52 research outputs found
Stability and Distributed Power Control in MANETs with Outages and Retransmissions
In the current work the effects of hop-by-hop packet loss and retransmissions
via ARQ protocols are investigated within a Mobile Ad-hoc NET-work (MANET).
Errors occur due to outages and a success probability function is related to
each link, which can be controlled by power and rate allocation. We first
derive the expression for the network's capacity region, where the success
function plays a critical role. Properties of the latter as well as the related
maximum goodput function are presented and proved. A Network Utility
Maximization problem (NUM) with stability constraints is further formulated
which decomposes into (a) the input rate control problem and (b) the scheduling
problem. Under certain assumptions problem (b) is relaxed to a weighted sum
maximization problem with number of summants equal to the number of nodes. This
further allows the formulation of a non-cooperative game where each node
decides independently over its transmitting power through a chosen link. Use of
supermodular game theory suggests a price based algorithm that converges to a
power allocation satisfying the necessary optimality conditions of (b).
Implementation issues are considered so that minimum information exchange
between interfering nodes is required. Simulations illustrate that the
suggested algorithm brings near optimal results.Comment: 25 pages, 6 figures, 1 table, submitted to the IEEE Trans. on
Communication
Optimal Geographic Caching In Cellular Networks
In this work we consider the problem of an optimal geographic placement of
content in wireless cellular networks modelled by Poisson point processes.
Specifically, for the typical user requesting some particular content and whose
popularity follows a given law (e.g. Zipf), we calculate the probability of
finding the content cached in one of the base stations. Wireless coverage
follows the usual signal-to-interference-and noise ratio (SINR) model, or some
variants of it. We formulate and solve the problem of an optimal randomized
content placement policy, to maximize the user's hit probability. The result
dictates that it is not always optimal to follow the standard policy "cache the
most popular content, everywhere". In fact, our numerical results regarding
three different coverage scenarios, show that the optimal policy significantly
increases the chances of hit under high-coverage regime, i.e., when the
probabilities of coverage by more than just one station are high enough.Comment: 6 pages, 6 figures, conferenc
Optimal Control of a Single Queue with Retransmissions: Delay-Dropping Tradeoffs
A single queue incorporating a retransmission protocol is investigated,
assuming that the sequence of per effort success probabilities in the Automatic
Retransmission reQuest (ARQ) chain is a priori defined and no channel state
information at the transmitter is available. A Markov Decision Problem with an
average cost criterion is formulated where the possible actions are to either
continue the retransmission process of an erroneous packet at the next time
slot or to drop the packet and move on to the next packet awaiting for
transmission. The cost per slot is a linear combination of the current queue
length and a penalty term in case dropping is chosen as action. The
investigation seeks policies that provide the best possible average packet
delay-dropping trade-off for Quality of Service guarantees. An optimal
deterministic stationary policy is shown to exist, several structural
properties of which are obtained. Based on that, a class of suboptimal
-policies is introduced. These suggest that it is almost optimal to use a
K-truncated ARQ protocol as long as the queue length is lower than L, else send
all packets in one shot. The work concludes with an evaluation of the optimal
delay-dropping tradeoff using dynamic programming and a comparison between the
optimal and suboptimal policies.Comment: 29 pages, 8 figures, submitted to IEEE Transactions on Wireless
Communication
Performance Analysis of Online Social Platforms
We introduce an original mathematical model to analyze the diffusion of posts
within a generic online social platform. Each user of such a platform has his
own Wall and Newsfeed, as well as his own self-posting and re-posting activity.
As a main result, using our developed model, we derive in closed form the
probabilities that posts originating from a given user are found on the Wall
and Newsfeed of any other. These probabilities are the solution of a linear
system of equations. Conditions of existence of the solution are provided, and
two ways of solving the system are proposed, one using matrix inversion and
another using fixed-point iteration. Comparisons with simulations show the
accuracy of our model and its robustness with respect to the modeling
assumptions. Hence, this article introduces a novel measure which allows to
rank users by their influence on the social platform, by taking into account
not only the social graph structure, but also the platform design, user
activity (self- and re-posting), as well as competition among posts.Comment: Preliminary version of accepted paper at INFOCOM 2019 (Paris, France
Analyzing Interference from Static Cellular Cooperation using the Nearest Neighbour Model
The problem of base station cooperation has recently been set within the
framework of Stochastic Geometry. Existing works consider that a user
dynamically chooses the set of stations that cooperate for his/her service.
However, this assumption often does not hold. Cooperation groups could be
predefined and static, with nodes connected by fixed infrastructure. To analyse
such a potential network, in this work we propose a grouping method based on
proximity. It is a variation of the so called Nearest Neighbour Model. We
restrict ourselves to the simplest case where only singles and pairs of base
stations are allowed to be formed. For this, two new point processes are
defined from the dependent thinning of a Poisson Point Process, one for the
singles and one for the pairs. Structural characteristics for the two are
provided, including their density, Voronoi surface, nearest neighbour, empty
space and J-function. We further make use of these results to analyse their
interference fields and give explicit formulas to their expected value and
their Laplace transform. The results constitute a novel toolbox towards the
performance evaluation of networks with static cooperation.Comment: 10 pages, 6 figures, 12 total subfigures, WIOPT-SPASWIN 201
Analysis of Static Cellular Cooperation between Mutually Nearest Neighboring Nodes
Cooperation in cellular networks is a promising scheme to improve system
performance. Existing works consider that a user dynamically chooses the
stations that cooperate for his/her service, but such assumption often has
practical limitations. Instead, cooperation groups can be predefined and
static, with nodes linked by fixed infrastructure. To analyze such a potential
network, we propose a grouping method based on node proximity. With the
Mutually Nearest Neighbour Relation, we allow the formation of singles and
pairs of nodes. Given an initial topology for the stations, two new point
processes are defined, one for the singles and one for the pairs. We derive
structural characteristics for these processes and analyse the resulting
interference fields. When the node positions follow a Poisson Point Process
(PPP) the processes of singles and pairs are not Poisson. However, the
performance of the original model can be approximated by the superposition of
two PPPs. This allows the derivation of exact expressions for the coverage
probability. Numerical evaluation shows coverage gains from different signal
cooperation that can reach up to 15% compared to the standard noncooperative
coverage. The analysis is general and can be applied to any type of cooperation
in pairs of transmitting nodes.Comment: 17 pages, double column, Appendices A-D, 9 Figures, 18 total
subfigures. arXiv admin note: text overlap with arXiv:1604.0464
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