1,309 research outputs found
Approaching Optimal Centralized Scheduling with CSMA-based Random Access over Fading Channels
Carrier Sense Multiple Access (CSMA) based distributed algorithms can attain
the largest capacity region as the centralized Max-Weight policy does. Despite
their capability of achieving throughput-optimality, these algorithms can
either incur large delay and have large complexity or only operate over
non-fading channels. In this letter, by assuming arbitrary back-off time we
first propose a fully distributed randomized algorithm whose performance can be
pushed to the performance of the centralized Max-Weight policy not only in
terms of throughput but also in terms of delay for completely-connected
interference networks with fading channels. Then, inspired by the proposed
algorithm we introduce an implementable distributed algorithm for practical
networks with a reservation scheme. We show that the proposed practical
algorithm can still achieve the performance of the centralized Max-Weight
policy.Comment: accepted to IEEE Communications Letter
Collision Helps - Algebraic Collision Recovery for Wireless Erasure Networks
Current medium access control mechanisms are based on collision avoidance and
collided packets are discarded. The recent work on ZigZag decoding departs from
this approach by recovering the original packets from multiple collisions. In
this paper, we present an algebraic representation of collisions which allows
us to view each collision as a linear combination of the original packets. The
transmitted, colliding packets may themselves be a coded version of the
original packets.
We propose a new acknowledgment (ACK) mechanism for collisions based on the
idea that if a set of packets collide, the receiver can afford to ACK exactly
one of them and still decode all the packets eventually. We analytically
compare delay and throughput performance of such collision recovery schemes
with other collision avoidance approaches in the context of a single hop
wireless erasure network. In the multiple receiver case, the broadcast
constraint calls for combining collision recovery methods with network coding
across packets at the sender. From the delay perspective, our scheme, without
any coordination, outperforms not only a ALOHA-type random access mechanisms,
but also centralized scheduling. For the case of streaming arrivals, we propose
a priority-based ACK mechanism and show that its stability region coincides
with the cut-set bound of the packet erasure network
Wireless Power Transfer and Data Collection in Wireless Sensor Networks
In a rechargeable wireless sensor network, the data packets are generated by
sensor nodes at a specific data rate, and transmitted to a base station.
Moreover, the base station transfers power to the nodes by using Wireless Power
Transfer (WPT) to extend their battery life. However, inadequately scheduling
WPT and data collection causes some of the nodes to drain their battery and
have their data buffer overflow, while the other nodes waste their harvested
energy, which is more than they need to transmit their packets. In this paper,
we investigate a novel optimal scheduling strategy, called EHMDP, aiming to
minimize data packet loss from a network of sensor nodes in terms of the nodes'
energy consumption and data queue state information. The scheduling problem is
first formulated by a centralized MDP model, assuming that the complete states
of each node are well known by the base station. This presents the upper bound
of the data that can be collected in a rechargeable wireless sensor network.
Next, we relax the assumption of the availability of full state information so
that the data transmission and WPT can be semi-decentralized. The simulation
results show that, in terms of network throughput and packet loss rate, the
proposed algorithm significantly improves the network performance.Comment: 30 pages, 8 figures, accepted to IEEE Transactions on Vehicular
Technolog
Centralized scheduling, routing tree in WiMAX mesh networks
In the last few years, demand for high speed internet access service has increased greatly so the IEEE 802.16 working group on broadband wireless access (BWA) is developing the worldwide interoperability for microwave access (WiMAX) standard for wireless metropolitan area networks (MANs) which aims to provide broadband wireless last mile access, easy deployment, and high speed data rate for large spanning area. This paper propose an efficient routing and collision free centralized scheduling (CS) algorithms using single channel single transceiver system in WiMAX mesh network, which introduces the cross layer concept between the network layer and media access controller (MAC) layer. The proposed approach has improved the system performance in the aspects of scheduling length, channel utilization ratio (CUR), and the throughput of the system
Towards a System Theoretic Approach to Wireless Network Capacity in Finite Time and Space
In asymptotic regimes, both in time and space (network size), the derivation
of network capacity results is grossly simplified by brushing aside queueing
behavior in non-Jackson networks. This simplifying double-limit model, however,
lends itself to conservative numerical results in finite regimes. To properly
account for queueing behavior beyond a simple calculus based on average rates,
we advocate a system theoretic methodology for the capacity problem in finite
time and space regimes. This methodology also accounts for spatial correlations
arising in networks with CSMA/CA scheduling and it delivers rigorous
closed-form capacity results in terms of probability distributions. Unlike
numerous existing asymptotic results, subject to anecdotal practical concerns,
our transient one can be used in practical settings: for example, to compute
the time scales at which multi-hop routing is more advantageous than single-hop
routing
Low-complexity medium access control protocols for QoS support in third-generation radio access networks
One approach to maximizing the efficiency of
medium access control (MAC) on the uplink in a future wideband
code-division multiple-access (WCDMA)-based third-generation
radio access network, and hence maximize spectral efficiency,
is to employ a low-complexity distributed scheduling control
approach. The maximization of spectral efficiency in third-generation
radio access networks is complicated by the need to
provide bandwidth-on-demand to diverse services characterized
by diverse quality of service (QoS) requirements in an interference
limited environment. However, the ability to exploit the full
potential of resource allocation algorithms in third-generation
radio access networks has been limited by the absence of a metric
that captures the two-dimensional radio resource requirement,
in terms of power and bandwidth, in the third-generation radio
access network environment, where different users may have
different signal-to-interference ratio requirements. This paper
presents a novel resource metric as a solution to this fundamental
problem. Also, a novel deadline-driven backoff procedure has
been presented as the backoff scheme of the proposed distributed
scheduling MAC protocols to enable the efficient support of
services with QoS imposed delay constraints without the need
for centralized scheduling. The main conclusion is that low-complexity
distributed scheduling control strategies using overload
avoidance/overload detection can be designed using the proposed
resource metric to give near optimal performance and thus maintain
a high spectral efficiency in third-generation radio access
networks and that importantly overload detection is superior to
overload avoidance
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