26 research outputs found
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
A control theoretic approach to achieve proportional fairness in 802.11e EDCA WLANs
This paper considers proportional fairness amongst ACs in an EDCA WLAN for
provision of distinct QoS requirements and priority parameters. A detailed
theoretical analysis is provided to derive the optimal station attempt
probability which leads to a proportional fair allocation of station
throughputs. The desirable fairness can be achieved using a centralised
adaptive control approach. This approach is based on multivariable statespace
control theory and uses the Linear Quadratic Integral (LQI) controller to
periodically update CWmin till the optimal fair point of operation. Performance
evaluation demonstrates that the control approach has high accuracy performance
and fast convergence speed for general network scenarios. To our knowledge this
might be the first time that a closed-loop control system is designed for EDCA
WLANs to achieve proportional fairness
Thwarting Selfish Behavior in 802.11 WLANs
The 802.11e standard enables user configuration of several MAC parameters,
making WLANs vulnerable to users that selfishly configure these parameters to
gain throughput. In this paper we propose a novel distributed algorithm to
thwart such selfish behavior. The key idea of the algorithm is for honest
stations to react, upon detecting a selfish station, by using a more aggressive
configuration that penalizes this station. We show that the proposed algorithm
guarantees global stability while providing good response times. By conducting
a game theoretic analysis of the algorithm based on repeated games, we also
show its effectiveness against selfish stations. Simulation results confirm
that the proposed algorithm optimizes throughput performance while discouraging
selfish behavior. We also present an experimental prototype of the proposed
algorithm demonstrating that it can be implemented on commodity hardware.Comment: 14 pages, 7 figures, journa
Proportional Fair MU-MIMO in 802.11 WLANs
We consider the proportional fair rate allocation in an 802.11 WLAN that
supports multi-user MIMO (MU-MIMO) transmission by one or more stations. We
characterise, for the first time, the proportional fair allocation of MU-MIMO
spatial streams and station transmission opportunities. While a number of
features carry over from the case without MU-MIMO, in general neither flows nor
stations need to be allocated equal airtime when MU-MIMO is available
A control theoretic approach to achieve proportional fairness in 802.11e EDCA WLANs
This paper considers proportional fairness amongst ACs in an EDCA WLAN redfor provision of distinct QoS requirements and priority parameters. A detailed theoretical analysis is provided to derive the optimal station attempt probability which leads to a proportional fair allocation of station throughputs. The desirable fairness can be achieved using a centralised adaptive
control approach. This approach is based on multivariable statespace control theory and uses the Linear Quadratic Integral
(LQI) controller to periodically update CWmin till the optimal fair point of operation. Performance evaluation demonstrates that the control approach has high accuracy performance and fast convergence speed for general network scenarios. To our knowledge this might be the first time that a closed-loop control
system is designed for EDCA WLANs to achieve proportional fairness
Thwarting selfish behavior in 802.11 WLANs
The 802.11e standard enables user configuration of several MAC parameters, making WLANs vulnerable to users that selfishly configure these parameters to gain throughput. In this paper, we propose a novel distributed algorithm to thwart such selfish behavior. The key idea of the algorithm is for stations to react, upon detecting a misbehavior, by using a more aggressive configuration that penalizes the misbehaving station. We show that the proposed algorithm guarantees global stability while providing good response times. By conducting an analysis of the effectiveness of the algorithm against selfish behaviors, we also show that a misbehaving station cannot obtain any gain by deviating from the algorithm. Simulation results confirm that the proposed algorithm optimizes throughput performance while discouraging selfish behavior. We also present an experimental prototype of the proposed algorithm demonstrating that it can be implemented on commodity hardware.This work was supported by the European Community under the CROWD Project FP7-ICT-318115 and the Centro Universitario de la Defensa under Project CUD2013-05
Rigorous and Practical Proportional-fair Allocation for Multi-rate Wi-Fi
Recent experimental studies confirm the prevalence of the widely known performance anomaly
problem in current Wi-Fi networks, and report on the severe network utility degradation caused by
this phenomenon. Although a large body of work addressed this issue, we attribute the refusal of
prior solutions to their poor implementation feasibility with off-the-shelf hardware and their impre-
cise modelling of the 802.11 protocol. Their applicability is further challenged today by very high
throughput enhancements (802.11n/ac) whereby link speeds can vary by two orders of magnitude.
