662 research outputs found
Connection Between System Parameters and Localization Probability in Network of Randomly Distributed Nodes
This article deals with localization probability in a network of randomly
distributed communication nodes contained in a bounded domain. A fraction of
the nodes denoted as L-nodes are assumed to have localization information while
the rest of the nodes denoted as NL nodes do not. The basic model assumes each
node has a certain radio coverage within which it can make relative distance
measurements. We model both the case radio coverage is fixed and the case radio
coverage is determined by signal strength measurements in a Log-Normal
Shadowing environment. We apply the probabilistic method to determine the
probability of NL-node localization as a function of the coverage area to
domain area ratio and the density of L-nodes. We establish analytical
expressions for this probability and the transition thresholds with respect to
key parameters whereby marked change in the probability behavior is observed.
The theoretical results presented in the article are supported by simulations.Comment: To appear on IEEE Transactions on Wireless Communications, November
200
On the Throughput Allocation for Proportional Fairness in Multirate IEEE 802.11 DCF
This paper presents a modified proportional fairness (PF) criterion suitable
for mitigating the \textit{rate anomaly} problem of multirate IEEE 802.11
Wireless LANs employing the mandatory Distributed Coordination Function (DCF)
option. Compared to the widely adopted assumption of saturated network, the
proposed criterion can be applied to general networks whereby the contending
stations are characterized by specific packet arrival rates, , and
transmission rates .
The throughput allocation resulting from the proposed algorithm is able to
greatly increase the aggregate throughput of the DCF while ensuring fairness
levels among the stations of the same order of the ones available with the
classical PF criterion. Put simply, each station is allocated a throughput that
depends on a suitable normalization of its packet rate, which, to some extent,
measures the frequency by which the station tries to gain access to the
channel. Simulation results are presented for some sample scenarios, confirming
the effectiveness of the proposed criterion.Comment: Submitted to IEEE CCNC 200
On the Behavior of the Distributed Coordination Function of IEEE 802.11 with Multirate Capability under General Transmission Conditions
The aim of this paper is threefold. First, it presents a multi-dimensional
Markovian state transition model characterizing the behavior of the IEEE 802.11
protocol at the Medium Access Control layer which accounts for packet
transmission failures due to channel errors modeling both saturated and
non-saturated traffic conditions. Second, it provides a throughput analysis of
the IEEE 802.11 protocol at the data link layer in both saturated and
non-saturated traffic conditions taking into account the impact of both the
physical propagation channel and multirate transmission in Rayleigh fading
environment. The general traffic model assumed is M/M/1/K. Finally, it shows
that the behavior of the throughput in non-saturated traffic conditions is a
linear combination of two system parameters; the payload size and the packet
rates, , of each contending station. The validity interval of
the proposed model is also derived.
Simulation results closely match the theoretical derivations, confirming the
effectiveness of the proposed models.Comment: Submitted to IEEE Transactions on Wireless Communications, October
21, 200
A Model of the IEEE 802.11 DCF in Presence of Non Ideal Transmission Channel and Capture Effects
In this paper, we provide a throughput analysis of the IEEE 802.11 protocol
at the data link layer in non-saturated traffic conditions taking into account
the impact of both transmission channel and capture effects in Rayleigh fading
environment. Impacts of both non-ideal channel and capture become important in
terms of the actual observed throughput in typical network conditions whereby
traffic is mainly unsaturated, specially in an environment of high
interference.
We extend the multi-dimensional Markovian state transition model
characterizing the behavior at the MAC layer by including transmission states
that account for packet transmission failures due to errors caused by
propagation through the channel, along with a state characterizing the system
when there are no packets to be transmitted in the buffer of a station.Comment: Accepted for oral presentation to IEEE Globecom 2007, Washington
D.C., November 200
On The Linear Behaviour of the Throughput of IEEE 802.11 DCF in Non-Saturated Conditions
We propose a linear model of the throughput of the IEEE 802.11 Distributed
Coordination Function (DCF) protocol at the data link layer in non-saturated
traffic conditions. We show that the throughput is a linear function of the
packet arrival rate (PAR) with a slope depending on both the number
of contending stations and the average payload length. We also derive the
interval of validity of the proposed model by showing the presence of a
critical , above which the station begins operating in saturated
traffic conditions.
