261 research outputs found
Dish networks: Protocols, strategies, analysis, and implementation
Ph.DDOCTOR OF PHILOSOPH
Performance Optimization in Wireless Local Area Networks
Wireless Local Area Networks (WLAN) are becoming more and more important
for providing wireless broadband access. Applications and networking
scenarios evolve continuously and in an unpredictable way, attracting the
attention of academic institutions, research centers and industry. For designing
an e cient WLAN is necessary to carefully plan coverage and to
optimize the network design parameters, such as AP locations, channel assignment,
power allocation, MAC protocol, routing algorithm, etc... In this
thesis we approach performance optimization in WLAN at di erent layer
of the OSI model. Our rst approach is at Network layer. Starting from
a Hybrid System modeling the
ow of tra c in the network, we propose a
Hybrid Linear Varying Parameter algorithm for identifying the link quality
that could be used as metric in routing algorithms. Go down to Data Link,
it is well known that CSMA (Carrier Sense Multiple Access) protocols exhibit
very poor performance in case of multi-hop transmissions, because of
inter-link interference due to imperfect carrier sensing. We propose two novel
algorithms, that are combining Time Division Multiple Access for grouping
contending nodes in non-interfering sets with Carrier Sense Multiple Access
for managing the channel access behind a set. In the rst solution, a game
theoretical study of intra slot contention is introduced, in the second solution
we apply an optimization algorithm to nd the optimal degree between
contention and scheduling. Both the presented solutions improve the network
performance with respect to CSMA and TDMA algorithms. Finally we
analyze the network performance at Physical Layer. In case of WLAN, we
can only use three orthogonal channels in an unlicensed spectrum, so the frequency
assignments should be subject to frequent adjustments, according to
the time-varying amount of interference which is not under the control of the
provider. This problem make necessary the introduction of an automatic network
planning solution, since a network administrator cannot continuously
monitor and correct the interference conditions su ered in the network. We
propose a novel protocol based on a distributed machine learning mechanism
in which the nodes choose, automatically and autonomously in each time
slot, the optimal channel for transmitting through a weighted combination
of protocols
Airborne Directional Networking: Topology Control Protocol Design
This research identifies and evaluates the impact of several architectural design choices in relation to airborne networking in contested environments related to autonomous topology control. Using simulation, we evaluate topology reconfiguration effectiveness using classical performance metrics for different point-to-point communication architectures. Our attention is focused on the design choices which have the greatest impact on reliability, scalability, and performance. In this work, we discuss the impact of several practical considerations of airborne networking in contested environments related to autonomous topology control modeling. Using simulation, we derive multiple classical performance metrics to evaluate topology reconfiguration effectiveness for different point-to-point communication architecture attributes for the purpose of qualifying protocol design elements
A Comprehensive Survey of Potential Game Approaches to Wireless Networks
Potential games form a class of non-cooperative games where unilateral
improvement dynamics are guaranteed to converge in many practical cases. The
potential game approach has been applied to a wide range of wireless network
problems, particularly to a variety of channel assignment problems. In this
paper, the properties of potential games are introduced, and games in wireless
networks that have been proven to be potential games are comprehensively
discussed.Comment: 44 pages, 6 figures, to appear in IEICE Transactions on
Communications, vol. E98-B, no. 9, Sept. 201
Enabling Technologies for Ultra-Reliable and Low Latency Communications: From PHY and MAC Layer Perspectives
© 1998-2012 IEEE. Future 5th generation networks are expected to enable three key services-enhanced mobile broadband, massive machine type communications and ultra-reliable and low latency communications (URLLC). As per the 3rd generation partnership project URLLC requirements, it is expected that the reliability of one transmission of a 32 byte packet will be at least 99.999% and the latency will be at most 1 ms. This unprecedented level of reliability and latency will yield various new applications, such as smart grids, industrial automation and intelligent transport systems. In this survey we present potential future URLLC applications, and summarize the corresponding reliability and latency requirements. We provide a comprehensive discussion on physical (PHY) and medium access control (MAC) layer techniques that enable URLLC, addressing both licensed and unlicensed bands. This paper evaluates the relevant PHY and MAC techniques for their ability to improve the reliability and reduce the latency. We identify that enabling long-term evolution to coexist in the unlicensed spectrum is also a potential enabler of URLLC in the unlicensed band, and provide numerical evaluations. Lastly, this paper discusses the potential future research directions and challenges in achieving the URLLC requirements
Enabling Parallel Wireless Communication in Mobile Robot Teams
Wireless inter-robot communication enables robot teams to cooperatively solve complex problems that cannot be addressed by a single robot. Applications for cooperative robot teams include search and rescue, exploration and surveillance. Communication is one of the most important components in future autonomous robot systems and is essential for core functions such as inter-robot coordination, neighbour discovery and cooperative control algorithms. In environments where communication infrastructure does not exist, decentralised multi-hop networks can be constructed using only the radios on-board each robot. These are known as wireless mesh networks (WMNs). However existing WMNs have limited capacity to support even small robot teams. There is a need for WMNs where links act like dedicated point-to-point connections such as in wired networks. Addressing this problem requires a fundamentally new approach to WMN construction and this thesis is the first comprehensive study in the multi-robot literature to address these challenges. In this thesis, we propose a new class of communication systems called zero mutual interference (ZMI) networks that are able to emulate the point-to-point properties of a wired network over a WMN implementation. We instantiate the ZMI network using a multi-radio multi-channel architecture that autonomously adapts its topology and channel allocations such that all network edges communicate at the full capacity of the radio hardware. We implement the ZMI network on a 100-radio testbed with up to 20-individual nodes and verify its theoretical properties. Mobile robot experiments also demonstrate these properties are practically achievable. The results are an encouraging indication that the ZMI network approach can facilitate the communication demands of large cooperative robot teams deployed in practical problems such as data pipe-lining, decentralised optimisation, decentralised data fusion and sensor networks
Interference and power control in ad hoc wireless networks
This thesis looks at the problem of interference when Power Control is applied to maximize the network capacity. In ad hoc networks, the RTS/CTS dialog or virtual carrier sensing is less effective since a transmission takes place over three ranges: interference range, carrier sense range and transmission range. The values of interference range do not interrupt a transmission if it is close to noise floor, however the carrier sense range is capable of disrupting a transmission. Location, packet size and the traffic must be considered as important parameters in power control protocols. The majority of the work is focused at the physical and link layers
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