2,058 research outputs found
A Relay Can Increase Degrees of Freedom in Bursty Interference Networks
We investigate the benefits of relays in multi-user wireless networks with
bursty user traffic, where intermittent data traffic restricts the users to
bursty transmissions. To this end, we study a two-user bursty MIMO Gaussian
interference channel with a relay, where two Bernoulli random states govern the
bursty user traffic. We show that an in-band relay can provide a degrees of
freedom (DoF) gain in this bursty channel. This beneficial role of in-band
relays in the bursty channel is in direct contrast to their role in the
non-bursty channel which is not as significant to provide a DoF gain. More
importantly, we demonstrate that for certain antenna configurations, an in-band
relay can help achieve interference-free performances with increased DoF. We
find the benefits particularly substantial with low data traffic, as the DoF
gain can grow linearly with the number of antennas at the relay. In this work,
we first derive an outer bound from which we obtain a necessary condition for
interference-free DoF performances. Then, we develop a novel scheme that
exploits information of the bursty traffic states to achieve them.Comment: submitted to the IEEE Transactions on Information Theor
Channel-Aware Random Access in the Presence of Channel Estimation Errors
In this work, we consider the random access of nodes adapting their
transmission probability based on the local channel state information (CSI) in
a decentralized manner, which is called CARA. The CSI is not directly available
to each node but estimated with some errors in our scenario. Thus, the impact
of imperfect CSI on the performance of CARA is our main concern. Specifically,
an exact stability analysis is carried out when a pair of bursty sources are
competing for a common receiver and, thereby, have interdependent services. The
analysis also takes into account the compound effects of the multipacket
reception (MPR) capability at the receiver. The contributions in this paper are
twofold: first, we obtain the exact stability region of CARA in the presence of
channel estimation errors; such an assessment is necessary as the errors in
channel estimation are inevitable in the practical situation. Secondly, we
compare the performance of CARA to that achieved by the class of stationary
scheduling policies that make decisions in a centralized manner based on the
CSI feedback. It is shown that the stability region of CARA is not necessarily
a subset of that of centralized schedulers as the MPR capability improves.Comment: The material in this paper was presented in part at the IEEE
International Symposium on Information Theory, Cambridge, MA, USA, July 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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