Abstract: In this paper, we study the data collection problem in
Wireless Sensor Networks (WSNs) adopting the two interference
models: The graph model and the more realistic physical interference
model known as Signal-to-Interference-Noise-Ratio (SINR). The
main issue of the problem is to compute schedules with the minimum
number of timeslots, that is, to compute the minimum latency
schedules, such that data from every node can be collected without
any collision or interference to a sink node. While existing works
studied the problem with unit-sized and unbounded-sized message
models, we investigate the problem with the bounded-sized message
model, and introduce a constant factor approximation algorithm.
To the best known of our knowledge, our result is the first result
of the data collection problem with bounded-sized model in both
interference models.
Abstract: Femtocells are regarded as a milestone for next
generation cellular networks. As femtocells are deployed in an
unplanned manner, there is a chance of assigning same resource to
neighboring femtocells. This scenario may induce co-channel
interference and may seriously affect the service quality of
neighboring femtocells. In addition, the dominant transmit power of a
femtocell will induce co-tier interference to neighboring femtocells.
Thus to jointly handle co-tier and co-channel interference, we
propose an interference-free power and resource block allocation
(IFPRBA) algorithm for closely located, closed access femtocells.
Based on neighboring list, inter-femto-base station distance and
uplink noise power, the IFPRBA algorithm assigns non-interfering
power and resource to femtocells. The IFPRBA algorithm also
guarantees the quality of service to femtouser based on the
knowledge of resource requirement, connection type, and the
tolerable delay budget. Simulation result shows that the interference
power experienced in IFPRBA algorithm is below the tolerable
interference power and hence the overall service success ratio, PRB
efficiency and network throughput are maximum when compared to
conventional resource allocation framework for femtocell (RAFF)
algorithm.
Abstract: Because support interference corrections are not properly
understood, engineers mostly rely on expensive dummy measurements
or CFD calculations. This paper presents a method based on uncorrected wind tunnel measurements and fast calculation techniques
(it is a hybrid method) to calculate wall interference, support interference and residual interference (when e.g. a support member
closely approaches the wind tunnel walls) for any type of wind tunnel and support configuration. The method provides with a simple formula
for the calculation of the interference gradient. This gradient is
based on the uncorrected measurements and a successive calculation
of the slopes of the interference-free aerodynamic coefficients. For the latter purpose a new vortex-lattice routine is developed that corrects
the slopes for viscous effects. A test case of a measurement on a wing proves the value of this hybrid method as trends and orders of
magnitudes of the interference are correctly determined.