41,301 research outputs found
Two-Hop Connectivity to the Roadside in a VANET Under the Random Connection Model
We compute the expected number of cars that have at least one two-hop path to
a fixed roadside unit in a one-dimensional vehicular ad hoc network in which
other cars can be used as relays to reach a roadside unit when they do not have
a reliable direct link. The pairwise channels between cars experience Rayleigh
fading in the random connection model, and so exist, with probability function
of the mutual distance between the cars, or between the cars and the roadside
unit. We derive exact equivalents for this expected number of cars when the car
density tends to zero and to infinity, and determine its behaviour using
an infinite oscillating power series in , which is accurate for all
regimes. We also corroborate those findings to a realistic situation, using
snapshots of actual traffic data. Finally, a normal approximation is discussed
for the probability mass function of the number of cars with a two-hop
connection to the origin. The probability mass function appears to be well
fitted by a Gaussian approximation with mean equal to the expected number of
cars with two hops to the origin.Comment: 21 pages, 7 figure
Large-scale Join-Idle-Queue system with general service times
A parallel server system with identical servers is considered. The
service time distribution has a finite mean , but otherwise is
arbitrary. Arriving customers are be routed to one of the servers immediately
upon arrival. Join-Idle-Queue routing algorithm is studied, under which an
arriving customer is sent to an idle server, if such is available, and to a
randomly uniformly chosen server, otherwise. We consider the asymptotic regime
where and the customer input flow rate is . Under the
condition , we prove that, as , the sequence of
(appropriately scaled) stationary distributions concentrates at the natural
equilibrium point, with the fraction of occupied servers being constant equal
. In particular, this implies that the steady-state probability of
an arriving customer waiting for service vanishes.Comment: Revision. 11 page
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