Resource Allocation in Relay Networks

Demand for high data rates is increasing rapidly, due to the rapid rise of mobile data traffic volume. In order to meet the demands, the future generation of wireless communication systems has to support higher data rates and quality of service. The inherent unreliable and unpredictable nature of wireless medium provides a challenge for increasing the data rate. Cooperative communications, is a prominent technique to combat the detrimental fading effect in wireless communications. Adding relay nodes to the network, and creating s virtual multiple-input multiple-output (MIMO) antenna array is proven to be an efficient method to mitigate the multipath fading and expand the network coverage. Therefore, cooperative relaying is considered as a fundamental element in the Long Term Evolution (LTE)-Advanced standard. In this thesis, we address the problem of resource allocation in cooperative networks. We provide a detailed review on the resource allocation problem. We look at the joint subcarrier-relay assignment and power allocation. The objective of this optimization problem is to allocate the resources fairly, so even the cell-edge users with weakest communication links receive a fair share of resources. We propose a simple and practical algorithm to find the optimal solution. We assess the performance of the proposed algorithm by providing simulations. Furthermore, we investigate the optimality and complexity of the proposed algorithm. Due to the layered architecture of the wireless networks, to achieve the optimal performance it is necessary that the design of the algorithms be based on the underlying physical and link layers. For a cooperative network with correlated channels, we propose a cross-layer algorithm for relay selection, based on both the physical and link-layer characteristics, in order to maximize the linklayer throughput. The performance of the proposed algorithm is studied in different network models. Furthermore, we investigate the optimum number of relays required for cooperation in order to achieve maximum throughput. Buffering has proven to improve the performance of the cooperative network. In light of this, we study the performance of buffer-aided relay selection. In order to move one step closer to the practical applications, we consider a system with coded transmissions. We study three different coding schemes: convolutional code, Turbo code, and distributed Turbo code (DTC). For each scheme, the performance of the system is simulated and assessed analytically. We derive a closed form expression of the average throughput. Using the analysis results, we investigate the diversity gain of the system in asymptotic conditions. Further, we investigate the average transmission delay for different schemes

Detection and Resource Allocation Algorithms for Cooperative MIMO Relay Systems

Cooperative communications and multiple-input multiple-output (MIMO) communication systems are important topics in current research that will play key roles in the future of wireless networks and standards. In this thesis, the various challenges in accurately detecting and estimating data signals and allocating resources in the cooperative systems are investigated. Firstly, we propose a cross-layer design strategy that consists of a cooperative maximum likelihood (ML) detector operating in conjunction with link selection for a cooperative MIMO network. Two new link selection schemes are proposed, along with an iterative detection and decoding (IDD) scheme that utilises channel coding techniques. Simulation results show the performance and potential gains of the proposed schemes. Secondly, a successive interference cancellation (SIC) detector is proposed for a MIMO system that has dynamic ordering based on a reliability ordering (RO), and an alternative multiple feedback (MF) candidate cancellation method. The complexity of these schemes is analysed and a hard decision feedback IDD system is also proposed. Results show that the proposed detector can give gains over existing schemes for a minimal amount of extra complexity. Lastly, a detector is proposed that is based upon the method of widely linear (WL) filtering and a multiple branch (MB) SIC, for an overloaded, multi-user cooperative MIMO system. The use of WL methods is explained, and a new method of choosing cancellation branches for an MB detector is proposed with an analysis of the complexity required. A list-based IDD system is developed, and simulation results show that the proposed detector can operate in an overloaded system and provide improved performance gains

