176 research outputs found
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
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 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
Throughput Analysis of CSMA Wireless Networks with Finite Offered-load
This paper proposes an approximate method, equivalent access intensity (EAI),
for the throughput analysis of CSMA wireless networks in which links have
finite offered-load and their MAC-layer transmit buffers may be empty from time
to time. Different from prior works that mainly considered the saturated
network, we take into account in our analysis the impacts of empty transmit
buffers on the interactions and dependencies among links in the network that is
more common in practice. It is known that the empty transmit buffer incurs
extra waiting time for a link to compete for the channel airtime usage, since
when it has no packet waiting for transmission, the link will not perform
channel competition. The basic idea behind EAI is that this extra waiting time
can be mapped to an equivalent "longer" backoff countdown time for the
unsaturated link, yielding a lower link access intensity that is defined as the
mean packet transmission time divided by the mean backoff countdown time. That
is, we can compute the "equivalent access intensity" of an unsaturated link to
incorporate the effects of the empty transmit buffer on its behavior of channel
competition. Then, prior saturated ideal CSMA network (ICN) model can be
adopted for link throughput computation. Specifically, we propose an iterative
algorithm, "Compute-and-Compare", to identify which links are unsaturated under
current offered-load and protocol settings, compute their "equivalent access
intensities" and calculate link throughputs. Simulation shows that our
algorithm has high accuracy under various offered-load and protocol settings.
We believe the ability to identify unsaturated links and compute links
throughputs as established in this paper will serve an important first step
toward the design and optimization of general CSMA wireless networks with
offered-load control.Comment: 6 pages. arXiv admin note: text overlap with arXiv:1007.5255 by other
author
Max-min Fairness in 802.11 Mesh Networks
In this paper we build upon the recent observation that the 802.11 rate
region is log-convex and, for the first time, characterise max-min fair rate
allocations for a large class of 802.11 wireless mesh networks. By exploiting
features of the 802.11e/n MAC, in particular TXOP packet bursting, we are able
to use this characterisation to establish a straightforward, practically
implementable approach for achieving max-min throughput fairness. We
demonstrate that this approach can be readily extended to encompass time-based
fairness in multi-rate 802.11 mesh networks
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