Frame aggregation is one of the major MAC layer enhancements in the IEEE 802.11 family that boosts the network throughput performance. It aims to achieve higher throughput by transmitting huge amount of data in a single transmit oppor- tunity. With the increasing awareness of energy e ciency, it has become vital to rethink about the design of such frame aggregation protocol. Aggregation techniques help to reduce energy consumption over ideal channel conditions. However, in a noisy channel environment, a new energy-aware frame aggregation scheme is required. In this thesis, a novel Green Frame Aggregation (GFA) scheduling scheme has been proposed and evaluated. GFA optimizes the aggregate size based on channel quality in order to minimize the consumed energy. GFA selects the optimal sub-frame size that satisfies the loss constraint for real-time applications as well as the energy budget of the ideal channel situations. The design, the implementation, and evaluation of GFA using testbed deployment is done. The experimental analysis shows that GFA outperforms the conventional frame aggregation methodology in terms of energy e ciency by about 6⇥ in the presence of severe interference conditions. Moreover, GFA also outperforms the static frame sizing method in terms of network goodput and maintains almost the same end- to-end latency.

The accuracy of current intrusion detection systems (IDSes) is hindered by the limited capability of regular expressions (REs) to express the exact vulnerability. Recent advances have proposed vulnerability-based IDSes that parse traffic and retrieve protocol semantics to describe the vulnerability. Such a description of attacks is analogous to subscriptions that specify events of interest in event processing systems. However, the matching engine of state-of-the-art IDSes lacks efficient matching algorithms that can process many signatures simultaneously. In this work, we place event processing in the core of the IDS and propose novel algorithms to efficiently parse and match vulnerability signatures. Also, we are among the first to detect complex attacks such as the Conficker worm which requires correlating multiple protocol data units (MPDUs) while maintaining a small memory footprint. Our approach incurs neglibile overhead when processing clean traffic, is resilient to attacks, and is faster than existing systems.

The accuracy of current intrusion detection systems (IDSes) is hindered by the limited capability of regular expressions (REs) to express the exact vulnerability. Recent advances have proposed vulnerability-based IDSes that parse traffic and retrieve protocol semantics to describe the vulnerability. Such a description of attacks is analogous to subscriptions that specify events of interest in event processing systems. However, the matching engine of state-of-the-art IDSes lacks efficient matching algorithms that can process many signatures simultaneously. In this work, we place event processing in the core of the IDS and propose novel algorithms to efficiently parse and match vulnerability signatures. Also, we are among the first to detect complex attacks such as the Conficker worm which requires correlating multiple protocol data units (MPDUs) while maintaining a small memory footprint. Our approach incurs neglibile overhead when processing clean traffic, is resilient to attacks, and is faster than existing systems.

[pt] Cada vez mais as redes locais sem fio conhecidas por WLAN estão presentes no meio em que vivemos, seja em nossas casas como em escritórios, aeroportos e outros locais públicos. Na busca de possibilitar que mais aplicações sejam viabilizadas pelas redes sem fio, tais como fluxos de vídeo, a qual requer uma maior largura de banda, o IEEE desenvolveu um novo padrão da família do 802.11, o IEEE 802.11n que é capaz de oferecer uma capacidade de transmissão significativamente maior que os padrões 802.11 anteriores. Em principio, o grande aumento de capacidade na camada física deveria ser suficiente para oferta de aplicações de multimídia, inclusive com vídeo em alta definição. Entretanto, a baixa eficiência da camada de controle de acesso ao meio (camada MAC) e de alguns protocolos da camada física poderiam restringir o uso de aplicações que necessitam de altas taxas de transmissão. Para resolver essa questão o padrão 802.11n contempla o recurso de agregação dos quadros que possui dois métodos distintos, A-MPDU (Aggregated MAC Protocol Data Unit) e A-MSDU (Aggregated MAC Service Data Unit). Neste trabalho foram realizadas simulações com sinais de vídeos reais e apresentados resultados que permitem comparar o desempenho destes métodos e avaliar se o uso de agregação permite efetivamente que o padrão 802.11n atenda os requisitos da transmissão de vídeo. Foram também sugeridos valores para os parâmetros da tecnologia 802.11n que permitem que um melhor desempenho seja alcançado. / [en] Wireless LANs are gradually playing an increasingly important role in our day-to-day life. It is common now to find them in airports, hotels, office buildings as well as in individual residences. Due to this success there was an effort at IEEE to develop a new standard that would allow new high data rate applications, such as video streaming, to be provided through a WiFi access point. This new standard added to the IEEE 802.11 family is known as IEEE 802.11n and it offers a significantly higher capacity physical layer. However, to derive the full benefits of this new very powerful physical layer it was necessary to improve the efficiency of the MAC layer as well as of some physical layer protocols. One of techniques included in the standard, to allow high bandwidth services with good quality, was frame aggregation. The 802.11n standard contemplates two forms of aggregation, namely: A-MPDU (Aggregated MAC Protocol Data Unit) and AMSDU (Aggregated MAC Service Data Unit). In this work, simulations were performed to evaluate the performance of both methods of aggregation when transporting real video signals. The objective was to verify whether 802.11n, with the use of aggregation, can indeed provide video and multimedia services with the required quality. We also suggest values for 802.11n system parameters that provide improved performance.

<p>There are several standards for wireless communication. People that are involved in computers and networking recognize names like Bluetooth, HiperLAN and IEEE 802.11. The last one was standardized in 1997 [2,6]and has begun to reach acceptance as a solid ground for wireless networking. A fundamental part of an IEEE 802.11 node is the Medium Access Controller, or MAC. It establishes and controls communication with other nodes, using a physical layer unit. </p><p>The work has been carried out as final project at Linkopings Universitet, it has been about the improvement of the functions of MAC layer. I have developed some of the required functions that PUM uses to interact with the MAC layer. Because of that, I have implemented the Reception functions of MAC layer, having the possibility of using short control frames RTS/CTS to minimize collision.</p>

There are several standards for wireless communication. People that are involved in computers and networking recognize names like Bluetooth, HiperLAN and IEEE 802.11. The last one was standardized in 1997 [2,6]and has begun to reach acceptance as a solid ground for wireless networking. A fundamental part of an IEEE 802.11 node is the Medium Access Controller, or MAC. It establishes and controls communication with other nodes, using a physical layer unit. The work has been carried out as final project at Linkopings Universitet, it has been about the improvement of the functions of MAC layer. I have developed some of the required functions that PUM uses to interact with the MAC layer. Because of that, I have implemented the Reception functions of MAC layer, having the possibility of using short control frames RTS/CTS to minimize collision.