Design of Media Access Control Schemes for Performance Enhancement of Future Generation Wireless Systems

Wireless Local Area Networks (WLANs) now provide connectivity to many businesses, homes and educational institutions. The wireless channel itself is plagued with numerous problems, such as it does not natively allow sharing of the wireless resource. WLAN devices utilize a complex medium access control (MAC) mechanism to allow multiple users to share the wireless resource. The distributed coordination function (DCF) is the most commonly used multiple access scheme in WLANs and a member of the 802.11 standard [1]. In this thesis, two major roles of MAC protocols are examined: maximizing network throughput and service differentiation. Firstly, a novel MAC scheme is proposed that makes use of Multiple-Input, Multiple-Output (MIMO) antenna technology to improve overall network throughput. The proposed MIMO-Aware MAC (MA-MAC) scheme utilizes the beamforming feature available in MIMO systems to allow two simultaneous transmissions of the wireless channel overlapped in time. This results in increased aggregate network throughput. This proposed scheme is shown to offer better throughput and delay performance versus existing MAC schemes proposed for simultaneous transmission. In addition, this MAC scheme is able to achieve this performance in a manner compatible with the existing standard. The latter part of this thesis proposes a new Time Division Multiple Access (TDMA) based scheme for providing video, voice and data services (also known as the Triple-Play services) in a point-to-multipoint network. By dynamically allocating transmission slots, the proposed Television TDMA (TV-TDMA) scheme is shown to better meet delay requirements for video and voice traffic, and is able to achieve higher overall saturation throughput for best-effort traffic than existing Quality of Service enabled protocols

Surface Modifications of Poly(dimethylsiloxane) for Biological Application of Microfluidic Devices

The spatial control of cellular adhesion is fundamental to the development of studies of cell interaction, cellular microarrays, and cell based biosensors. The ability to pattern cell adhesion on flat substrates and in microfluidic channels is important for locating cell near microdetectors in cell based biosensor devices. Cell adhesion can be controlled by patterning a material\u27s wettability, as cells are able to adhere to hydrophilic surface and will generally avoid hydrophobic materials. This thesis focuses on patterning the surface wettability of poly(dimethylsilox-ane) (PDMS) in order to spatially control cell adhesion. The polymer is selectively modifed by the deposition of aluminum through a stencil mask in a magnetron sputtering system. After etching away the aluminum layer, a hydrophilic oxygen rich silica-like layer is exposed. This technique permits the creation of hydrophilic dots which are surrounded by the hydrophobic native PDMS. A second technique involving the use of photolithography results in a surface that can undergo hydrophobic recovery. By contrast, the selected areas covered by aluminum are protected against hydrophobic recovery. Finally, photolithography is used to selectively react a methyl terminated alkyl silane with the modified surface. Each surface modification was characterized by X-ray photoelectron spectros-copy, atomic force microscopy, contact angle measurements, force distance curves, cell attachment and viability tests; the effectiveness of the techniques to pattern wettability and cell adhesion was assessed. The relative adsorption of fibronectin and fibrinogen was visualized on the patterned surface. Further, the relative availability of the cell binding sites were also visualized on the surface through immunofluorescent labeling. While all patterning methods were effective at controlling surface wettability, cells did not show any selectivity on the surfaces patterned for hydrophobic recovery. The use of an alkyl silane proved more effective, as cell attachment did show some selectivity. However, cells were able to adhere and grow on the hydrophobic silanized regions. The stencil mask patterned surfaces showed cell selectivity, with cells almost completely avoiding the native hydrophobic PDMS background. Overall, the stencil mask patterning technique proved to be the most effective at controlling cell adhesion. Thus this surface patterning technique was integrated into reversibly and irreversible sealed microfluidic channels

Preferred Provider Organization Structures and Agreements

Preferred provider organizations can be created with both positive and negative consequences. Certain structures meet certain needs, and many contract terms can benefit the parties or create pitfalls

Design of Media Access Control Schemes for Performance Enhancement of Future Generation Wireless Systems

