279 research outputs found
Soft real-time communications over Bluetooth under interferences from ISM devices
Bluetooth is a suitable technology to support soft real-time applications like multimedia streams at the
personal area network level. In this paper, we analytically evaluate the worst-case deadline failure
probability of Bluetooth packets under co-channel interference as a way to provide statistical guarantees
when transmitting soft real-time traffic using ACL links. We consider the interference from independent
Bluetooth devices, as well as from other devices operating in the ISM band like 802.11b/g and Zigbee.
Finally, we show as an example how to use our model to obtain some results for the transmission of a voice
stream.Ministerio de Ciencia y Tecnología TIC2001-1868-C03-0
Radio Communications
In the last decades the restless evolution of information and communication technologies (ICT) brought to a deep transformation of our habits. The growth of the Internet and the advances in hardware and software implementations modified our way to communicate and to share information. In this book, an overview of the major issues faced today by researchers in the field of radio communications is given through 35 high quality chapters written by specialists working in universities and research centers all over the world. Various aspects will be deeply discussed: channel modeling, beamforming, multiple antennas, cooperative networks, opportunistic scheduling, advanced admission control, handover management, systems performance assessment, routing issues in mobility conditions, localization, web security. Advanced techniques for the radio resource management will be discussed both in single and multiple radio technologies; either in infrastructure, mesh or ad hoc networks
Adaptive buffer power save mechanism for mobile multimedia streaming
With the proliferation of wireless networks, the use of mobile devices to stream multimedia is growing in popularity. Although the devices are improving in that they are becoming smaller, more complex and capable of running more applications than ever before, there is one aspect of them that is lagging behind. Batteries have seen little development, even though they are one of the most important parts of the devices.
Multimedia streaming puts extra pressure on batteries, causing them to discharge faster. This often means that streaming tasks can not be completed, resulting in significant user dissatisfaction. Consequently, effort is required to devise mechanisms to enable and increase in battery life while streaming multimedia.
In this context, this thesis presents a novel algorithm to save power in mobile devices during the streaming of multimedia content. The proposed Adaptive-Buffer Power Save Mechanism (AB-PSM) controls how the data is sent over wireless networks, achieving significant power savings. There is little or no effect on the user and the algorithm is very simple to implement. The thesis describes tests which show the effectiveness of AB-PSM in comparison with the legacy power save mechanism present in IEEE 802.11.
The thesis also presents a detailed overview of the IEEE 802.11 protocols and an in-depth literature review in the area of power saving during multimedia streaming. A novel analysis of how the battery of a mobile device is affected by multimedia streaming in its different stages is given. A total-power-save algorithm is then described as a possible extension to the Adaptive-Buffer Power Save Mechanism
Towards Massive Machine Type Communications in Ultra-Dense Cellular IoT Networks: Current Issues and Machine Learning-Assisted Solutions
The ever-increasing number of resource-constrained Machine-Type Communication
(MTC) devices is leading to the critical challenge of fulfilling diverse
communication requirements in dynamic and ultra-dense wireless environments.
Among different application scenarios that the upcoming 5G and beyond cellular
networks are expected to support, such as eMBB, mMTC and URLLC, mMTC brings the
unique technical challenge of supporting a huge number of MTC devices, which is
the main focus of this paper. The related challenges include QoS provisioning,
handling highly dynamic and sporadic MTC traffic, huge signalling overhead and
Radio Access Network (RAN) congestion. In this regard, this paper aims to
identify and analyze the involved technical issues, to review recent advances,
to highlight potential solutions and to propose new research directions. First,
starting with an overview of mMTC features and QoS provisioning issues, we
present the key enablers for mMTC in cellular networks. Along with the
highlights on the inefficiency of the legacy Random Access (RA) procedure in
the mMTC scenario, we then present the key features and channel access
mechanisms in the emerging cellular IoT standards, namely, LTE-M and NB-IoT.
