129 research outputs found
Propagation modelling and resource allocation in mobile radio communications
Over the past years, ray tracing (RT) models popularity has been increasing. From
the nineties, RT has been used for field prediction in environment such as indoor
and urban environments. Nevertheless, with the advent of new technologies, the
channel model has become decidedly more dynamic and to perform RT simulations
at each discrete time instant become computationally expensive. In this thesis, a new
dynamic ray tracing (DRT) approach is presented in which from a single ray tracing
simulation at an initial time t0, through analytical formulas we are able to track
the motion of the interaction points. The benefits that this approach bring are that
Doppler frequencies and channel prediction can be derived at every time instant,
without recurring to multiple RT runs and therefore shortening the computation
time. DRT performance was studied on two case studies and the results shows the
accuracy and the computational gain that derives from this approach.
Another issue that has been addressed in this thesis is the licensed band exhaustion of some frequency bands. To deal with this problem, a novel unselfish
spectrum leasing scheme in cognitive radio networks (CRNs) is proposed that offers
an energy-efficient solution minimizing the environmental impact of the network. In
addition, a network management architecture is introduced and resource allocation
is proposed as a constrained sum energy efficiency maximization problem. System
simulations demonstrate an increment in the energy efficiency of the primary users’
network compared with previously proposed algorithms
sustainable wireless broadband access to the future internet the earth project
In a world of continuous growth of economies and global population eco-sustainability is of outmost relevance. Especially, mobile broadband networks are facing an exponential growing traffic volume and so the sustainability of these networks comes into focus. The recently completed European funded Seventh Framework Programme (FP7) project EARTH has studied the impact of traffic growth on mobile broadband network energy consumption and carbon footprint, pioneering this field. This chapter summarizes the key insights of EARTH on questions like "How does the exploding traffic impact the sustainability?", "How can energy efficiency be rated and predicted?", "What are the key solutions to improve the energy efficiency and how to efficiently integrate such solutions?" The results are representing the foundation of the maturing scientific engineering discipline of Energy Efficient Wireless Access, targeting the standardisation in IETF and 3GPP, strongly influencing academic research trends, and will soon be reflected in products and deployments of the European telecommunications industry
Separation Framework: An Enabler for Cooperative and D2D Communication for Future 5G Networks
Soaring capacity and coverage demands dictate that future cellular networks
need to soon migrate towards ultra-dense networks. However, network
densification comes with a host of challenges that include compromised energy
efficiency, complex interference management, cumbersome mobility management,
burdensome signaling overheads and higher backhaul costs. Interestingly, most
of the problems, that beleaguer network densification, stem from legacy
networks' one common feature i.e., tight coupling between the control and data
planes regardless of their degree of heterogeneity and cell density.
Consequently, in wake of 5G, control and data planes separation architecture
(SARC) has recently been conceived as a promising paradigm that has potential
to address most of aforementioned challenges. In this article, we review
various proposals that have been presented in literature so far to enable SARC.
More specifically, we analyze how and to what degree various SARC proposals
address the four main challenges in network densification namely: energy
efficiency, system level capacity maximization, interference management and
mobility management. We then focus on two salient features of future cellular
networks that have not yet been adapted in legacy networks at wide scale and
thus remain a hallmark of 5G, i.e., coordinated multipoint (CoMP), and
device-to-device (D2D) communications. After providing necessary background on
CoMP and D2D, we analyze how SARC can particularly act as a major enabler for
CoMP and D2D in context of 5G. This article thus serves as both a tutorial as
well as an up to date survey on SARC, CoMP and D2D. Most importantly, the
article provides an extensive outlook of challenges and opportunities that lie
at the crossroads of these three mutually entangled emerging technologies.Comment: 28 pages, 11 figures, IEEE Communications Surveys & Tutorials 201
Performance enhancement of wireless communication systems through QoS optimisation
Providing quality of service (QoS) in a communication network is essential but challenging, especially when the complexities of wireless and mobile networks are added. The issues of how to achieve the intended performances, such as reliability and efficiency, at the minimal resource cost for wireless communications and networking have not been fully addressed. In this dissertation, we have investigated different data transmission schemes in different wireless communication systems such as wireless sensor network, device-to-device communications and vehicular networks. We have focused on cooperative communications through relaying and proposed a method to maximise the QoS performance by finding optimum transmission schemes. Furthermore, the performance trade-offs that we have identified show that both cooperative and non-cooperative transmission schemes could have advantages as well as disadvantages in offering QoS. In the analytical approach, we have derived the closed-form expressions of the outage probability, throughput and energy efficiency for different transmission schemes in wireless and mobile networks, in addition to applying other QoS metrics such as packet delivery ratio, packet loss rate and average end-to-end delay. We have shown that multi-hop relaying through cooperative communications can outperform non-cooperative transmission schemes in many cases. Furthermore, we have also analysed the optimum required transmission power for different transmission ranges to obtain the maximum energy efficiency or maximum achievable data rate with the minimum outage probability and bit error rate in cellular network. The proposed analytical and modelling approaches are used in wireless sensor networks, device-to-device communications and vehicular networks. The results generated have suggested an adaptive transmission strategy where the system can decide when and how each of transmission schemes should be adopted to achieve the best performance in varied conditions. In addition, the system can also choose proper transmitting power levels under the changing transmission distance to increase and maintain the network reliability and system efficiency accordingly. Consequently, these functions will lead to the optimized QoS in a given network
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