Cellular network operators are now facing considerable challenges in terms of network capacity and a need to reduce energy consumption by rolling out energy efficient radio access networks (RANs). Use of Distributed Antenna Systems (DAS) is one feature of RAN architecture that can enhance capacity and provide ubiquitous coverage. This thesis sets out to appraise the energy savings of outdoor DAS deployments through simulations. DAS is modelled by placing Remote Radio Heads (RRHs) in a hexagonal cellular network layout and potential energy savings are evaluated using large scale propagation modelling, network equipment power consumption models and energy metrics. The conventional macro cell deployment is used as the benchmark. This research has addressed remote antell11a location, power distribution between base station and RRH and impact of user density and location on the energy efficiency gains of DAS. The results were shown to be sensitive to equipment power consumption models indicating the vital need for energy efficient equipment and backhaul in order to reap energy gains via use of DAS. The analysis shows that DAS deployments provide transmit energy savings of up to 83% over the conventional system. When the comparison is based on total operational power of the cell (including power consumed by base station, RRHs and backhaul) the energy gains depend on network equipment parameters and deployment scenarios. RRH location is found to affect DAS performance significantly since location determines if an RRH adds value in terms of throughput or suffers from inter cell interference. Further, Single Antenna Selection (S-AS) is shown to provide better energy savings than blanket transmission due to a combination of reduced transmit power and enhanced throughput. DAS is also shown to provide more energy savings in hotspot scenarios than in uniform user location cases. Energy savings can vary by +/- 22% depending upon user distribution. For a uniform user distribution, RRH placement based on shadowing knowledge can provide better performance than that based on SINR knowledge thus reducing the need for drive testing. Further, planning RRH locations to cover hotspots has been shown to provide greater energy savings and the savings increase with the number of users per hotspot. For a maximum RRH transmit power of 1W, it was observed that energy savings were 26.4% and 16.9% for S-AS and blanket transmission respectively while for the unplam1ed scenario, these values dropped to 2.9% and -5.9% respectively.

This thesis is dedicated to the investigation, development and practical verification of header compression and signal processing techniques over TErrestrial Trunked RAdio (TETRA), TETRA Enhanced Data Services (TEDS) and Power Line Communication (PLC). TETRA release I is a narrowband private mobile radio technology used by safety and security organizations, while TEDS is a widebandsystem. With the introduction of IP support, TEDS enables multimedia based applications and services to communicate across communication systems. However the IP extension for TEDS comes at a cost of significant header contributions with the payload. With small application payloads and fast rate application traffic profiles, the header contribution in the total size of the packet is considerably more than the actual application payload. This overhead constitutes the considerable slot capacity at the physical layer of TEDS and PLC. Advanced header compression techniques such as Robust Header Compression (RoHC) compress the huge header sizes and offer significant compression gain without compromising quality of service (QoS). Systems can utilize this bandwidth to transmit more information payload than control information. In this study, the objective is to investigate the integration of RoRC in TEDS and design a novel IPv6 enabled protocol stack for PLC with integrated RoHC. The purpose of the study is also to investigate the throughput optimization technique such as RoHC over TEDS and PLC by simulating different traffic profile classes and to illustrate the benefit of using RoHC over TEDS and PLC. The thesis also aims to design and simulate the TEDS physical layer for the purpose of investigating the performance of higher order modulation schemes. Current TEDS, standards are based on the transmission frequencies above 400MHz range, however with delays in the standardization of broadband TETRA, it is important to explore all possible avenues to extend the capacity of the system. The research concludes the finding of the application of RoHC for TEDS and PLC, against different traffic classes and propagation channels. The benefit of using RoHC in terms of saving bandwidth, slot capacity and other QoS parameters is presented along with integration aspects into TEDS and PLC comnunication stacks. The study also presents the TEDS physical layer simulation results for modulation schemes and transmission frequency other than specified in the standard. The research results presented in this thesis have been published in international symposiums and professional journals. The application of the benefits of using RoHC for TEDS has been proposed to the ETSI TETRA for contribution to the TETRA standard under STF 378. Simulation results for the investigation of characteristics of nl4 DQPSK performance below 200 MHz have also been also presented to ETSI TETRA as a contribution to the existing TEDS standard. The Results presented for the design of IPv6 enabled stacked with integrated RoHC have been submitted as deliverable under the FP-7 project DLC+VIT4IP. All the results, simulations and investigations presented in the thesis have been carried out through the platform provided by HW Communication Ltd.