Subsequently, we present a framework for the performance analysis of
transmission scheduling with the QoS support along with the issues involved in
short data packet transmission. Next, we provide a detailed overview of the
existing and emerging solutions towards addressing RAN congestion problem, and
then identify potential advantages, challenges and use cases for the
applications of emerging Machine Learning (ML) techniques in ultra-dense
cellular networks. Out of several ML techniques, we focus on the application of
low-complexity Q-learning approach in the mMTC scenarios. Finally, we discuss
some open research challenges and promising future research directions.Comment: 37 pages, 8 figures, 7 tables, submitted for a possible future
publication in IEEE Communications Surveys and Tutorial
Flexible application driven network striping over Wireless Wide Area Networks
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.Includes bibliographical references (p. 157-161).Inverse multiplexing, or network striping, allows the construction of a high-bandwidth virtual channel from a collection of multiple low-bandwidth network channels. Striping systems usually employ a packet scheduling policy that allows applications to be oblivious of the way in which packets are routed to specific network channels. Though this is appropriate for many applications, many other applications can benefit from an approach that explicitly involves the application in the determination of the striping policy. Horde is middleware that facilitates flexible striping over Wireless Wide Area Network (WWAN) channels. Horde is unusual in that it separates the striping policy from the striping mechanism. It allows applications to describe network Quality-of-Service (QoS) objectives that the striping mechanism attempts to satisfy. Horde can be used by a set of data streams, each with its own QoS policy, to stripe data over a set of WWAN channels. The WWAN QoS variations observed across different channels and in time, provide opportunities to modulate stream QoS through scheduling. The key technical challenge in Horde is giving applications control over certain aspects of the data striping operation while at the same time shielding the application from low-level details. Horde exports a set of flexible abstractions replacing the application's network stack. Horde allows applications to express their policy goals as succinct network-QoS objectives. Each objective says something, relatively simple, about the sort of network QoS an application would like for some data stream(s). We present the Horde architecture, describe an early implementation, and examine how different policies can be used to modulate the quality-of-service observed across different independent data streams. Through experiments conducted on real and simulated network channels, we confirm our belief that the kind of QoS modulation Horde aims to achieve is realistic for actual applications.by Asfandyar Qureshi.M.Eng
Comparison of vertical handover decision-based techniques in heterogeneous networks
Industry leaders are currently setting out standards for 5G Networks projected for 2020 or even sooner. Future generation networks will be heterogeneous in nature because no single network type is capable of optimally meeting all the rapid changes in customer demands. Heterogeneous networks are typically characterized by some network architecture, base stations of varying transmission power, transmission solutions and the deployment of a mix of technologies (multiple radio access technologies). In heterogeneous networks, the processes involved when a mobile node successfully switches from one radio access technology to the other for the purpose of quality of service continuity is termed vertical handover or vertical handoff. Active calls that get dropped, or cases where there is discontinuity of service experienced by mobile users can be attributed to the phenomenon of delayed handover or an outright case of an unsuccessful handover procedure. This dissertation analyses the performance of a fuzzy-based VHO algorithm scheme in a Wi-Fi, WiMAX, UMTS and LTE integrated network using the OMNeT++ discrete event simulator. The loose coupling type network architecture is adopted and results of the simulation are analysed and compared for the two major categories of handover basis; multiple and single criteria based handover methods. The key performance indices from the simulations showed better overall throughput, better call dropped rate and shorter handover time duration for the multiple criteria based decision method compared to the single criteria based technique. This work also touches on current trends, challenges in area of seamless handover and initiatives for future Networks (Next Generation Heterogeneous Networks)
Improving forwarding mechanisms for mobile personal area networks
This thesis presents novel methods for improving forwarding mechanisms for personal area networks.
Personal area networks are formed by interconnecting personal devices such as personal digital assistants,
portable multimedia devices, digital cameras and laptop computers, in an ad hoc fashion. These
devices are typically characterised by low complexity hardware, low memory and are usually batterypowered.
Protocols and mechanisms developed for general ad hoc networking cannot be directly applied
to personal area networks as they are not optimised to suit their specific constraints.
The work presented herein proposes solutions for improving error control and routing over personal
area networks, which are very important ingredients to the good functioning of the network. The proposed
Packet Error Correction (PEC) technique resends only a subset of the transmitted packets, thereby
reducing the overhead, while ensuring improved error rates. PEC adapts the number of re-transmissible
packets to the conditions of the channel so that unnecessary retransmissions are avoided. It is shown by
means of computer simulation that PEC behaves better, in terms of error reduction and overhead, than
traditional error control mechanisms, which means that it is adequate for low-power personal devices.
The proposed C2HR routing protocol, on the other hand, is designed such that the network lifetime
is maximised. This is achieved by forwarding packets through the most energy efficient paths. C2HR
is a hybrid routing protocol in the sense that it employs table-driven (proactive) as well as on-demand
(reactive) components. Proactive routes are the primary routes, i.e., packets are forwarded through those
paths when the network is stable; however, in case of failures, the protocol searches for alternative routes
on-demand, through which data is routed temporarily. The advantage of C2HR is that data can still be
forwarded even when routing is re-converging, thereby increasing the throughput. Simulation results
show that the proposed routing method is more energy efficient than traditional least hops routing, and
results in higher data throughput.
C2HR relies on a network leader for collecting and distributing topology information, which in turn
requires an estimate of the underlying topology. Thus, this thesis also proposes a new cooperative leader
election algorithm and techniques for estimating network characteristics in mobile environments. The
proposed solutions are simulated under various conditions and demonstrate appreciable behaviour
Easing the Transition from Inspiration to Implementation: A Rapid Prototyping Platform for Wireless Medium Access Control Protocols
Packet broadcast networks are in widespread use in modern wireless communication systems. Medium access control is a key functionality within such technologies. A substantial research effort has been and continues to be invested into the study of existing protocols and the development of new and specialised ones. Academic researchers are
restricted in their studies by an absence of suitable wireless MAC protocol development methods.
This thesis describes an environment which allows rapid prototyping and evaluation of wireless medium access control protocols. The proposed design flow allows specification of the protocol using the specification and description language (SDL) formal description technique. A tool is presented to convert the SDL protocol description into a C++ model suitable for integration into both simulation and implementation environments.
Simulations at various levels of abstraction are shown to be relevant at different stages of protocol design. Environments based on the
Cinderella SDL simulator and the ns-2 network simulator have been developed which allow early functional verification, along with detailed and accurate performance analysis of protocols under
development.
A hardware platform is presented which allows implementation of protocols with flexibility in the hardware/software trade-off. Measurement facilities are integral to the hardware framework, and provide a means for accurate real-world feedback on protocol performance
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