2,294 research outputs found
A Fast-CSMA Algorithm for Deadline-Constrained Scheduling over Wireless Fading Channels
Recently, low-complexity and distributed Carrier Sense Multiple Access
(CSMA)-based scheduling algorithms have attracted extensive interest due to
their throughput-optimal characteristics in general network topologies.
However, these algorithms are not well-suited for serving real-time traffic
under time-varying channel conditions for two reasons: (1) the mixing time of
the underlying CSMA Markov Chain grows with the size of the network, which, for
large networks, generates unacceptable delay for deadline-constrained traffic;
(2) since the dynamic CSMA parameters are influenced by the arrival and channel
state processes, the underlying CSMA Markov Chain may not converge to a
steady-state under strict deadline constraints and fading channel conditions.
In this paper, we attack the problem of distributed scheduling for serving
real-time traffic over time-varying channels. Specifically, we consider
fully-connected topologies with independently fading channels (which can model
cellular networks) in which flows with short-term deadline constraints and
long-term drop rate requirements are served. To that end, we first characterize
the maximal set of satisfiable arrival processes for this system and, then,
propose a Fast-CSMA (FCSMA) policy that is shown to be optimal in supporting
any real-time traffic that is within the maximal satisfiable set. These
theoretical results are further validated through simulations to demonstrate
the relative efficiency of the FCSMA policy compared to some of the existing
CSMA-based algorithms.Comment: This work appears in workshop on Resource Allocation and Cooperation
in Wireless Networks (RAWNET), Princeton, NJ, May, 201
Wireless industrial monitoring and control networks: the journey so far and the road ahead
While traditional wired communication technologies have played a crucial role in industrial monitoring and control networks over the past few decades, they are increasingly proving to be inadequate to meet the highly dynamic and stringent demands of today’s industrial applications, primarily due to the very rigid nature of wired infrastructures. Wireless technology, however, through its increased pervasiveness, has the potential to revolutionize the industry, not only by mitigating the problems faced by wired solutions, but also by introducing a completely new class of applications. While present day wireless technologies made some preliminary inroads in the monitoring domain, they still have severe limitations especially when real-time, reliable distributed control operations are concerned. This article provides the reader with an overview of existing wireless technologies commonly used in the monitoring and control industry. It highlights the pros and cons of each technology and assesses the degree to which each technology is able to meet the stringent demands of industrial monitoring and control networks. Additionally, it summarizes mechanisms proposed by academia, especially serving critical applications by addressing the real-time and reliability requirements of industrial process automation. The article also describes certain key research problems from the physical layer communication for sensor networks and the wireless networking perspective that have yet to be addressed to allow the successful use of wireless technologies in industrial monitoring and control networks
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