The analysis is based on the multi-dimensional Markovian state transition
model proposed by Liaw \textit{et al.} with the aim of describing the behaviour
of the MAC layer in unsaturated traffic conditions. Simulation results closely
match the theoretical derivations, confirming the effectiveness of the proposed
linear model.Comment: To appear on IEEE Communications Letters, November 200
Unsaturated Throughput Analysis of IEEE 802.11 in Presence of Non Ideal Transmission Channel and Capture Effects
In this paper, we provide a throughput analysis of the IEEE 802.11 protocol
at the data link layer in non-saturated traffic conditions taking into account
the impact of both transmission channel and capture effects in Rayleigh fading
environment. The impact of both non-ideal channel and capture become important
in terms of the actual observed throughput in typical network conditions
whereby traffic is mainly unsaturated, especially in an environment of high
interference.
We extend the multi-dimensional Markovian state transition model
characterizing the behavior at the MAC layer by including transmission states
that account for packet transmission failures due to errors caused by
propagation through the channel, along with a state characterizing the system
when there are no packets to be transmitted in the buffer of a station.
Finally, we derive a linear model of the throughput along with its interval of
validity.
Simulation results closely match the theoretical derivations confirming the
effectiveness of the proposed model.Comment: To appear on IEEE Transactions on Wireless Communications, 200
Saturation Throughput Analysis of IEEE 802.11 in Presence of Non Ideal Transmission Channel and Capture Effects
In this paper, we provide a saturation throughput analysis of the IEEE 802.11
protocol at the data link layer by including the impact of both transmission
channel and capture effects in Rayleigh fading environment. Impacts of both
non-ideal channel and capture effects, specially in an environment of high
interference, become important in terms of the actual observed throughput. As
far as the 4-way handshaking mechanism is concerned, we extend the
multi-dimensional Markovian state transition model characterizing the behavior
at the MAC layer by including transmission states that account for packet
transmission failures due to errors caused by propagation through the channel.
This way, any channel model characterizing the physical transmission medium can
be accommodated, including AWGN and fading channels. We also extend the Markov
model in order to consider the behavior of the contention window when employing
the basic 2-way handshaking mechanism.
Under the usual assumptions regarding the traffic generated per node and
independence of packet collisions, we solve for the stationary probabilities of
the Markov chain and develop expressions for the saturation throughput as a
function of the number of terminals, packet sizes, raw channel error rates,
capture probability, and other key system parameters. The theoretical
derivations are then compared to simulation results confirming the
effectiveness of the proposed models.Comment: To appear on IEEE Transactions on Communications, 200
Visual Art, a Pedagogical Tool of Plural Knowledge between Creative Productions and Community Ties: a Theoretical-Practical Research Between Italy and Kenya
Educational places are changed into meaningful spaces where it is possible to unleash creativity and discover plural perspectives when visual art becomes a
pedagogical tool, which activates cooperative dynamics, co-building knowledge, and relational skills. This hypothesis was verified as a part of the European project «TICASS» – Technologies of Imaging in Communication, Art and Social Sciences (2017-2021) –, carried out between Europe and Africa. Starting from the reference framework, various interpretations of visual languages and ways of perception of individuals belonging to different socio-cultural contexts were investigated (Lester, 2010). This contribution introduces paths and outcomes of the research action interventions, carried out by a psycho-pedagogical research team in kindergartens and primary schools since 2018, involving over 100 children aged 3 to 5 in Italy and over 300 children aged 8 to 12 in Kenya (Deluigi, 2019; Deluigi, Machova & Stara, 2021). Methodology: The collection of qualitative data took place through participatory observation, supervision of the workshops, and the ongoing critical reflection of the research group. This analysis deals with the
use of the image as a stimulus carefully researched and introduced through silent books (Zizioli, 2017) with a less structured input to leave room for a creative process. Thus, children become producers of images and imaginaries drawn from their very personal creativity (Malaguzzi, 1998).
Results/Conclusions: The results of the workshops carried out can motivate educators, teachers, and pedagogues to design interactive experiences among peers (including adults), through the use of creative languages as mediators of community learning processes in an intercultural and transcultural framework (Cooper & Sjostrom, 2006)
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