48,248 research outputs found
Applications of Geometric Algorithms to Reduce Interference in Wireless Mesh Network
In wireless mesh networks such as WLAN (IEEE 802.11s) or WMAN (IEEE 802.11),
each node should help to relay packets of neighboring nodes toward gateway
using multi-hop routing mechanisms. Wireless mesh networks usually intensively
deploy mesh nodes to deal with the problem of dead spot communication. However,
the higher density of nodes deployed, the higher radio interference occurred.
This causes significant degradation of system performance. In this paper, we
first convert network problems into geometry problems in graph theory, and then
solve the interference problem by geometric algorithms. We first define line
intersection in a graph to reflect radio interference problem in a wireless
mesh network. We then use plan sweep algorithm to find intersection lines, if
any; employ Voronoi diagram algorithm to delimit the regions among nodes; use
Delaunay Triangulation algorithm to reconstruct the graph in order to minimize
the interference among nodes. Finally, we use standard deviation to prune off
those longer links (higher interference links) to have a further enhancement.
The proposed hybrid solution is proved to be able to significantly reduce
interference in a wireless mesh network in O(n log n) time complexity.Comment: 24 Pages, JGraph-Hoc Journal 201
Frequency reassignment in cellular phone networks
In cellular communications networks, cells use beacon frequencies to ensure the smooth operation of the network, for example in handling call handovers from one cell to another. These frequencies are assigned according to a frequency plan, which is updated from time to time, in response to evolving network requirements. The migration from one frequency plan to a new one proceeds in stages, governed by the network's base station controllers. Existing methods result in periods of reduced network availability or performance during the reassgnment process.
The problem posed to the Study Group was to develop a dynamic reassignment algorithm for implementing a new frequency plan so that there is little or no disruption of the network's performance during the transition. This problem was naturally formulated in terms of graph colouring and an effective algorithm was developed based on a straightforward approach of search and random colouring
Asymptotic Close To Optimal Joint Resource Allocation and Power Control in the Uplink of Two-cell Networks
In this paper, we investigate joint resource allocation and power control
mechanisms for two-cell networks, where each cell has some sub-channels which
should be allocated to some users. The main goal persuaded in the current work
is finding the best power and sub-channel assignment strategies so that the
associated sum-rate of network is maximized, while a minimum rate constraint is
maintained by each user. The underlying optimization problem is a highly
non-convex mixed integer and non-linear problem which does not yield a trivial
solution. In this regard, to tackle the problem, using an approximate function
which is quite tight at moderate to high signal to interference plus noise
ratio (SINR) region, the problem is divided into two disjoint sub-channel
assignment and power allocation problems. It is shown that having fixed the
allocated power of each user, the subchannel assignment can be thought as a
well-known assignment problem which can be effectively solved using the
so-called Hungarian method. Then, the power allocation is analytically derived.
Furthermore, it is shown that the power can be chosen from two extremal points
of the maximum available power or the minimum power satisfying the rate
constraint. Numerical results demonstrate the superiority of the proposed
approach over the random selection strategy as well as the method proposed in
[3] which is regarded as the best known method addressed in the literature
A Constant-Factor Approximation for Wireless Capacity Maximization with Power Control in the SINR Model
In modern wireless networks, devices are able to set the power for each
transmission carried out. Experimental but also theoretical results indicate
that such power control can improve the network capacity significantly. We
study this problem in the physical interference model using SINR constraints.
In the SINR capacity maximization problem, we are given n pairs of senders
and receivers, located in a metric space (usually a so-called fading metric).
The algorithm shall select a subset of these pairs and choose a power level for
each of them with the objective of maximizing the number of simultaneous
communications. This is, the selected pairs have to satisfy the SINR
constraints with respect to the chosen powers.
We present the first algorithm achieving a constant-factor approximation in
fading metrics. The best previous results depend on further network parameters
such as the ratio of the maximum and the minimum distance between a sender and
its receiver. Expressed only in terms of n, they are (trivial) Omega(n)
approximations.
Our algorithm still achieves an O(log n) approximation if we only assume to
have a general metric space rather than a fading metric. Furthermore, by using
standard techniques the algorithm can also be used in single-hop and multi-hop
scheduling scenarios. Here, we also get polylog(n) approximations.Comment: 17 page
Multi-Granular Optical Cross-Connect: Design, Analysis, and Demonstration
A fundamental issue in all-optical switching is to offer efficient and cost-effective transport services for a wide range of bandwidth granularities. This paper presents multi-granular optical cross-connect (MG-OXC) architectures that combine slow (ms regime) and fast (ns regime) switch elements, in order to support optical circuit switching (OCS), optical burst switching (OBS), and even optical packet switching (OPS). The MG-OXC architectures are designed to provide a cost-effective approach, while offering the flexibility and reconfigurability to deal with dynamic requirements of different applications. All proposed MG-OXC designs are analyzed and compared in terms of dimensionality, flexibility/reconfigurability, and scalability. Furthermore, node level simulations are conducted to evaluate the performance of MG-OXCs under different traffic regimes. Finally, the feasibility of the proposed architectures is demonstrated on an application-aware, multi-bit-rate (10 and 40 Gbps), end-to-end OBS testbed
Reconstruction and Selection of Single Top + Higgs to events at CMS in pp Collisions at = 13 TeV
The associated production of a single top quark together with a Higgs boson
at the LHC can be used to lift the degeneracy regarding the sign of the top
quark Yukawa coupling. Therefore, t-channel and tW-channel production where the
Higgs boson is decaying into a pair is
inspected. Boosted decision trees are used to assign jets to the quarks in the
final state and classify the events. To maximize the separation between the
signal and the dominating background each
event is reconstructed under a signal and a
hypothesis. The poster focuses on the event selection and the reconstruction of
events.Comment: Proceeding Top 201
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