Transmitting the maximum amount of information in minimum possible bandwidth is always desired . Multiple access (MA) communication is often used to achieve this objective. However, the mutual interference among the users handicaps the performance considerably. Addition of redundancy bits for reliable transmission demands more bandwidth. Power line communication (PLC) is considered an attractive candidate to overcome the scarcity of the bandwidth and the associated huge cost. PLC uses power lines as a communication medium which were originally designed for power distribution rather than data transmission and are more harsh compared to other communication media. Frequency-selective fading and inter-symbol-interference (ISI) due to multipaths degrade the bit error rate (BER) substantially. Furthermore, devices connected to the grid introduce impulsive noise on the network. Robust coding and modulation schemes are therefore required to increase the communication reliability. Multi-fold turbo coding is a technique used to improve the error performance of conventional turbo codes. Multi-fold turbo coding increases the randomness of a turbo code by dividing the long information sequence in small subsequences and making use of multiple pseudo random interleavers. Multiple interleavers spread the error burst over several symbols making the errors appear in random. Orthogonal frequency-division multiplex (OFDM) distributes the overall transmitted data in parallel on several orthogonal subcarriers and transforms a frequency-selective fading channel to a group of many flat-fading channels. OFDM possesses a unique property which disperses impulsive noise burst across its several sub-carriers; hence Abstract is able to cope better in an impulsive noise environment. This thesis presents multi-fold turbo coding scheme for MA channels. Specifically, a member of multi-fold family called two-fold has been adopted for the simplest MA channel, the two-user binary adder channel (2-BAC). Each user uses a distinct code to encode the information and the decoder employed uses iterative decoding to decode the received signal. Making use of distinct codes not only allows the correction of errors due to noise but also the correction of errors due to interference between users. Performance of multi-fold turbo codes has been evaluated under Gaussian and power-line conditions. Depedance of performance on number of iterations and blocklength is also presented. A simplified multipath model approach is introduced for complex power-line channels in which the power-line network is divided into number of small segments and each segment is considered as an independent sub-channel. Transfer function of each sub-channel is determined. The transfer function of the whole network is taken as a product of all component transfer functions. The approach has been applied to model two PLC networks that are used as reference channels for the work presented in the thesis. Multi-fold turbo codes can be modified to provide unequal error protection (UEP) levels to the information having different ranks of importance where the most significant information is protected more than the information with least importance. To demonstrate the practicality of the UEP mechanism for the 2-BAC, two test images are decomposed into luminance (£), saturation (8) and hue (if) components. The L component of each image is protected twice than the other two components. The performance of the modified multi-fold turbo codes is compared with the multi-fold turbo codes and conventional turbo codes in terms of pixel error rate (PER.) in Gaussian and power-line environments. The visual effects of PER. for each image are also presented.

Today, mobile phones provide a versatile platform that is able to support a multitude of new applications. However, an inherent obstacle with mobile phones is their limited output capabilities. This poses constraints on the user's ability to find and interact with the software applications installed due to factors such as the limited screen size of the device. The goal of the herein work is to extend the phone's user interface to the physical environment. The user's interactions with the physical environment are through phone touches; thus, explicit and direct. Moreover, in addition to the environment providing spatial awareness visually, the phones also lend their capabilities (e.g. input modalities, display, storage, etc.) to the interaction. The approach taken in this thesis is to support touch-based object interaction through the use of tagging technologies. This involves augmenting the physical environment with devices that can be sensed by the phone. If the data stored on the device represents the physical object, the phone can effectively sense this object. Furthermore, the advantage of tagging technologies is the freedom provided to create a variety of different user interfaces. Currently, the majority of implemented solutions focus on single-tag interaction paradigms whereby the phone reads only one tag to accomplish a goal. In order to explore the potential of touch-based mobile interaction further, mUltiple touches (using multiple tags) could be concatenated to achieve expressive interactions. The contribution of this project is the fut1her analysis of touch-based object interactions and the creation of guidelines for the development of such systems, as well as to establish developer supp0l1 for the future development.

