5,621 research outputs found
Robust Cooperative Spectrum Sensing Scheduling Optimization in Multi-Channel Dynamic Spectrum Access Networks
Dynamic spectrum access (DSA) enables secondary networks to find and
efficiently exploit spectrum opportunities. A key factor to design a DSA
network is the spectrum sensing algorithms for multiple channels with multiple
users. Multi-user cooperative channel sensing reduces the sensing time, and
thus it increases transmission throughput. However, in a multi-channel system,
the problem becomes more complex since the benefits of assigning users to sense
channels in parallel must also be considered. A sensing schedule, indicating to
each user the channel that it should sense at different sensing moments, must
be thus created to optimize system performance. In this paper, we formulate the
general sensing scheduling optimization problem and then propose several
sensing strategies to schedule the users according to network parameters with
homogeneous sensors. Later on we extend the results to heterogeneous sensors
and propose a robust scheduling design when we have traffic and channel
uncertainty. We propose three sensing strategies, and, within each one of them,
several solutions, striking a balance between throughput performance and
computational complexity, are proposed. In addition, we show that a sequential
channel sensing strategy is the one to be preferred when the sensing time is
small, the number of channels is large, and the number of users is small. For
all the other cases, a parallel channel sensing strategy is recommended in
terms of throughput performance. We also show that a proposed hybrid
sequential-parallel channel sensing strategy achieves the best performance in
all scenarios at the cost of extra memory and computation complexity
Markov Decision Processes with Applications in Wireless Sensor Networks: A Survey
Wireless sensor networks (WSNs) consist of autonomous and resource-limited
devices. The devices cooperate to monitor one or more physical phenomena within
an area of interest. WSNs operate as stochastic systems because of randomness
in the monitored environments. For long service time and low maintenance cost,
WSNs require adaptive and robust methods to address data exchange, topology
formulation, resource and power optimization, sensing coverage and object
detection, and security challenges. In these problems, sensor nodes are to make
optimized decisions from a set of accessible strategies to achieve design
goals. This survey reviews numerous applications of the Markov decision process
(MDP) framework, a powerful decision-making tool to develop adaptive algorithms
and protocols for WSNs. Furthermore, various solution methods are discussed and
compared to serve as a guide for using MDPs in WSNs
Green Cellular Networks: A Survey, Some Research Issues and Challenges
Energy efficiency in cellular networks is a growing concern for cellular
operators to not only maintain profitability, but also to reduce the overall
environment effects. This emerging trend of achieving energy efficiency in
cellular networks is motivating the standardization authorities and network
operators to continuously explore future technologies in order to bring
improvements in the entire network infrastructure. In this article, we present
a brief survey of methods to improve the power efficiency of cellular networks,
explore some research issues and challenges and suggest some techniques to
enable an energy efficient or "green" cellular network. Since base stations
consume a maximum portion of the total energy used in a cellular system, we
will first provide a comprehensive survey on techniques to obtain energy
savings in base stations. Next, we discuss how heterogeneous network deployment
based on micro, pico and femto-cells can be used to achieve this goal. Since
cognitive radio and cooperative relaying are undisputed future technologies in
this regard, we propose a research vision to make these technologies more
energy efficient. Lastly, we explore some broader perspectives in realizing a
"green" cellular network technologyComment: 16 pages, 5 figures, 2 table
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