bridge the gap left by the current applications. In particular it investigates the use of ~ Bluetooth and NFC in to locate the mobile user. The approach taken by this research is to look at utilisation of implied location technologies across a range of applications and services through real world experimentation. In particular their effectiveness has been researched in relation to three areas considered likely to benefit most from location based information: mobile advertising, mixed reality gaming and mobile social applications. Work carried out on providing location based advertising for existing mobile users via Bluetooth has shown that implied location technologies can be very useful to improve the diminishing response to mobile advertising. Mixed reality game, Pac-Lan demonstrates that NFC can not only be utilised as an implied location positioning scheme but also for improving user interaction with the real world. It has also shown that effective user interaction with physical objects can be achieved through NFC resulting in an enhanced user experience. Results presented within have also shown that implied location positioning schemes are effective in mixed reality gaming context and can lead to interesting tactics developing over subsequent game play. From a mobile social application perspective the work presented here shows that through use of NFC social inclusion can be achieved at both individual and group level. Moreover utilising NFC for mobile social applications can help achieve a symbiosis between user, device and environment where interaction space is not simply the space where interaction amongst users takes place but is an integral part the of the experience.

4G communications technologies such as WiMAX and LTE have been developed to satisfy the demand for higher and higher wireless data rates. These use spectral\y efficient modulation schemes which have large channel bandwidths and high peak to average power ratios, challenging the communications engineer to design highly linear power amplifiers. At the same time, reducing power consumption is essential as part of mobile operator's commitments to "Green Radio", This comes with a commercial incentive too, with operators needing to cut costs in developed countries in order to remain competitive and to reduce the cost of power generation equipment in rapidly growing emerging markets where access to a reliable power source is not guaranteed. The radio frequency power amplifier (RFPA) is the single greatest consumer of power in a base station and is typically one of the least efficient components. Switching-mode power amplifiers offer one possible solution. They have a much higher potential efficiency than traditional classes of operation yielding a maximum theoretical efficiency of 100%. They are, however, complex to design, requiring accurate fundamental and harmonic impedance termination. This thesis presents a simple design process for GaN devices operated as high -efficiency, green RFPAs. A switch-based equivalent circuit element model for GaN devices is proposed and a sensitivity analysis shows that the device's parasitic capacitances have the greatest effect on the efficiency and output power of a switching-mode power amplifier. Furthermore, manufacturing variations in device parasitic can lead to significant performance penalties if left unmitigated. A simple extraction method using S-parameter measurements of the "cold" device with no drain bias provides an initial characterisation of the device from which more accurate models can be derived. Waveform measurements of a "hot" device under typical operating conditions are used to characterise the non-linear "intrinsic" device as an alternative to using more specialised load-pulling equipment and to verify the mode of operation using de-embedded waveforms. Finally, this model is used as part of a design process for creating switching-mode power amplifiers and verified using continuous c1ass-F, c1ass-J and Doherty designs.

Long- Term Evolution (LTE) is standardized by the 3rd Generation Partnership Project (3GPP) to meet the customers' need of high data-rate mobile communications in the next 10 years and beyond. A popular technique, orthogonal frequency division multiple access (OFDMA), is employed in the LTE down link. However, the high peak- to-average ratio (PAPR) of OFDMA transmit signals leads to low power efficiency that is particular undesirable for power-limited mobile handsets. Single-carrier frequency division multiple access (SC-FDMA) is employed in the LTE uplink due to its inherent low-PAPR property, simple frequency domain equalization (FDE) and flexible resource allocation. Working within the physical (PHY) layer, this thesis focuses on decision- feedback equalization (DFE) and channel estimation for SC-FDMA systems. In this thesis, DFE is investigated to improve the equalization performance of SC- FDMA. Hybrid-DFE and iterative block decision-feedback equalization (IB-DFE) are considered. It is shown that hybrid-DFE is liable to error propagation, especially in channel-coded systems. IB-DFE is robust to error propagation due to the feedback (FB) reliability information. Since the FB reliability is the key to optimize the performance of IB-DFE, but is generally unknown at the receiver, FB reliability estimation techniques are presented. Furthermore, several transform-based channel estimation techniques are presented. Various filter design algorithms for discrete Fourier transform (DFT) based channel estimation are presented and a novel uniform-weighted filter design is derived. Also, channel estimation techniques based on different transforms are provided and a novel pre-interleaved DFT (PI-DFT) scheme is presented. It is shown that SC-FDMA employing the PI-DFT based channel estimator gives a close error rate performance to the optimal linear minimum mean square error (LMMSE) channel estimator but with a much lower complexity. In addition, a novel windowed DFT-based noise variance estimator that remains unbiased up to an SNR of 50dB is presented. Finally, pilot design and channel estimation schemes for uplink block-spread code division multiple access (BS-CDMA) are presented. It is demonstrated that the recently proposed bandwidth-efficient BS-CDMA system is a member of the SC-FDMA family. From the viewpoint of CDMA systems, novel pilot design and placement schemes are proposed and a channel tracking algorithm is provided. It is shown that the performance of the proposed schemes remain robust at a Doppler frequency of 500Hz, while the pilot block scheme specified in the LTE uplink fails to work in such a rapidly time-varying channel.

