1,473 research outputs found
Adaptive load balancing routing algorithms for the next generation wireless telecommunications networks
This thesis was submitted for the degree of Doctor of Philosophy and was awarded by Brunel UniversityWith the rapid development of wireless networks, mesh networks are evolving as a new important technology, presenting a high research and commercial interest. Additionally, wireless mesh networks have a wide variety of applications, offering the ability to provide network access in both rural and urban areas with low cost of maintenance. One of the main functionalities of a wireless mesh network is load balancing routing, which is the procedure of finding the best, according to some criteria, routes that data need to follow to transfer from one node to another. Routing is one of the state-of-the-art areas of research because the current algorithms and protocols are not efficient and effective due to the diversity of the characteristics of these networks. In this thesis, two new routing algorithms have been developed for No Intra-Cell Interference (NICI) and Limited Intra-Cell Interference (LICI) networks based on WiMAX, the most advanced wireless technology ready for deployment. The algorithms created are based on the classical Dijkstra and Ford-Fulkerson algorithms and can be implemented in the cases of unicast and multicast transmission respectively.State scholarships foundation of Greece
Multi-cell Coordination Techniques for DL OFDMA Multi-hop Cellular Networks
The main objective of this project is to design coordinated spectrum sharing and reuse
techniques among cells with the goal of mitigating interference at the cell edge and
enhance the overall system capacity. The performance of the developed algorithm will be
evaluated in an 802.16m (WiMAX) environment.
In conventional cellular networks, frequency planning is usually considered to keep an
acceptable signal-to-interference-plus noise ratio (SINR) level, especially at cell
boundaries. Frequency assignations are done under a cell-by-cell basis, without any
coordination between them to manage interference. Particularly this approach, however,
hampers the system spectral efficiency at low reuse rates. For a specific reuse factor, the
system throughput depends highly on the mobile station (MS) distribution and the channel
conditions of the users to be served. If users served from different base stations (BS)
experience a low level of interference, radio resources may be reused, applying a high
reuse factor and thus, increasing the system spectral efficiency. On the other side, if the
served users experience large interference, orthogonal transmissions are better and
therefore a lower frequency reuse factor should be used. As a consequence, a dynamic
reuse factor is preferable over a fixed one.
This work addresses the design of joint multi-cell resource allocation and scheduling with
coordination among neighbouring base stations (outer coordination) or sectors belonging to
the same one (inner coordination) as a way to achieve flexible reuse factors. We propose a
convex optimization framework to address the problem of coordinating bandwidth
allocation in BS coordination problems.
The proposed framework allows for different scheduling policies, which have an impact on
the suitability of the reuse factor, since they determine which users have to be served.
Therefore, it makes sense to consider the reuse factor as a result of the scheduling decision.
To support the proposed techniques the BSs shall be capable of exchanging information
with each other (decentralized approach) or with some control element in the back-haul
network as an ASN gateway or some self-organization control entity (centralized
approach)
WIMAX Basics from PHY Layer to Scheduling and Multicasting Approaches
WiMAX (Worldwide Interoperability for Microwave Access) is an emerging broadband wireless technology for providing Last mile solutions for supporting higher bandwidth and multiple service classes with various quality of service requirement. The unique architecture of the WiMAX MAC and PHY layers that uses OFDMA to allocate multiple channels with different modulation schema and multiple time slots for each channel allows better adaptation of heterogeneous user’s requirements. The main architecture in WiMAX uses PMP (Point to Multipoint), Mesh mode or the new MMR (Mobile Multi hop Mode) deployments where scheduling and multicasting have different approaches. In PMP SS (Subscriber Station) connects directly to BS (Base Station) in a single hop route so channel conditions adaptations and supporting QoS for classes of services is the key points in scheduling, admission control or multicasting, while in Mesh networks SS connects to other SS Stations or to the BS in a multi hop routes, the MMR mode extends the PMP mode in which the SS connects to either a relay station (RS) or to Bs. Both MMR and Mesh uses centralized or distributed scheduling with multicasting schemas based on scheduling trees for routing. In this paper a broad study is conducted About WiMAX technology PMP and Mesh deployments from main physical layers features with differentiation of MAC layer features to scheduling and multicasting approaches in both modes of operations
A Survey on Scheduling in IEEE 802.16 Mesh Mode
Cataloged from PDF version of article.IEEE 802.16 standard (also known as WiMAX)
defines the wireless broadband network technology which aims
to solve the so called last mile problem via providing high
bandwidth Internet even to the rural areas for which the cable
deployment is very costly. The standard mainly focuses on the
MAC and PHY layer issues, supporting two transmission modes:
PMP (Point-to-Multipoint) and mesh modes. Mesh mode is an
optional mode developed as an extension to PMP mode and it
has the advantage of having an improving performance as more
subscribers are added to the system using multi-hop routes. In
802.16 MAC protocol, mesh mode slot allocation and reservation
mechanisms are left open which makes this topic a hot research
area. Hence, the focus of this survey will mostly be on the mesh
mode, and the proposed scheduling algorithms and performance
evaluation methods
Cooperative control of relay based cellular networks
PhDThe increasing popularity of wireless communications and the higher data
requirements of new types of service lead to higher demands on wireless networks.
