234 research outputs found
Reinforcement-based data transmission in temporally-correlated fading channels: Partial CSIT scenario
Reinforcement algorithms refer to the schemes where the results of the
previous trials and a reward-punishment rule are used for parameter setting in
the next steps. In this paper, we use the concept of reinforcement algorithms
to develop different data transmission models in wireless networks. Considering
temporally-correlated fading channels, the results are presented for the cases
with partial channel state information at the transmitter (CSIT). As
demonstrated, the implementation of reinforcement algorithms improves the
performance of communication setups remarkably, with the same feedback
load/complexity as in the state-of-the-art schemes.Comment: Accepted for publication in ISWCS 201
Cooperative Spectrum Sensing in Cognitive Radio Networks Using Multidimensional Correlations
In this paper, a multidimensional-correlation-based sensing scheduling algorithm, (CORN)2, is developed for cognitive radio networks to minimize energy consumption. A sensing quality metric is defined as a measure of the correctness of spectral availability information based on the fact that spectrum sensing information at a given space and time can represent spectrum information at a different point in space and time. The scheduling algorithm is shown to achieve a cost of sensing (e.g., energy consumption, sensing duration) arbitrarily close to the possible minimum, while meeting the sensing quality requirements. To this end, (CORN)2 utilizes a novel sensing deficiency virtual queue concept and exploits the correlation between spectrum measurements of a particular secondary user and its collaborating neighbors. The proposed algorithm is proved to achieve a distributed and arbitrarily close to optimal solution under certain, easily satisfied assumptions. Furthermore, a distributed Selective-(CORN)2 (S-(CORN)2) is introduced by extending the distributed algorithm to allow secondary users to select collaboration neighbors in densely populated cognitive radio networks. In addition to the theoretically proved performance guarantees, the algorithms are evaluated through simulations
Cooperative Spectrum Sensing in Cognitive Radio Networks Using Multidimensional Correlations
In this paper, a multidimensional-correlation-based sensing scheduling algorithm, (CORN)2, is developed for cognitive radio networks to minimize energy consumption. A sensing quality metric is defined as a measure of the correctness of spectral availability information based on the fact that spectrum sensing information at a given space and time can represent spectrum information at a different point in space and time. The scheduling algorithm is shown to achieve a cost of sensing (e.g., energy consumption, sensing duration) arbitrarily close to the possible minimum, while meeting the sensing quality requirements. To this end, (CORN)2 utilizes a novel sensing deficiency virtual queue concept and exploits the correlation between spectrum measurements of a particular secondary user and its collaborating neighbors. The proposed algorithm is proved to achieve a distributed and arbitrarily close to optimal solution under certain, easily satisfied assumptions. Furthermore, a distributed Selective-(CORN)2 (S-(CORN)2) is introduced by extending the distributed algorithm to allow secondary users to select collaboration neighbors in densely populated cognitive radio networks. In addition to the theoretically proved performance guarantees, the algorithms are evaluated through simulations
Flexible application driven network striping over Wireless Wide Area Networks
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.Includes bibliographical references (p. 157-161).Inverse multiplexing, or network striping, allows the construction of a high-bandwidth virtual channel from a collection of multiple low-bandwidth network channels. Striping systems usually employ a packet scheduling policy that allows applications to be oblivious of the way in which packets are routed to specific network channels. Though this is appropriate for many applications, many other applications can benefit from an approach that explicitly involves the application in the determination of the striping policy. Horde is middleware that facilitates flexible striping over Wireless Wide Area Network (WWAN) channels. Horde is unusual in that it separates the striping policy from the striping mechanism. It allows applications to describe network Quality-of-Service (QoS) objectives that the striping mechanism attempts to satisfy. Horde can be used by a set of data streams, each with its own QoS policy, to stripe data over a set of WWAN channels. The WWAN QoS variations observed across different channels and in time, provide opportunities to modulate stream QoS through scheduling. The key technical challenge in Horde is giving applications control over certain aspects of the data striping operation while at the same time shielding the application from low-level details. Horde exports a set of flexible abstractions replacing the application's network stack. Horde allows applications to express their policy goals as succinct network-QoS objectives. Each objective says something, relatively simple, about the sort of network QoS an application would like for some data stream(s). We present the Horde architecture, describe an early implementation, and examine how different policies can be used to modulate the quality-of-service observed across different independent data streams. Through experiments conducted on real and simulated network channels, we confirm our belief that the kind of QoS modulation Horde aims to achieve is realistic for actual applications.by Asfandyar Qureshi.M.Eng
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
Optimizing Age of Information with Correlated Sources
We develop a simple model for the timely monitoring of correlated sources
over a wireless network. Using this model, we study how to optimize
weighted-sum average Age of Information (AoI) in the presence of correlation.
First, we discuss how to find optimal stationary randomized policies and show
that they are at-most a factor of two away from optimal policies in general.
Then, we develop a Lyapunov drift-based max-weight policy that performs better
than randomized policies in practice and show that it is also at-most a factor
of two away from optimal. Next, we derive scaling results that show how AoI
improves in large networks in the presence of correlation. We also show that
for stationary randomized policies, the expression for average AoI is robust to
the way in which the correlation structure is modeled. Finally, for the setting
where correlation parameters are unknown and time-varying, we develop a
heuristic policy that adapts its scheduling decisions by learning the
correlation parameters in an online manner. We also provide numerical
simulations to support our theoretical results.Comment: To be presented at ACM MobiHoc 202
IST-2000-30148 I-METRA: D4 Performance evaluation
This document considers the performance of multiantenna transmit/receive techniques in high-speed downlink and uplink packet access. The evaluation is done using both link and system level simulations by taking into account link adaptation and packet retransmissions. The document is based on the initial studies carried out in deliverables D3.1 and D3.2.Preprin
Quantum computer error structure probed by quantum error correction syndrome measurements
With quantum devices rapidly approaching qualities and scales needed for
fault tolerance, the validity of simplified error models underpinning the study
of quantum error correction needs to be experimentally evaluated. In this work,
we have directly assessed the performance of superconducting devices
implementing heavy-hexagon code syndrome measurements with increasing circuit
sizes up to 23 qubits, against the error assumptions underpinning code
threshold calculations. Data from 16 repeated syndrome measurement cycles was
found to be inconsistent with a uniform depolarizing noise model, favouring
instead biased and inhomogeneous noise models. Spatial-temporal correlations
investigated via stabilizer measurements revealed significant temporal
correlation in detection events. These results highlight the non-trivial
structure which may be present in the noise of quantum error correction
circuits and support the development of noise-tailored codes and decoders to
adapt
Interference mitigation using group decoding in multiantenna systems
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