Xiaodong Wang
Cooperative Sequential Spectrum Sensing Based on Level-triggered Sampling.
Wed, 11/23/2011 - 15:01 — SomNambulAuthors: Xiaodong Wang, Yasin Yilmaz, George Moustakides
Subjects: Applications
AbstractWe propose a new framework for cooperative spectrum sensing in cognitive
radio networks, that is based on a novel class of non-uniform samplers, called
the event-triggered samplers, and sequential detection. In the proposed scheme,
each secondary user computes its local sensing decision statistic based on its
own channel output; and whenever such decision statistic crosses certain
predefined threshold values, the secondary user will send one (or several) bit
of information to the fusion center.Joint Detection and Estimation: Optimum Tests and Applications.
Thu, 01/27/2011 - 16:01 — SomNambulAuthors: George V. Moustakides, Xiaodong Wang, Ali Tajer, Guido H. Jajamovich
Subjects: Applications
AbstractWe consider a well defined joint detection and parameter estimation problem.
By combining the Baysian formulation of the estimation subproblem with suitable
constraints on the detection subproblem we develop optimum one- and two-step
test for the joint detection/estimation case. The proposed combined strategies
have the very desirable characteristic to allow for the trade-off between
detection power and estimation efficiency. Our theoretical developments are
then applied to the problems of retrospective changepoint detection and MIMO
radar.Superimposed XOR: Approaching Capacity Bounds of the Two-Way Relay Channels.
Thu, 08/05/2010 - 15:01 — SomNambulAuthors: Xiaodong Wang, Meixia Tao, Jianquan Liu, Youyun Xu
Subjects: Information Theory
AbstractIn two-way relay channels, bitwise XOR and symbol-level superposition coding
are two popular network-coding based relaying schemes. However, neither of them
can approach the capacity bound when the channels in the broadcast phase are
asymmetric. In this paper, we present a new physical layer network coding
(PLNC) scheme, called \emph{superimposed XOR}. The new scheme advances the
existing schemes by specifically taking into account the channel asymmetry as
well as information asymmetry in the broadcast phase.Multiuser Diversity Gain in Cognitive Networks.
Mon, 04/05/2010 - 15:01 — SomNambulAuthors: Xiaodong Wang, Ali Tajer
Subjects: Information Theory
AbstractDynamic allocation of resources to the \emph{best} link in large multiuser
networks offers considerable improvement in spectral efficiency. This gain,
often referred to as \emph{multiuser diversity gain}, can be cast as
double-logarithmic growth of the network throughput with the number of users.
In this paper we consider large cognitive networks granted concurrent spectrum
access with license-holding users. The primary network affords to share its
under-utilized spectrum bands with the secondary users.Rigidity Theorems for Compact Manifolds with Boundary and Positive Ricci Curvature.
Tue, 11/03/2009 - 16:01 — SomNambulAuthors: Xiaodong Wang, Fengbo Hang
Subjects: Differential Geometry
AbstractWe prove some boundary rigidity results for the hemisphere under a lower
bound for Ricci curvature. The main result can be viewed as the Ricci version
of a conjecture of Min-Oo.Boundary effect on compact manifolds with nonnegative scalar curvature--a generalization of a theorem of Shi and Tam.
Tue, 11/03/2009 - 16:01 — SomNambulAuthors: Xiaodong Wang
Subjects: Differential Geometry
AbstractWe generalize a theorem of Shi and Tam on the boundary effect of nonnegative
scalar curvature on compact manifolds with boundary.An integral formula for the volume entropy with an application to rigidity.
Tue, 11/03/2009 - 16:01 — SomNambulAuthors: Francois Ledrappier, Xiaodong Wang
Subjects: Differential Geometry
AbstractWe extend the theory of Patterson-Sullivan measure to any regular covering of
a compact manifold using the Busemann compactification and derive an integral
formula for the volume entropy. As an application we prove a rigidity theorem
for the volume entropy
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