Search results for "access"
showing 10 items of 1232 documents
Refinements on IEEE 802.11 Distributed Coordination Function Modeling Approaches
2010
With the popularity of the IEEE 802.11 standards, many analytical saturation throughput studies for the distributed coordination function (DCF) have been reported. In this paper, we outline a number of issues and criticalities raised by previously proposed models. In particular, a careful look at backoff counter decrement rules allows us to conclude that, under saturation conditions, the slot immediately following a successful transmission can be accessed only by the station (STA) that has successfully transmitted in the previous channel access. Moreover, due to the specific acknowledgment (ACK) timeout setting adopted in the standard, the slot immediately following a collision cannot be ac…
Does the law matter? An empirical study on the accessibility of Finnish higher education institutions’ web pages
2022
AbstractInformation and communication technology (ICT) has made higher education available to many students in a new way. The role of online learning in higher education institutions (HEIs) has grown to an unprecedented scale due to the COVID-19 pandemic. The diversity of higher education students has increased, and accessible solutions are needed. New European and national regulations support these trends. The research reported in this paper was conducted in Finland, which is one of the leading European countries in terms of high technology and digitalisation. The aim of this research is to explore the accessibility of all Finnish HEIs’ (N = 38) landing pages based on Web Content Accessibi…
Parallelizing Epistasis Detection in GWAS on FPGA and GPU-Accelerated Computing Systems
2015
This is a post-peer-review, pre-copyedit version of an article published in IEEE - ACM Transactions on Computational Biology and Bioinformatics. The final authenticated version is available online at: http://dx.doi.org/10.1109/TCBB.2015.2389958 [Abstract] High-throughput genotyping technologies (such as SNP-arrays) allow the rapid collection of up to a few million genetic markers of an individual. Detecting epistasis (based on 2-SNP interactions) in Genome-Wide Association Studies is an important but time consuming operation since statistical computations have to be performed for each pair of measured markers. Computational methods to detect epistasis therefore suffer from prohibitively lon…
Enhancing HSUPA system level performance with dual carrier capability
2010
The purpose of this paper is to analyze how dual carrier capability can enhance High Speed Uplink Packet Access performance in comparison to using only single carrier. Dual carrier operation gives the User Equipment the possibility to transmit simultaneously using two 5 MHz bands, theoretically doubling the peak data rates and user throughput. The analysis is conducted with a system level simulation tool. This paper first indicates with single carrier simulations that, especially in small cells, terminals have spare power available for dual carrier operation. These observations are verified with dual carrier simulations by showing that the burst throughput can be practically doubled. In the…
Out-of-Band Signaling Scheme for High Speed Wireless LANs
2007
In recent years, the physical layer data rate provided by 802.11 Wireless LANs has dramatically increased thanks to significant advances in the modulation and coding techniques employed. However, previous studies show that the 802.11 MAC operation, namely the distributed coordination function (DCF), represents a limiting factor: the throughput efficiency drops as the channel bit rate increases, and a throughput upper limit does indeed exist when the channel bit rate goes to infinite high. These findings indicate that the performance of the DCF protocol will not be efficiently improved by merely increasing the channel bit rate. This paper shows that the DCF performance may significantly bene…
Measuring the weather’s impact on MAC layer over 2.4GHz outdoor radio links
2015
The weather s impact on the performance of a radio link at the 2.4 GHz ISM (Industry, Scientific and Medical) band had not been yet studied in great detail up to now as it is generally believed that the ultra-high frequency band is not significantly affected by weather conditions. However, our study shows significant correlations between meteorological variables and control frame errors at MAC (Medium Access Control) layer of the IEEE 802.11b/g standard. This study is performed over an outdoor radio link setting which has been monitored for several months. Moreover, we check if link distance and so modulation scheme and data rate are also decisive features of such impact. Our real scenario …
A touchless gestural system for extended information access within a campus
2017
In the last two decades, we have witnessed a growing spread of touchless interfaces, facilitated by higher performances of computational systems, as well as the increased availability of cheaper sensors and devices. Putting the focus on gestural input, several researchers and designers used Kinect-like devices to implement touchless gestural interfaces. The latter extends the possible deployments and usage of public interactive displays. For example, wall-sized displays may become interactive even if they are unreachable by touch. Moreover, billboard-sized displays may be placed in safe cases to avoid vandalism, while still maintaining their interactivity. Finally, people with temporary or …
Remarks on IEEE 802.11 DCF performance analysis
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.
Joint Usage of Dynamic Sensitivity Control and Time Division Multiple Access in Dense 802.11ax Networks
2016
It is well known that in case of high density deployments, Wi-Fi networks suffer from serious performance impairments due to hid- den and exposed nodes. The problem is explicitly considered by the IEEE 802.11ax developers in order to improve spectrum efficiency. In this pa- per, we propose and evaluate the joint usage of dynamic sensitivity con- trol (DSC) and time division multiple access (TDMA) for improving the spectrum allocation among overlapping 802.11ax BSSs. To validate the solution, apart from simulation, we used a testbed based on the Wireless MAC Processor (WMP), a prototype of a programmable wireless card.
Outage Analysis of Relay-Aided Non-Orthogonal Multiple Access with Partial Relay Selection
2018
Non-Orthogonal multiple access (NOMA) holds promise as a spectrally efficient multiple access scheme for 5G communication networks. This work investigates the performance of NOMA in a dual-hop amplify-and-forward (AF) relaying network, which is subject to Nakagami-$m$ fading. Specifically, we obtain a novel closed-form expression of the outage probability for the near and far users when the partial relay selection (PRS) scheme is used for selecting the best among $N$ intermediate relays. The users are considered to employ selection combining technique in order to combine the relayed and the direct transmission signals for an increased reliability of detection. Then, we evaluate the impact o…