Practical design of optimal wireless metropolitan area networks: model and algorithms for OFDMA networks

A thesis submitted to the University of Bedfordshire, in partial fulfilment of the requirements for the degree of Ph.D.This thesis contributes to the study of the planning and optimisation of wireless metropolitan area networks, in particular to the access network design of OFDMAbased systems, where different parameters like base station position, antenna tilt and azimuth need to be configured during the early stages of the network life. A practical view for the solution of this problem is presented by means of the development of a novel design framework and the use of multicriteria optimisation. A further consideration of relaying and cooperative communications in the context of the design of this kind of networks is done, an area little researched. With the emergence of new technologies and services, it is very important to accurately identify the factors that affect the design of the wireless access network and define how to take them into account to achieve optimally performing and cost-efficient networks. The new features and flexibility of OFDMA networks seem particularly suited to the provision of different broadband services to metropolitan areas. However, until now, most existing efforts have been focused on the basic access capability networks. This thesis presents a way to deal with the trade-offs generated during the OFDMA access network design, and presents a service-oriented optimization framework that offers a new perspective for this process with consideration of the technical and economic factors. The introduction of relay stations in wireless metropolitan area networks will bring numerous advantages such as coverage extension and capacity enhancement due to the deployment of new cells and the reduction of distance between transmitter and receiver. However, the network designers will also face new challenges with the use of relay stations, since they involve a new source of interference and a complicated air interface; and this need to be carefully evaluated during the network design process. Contrary to the well known procedure of cellular network design over regular or hexagonal scenarios, the wireless network planning and optimization process aims to deal with the non-uniform characteristics of realistic scenarios, where the existence of hotspots, different channel characteristics for the users, or different service requirements will determine the final design of the wireless network. This thesis is structured in three main blocks covering important gaps in the existing literature in planning (efficient simulation) and optimisation. The formulation and ideas proposed in the former case can still be evaluated over regular scenarios, for the sake of simplicity, while the study of latter case needs to be done over specific scenarios that will be described when appropriate. Nevertheless, comments and conclusions are extrapolated to more general cases throughout this work. After an introduction and a description of the related work, this thesis first focuses on the study of models and algorithms for classical point-to-multipoint networks on Chapter 3, where the optimisation framework is proposed. Based on the framework, this work: - Identifies the technology-specific physical factors that affect most importantly the network system level simulation, planning and optimization process. - It demonstrates how to simplify the problem and translate it into a formal optimization routine with consideration of economic factors. - It provides the network provider, a detailed and clear description of different scenarios during the design process so that the most suitable solution can be found. Existing works on this area do not provide such a comprehensive framework. In Chapter 4: - The impact of the relay configuration on the network planning process is analysed. - A new simple and flexible scheme to integrate multihop communications in the Mobile WiMAX frame structure is proposed and evaluated. - Efficient capacity calculations that allow intensive system level simulations in a multihop environment are introduced. In Chapter 5: - An analysis of the optimisation procedure with the addition of relay stations and the derived higher complexity of the process is done. - A frequency plan procedure not found in the existing literature is proposed, which combines it with the use of the necessary frame fragmentation of in-band relay communications and cooperative procedures. - A novel joint two-step process for network planning and optimisation is proposed. Finally, conclusions and open issues are exposed

Millimeter Wave Cellular Networks: A MAC Layer Perspective

The millimeter wave (mmWave) frequency band is seen as a key enabler of multi-gigabit wireless access in future cellular networks. In order to overcome the propagation challenges, mmWave systems use a large number of antenna elements both at the base station and at the user equipment, which lead to high directivity gains, fully-directional communications, and possible noise-limited operations. The fundamental differences between mmWave networks and traditional ones challenge the classical design constraints, objectives, and available degrees of freedom. This paper addresses the implications that highly directional communication has on the design of an efficient medium access control (MAC) layer. The paper discusses key MAC layer issues, such as synchronization, random access, handover, channelization, interference management, scheduling, and association. The paper provides an integrated view on MAC layer issues for cellular networks, identifies new challenges and tradeoffs, and provides novel insights and solution approaches.Comment: 21 pages, 9 figures, 2 tables, to appear in IEEE Transactions on Communication

A review of relay network on UAVS for enhanced connectivity

One of the best evolution in technology breakthroughs is the Unmanned Aerial Vehicle (UAV). This aerial system is able to perform the mission in an agile environment and can reach the hard areas to perform the tasks autonomously. UAVs can be used in post-disaster situations to estimate damages, to monitor and to respond to the victims. The Ground Control Station can also provide emergency messages and ad-hoc communication to the Mobile Users of the disaster-stricken community using this network. A wireless network can also extend its communication range using UAV as a relay. Major requirements from such networks are robustness, scalability, energy efficiency and reliability. In general, UAVs are easy to deploy, have Line of Sight options and are flexible in nature. However, their 3D mobility, energy constraints, and deployment environment introduce many challenges. This paper provides a discussion of basic UAV based multi-hop relay network architecture and analyses their benefits, applications, and tradeoffs. Key design considerations and challenges are investigated finding fundamental issues and potential research directions to exploit them. Finally, analytical tools and frameworks for performance optimizations are presented