This research documents the development of three novel mobile applications and the subsequent user experiences observed during the deployment of these applications using an 'in the wild' methodology. These experiences were aimed at evaluating the use of anchors that help to bridge the gap between digital and tangible. Two distinct avenues of interest are explored, firstly an investigation was carried out into the use of a physical anchor (an ambient device); and then progresses on to review more contextual anchors that manifest from the use of location, environmental, spatial and temporal data, with the intention this will positively impact the participant experience. The first application was designed to encourage novel interactions between the user and a physical anchor via the use of a mobile phone. The aim here was to identify the patterns in user behaviour when communicating in this way. The key finding of this research was that unanticipated interactions developed, especially regarding how the evolving nature of how the device was used. Based upon the observed emergent behaviour in the first project, the research progresses to document how users interact with more contextual anchors through two location based games. These games were inspired by existing location based experiences, such as Geocaching, and sought to encourage emergent behaviour by providing the user with a format that was flexible enough for them to fonn their own interpretations of how it should be played. The major findings here focus upon participation inequality, and the approach of using context to fonn a games rule-set being a facilitator in encouraging emergent behaviour.

The massive deployment of Location Based Services has been predicted for many years, but progress so far has been slow. The benefits for business operation, efficiency and customer choice in commerce have been identified by researchers, and a whole range of new services for customers can be conceived. Yet there are clearly barriers to implementation. One barrier to deployment is user concern over loss of privacy, where it is believed that early adopters will demonstrate the tangible benefits from using these technologies far outweigh the worries over privacy. A second barrier is the lack of a suitable location technology, in that: • GPS receivers have been built into mobile phones, but suffer from high power consumption and poor performance indoors and in urban areas. • Cellular positioning techniques require little additional power, but provide insufficient precision for many applications, particularly for indoor positioning . The research conducted in this PhD has been concentrated on real-world applications, and the methodologies to provide accurate indoor positioning and context acquisition on standard mobile phones. Key outcomes from the novel research completed include: • Investigations into Classification techniques which can reduce the computational complexity of running positioning algorithms on standard mobile phones. Improvements in accuracy and scalability for W-LAN indoor fingerprinting location estimation algorithms. • Abstraction of Contextual information from low level sensors which may be used to compliment location estimation algorithms The originality of the research completed has resulted in four publications that have concentrated on practical approaches for 'Any time, Anywhere' accurate positioning.

OFDMA is accepted as the most appropriate air-interface for 4G OFDMA based systems by both researchers in industry and academia. A major problem that arises in OFDMA based systems is inter-cell interference that stems from aggressive frequency reuse and is particularly worse in cell-edge areas. Therefore, Inter-Cell Interference Coordination (ICIC) has been proposed as a promising method to mitigate inter-cell interference (ICI) mainly in the overlapping (cell-edge) areas of a multi-cell cellular network. The main objectives of this thesis are to investigate inter-cell interference in a heterogeneous system comprising of both macro and femto cells, propose and evaluate less complex novel inter-cell interference coordination/avoidance techniques that increase both cell-edge throughput and overall cell throughput. Initially, our scenario focuses on the investigation of co-channel interference in macrocell deployments. In this direction, we propose a static ICIC technique for OFDMA macrocell networks based on cyclic difference sets a branch of combinatorial mathematics to minimize the inter-cell interference. Then, we formulate the dynamic ICIC problem in a linear way in order to minimize the complexity issues with the scalability of the problem. We show that with minimal loss of optimality, this linear problem can be simplified into two smaller problems i.e. the multi-user scheduling (base station) problem and the multi-cell scheduling (network) problem. Simulation results confirm the increased effectiveness of proposed ICIC schemes in both metrics (i.e. cell-edge and total cell throughput) over a number of state-of-the-art (static and dynamic) interference avoidance schemes. After, the ICIC technique is optimized to minimize the total transmit power by employing inter-cell and intra-cell power control without compromising the cell-edge throughput. Here, we formulate the multi-objective problem as a multi-dimensional knapsack problem. Our simulation results of the proposed scheme show its increased energy efficiency and user fairness compared with the state-of-the-art energy efficient schemes. Finally, the complexity of the ICIC problem and the need of a centralised controller are further reduced in order to benefit small-cell deployments. Here, it is shown that the complexity of the ICIC version can be further reduced by employing a dual decomposition method from optimization theory. Extensive simulation results show a significant improvement of the proposed scheme compared with some distributed reference schemes in terms of cell-edge and total cell throughput and thus it is a promising candidate for next generation mobile systems.

