611 research outputs found
Digital RoF Aided Cooperative Distributed Antennas with FFR in Multicell Multiuser Networks
The achievable throughput of the entire cellular area is investigated, when employing fractional frequency reuse techniques in conjunction with realistically modelled imperfect optical fibre aided distributed antenna systems (DAS). Given a fixed total transmit power, a substantial improvement of the cell-edge areaâs throughput can be achieved without reducing the cell-centreâs throughput. The cell-edgeâs throughput supported in the worst-case direction is significantly enhanced by the cooperative linear transmit processing technique advocated. Explicitly, a cell-edge throughput of η = 5 bits/s/Hz may be maintained for a imperfect optical fibre model, regardless of the specific geographic distribution of the users
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
Energy efficiency in heterogeneous wireless access networks
In this article, we bring forward the important aspect of energy savings in wireless access networks. We specifically focus on the energy saving opportunities in the recently evolving heterogeneous networks (HetNets), both Single- RAT and Multi-RAT. Issues such as sleep/wakeup cycles and interference management are discussed for co-channel Single-RAT HetNets. In addition to that, a simulation based study for LTE macro-femto HetNets is presented, indicating the need for dynamic energy efficient resource management schemes. Multi-RAT HetNets also come with challenges such as network integration, combined resource management and network selection. Along with a discussion on these challenges, we also investigate the performance of the conventional WLAN-first network selection mechanism in terms of energy efficiency (EE) and suggest that EE can be improved by the application of intelligent call admission control policies
Joint Concurrent Routing and Multi-Pointer Packet Scheduling in IEEE 802.16 Mesh Networks
IEEE 802.16, also known as Worldwide Interoperability for Microwave Access
(WiMAX), is a standardization effort carried out by the IEEE to provide last-mile
broadband access to end users. The IEEE 802.16 standard
supports two medium access control (MAC) modes - a mandatory point to multipoint
(PMP) mode and an optional mesh mode. In this paper, we propose an
asymmetric interference aware routing algorithm and a new multipointer approach in
implementing scheduling algorithms for IEEE 802.16 mesh networks. We modify three
different centralized scheduling algorithms, fixed scheduling,
ordered scheduling and per-slot scheduling using multipointer approach to allow for
spatial reuse (SR) in IEEE 802.16 mesh networks. Simulation results
reveal that fixed scheduling with SR provides the best performance
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