Search results for "WLAN"
showing 10 items of 52 documents
Diversity and endemism of woody plant species in the Equatorial Pacific seasonally dry forests
2009
The biodiversity hotspot of the Equatorial Pacific region in western Ecuador and northwestern Peru comprises the most extensive seasonally dry forest formations west of the Andes. Based on a recently assembled checklist of the woody plants occurring in this region, we analysed their geographical and altitudinal distribution patterns. The montane seasonally dry forest region (at an altitude between 1,000 and 1,100 m, and the smallest in terms of area) was outstanding in terms of total species richness and number of endemics. The extensive seasonally dry forest formations in the Ecuadorean and Peruvian lowlands and hills (i.e., forests below 500 m altitude) were comparatively much more specie…
The genome sequencing of an albino Western lowland gorilla reveals inbreeding in the wild
2013
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License.-- et al.
Materiały do poznania fauny Kampinoskiego Parku Narodowego: Apionidae i Nanophyidae (Coleoptera: Curculionoidea)
2013
New localities of 35 species of Apionidae and 2 species of Nanophyidae in the Kampinos National Park are presented, among them respectively 26 and 2 species new for the studied area. Regarding Apionidae, 8 of 9 species recorded from the Kampinos National Park in literature, were confirmed to occur there. Perapion oblongum (GYLL.) has been recorded from the Mazovian Lowland for the first time
Wireless MAC processors: programming MAC protocols on commodity hardware
2012
Programmable wireless platforms aim at responding to the quest for wireless access flexibility and adaptability. This paper introduces the notion of wireless MAC processors. Instead of implementing a specific MAC protocol stack, Wireless MAC processors do support a set of Medium Access Control “commands” which can be run-time composed (programmed) through software-defined state machines, thus providing the desired MAC protocol operation. We clearly distinguish from related work in this area as, unlike other works which rely on dedicated DSPs or programmable hardware platforms, we experimentally prove the feasibility of the wireless MAC processor concept over ultra-cheap commodity WLAN hardw…
A Kalman Filter Approach for Distinguishing Channel and Collision Errors in IEEE 802.11 Networks
2008
In the last years, several strategies for maximizing the throughput performance of IEEE 802.11 networks have been proposed in literature. Specifically, it has been shown that optimizations are possible both at the medium access control (MAC) layer, and at the physical (PHY) layer. In fact, at the MAC layer, it is possible to minimize the channel waste due to collisions and backoff expiration times, by tuning the minimum contention window as a function of the network congestion level. At the PHY layer, it is possible to improve the transmission robustness, by selecting a suitable modulation/coding scheme as a function of the channel quality perceived by the stations. However, the feasibility…
The role of the Access Point in Wi-Fi networks with selfish nodes
2009
In Wi-Fi networks, mobile nodes compete for accessing the shared channel by means of a random access protocol called Distributed Coordination Function (DCF), which is long term fair. But recent drivers allow users to configure protocol parameters differently from their standard values in order to break the protocol fairness and obtain a larger share of the available bandwidth at the expense of other users. This motivates a game theoretical analysis of DCF. Previous studies have already modeled access to a shared wireless channel in terms of non-cooperative games among the nodes, but they have mainly considered ad hoc mode operation. In this paper we consider the role of the Access Point (AP…
ErrorSense: Characterizing WiFi Error Patterns for Detecting ZigBee Interference
2014
Recent years have witnessed the increasing adoption of heterogeneous wireless networks working in unlicensed ISM bands, thus creating serious problems of spectrum overcrowding. Although ZigBee, Bluetooth and WiFi networks have been natively designed for working in presence of interference, it has been observed that several performance impairments may occur because of heterogeneous sensitivity to detect or react to the presence of other technologies. In this paper we focus on the WiFi capability to detect interfering ZigBee links. Despite of the narrowband transmissions performed by ZigBee, in emerging scenarios ZigBee interference can have a significant impact on WiFi performance. Therefore…
Kalman filter estimation of the contention dynamics in error-prone IEEE 802.11 networks
2008
In the last years, several strategies for maximizing the throughput performance of IEEE 802.11 networks have been proposed in literature. Specifically, it has been shown that optimizations are possible both at the medium access control (MAC) layer, and at the physical (PHY) layer. In fact, at the MAC layer, it is possible to minimize the channel wastes due to collisions and backoff expiration times, by tuning the minimum contention window as a function of the number n of competing stations. At the PHY layer, it is possible to improve the transmission robustness, by selecting a suitable modulation/coding scheme as a function of the channel quality perceived by the stations. However, the feas…
Efficiency analysis of burst transmissions with block ACK in contention-based 802.11e WLANs
2005
The channel utilization efficiency of the standard 802.11 networks is severely compromised when high data transmission rates are employed, since physical layer headers and control frames are transmitted at low rate, thus wasting more channel time, proportionally. The extensions defined in the emerging 802.11e for quality-of-service (QoS) provisioning include some new mechanisms developed in order to improve the efficiency. Those include data transmission bursting (referred to as TXOP operation) and acknowledgment aggregation (referred to as block ACK). These two features allow it to offer new data transmission services, in which the data delivery and acknowledgment unit is not a single fram…
Nowe dla Niziny Mazowieckiej i rzadkie gatunki ryjkowcowatych (Coleoptera: Curculionidae) z Kampinoskiego Parku Narodowego
2013
New data on the occurrence of 16 weevil species from the Kampinos National Park are presented, of which 7 species are recorded from the Mazovia Lowland for the first time. Among them two, Otiorhynchus repletus BOHEMAN and Larinus sturnus (SCHALLER) figure in the "Polish Red List".