3,271 research outputs found
The Minimum Backlog Problem
We study the minimum backlog problem (MBP). This online problem arises, e.g.,
in the context of sensor networks. We focus on two main variants of MBP.
The discrete MBP is a 2-person game played on a graph . The player
is initially located at a vertex of the graph. In each time step, the adversary
pours a total of one unit of water into cups that are located on the vertices
of the graph, arbitrarily distributing the water among the cups. The player
then moves from her current vertex to an adjacent vertex and empties the cup at
that vertex. The player's objective is to minimize the backlog, i.e., the
maximum amount of water in any cup at any time.
The geometric MBP is a continuous-time version of the MBP: the cups are
points in the two-dimensional plane, the adversary pours water continuously at
a constant rate, and the player moves in the plane with unit speed. Again, the
player's objective is to minimize the backlog.
We show that the competitive ratio of any algorithm for the MBP has a lower
bound of , where is the diameter of the graph (for the discrete
MBP) or the diameter of the point set (for the geometric MBP). Therefore we
focus on determining a strategy for the player that guarantees a uniform upper
bound on the absolute value of the backlog.
For the absolute value of the backlog there is a trivial lower bound of
, and the deamortization analysis of Dietz and Sleator gives an
upper bound of for cups. Our main result is a tight upper
bound for the geometric MBP: we show that there is a strategy for the player
that guarantees a backlog of , independently of the number of cups.Comment: 1+16 pages, 3 figure
An Examination of the Benefits of Scalable TTI for Heterogeneous Traffic Management in 5G Networks
The rapid growth in the number and variety of connected devices requires 5G
wireless systems to cope with a very heterogeneous traffic mix. As a
consequence, the use of a fixed TTI during transmission is not necessarily the
most efficacious method when heterogeneous traffic types need to be
simultaneously serviced.This work analyzes the benefits of scheduling based on
exploiting scalable TTI, where the channel assignment and the TTI duration are
adapted to the deadlines and requirements of different services. We formulate
an optimization problem by taking individual service requirements into
consideration. We then prove that the optimization problem is NP-hard and
provide a heuristic algorithm, which provides an effective solution to the
problem. Numerical results show that our proposed algorithm is capable of
finding near-optimal solutions to meet the latency requirements of mission
critical communication services, while providing a good throughput performance
for mobile broadband services.Comment: RAWNET Workshop, WiOpt 201
Network coding in wireless queueing networks: tandem network case
Abstract — In this paper, we compare the effects of the saturated and possibly emptying packet queues on wireless network coding (or plain routing as a special case) in a simple tandem network. We consider scheduled or random access with omnidirectional transmissions and assume the classical collision channel model without simultaneous transmission and reception by any node. For the case of multiple source nodes, we evaluate the multicast throughput rates jointly achievable by different sourcedestination pairs under the separate assumptions of network coding and plain routing only. Particularly, we specify the throughput region for saturated queues and stability region for possibly emptying queues. We also evaluate the fundamental trade-offs among the performance objectives of throughput and transmission and processing energy costs. Finally, we extend the analysis to non-cooperative network operation with selfish nodes competing for limited network resources. We point at the inefficiency of competitive medium access control and network coding (or plain routing) decisions at individual nodes, and introduce a pricing-based cooperation stimulation mechanism to improve the throughput and energy efficiency performance. I
Optimal Joint Routing and Scheduling in Millimeter-Wave Cellular Networks
Millimeter-wave (mmWave) communication is a promising technology to cope with
the expected exponential increase in data traffic in 5G networks. mmWave
networks typically require a very dense deployment of mmWave base stations
(mmBS). To reduce cost and increase flexibility, wireless backhauling is needed
to connect the mmBSs. The characteristics of mmWave communication, and
specifically its high directional- ity, imply new requirements for efficient
routing and scheduling paradigms. We propose an efficient scheduling method,
so-called schedule-oriented optimization, based on matching theory that
optimizes QoS metrics jointly with routing. It is capable of solving any
scheduling problem that can be formulated as a linear program whose variables
are link times and QoS metrics. As an example of the schedule-oriented
optimization, we show the optimal solution of the maximum throughput fair
scheduling (MTFS). Practically, the optimal scheduling can be obtained even for
networks with over 200 mmBSs. To further increase the runtime performance, we
propose an efficient edge-coloring based approximation algorithm with provable
performance bound. It achieves over 80% of the optimal max-min throughput and
runs 5 to 100 times faster than the optimal algorithm in practice. Finally, we
extend the optimal and approximation algorithms for the cases of multi-RF-chain
mmBSs and integrated backhaul and access networks.Comment: To appear in Proceedings of INFOCOM '1
Maximizing Energy Efficiency in Multiple Access Channels by Exploiting Packet Dropping and Transmitter Buffering
Quality of service (QoS) for a network is characterized in terms of various
parameters specifying packet delay and loss tolerance requirements for the
application. The unpredictable nature of the wireless channel demands for
application of certain mechanisms to meet the QoS requirements. Traditionally,
medium access control (MAC) and network layers perform these tasks. However,
these mechanisms do not take (fading) channel conditions into account. In this
paper, we investigate the problem using cross layer techniques where
information flow and joint optimization of higher and physical layer is
permitted. We propose a scheduling scheme to optimize the energy consumption of
a multiuser multi-access system such that QoS constraints in terms of packet
loss are fulfilled while the system is able to maximize the advantages emerging
from multiuser diversity. Specifically, this work focuses on modeling and
analyzing the effects of packet buffering capabilities of the transmitter on
the system energy for a packet loss tolerant application. We discuss low
complexity schemes which show comparable performance to the proposed scheme.
The numerical evaluation reveals useful insights about the coupling effects of
different QoS parameters on the system energy consumption and validates our
analytical results.Comment: in IEEE trans. Wireless communications, 201
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