This Thesis introduces a novel analysis of the interference experienced in modern wireless cellular communication systems. The analysis here is applied on Code Division Multiple access (CDMA) and Multiple Input Multiple Output (MIMO) systems. The separation between constructive and destructive interference, inherent in a wireless communication system, is established by mathematical expressions and matrix representations. The presented interference study is generic and can be therefore applied to a wide range of signal enhancement schemes.

The mobile workforce needs the ability to communicate with customers, partners, and fellow workers anywhere, anytime and get access to relevant business applications and tools to carry out business effectively and with this the Transmission Control Protocol / Internet Protocol (TCP/IP) plays a major part. The TCP/IP which forms the main platform for networking and how data packets are handled by the Internet fits well within the OSI model which consists of the physical layer, data link layer, network layer, transport layer, session layer, presentation layer and the application layer.

In Mobile Ad hoc Networks (MANETs), mobile nodes communicate over an error prone wireless channel without any centralized control. MANETs have n9 fixed topology because mobile nodes can freely join or leave the network at any time. As a consequence, it is difficult to guarantee Quality of Service (QoS) in these networks. The current routing , protocols provide only best effort services to the applications. Multimedia communications become very popular and require various types of QoS guarantee from the network such as guranteed throughput, bounded end-to-end delay. The QoS-aware routing (QA) and Admission Control (AC) protocols try to address the issue of QoS to some extent. In this work, a novel Flow Aware Admission Control (FAAC) protocol is designed to assure the guaranteed throughput to data sessions. It utilizes the route cache of routing protocol and devises a new admission technique to accept or reject data session to the network. It is partially coupled with the Oynamic Source Routing (OSR) protocol as it has used the basic functionality of route search of the OSR protocol. The protocol has two phases: (i) route discovery and (ii) test the route nodes resources for a data session entry. The performance evaluations show that the protocol outperforms the existing best effort routing and QAR and AC protocols such as OSR and Contention Aware Admission Control (CACP) protocols in providing QoS in MANETs. Mobility is a big challenge to assure guaranteed throughput to data sessions. To address this issue, we have designed F AAC-Multipath protocol that uses multiple routes for data transmission. The protocol maintains two tested routes for each data session and devises new fast switching mechanisms that switch the data flow from one route to another to guarantee the throughput. Multimedia applications require guaranteed throughput as well as bounded end-to-end delay. To address this issue we.have designed Flow Aware Admission Control-Multipath with Multiple constraints (F AAC-MM). This protocol assures the application with guaranteed throughput as well as bounded end-to-end delay. FAAC-MM switches the data flow from primary to secondary route on the basis of achieved throughput and end-to-end delay. We have also analyzed and compared the proposed protocols with the state of the art protocols such as CACP and Multi-path for Mobile Ad Hoc Networks. The simulation results show that our protocol outperforms the above mentioned protocols.

With the rapid development of wirelessly networked applications, components interact with each other more frequently. An essential challenge for security is to determine how one network entity can trust another. Most existing trust models evaluate trust, Choosing a single probability-based parameter based on probabilistic estimation. However malicious nodes can take advantage of this to either gain unfair trust values for themselves, or to degrade the trust values of other nodes. A multi-parameter trust framework for MANETs (MTFM) presented in this thesis employs multiple types of parameters for the evaluation of trust based on Grey theory. The proposed framework classifies the trust relationships into three types: direct, recommendation and indirect. The mobility of the MANET nodes in a trust grouping may cause large variances in the trust values. Simulations conducted in 6-node network demonstrate that MTFM can maintain consistent total trust values in the presence of various types of mobility. Misbehaviour detection strategies for the MTFM apply weight vector groups for multiple parameters, based on the design of an Analytic Hierarchy Process. This approach brings a significant benefit; the MTFM can not only detect misbehaviour, but can also detect the particular parameter use<:! in the strategy of the malicious node. A new combined prediction model provides a boundary to permit discrimination between normal and abnormal behaviour. And additional contribution is the issue of the trust group size. Although the resulting trust value can be resilient to unfair evaluation from malicious neighbour nodes, however, due to their limited recourses, having a lot of neighbours is not practical for wireless mobile nodes. Therefore. there needs to be a balance between maintaining trust values and the insensitivity of a subgroup to a changed trust value. Results and analysis are presented to indicate the preferred Size of a subgroup among a much larger network.