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The ubiquity and widespread availability of wireless mobile devices with ever increasing inter-connectivity (e. g. by means of Bluetooth, WiFi or UWB) have led to new and emerging next generation mobile communication paradigms, such as the Mobile Ad-hoc NETworks (MANETs). MANETs are differentiated from traditional mobile systems by their unique properties, e. g. unpredictable nodal location, unstable topology and multi-hop packet relay. The success of on-going research in communications involving MANETs has encouraged their applications in areas with stringent performance requirements such as the e-healthcare, e. g. to connect them with existing systems to deliver e-healthcare services anytime anywhere. However, given that the capacity of mobile devices is restricted by their resource constraints (e. g. computing power, energy supply and bandwidth), a fundamental challenge in MANETs is how to realize the crucial performance/Quality of Service (QoS) expectations of communications in a network of high dynamism without overusing the limited resources. A variety of networking technologies (e. g. routing, mobility estimation and connectivity prediction) have been developed to overcome the topological instability and unpredictability and to enable communications in MANETs with satisfactory performance or QoS. However, these technologies often feature a high consumption of power and/or bandwidth, which makes them unsuitable for resource constrained handheld or embedded mobile devices. In particular, existing strategies of routing and mobility characterization are shown to achieve fairly good performance but at the expense of excessive traffic overhead or energy consumption. For instance, existing hybrid routing protocols in dense MANETs are based in two-dimensional organizations that produce heavy proactive traffic. In sparse MANETs, existing packet delivery strategy often replicates too many copies of a packet for a QoS target. In addition, existing tools for measuring nodal mobility are based on either the GPS or GPS-free positioning systems, which incur intensive communications/computations that are costly for battery-powered terminals. There is a need to develop economical networking strategies (in terms of resource utilization) in delivering the desired performance/soft QoS targets. The main goal of this project is to develop new networking strategies (in particular, for routing and mobility characterization) that are efficient in terms of resource consumptions while being effective in realizing performance expectations for communication services (e. g. in the scenario of e-healthcare emergency) with critical QoS requirements in resource-constrained MANETs. The main contributions of the thesis are threefold: (1) In order to tackle the inefficient bandwidth utilization of hybrid service/routing discovery in dense MANETs, a novel "track-based" scheme is developed. The scheme deploys a one-dimensional track-like structure for hybrid routing and service discovery. In comparison with existing hybrid routing/service discovery protocols that are based on two-dimensional structures, the track-based scheme is more efficient in terms of traffic overhead (e. g. about 60% less in low mobility scenarios as shown in Fig. 3.4). Due to the way "provocative tracks" are established, the scheme has also the capability to adapt to the network traffic and mobility for a better performance. (2) To minimize the resource utilization of packet delivery in sparse MANETs where wireless links are intermittently connected, a store-and-forward based scheme, "adaptive multicopy routing", was developed for packet delivery in sparse mobile ad-hoc networks. Instead of relying on the source to control the delivery overhead as in the conventional multi-copy protocols, the scheme allows each intermediate node to independently decide whether to forward a packet according to the soft QoS target and local network conditions. Therefore, the scheme can adapt to varying networking situations that cannot be anticipated in conventional source-defined strategies and deliver packets for a specific QoS targets using minimum traffic overhead. ii (3) The important issue of mobility measurement that imposes heavy communication/computation burdens on a mobile is addressed with a set of resource-efficient "GPS-free" soluti ons, which provide mobility characterization with minimal resource utilization for ranging and signalling by making use of the information of the time-varying ranges between neighbouring mobile nodes (or groups of mobile nodes). The range-based solutions for mobility characterization consist of a new mobility metric for network-wide performance measurement, two velocity estimators for approximating the inter-node relative speeds, and a new scheme for characterizing the nodal mobility. The new metric and its variants are capable of capturing the mobility of a network as well as predicting the performance. The velocity estimators are used to measure the speed and orientation of a mobile relative to its neighbours, given the presence of a departing node. Based on the velocity estimators, the new scheme for mobility characterization is capable of characterizing the mobility of a node that are associated with topological stability, i. e. the node's speeds, orientations relative to its neighbouring nodes and its past epoch time. iii

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