Unlike earlier approaches, in this paper we introduce the first rigorous analytical model of 802.11
stations’ throughput and airtime in multi-rate settings, without sacrificing accuracy for tractability.
We use the proportional-fair allocation criterion to formulate network utility maximisation as a con-
vex optimisation problem for which we give a closed-form solution. We present a fully functional
light-weight implementation of our scheme on commodity access points and evaluate this extensively
via experiments in a real deployment, over a broad range of network conditions. Results demonstrate
that our proposal achieves up to 100% utility gains, can double video streaming goodput and reduces
TCP download times by 8x
Coding in 802.11 WLANs
Forward error correction (FEC) coding is widely used in communication systems to correct transmis-
sion errors. In IEEE 802.11a/g transmitters, convolutional codes are used for FEC at the physical
(PHY) layer. As is typical in wireless systems, only a limited choice of pre-speci¯ed coding rates is
supported. These are implemented in hardware and thus di±cult to change, and the coding rates are
selected with point to point operation in mind.
This thesis is concerned with using FEC coding in 802.11 WLANs in more interesting ways that are
better aligned with application requirements. For example, coding to support multicast tra±c rather
than simple point to point tra±c; coding that is cognisant of the multiuser nature of the wireless
channel; and coding which takes account of delay requirements as well as losses. We consider layering
additional coding on top of the existing 802.11 PHY layer coding, and investigate the tradeo® between
higher layer coding and PHY layer modulation and FEC coding as well as MAC layer scheduling.
Firstly we consider the joint multicast performance of higher-layer fountain coding concatenated
with 802.11a/g OFDM PHY modulation/coding. A study on the optimal choice of PHY rates with and
without fountain coding is carried out for standard 802.11 WLANs. We ¯nd that, in contrast to studies
in cellular networks, in 802.11a/g WLANs the PHY rate that optimizes uncoded multicast performance
is also close to optimal for fountain-coded multicast tra±c. This indicates that in 802.11a/g WLANs
cross-layer rate control for higher-layer fountain coding concatenated with physical layer modulation
and FEC would bring few bene¯ts.
Secondly, using experimental measurements taken in an outdoor environment, we model the chan-
nel provided by outdoor 802.11 links as a hybrid binary symmetric/packet erasure channel. This
hybrid channel o®ers capacity increases of more than 100% compared to a conventional packet erasure
channel (PEC) over a wide range of RSSIs. Based upon the established channel model, we further
consider the potential performance gains of adopting a binary symmetric channel (BSC) paradigm for
multi-destination aggregations in 802.11 WLANs. We consider two BSC-based higher-layer coding
approaches, i.e. superposition coding and a simpler time-sharing coding, for multi-destination aggre-
gated packets. The performance results for both unicast and multicast tra±c, taking account of MAC
layer overheads, demonstrate that increases in network throughput of more than 100% are possible
over a wide range of channel conditions, and that the simpler time-sharing approach yields most of
these gains and have minor loss of performance.
Finally, we consider the proportional fair allocation of high-layer coding rates and airtimes in 802.11
WLANs, taking link losses and delay constraints into account. We ¯nd that a layered approach of
separating MAC scheduling and higher-layer coding rate selection is optimal. The proportional fair
coding rate and airtime allocation (i) assigns equal total airtime (i.e. airtime including both successful
and failed transmissions) to every station in a WLAN, (ii) the station airtimes sum to unity (ensuring
operation at the rate region boundary), and (iii) the optimal coding rate is selected to maximise
goodput (treating packets decoded after the delay deadline as losses)
Large deviations for the stationary measure of networks under proportional fair allocations
We address a conjecture introduced by Massouli´e (2007), concerning the large deviations of the stationary measure of bandwidth-sharing networks functioning under the Proportional fair allocation. For Markovian networks, we prove that Proportional fair and an associated reversible allocation are geometrically ergodic and have the same large deviations characteristics using Lyapunov functions and martingale arguments. For monotone networks, we give a more direct proof of the same result relying on stochastic comparisons that hold for general service requirement distribution. These results comfort the intuition that Proportional fairness is ´close´ to allocations of service being insensitive to the service time requirement.Fil: Jonckheere, Matthieu Thimothy Samson. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "Luis A. Santaló"; Argentina. Universidad de Buenos Aires; ArgentinaFil: Lopez, S.. Universidad Nacional Autónoma de México; Méxic