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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Adaptive Predictive Handoff Scheme with Channel Borrowing in Cellular Network

Yu, Lei 07 August 2003 (has links)
Previously, we presented an extension of predictive channel reservation (PCR) scheme, called HPCR_CB, for handoff motivated by the rapid evolving technology of mobile positioning. In this thesis, the author proposes a new scheme, called adaptive PCR_CB (APCR_CB), which is an extension of HPCR_CB by incorporating the concept of adaptive guard channels. In APCR_CB, the number of guard channel(s) is adjusted automatically based on the average handoff blocking rate measured in the past certain time period. The handoff blocking rate is controlled under the designated threshold and the new call blocking rate is minimized. The performance evaluation of the APCR_CB scheme is done by simulation. The result shows the APCR_CB scheme outperforms the original PCR, GC, and HPCR_CB schemes by controlling a hard constraint on the handoff blocking probability. It is able to achieve the optimal performance by maximizing the resource utilization and by adapting to changing traffic conditions automatically.

Improving fairness in the 802.11 infrastructure wireless local area networks /

Lin, Xiaoyang. January 2005 (has links)
Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2005. / Includes bibliographical references (leaves 59-63). Also available in electronic version.

An investigation into the impact of the coexistence of indoor and wide area cellular systems

Atkinson, Robert Caddell January 2003 (has links)
No description available.

Predictive Wireless Antenna Selection for High Mobility Conditions

Abou Saleh, HASSAN 31 January 2013 (has links)
Accurate channel knowledge is indispensable to the practical success of channel-aware wireless communication technologies. However, channel estimates obtained from pilot symbols rapidly become outdated due to fast time variations of multipath fading channels. To reduce system cost, antenna subset selection reduces radio frequency (RF) chain components. For systems selecting a subset of a plurality of antennas for reception, this outdated channel information is a significant impediment to selection and data decoding reliability. In this thesis, training-based schemes for antenna selection (AS) for time-varying channels which account for practical constraints such as training, packetization and antenna switching time are proposed based on discrete prolate spheroidal sequences. They only operate with knowledge or estimates of the Doppler frequency and the channel signal-to-noise ratio (SNR), but do not require detailed statistical correlation knowledge. A pilot-based AS scheme for time-varying frequency-flat channels for single input-multiple output (SIMO) systems selecting one of a plurality of antennas using packet or symbol-rate antenna switching is first proposed. It is demonstrated that the presented scheme provides significant performance gain over AS methods using Fourier-based orthogonal training as well as over single antenna systems with perfect channel knowledge. Analytical expressions for the symbol error probability (SEP) of M-ary phase-shift keying (MPSK) for systems employing the suggested techniques are provided. The second part of this thesis investigates the more general case of selecting a subset of a plurality of receive antennas. A new pilot-based receive antenna subset selection algorithm for time-varying frequency-flat channels is presented. The proposed AS algorithm is shown to outperform AS methods based on Fourier prediction/estimation as well as SIMO systems with perfect channel knowledge. Analysis of MPSK and quadrature amplitude modulation (MQAM) SEP for systems with receive AS is provided. The combination of AS and orthogonal frequency division multiplexing (OFDM) over the more realistic time-varying and frequency-selective fading scenario is examined in the final part. Training schemes for receive AS using packet-rate antenna switching for SIMO and multiple input-multiple output (MIMO) OFDM systems are developed. The suggested schemes exhibit a superior performance over AS methods using either linear interpolation/extrapolation or Fourier prediction/estimation techniques. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2013-01-30 16:47:06.057

Out of group interference aware base station cooperation

Fang, Yiwei January 2011 (has links)
No description available.

Wireless LAN extension

Tay, Chye Bin 03 1900 (has links)
Approved for public release; distribution is unlimited / The proliferation of laptop computers within the organization combined with increasing need to mobilize the labor force have fuelled the demand for wireless networks. Until recently, wireless technology was a patchwork of incompatible systems from a variety of vendors. The technology was slow, expensive and used for mobile applications or environments where cabling was impractical or impossible. With the maturing of industry standards and the deployment of lightweight wireless networking hardware across a broad market section, wireless technology has come of age. Lowered prices and interoperability have attracted many organizations to the idea, especially in the retail, financial, education, and health-care fields. The availability of wireless networking and wireless Local Area Networks (LANs) can extend the freedom and mobility of a network user, solve various problems associated with hard-wired networks and even reduce network deployment costs in some cases. This thesis provides an introduction to wireless LAN technology and the wireless LAN design for the Software Metrics Laboratory in Ingersoll 158, with particular emphasis on the communication requirements and protocols for the implementation of the wireless LAN extension to the existing wired LAN. / Lieutenant Colonel, Republic of Singapore Air Force

