2,308 research outputs found
Interference and Deployment Issues for Cognitive Radio Systems in Shadowing Environments
In this paper we describe a model for calculating the aggregate interference
encountered by primary receivers in the presence of randomly placed cognitive
radios (CRs). We show that incorporating the impact of distance attenuation and
lognormal fading on each constituent interferer in the aggregate, leads to a
composite interference that cannot be satisfactorily modeled by a lognormal.
Using the interference statistics we determine a number of key parameters
needed for the deployment of CRs. Examples of these are the exclusion zone
radius, needed to protect the primary receiver under different types of fading
environments and acceptable interference levels, and the numbers of CRs that
can be deployed. We further show that if the CRs have apriori knowledge of the
radio environment map (REM), then a much larger number of CRs can be deployed
especially in a high density environment. Given REM information, we also look
at the CR numbers achieved by two different types of techniques to process the
scheduling information.Comment: to be presented at IEEE ICC 2009. This posting is the same as the
original one. Only author's list is updated that was unfortunately not
correctly mentioned in first versio
On the Statistics of Cognitive Radio Capacity in Shadowing and Fast Fading Environments (Journal Version)
In this paper we consider the capacity of the cognitive radio channel in
different fading environments under a low interference regime. First we derive
the probability that the low interference regime holds under shadow fading as
well as Rayleigh and Rician fast fading conditions. We demonstrate that this is
the dominant case, especially in practical cognitive radio deployment
scenarios. The capacity of the cognitive radio channel depends critically on a
power loss parameter, , which governs how much transmit power the
cognitive radio dedicates to relaying the primary message. We derive a simple,
accurate approximation to in Rayleigh and Rician fading environments
which gives considerable insight into system capacity. We also investigate the
effects of system parameters and propagation environment on and the
cognitive radio capacity. In all cases, the use of the approximation is shown
to be extremely accurate.Comment: Submitted to the IEEE Transactions on Wireless Commun. The conference
version of this paper appears in Proc. IEEE CrownCom, 200
Robotic Wireless Sensor Networks
In this chapter, we present a literature survey of an emerging, cutting-edge,
and multi-disciplinary field of research at the intersection of Robotics and
Wireless Sensor Networks (WSN) which we refer to as Robotic Wireless Sensor
Networks (RWSN). We define a RWSN as an autonomous networked multi-robot system
that aims to achieve certain sensing goals while meeting and maintaining
certain communication performance requirements, through cooperative control,
learning and adaptation. While both of the component areas, i.e., Robotics and
WSN, are very well-known and well-explored, there exist a whole set of new
opportunities and research directions at the intersection of these two fields
which are relatively or even completely unexplored. One such example would be
the use of a set of robotic routers to set up a temporary communication path
between a sender and a receiver that uses the controlled mobility to the
advantage of packet routing. We find that there exist only a limited number of
articles to be directly categorized as RWSN related works whereas there exist a
range of articles in the robotics and the WSN literature that are also relevant
to this new field of research. To connect the dots, we first identify the core
problems and research trends related to RWSN such as connectivity,
localization, routing, and robust flow of information. Next, we classify the
existing research on RWSN as well as the relevant state-of-the-arts from
robotics and WSN community according to the problems and trends identified in
the first step. Lastly, we analyze what is missing in the existing literature,
and identify topics that require more research attention in the future
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