Relay based cellular networks have been seen as an effective way to meet users’
increased data rate requirements while still retaining the benefits of a cellular
structure. However, maximizing the probability of providing service and spectrum
efficiency are still major challenges for network operators and engineers because of
the heterogeneous traffic demands, hard-to-predict user movements and complex
traffic models.
In a mobile network, load balancing is recognised as an efficient way to increase
the utilization of limited frequency spectrum at reasonable costs. Cooperative
control based on geographic load balancing is employed to provide flexibility for
relay based cellular networks and to respond to changes in the environment.
According to the potential capability of existing antenna systems, adaptive radio
frequency domain control in the physical layer is explored to provide coverage at
the right place at the right time.
This thesis proposes several effective and efficient approaches to improve
spectrum efficiency using network wide optimization to coordinate the coverage
offered by different network components according to the antenna models and
relay station capability. The approaches include tilting of antenna sectors,
changing the power of omni-directional antennas, and changing the assignment of
relay stations to different base stations. Experiments show that the proposed
approaches offer significant improvements and robustness in heterogeneous traffic
scenarios and when the propagation environment changes. The issue of predicting
the consequence of cooperative decisions regarding antenna configurations when
applied in a realistic environment is described, and a coverage prediction model is
proposed. The consequences of applying changes to the antenna configuration on
handovers are analysed in detail. The performance evaluations are based on a
system level simulator in the context of Mobile WiMAX technology, but the
concepts apply more generally
Recommended from our members
Multimedia delivery in the future internet
The term “Networked Media” implies that all kinds of media including text, image, 3D graphics, audio
and video are produced, distributed, shared, managed and consumed on-line through various networks,
like the Internet, Fiber, WiFi, WiMAX, GPRS, 3G and so on, in a convergent manner [1]. This white
paper is the contribution of the Media Delivery Platform (MDP) cluster and aims to cover the Networked
challenges of the Networked Media in the transition to the Future of the Internet.
Internet has evolved and changed the way we work and live. End users of the Internet have been confronted
with a bewildering range of media, services and applications and of technological innovations concerning
media formats, wireless networks, terminal types and capabilities. And there is little evidence that the pace
of this innovation is slowing. Today, over one billion of users access the Internet on regular basis, more
than 100 million users have downloaded at least one (multi)media file and over 47 millions of them do so
regularly, searching in more than 160 Exabytes1 of content. In the near future these numbers are expected
to exponentially rise. It is expected that the Internet content will be increased by at least a factor of 6, rising
to more than 990 Exabytes before 2012, fuelled mainly by the users themselves. Moreover, it is envisaged
that in a near- to mid-term future, the Internet will provide the means to share and distribute (new)
multimedia content and services with superior quality and striking flexibility, in a trusted and personalized
way, improving citizens’ quality of life, working conditions, edutainment and safety.
In this evolving environment, new transport protocols, new multimedia encoding schemes, cross-layer inthe
network adaptation, machine-to-machine communication (including RFIDs), rich 3D content as well as
community networks and the use of peer-to-peer (P2P) overlays are expected to generate new models of
interaction and cooperation, and be able to support enhanced perceived quality-of-experience (PQoE) and
innovative applications “on the move”, like virtual collaboration environments, personalised services/
media, virtual sport groups, on-line gaming, edutainment. In this context, the interaction with content
combined with interactive/multimedia search capabilities across distributed repositories, opportunistic P2P
networks and the dynamic adaptation to the characteristics of diverse mobile terminals are expected to
contribute towards such a vision.
Based on work that has taken place in a number of EC co-funded projects, in Framework Program 6 (FP6)
and Framework Program 7 (FP7), a group of experts and technology visionaries have voluntarily
contributed in this white paper aiming to describe the status, the state-of-the art, the challenges and the way
ahead in the area of Content Aware media delivery platforms
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