Nonlinear amplifier distortion in cooperative OFDM systems

OFDM (Orthogonal frequency division multiplexing) on lupaava langattoman tietoliikenteen teknologia johtuen sen hyvästä suorituskyvystä monitieympäristössä. Yhteistoiminnallisen tiedonvälityksen tekniikka on nykyisin jatkuvan tutkimuksen kohteena. Se hyödyntää muiden päätteiden antenneja virtuaalisen moniantennijärjestelmän luomiseen mahdollistaen moniantennijärjestelmille ominaisia kapasiteettihyötyjä. Tässä diplomityössä tutkitaan epälineaarista vahvistussäröä, kun näitä molempia tekniikoita käytetään yhdessä. Ensimmäiset kappaleet käsittelevät OFDM-järjestelmien ja epälineaaristen OFDM-järjestelmien särön sekä yhteistoiminnallisen tiedonvälityksen taustoja. Yhteistoiminnallisten OFDM-järjestelmien suorituskykyä mitataan simulaatioiden avulla epälineaarisen särön vaikuttaessa. Suorituskykyä mitataan bittivirhesuhteena käyttäen epäyhteistoiminnallista ja lineaarista yhteistoiminnallista järjestelmää vertailukohteena. Lisäksi särötermi myös analysoidaan. Systeemimalli sisältää epälineaarisen vahvistuksen välittimessä, jota mallinnetaan elektronisella tehovahvistimella. Lopuksi esitellään ja testataan tekniikka järjestelmän suorituskyvyn parantamiseen optimoimalla maksimisuhdeyhdistintä. Se optimoidaan mallintamalla vahvistussäröä normaalijakaumalla. Lisäksi esitellään ja testataan yhteistoiminnallisille järjestelmille sopiva tehovahvistimen epälineaarisuuden poistotekniikan muunnelma, jolla saadaan lähellä lineaarista tapausta olevia tuloksia.Orthogonal frequency division multiplexing (OFDM) is a promising technique for wireless communications because of its good performance under multipath environments. The concept of cooperative communications is currently under constant research. It uses antennas of other terminals to create virtual multiple input multiple output (MIMO) systems, providing capacity gains similar to those of MIMO systems. This thesis studies the issue of nonlinear amplifier distortion when these two techniques are used together. The first chapters give a background on OFDM systems, nonlinear distortion in OFDM systems, and Cooperative Communications. The performance of OFDM cooperative systems under nonlinear distortion are measured by simulations. The performance is measured in terms of BER using a non-cooperative system and a linear cooperative system as references. In addition, the distortion term is also analysed. The system model includes a non-linear amplifier at the relay, modelled as a solid state power amplifier (SSPA). A technique for improving the performance of the system, by optimising the maximum ratio combiner (MRC), is introduced and tested. The MRC is optimised by modelling the distortion noise as Gaussian. Also, a modification to the power amplifier nonlinearity cancellation (PANC) technique, suitable to cooperative systems, is introduced and tested, showing results close to the linear case

A Before-School Counselor Intervention that Promotes Peer Relational Skills and Influences Prosocial Behavior

The purpose of this dissertation was to understand the student experience and perception of change after participating in a before-school counselor intervention focused on learning prosocial behaviors and developing peer relational skills. This evaluation included both how students experienced the program and if they perceived any change in themselves after participating in the program. Qualitative methods are often used in evaluations because they tell the program\u27s story by capturing and communicating the participant\u27s stories (Patton, 2003, p. 2). The purpose of this type of method was to illuminate the process and outcomes of a program. The intent of qualitative findings was to deepen understanding through the eyes of the participants or to put faces on the statistics to deepen understanding (Patton, 2003, p. 2). In order to understand the student experience and perception of change, the researcher interviewed eight students who participated in a 12-week before-school program. The interviews were recorded, transcribed, and analyzed. Analysis of the data resulted in six separate findings. To summarize, the students found the before-school program to be a positive experience where they learned how to make friends more effectively, they felt good about helping others, and they found it difficult to cooperate on a consistent basis. Students evaluated the program as being fun and they spoke about 38 of the 52 activities. The bulk of the program evaluation centered unanimously around four specific activities. And each individual student came away from the 12 week program gaining a personally meaningful and unique skill. This study provided a qualitative evaluation of student perception of a before-school program. These findings are useful for school administrators, superintendents, and school counselors because they provide an understanding of the student experiences of change in group counseling which occurred before-school. This data can be used to support the value of group work outside of the traditional day. This program can be used to provide a model of psychoeducational prevention work to students when time for counseling groups in elementary school is becoming increasingly scarce

