997 research outputs found
Improving information centrality of a node in complex networks by adding edges
The problem of increasing the centrality of a network node arises in many
practical applications. In this paper, we study the optimization problem of
maximizing the information centrality of a given node in a network
with nodes and edges, by creating new edges incident to . Since
is the reciprocal of the sum of resistance distance
between and all nodes, we alternatively consider the problem of minimizing
by adding new edges linked to . We show that the
objective function is monotone and supermodular. We provide a simple greedy
algorithm with an approximation factor and
running time. To speed up the computation, we also present an
algorithm to compute -approximate
resistance distance after iteratively adding edges, the
running time of which is for any
, where the notation suppresses the factors. We experimentally demonstrate the effectiveness and
efficiency of our proposed algorithms.Comment: 7 pages, 2 figures, ijcai-201
Energy-Efficient User Access Control and Resource Allocation in HCNs with Non-Ideal Circuitry
In this paper, we study the energy-efficient user access control (UAC) based
on resource allocation (RA) in heterogeneous cellular networks (HCNs) with the
required downlink data rate under non-ideal power amplifiers (PAs) and circuit
power. It is proved that the energy consumption minimization is achieved when
the typical user accesses only one base station (BS), while the other BSs
remain in idle mode on the transmission resource allocated to this user. For
this purpose, we reformulate the original non-convex optimization problem into
a series of convex optimization problems where, in each case, the transmit
power and duration of the accessed BS are determined. Then, the BS with the
minimal energy consumption is selected for transmission. Considering the
approximate situation, it is showed that the optimal transmit duration of the
accessed BS can be estimated in closed form. The benefits of our proposed UAC
and RA schemes are validated using numerical simulations, which also
characterize the effect that non-ideal PAs have on the total energy consumption
of different transmission schemes.Comment: 6 pages, 4 figures, 2017 9th International Conference on Wireless
Communications and Signal Processing (WCSP
Optimal Pilot Symbols Ratio in terms of Spectrum and Energy Efficiency in Uplink CoMP Networks
In wireless networks, Spectrum Efficiency (SE) and Energy Efficiency (EE) can
be affected by the channel estimation that needs to be well designed in
practice. In this paper, considering channel estimation error and non-ideal
backhaul links, we optimize the pilot symbols ratio in terms of SE and EE in
uplink Coordinated Multi-point (CoMP) networks. Modeling the channel estimation
error, we formulate the SE and EE maximization problems by analyzing the system
capacity with imperfect channel estimation. The maximal system capacity in SE
optimization and the minimal transmit power in EE optimization, which both have
the closed-form expressions, are derived by some reasonable approximations to
reduce the complexity of solving complicated equations. Simulations are carried
out to validate the superiority of our scheme, verify the accuracy of our
approximation, and show the effect of pilot symbols ratio.Comment: 5 pages, 3 figures, 2017 IEEE 85th Vehicular Technology Conference
(VTC Spring
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