Wireless Local Area Networks (WLANs) now provide connectivity to many businesses, homes and educational institutions. The wireless channel itself is plagued with numerous problems, such as it does not natively allow sharing of the wireless resource. WLAN devices utilize a complex medium access control (MAC) mechanism to allow multiple users to share the wireless resource. The distributed coordination function (DCF) is the most commonly used multiple access scheme in WLANs and a member of the 802.11 standard [1]. In this thesis, two major roles of MAC protocols are examined: maximizing network throughput and service differentiation. Firstly, a novel MAC scheme is proposed that makes use of Multiple-Input, Multiple-Output (MIMO) antenna technology to improve overall network throughput. The proposed MIMO-A ware MAC (MA-MAC) scheme utilizes the beamforming feature available in MIMO systems to allow two simultaneous transmissions of the wireless channel overlapped in time. This results in increased aggregate network throughput. This proposed scheme is shown to offer better throughput and delay performance versus existing MAC schemes proposed for simultaneous transmission. In addition, this MAC scheme is able to achieve this performance in a manner compatible with the existing standard. The latter part of this thesis proposes a new Time Division Multiple Access (TDMA) based scheme for providing video, voice and data services (also known as the Triple-Play services) in a point-to-multipoint network. By dynamically allocating transmission slots, the proposed Television TDMA (TV-TDMA) scheme is shown to better meet delay requirements for video and voice traffic, and is able to achieve higher overall saturation throughput for best-effort traffic than existing Quality of Service enabled protocols

Energy Efficient Reduced Complexity Multi-Service, Multi-Channel Scheduling Techniques

The need for energy efficient communications is essential in current and next-generation wireless communications systems. A large component of energy expenditure in mobile devices is in the mobile radio interface. Proper scheduling and resource allocation techniques that exploit instantaneous and long-term average knowledge of the channel, queue state and quality of service parameters can be used to improve the energy efficiency of communication. This thesis focuses on exploiting queue and channel state information as well as quality of service parameters in order to design energy efficient scheduling techniques. The proposed designs are for multi-stream, multi-channel systems and in general have high computational complexity. The large contributions of this thesis are in both the design of optimal/near-optimal scheduling/resource allocation schemes for these systems as well as proposing complexity reduction methods in their design. Methods are proposed for both a MIMO downlink system as well as an LTE uplink system. The effect of power efficiency on quality of service parameters is well studied as well as complexity/efficiency comparisons between optimal/near optimal allocation

Design of Media Access Control Schemes for Performance Enhancement of Future Generation Wireless Systems

Wireless Local Area Networks (WLANs) now provide connectivity to many businesses, homes and educational institutions. The wireless channel itself is plagued with numerous problems, such as it does not natively allow sharing of the wireless resource. WLAN devices utilize a complex medium access control (MAC) mechanism to allow multiple users to share the wireless resource. The distributed coordination function (DCF) is the most commonly used multiple access scheme in WLANs and a member of the 802.11 standard [1]. In this thesis, two major roles of MAC protocols are examined: maximizing network throughput and service differentiation. Firstly, a novel MAC scheme is proposed that makes use of Multiple-Input, Multiple-Output (MIMO) antenna technology to improve overall network throughput. The proposed MIMO-Aware MAC (MA-MAC) scheme utilizes the beamforming feature available in MIMO systems to allow two simultaneous transmissions of the wireless channel overlapped in time. This results in increased aggregate network throughput. This proposed scheme is shown to offer better throughput and delay performance versus existing MAC schemes proposed for simultaneous transmission. In addition, this MAC scheme is able to achieve this performance in a manner compatible with the existing standard. The latter part of this thesis proposes a new Time Division Multiple Access (TDMA) based scheme for providing video, voice and data services (also known as the Triple-Play services) in a point-to-multipoint network. By dynamically allocating transmission slots, the proposed Television TDMA (TV-TDMA) scheme is shown to better meet delay requirements for video and voice traffic, and is able to achieve higher overall saturation throughput for best-effort traffic than existing Quality of Service enabled protocols

Alien Registration- Dechene, Rose (Lewiston, Androscoggin County)

https://digitalmaine.com/alien_docs/29560/thumbnail.jp

Alien Registration- Dechene, Irene E. (Auburn, Androscoggin County)

https://digitalmaine.com/alien_docs/30975/thumbnail.jp

Alien Registration- Dechene, Irene M. (Ashland, Aroostook County)

https://digitalmaine.com/alien_docs/27392/thumbnail.jp