Transforming Research Methods in the Social Sciences

Social science researchers in the global South, and in South Africa particularly, utilise research methods in innovative ways in order to respond to contexts characterised by diversity, racial and political tensions, socioeconomic disparities and gender inequalities. These methods often remain undocumented – a gap that this book starts to address. Written by experts from various methodological fields, Transforming Research Methods in the Social Sciences is a comprehensive collation of original essays and cutting-edge research that demonstrates the variety of novel techniques and research methods available to researchers responding to these context-bound issues. It is particularly relevant for study and research in the fields of applied psychology, sociology, ethnography, biography and anthropology. In addition to their unique combination of conceptual and application issues, the chapters also include discussions on ethical considerations relevant to the method in similar global South contexts. Transforming Research Methods in the Social Sciences has much to offer to researchers, professionals and others involved in social science research both locally and internationally

Security of Ubiquitous Computing Systems

The chapters in this open access book arise out of the EU Cost Action project Cryptacus, the objective of which was to improve and adapt existent cryptanalysis methodologies and tools to the ubiquitous computing framework. The cryptanalysis implemented lies along four axes: cryptographic models, cryptanalysis of building blocks, hardware and software security engineering, and security assessment of real-world systems. The authors are top-class researchers in security and cryptography, and the contributions are of value to researchers and practitioners in these domains. This book is open access under a CC BY license

Telemedicine

Telemedicine is a rapidly evolving field as new technologies are implemented for example for the development of wireless sensors, quality data transmission. Using the Internet applications such as counseling, clinical consultation support and home care monitoring and management are more and more realized, which improves access to high level medical care in underserved areas. The 23 chapters of this book present manifold examples of telemedicine treating both theoretical and practical foundations and application scenarios

Approximately there : positioning video-mediated interpreting in frontline police services

This study looks at how UK police forces make use of video interpreting services to complete standard police procedures. Two frontline police services were examined: video relay service (VRS) calls to a Police Scotland’s force control room (FRC); and video remote interpreted calls (VRI) to a Police Scotland custody suite. Both contexts were identified as areas for potential VRS/VRI expansion by Police Scotland. The research questions focused on how co-operation was negotiated during a video-mediated interpreting interaction in a frontline policing context and how co-operation affected the delivery of the combined service. To chart how co-operation was received or negotiated, this study combined Positioning Theory (Davies & Harré, 1990) with Actor-Network Theory (ANT) (Callon, 1986; Latour, 2005; Law, 2004). Using this hybrid framework, this study traced the capacity and willingness each participant displayed as they assumed, negotiated, or challenged the shared rights or duties (an interactive position), and considered the role non-human entities (e.g. technology, policies, artefacts) had in shaping these positioning moves. This study found a range of positioning moves that either work towards or become a copositioning arrangement. The establishment of co-positions means different actors have established a unified group of rights and duties that are mutually shared. The findings reaffirm the challenges of remote communication, as well as which features of communication promoted by call handlers, custody sergeant and interpreters appear to be mutually effective for frontline policing interactions. The police participant and the interpreter have a shared objective: to learn about the citizen and to construct an understanding of the issue at hand. Issues still exist regarding knowing how to adapt standard police procedures or generic responses to become meaningful to someone who is a deaf BSL user. Interpreters will sometimes become involved in these matters, advocating the deaf person’s right to receive parity of service beyond the VRS/VRI call. By focusing on standard police procedures and understanding what works and why, we can identify where and when VRS/VRI services could be used to increase citizen access to other areas of police services.SGSAH scholarship - Scottish Graduate School for Arts and Humanities Applied Research Collaboration Studentships (ARCS)