Search results for "WLAN"

MAClets: Active MAC Protocols over hard-coded devices

2012

We introduce MAClets, software programs uploaded and executed on-demand over wireless cards, and devised to change the card's real-time medium access control operation. MAClets permit seamless reconfiguration of the MAC stack, so as to adapt it to mutated context and spectrum conditions and perform tailored performance optimizations hardly accountable by an once-for-all protocol stack design. Following traditional active networking principles, MAClets can be directly conveyed within data packets and executed on hard-coded devices acting as virtual MAC machines. Indeed, rather than executing a pre-defined protocol, we envision a new architecture for wireless cards based on a protocol interpr…

“Vendor-Affected” WLAN experimental results: A Pandora’s Box?

2008

Design, Implementation and Experimental Evaluation of a Wireless MAC Processor over commercial WIFI cards

2014

In this thesis we face the problem of wireless network programmability as a solution for coping with context-dependent optimizations, moving from one-for-all standard solutions to the concept of programmable wireless interfaces. Although the wireless research and academic community has proposed interesting platforms (e.g. based on Software Defined Radio) for pushing forward dynamic reprogrammability of devices, we argue that it is important to identify a tradeoff between programmability space and usability of the programmable interface. In this direction, we introduce the concept of Wireless MAC Processor and developed a running prototype over an ultra-cheap wireless card. Wireless MAC proc…

Parenté et organisation sociale chez les Wayùu. Retour sur la question

2021

Dans cet article, l’auteur revient sur certaines questions concernant le domaine de la parenté et de l’organisation sociale des Wayùu de la péninsule de La Guajira, dans la zone frontalière du nord de la Colombie et du Venezuela. Prenant pour point de départ le désaccord entre Goulet et Saler sur l’existence de catégories et de groupes de lignages et sur la place de ceux-ci dans le monde social des Wayùu, il opte pour le point de vue de Saler, à savoir que ces catégories peuvent être considérées non seulement dans les mythes au sujet de l’origine de la société wayùu, mais aussi dans les différents concepts qui réfèrent à l’ancestralité utérine commune d’un groupe de gens apparentés, ainsi q…

Etude de l’infection la plante parasite Rhamphicarpa fistulosa en riziculture au Togo

2013

Rhamphicarpa fistulosa (Hochst.) Benth. is an annual facultative root-parasitic weed found in lowlands and floodplains in tropical Africa. It has been reported as the major constraint to rice cultivation in the savannah region of Togo. A survey was conducted in 2012 to access its distribution and to collect information on farmers' knowledge of its control. Rhamphicarpa fistulosa was found in 80% of the 33 visited lowlands. The period of abundance is in August-September when the highest infection (90%) was found on sandy and clay soils. When the parasite was present, 94 other weeds belonging to 24 botanical families were recorded. As management method, farmers use weeding and chemical fertil…

Dynamic MAC Parameters Configuration for Performance Optimization in 802.11e Networks

2006

Quality of service support in wireless LAN is a theme of current interest. Several solutions have been proposed in literature in order to protect time-sensitive traffic from best-effort traffic. According to the EDCA proposal, which is a completely distributed solution, the service differentiation is provided by giving probabilistically higher number of channel accesses to stations involved in real-time applications. To this purpose, the MAC parameter settings of each contending stations can be tuned dynamically. In this paper, we face the problem of tuning the EDCA MAC parameters in common scenarios in which a given number of low-rate delay-sensitive traffic flows share the channel with so…

Remarks on IEEE 802.11 DCF Performance Evaluation, IEEE Communication Letters, Vol. 9, Issue 8, Aug 2005 pp:765 - 767

2005

This letter presents a new approach to evaluate the throughput/delay performance of the 802.11 Distributed Coordination Function (DCF). Our approach relies on elementary conditional probability arguments rather than bidimensional Markov chains (as proposed in previous models), and can be easily extended to account for backoff operation more general than DCF's one

On the accuracy of some common modeling assumptions for EDCA analysis

2005

Several models have been discussed in literature in order to evaluate the performance of the EDCA differentiation mechanisms. Despite of the exponential back off rules, usually the EDCA protocol has been modeled as a persistent slotted access protocol, and summarized into a set of access probabilities. These models often show a very different complexity and accuracy, according to the basis assumptions. In this paper, we propose a new modeling approach for EDCA, in which the medium access is described in terms of backoff counter comparisons, contention by contention, and no restrictive hypothesis is considered. Through our model, we verify the applicability of the most common protocol simpli…

Improving IEEE 802.11 Performance in Chain Topologies through Distributed Polling and Network Coding

2009

Wireless multi-hop networks often rely on the use of IEEE 802.11 technology. Despite of the robustness of the IEEE 802.11 Distributed Coordination Function (DCF) for working in various network scenarios, it has been proven that critical inefficiencies can arise in the case of multi-hop packet forwarding. In this paper, we propose a MAC scheme, based on the virtualization of the Point Coordination Function, optimized for working on chain topologies with bidirectional traffic flows. Our scheme is based on a token-like access mechanism coupled with network coding. The basic idea is the use of multiple Point Coordinators (PCs) along the node chain, which are elected by passing special token fra…

Joint routing and per-flow fairness in wireless multihop networks

2008

In wireless multihop networks communication between two end-nodes is carried out by hopping over multiple short wireless links. Traditional CSMA/CA based media access control does not work satisfactory in a multihop scenario, since an intended target of a communication may be subject to mutual interference imposed by concurrent transmissions from nodes which cannot directly sense each other, causing unfair throughput allocation. Although TDMA seems to be a more promising solution, careful transmission scheduling is needed in order to achieve error-free communication and fairness. In our previous work, a TDMA scheduling algorithm has been proposed that schedules the transmissions in a fair m…