Quantifying Potential Energy Efficiency Gain in Green Cellular Wireless Networks

Conventional cellular wireless networks were designed with the purpose of providing high throughput for the user and high capacity for the service provider, without any provisions of energy efficiency. As a result, these networks have an enormous Carbon footprint. In this paper, we describe the sources of the inefficiencies in such networks. First we present results of the studies on how much Carbon footprint such networks generate. We also discuss how much more mobile traffic is expected to increase so that this Carbon footprint will even increase tremendously more. We then discuss specific sources of inefficiency and potential sources of improvement at the physical layer as well as at higher layers of the communication protocol hierarchy. In particular, considering that most of the energy inefficiency in cellular wireless networks is at the base stations, we discuss multi-tier networks and point to the potential of exploiting mobility patterns in order to use base station energy judiciously. We then investigate potential methods to reduce this inefficiency and quantify their individual contributions. By a consideration of the combination of all potential gains, we conclude that an improvement in energy consumption in cellular wireless networks by two orders of magnitude, or even more, is possible.Comment: arXiv admin note: text overlap with arXiv:1210.843

Distributed Artificial Intelligence Solution for D2D Communication in 5G Networks

Device to Device (D2D) Communication is one of the technology components of the evolving 5G architecture, as it promises improvements in energy efficiency, spectral efficiency, overall system capacity, and higher data rates. The above noted improvements in network performance spearheaded a vast amount of research in D2D, which have identified significant challenges that need to be addressed before realizing their full potential in emerging 5G Networks. Towards this end, this paper proposes the use of a distributed intelligent approach to control the generation of D2D networks. More precisely, the proposed approach uses Belief-Desire-Intention (BDI) intelligent agents with extended capabilities (BDIx) to manage each D2D node independently and autonomously, without the help of the Base Station. The paper includes detailed algorithmic description for the decision of transmission mode, which maximizes the data rate, minimizes the power consumptions, while taking into consideration the computational load. Simulations show the applicability of BDI agents in jointly solving D2D challenges.Comment: 10 pages,9 figure

Opportunities and Challenges in OFDMA-Based Cellular Relay Networks: A Radio Resource Management Perspective

The opportunities and flexibility in relay networks and orthogonal frequency-division multiple access (OFDMA) make the combination a suitable candidate network and air-interface technology for providing reliable and ubiquitous high-data-r

Recent advances in radio resource management for heterogeneous LTE/LTE-A networks

As heterogeneous networks (HetNets) emerge as one of the most promising developments toward realizing the target specifications of Long Term Evolution (LTE) and LTE-Advanced (LTE-A) networks, radio resource management (RRM) research for such networks has, in recent times, been intensively pursued. Clearly, recent research mainly concentrates on the aspect of interference mitigation. Other RRM aspects, such as radio resource utilization, fairness, complexity, and QoS, have not been given much attention. In this paper, we aim to provide an overview of the key challenges arising from HetNets and highlight their importance. Subsequently, we present a comprehensive survey of the RRM schemes that have been studied in recent years for LTE/LTE-A HetNets, with a particular focus on those for femtocells and relay nodes. Furthermore, we classify these RRM schemes according to their underlying approaches. In addition, these RRM schemes are qualitatively analyzed and compared to each other. We also identify a number of potential research directions for future RRM development. Finally, we discuss the lack of current RRM research and the importance of multi-objective RRM studies

Efficient cellular load balancing through mobility-enriched vehicular communications

Supporting effective load balancing is paramount for increasing network utilization efficiency and improving the perceivable user experience in emerging and future cellular networks. At the same time, it is becoming increasingly alarming that current communication practices lead to excessive energy wastes both at the infrastructure side and at the terminals. To address both these issues, this paper discusses an innovative communication approach enabled by the implementation of device-to-device (d2d) communication over cellular networks. The technique capitalizes on the delay tolerance of a significant portion of Internet applications and the inherent mobility of the nodes to achieve significant performance gains. For delay-tolerant messages, a mobile node can postpone message transmission—in a store–carry and forward manner—for a later time to allow the terminal to achieve communication over a shorter range or to postpone communication to when the terminal enters a cooler cell, before engaging in communication. Based on this framework, a theoretical model is introduced to study the generalized multihop d2d forwarding scheme where mobile nodes are allowed to buffer messages and carry them while in transit. Thus, a multiobjective optimization problem is introduced where both the communication cost and the varying load levels of multiple cells are to be minimized. We show that the mathematical programming model that arises can be efficiently solved in time. Furthermore, extensive numerical investigations reveal that the proposed scheme is an effective approach for both energy-efficient communication and offering significant gains in terms of load balancing in multicell topologies