Utilising power capture for service differentiation in wireless LANs

Nyandoro, Alfandika, Computer Science & Engineering, Faculty of Engineering, UNSW January 2006 (has links)
In recent years, wireless communication systems have become pervasive, allowing continuous connectivity for people on the move, at home and in the workplace. The advent of third generation (3G) systems with capabilities beyond traditional telephony, and the explosive uptake of wireless Local Area Networks (LANs) are but two factors that have contributed to this growth. By virtue of their appeal to the market, wireless LANs have proven to be a serious contender as the access technology of choice for traditional data as well as the emerging 3G networks. If wireless LANs are to be successful as an access technology, however, the issue of Quality of Service (QoS) support will need to be addressed. QoS support for wireless LANs is becoming increasingly important because applications requiring such support, e.g. voice and video, are becoming more common in today's hybrid wireless systems, with the trend expected to grow into the future. The dominant standard for wireless LANs is the IEEE's 802.11 of which the contention-based Medium Access Control (MAC) protocol; also known as the Distributed Coordination Function (DCF), is universally supported. While the DCF is widely supported, it provides no QoS support. In this work, we propose and study a new and different mechanism of achieving service differentiation in 802.11 wireless LANs. Our approach employs the capture effect as the vehicle for achieving QoS differentiation for the contention mode of the standard. This approach enriches current research efforts by providing another dimension to QoS provisioning in wireless LANs. Hitherto most proposals have focussed on the modification of some aspect of the protocol, such as the minimum contention window size (CWmin), the Distributed Inter-Frame Space (DIFS), or the maximum contention window size (CWmax), amongst others. Capture based service differentiation complements these efforts. It can be used alone or in conjunction with existing approaches to provide additional priority classes. In this thesis, the capture based service differentiation approach is proposed and studied through Markov chain modelling and simulation. From the study, the following conclusions were drawn. It was confirmed that capture based service differentiation is a feasible approach in wireless LANs and that it can be achieved with practical and sustainable power differences between the transmitters from different classes. A number of factors were found to influence the level of service differentiation, including the population ratios of hosts in the power classes, the power ratios of the transmitters as well as the capture threshold of the receiver. For practical considerations, a complete architectural framework is also proposed, including support functions such as Transmission Power Control (TPC), QoS Signalling and Admission Control.

Distributed DHCP for WMNs using IPv6

Molerón Bermudez, Daniel, Sánchez-Camacho Capilla, Sergio January 2007 (has links)
<p>In a Wireless Mesh Network (WMN) exists mobile nodes which have an</p><p>unpredictable behaviour, i.e. they can join, leave and free move around the</p><p>network. For this reason, a static network configuration is not proper for them. A</p><p>distributed Dynamic Host Configuration Protocol (DHCP) is needed due to the</p><p>unavailability of a centralized server in a network placed over a vast extension.</p><p>This report shows a Distributed DHCP for WMNs using IPv6 (Internet Protocol</p><p>version 6). It is fault tolerant, robust and durable. The algorithm was created using</p><p>counters Bloom filters as data structure. After, a complete simulation of the system</p><p>was done. The simulations showed that using 24 servers with 16Mbits of memory</p><p>each one is possible to manage around 9000000 clients without adding an excessive</p><p>network load. Therefore, the DDHCPv6 could be in a near future the host</p><p>configuration protocol in WMN.</p>

Efficient placement and routing algorithms for maximizing the lifetimes of wireless sensor networks /

Patel, Maulin, January 2006 (has links)
Thesis (Ph. D.)--University of Texas at Dallas, 2006. / Includes vita. Includes bibliographical references (leaves 101-103).

Analyzing video compression for transporting over wireless fading channels

Kannan, Karthik 30 October 2006 (has links)
Wireless video communication is becoming increasingly popular these days with new applications such as TV on mobile and video phones. Commercial success of these applications requires superior video quality at the receiver. So it is imperative to analyze the effect of a wireless channel on a video transmission. The aim of this research is to analyze the video transmission over Rayleigh fading channels for various bit error rates (BER), signal to noise ratios (Eb/N0) and Doppler rates, and to suggest which source coding scheme is best at which BER, Eb/N0 and Doppler rates. Alternative schemes such as hybrid (digital/analog) schemes were considered and their performances were compared with pure digital communication. It is also shown that the combination of digital and analog video communication does not yield any better performance compared to pure digital video communication.

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