13,880 research outputs found
Cross-layer Congestion Control, Routing and Scheduling Design in Ad Hoc Wireless Networks
This paper considers jointly optimal design of crosslayer congestion control, routing and scheduling for ad hoc
wireless networks. We first formulate the rate constraint and scheduling constraint using multicommodity flow variables, and formulate resource allocation in networks with fixed wireless channels (or single-rate wireless devices that can mask channel variations) as a utility maximization problem with these constraints.
By dual decomposition, the resource allocation problem
naturally decomposes into three subproblems: congestion control,
routing and scheduling that interact through congestion price.
The global convergence property of this algorithm is proved. We
next extend the dual algorithm to handle networks with timevarying
channels and adaptive multi-rate devices. The stability
of the resulting system is established, and its performance is
characterized with respect to an ideal reference system which
has the best feasible rate region at link layer.
We then generalize the aforementioned results to a general
model of queueing network served by a set of interdependent
parallel servers with time-varying service capabilities, which
models many design problems in communication networks. We
show that for a general convex optimization problem where a
subset of variables lie in a polytope and the rest in a convex set,
the dual-based algorithm remains stable and optimal when the
constraint set is modulated by an irreducible finite-state Markov
chain. This paper thus presents a step toward a systematic way
to carry out cross-layer design in the framework of “layering as
optimization decomposition” for time-varying channel models
Millimeter Wave Cellular Networks: A MAC Layer Perspective
The millimeter wave (mmWave) frequency band is seen as a key enabler of
multi-gigabit wireless access in future cellular networks. In order to overcome
the propagation challenges, mmWave systems use a large number of antenna
elements both at the base station and at the user equipment, which lead to high
directivity gains, fully-directional communications, and possible noise-limited
operations. The fundamental differences between mmWave networks and traditional
ones challenge the classical design constraints, objectives, and available
degrees of freedom. This paper addresses the implications that highly
directional communication has on the design of an efficient medium access
control (MAC) layer. The paper discusses key MAC layer issues, such as
synchronization, random access, handover, channelization, interference
management, scheduling, and association. The paper provides an integrated view
on MAC layer issues for cellular networks, identifies new challenges and
tradeoffs, and provides novel insights and solution approaches.Comment: 21 pages, 9 figures, 2 tables, to appear in IEEE Transactions on
Communication
On Energy Efficient Hierarchical Cross-Layer Design: Joint Power Control and Routing for Ad Hoc Networks
In this paper, a hierarchical cross-layer design approach is proposed to
increase energy efficiency in ad hoc networks through joint adaptation of
nodes' transmitting powers and route selection. The design maintains the
advantages of the classic OSI model, while accounting for the cross-coupling
between layers, through information sharing. The proposed joint power control
and routing algorithm is shown to increase significantly the overall energy
efficiency of the network, at the expense of a moderate increase in complexity.
Performance enhancement of the joint design using multiuser detection is also
investigated, and it is shown that the use of multiuser detection can increase
the capacity of the ad hoc network significantly for a given level of energy
consumption.Comment: To appear in the EURASIP Journal on Wireless Communications and
Networking, Special Issue on Wireless Mobile Ad Hoc Network
Beam-searching and Transmission Scheduling in Millimeter Wave Communications
Millimeter wave (mmW) wireless networks are capable to support multi-gigabit
data rates, by using directional communications with narrow beams. However,
existing mmW communications standards are hindered by two problems: deafness
and single link scheduling. The deafness problem, that is, a misalignment
between transmitter and receiver beams, demands a time consuming beam-searching
operation, which leads to an alignment-throughput tradeoff. Moreover, the
existing mmW standards schedule a single link in each time slot and hence do
not fully exploit the potential of mmW communications, where directional
communications allow multiple concurrent transmissions. These two problems are
addressed in this paper, where a joint beamwidth selection and power allocation
problem is formulated by an optimization problem for short range mmW networks
with the objective of maximizing effective network throughput. This
optimization problem allows establishing the fundamental alignment-throughput
tradeoff, however it is computationally complex and requires exact knowledge of
network topology, which may not be available in practice. Therefore, two
standard-compliant approximation solution algorithms are developed, which rely
on underestimation and overestimation of interference. The first one exploits
directionality to maximize the reuse of available spectrum and thereby
increases the network throughput, while imposing almost no computational
complexity. The second one is a more conservative approach that protects all
active links from harmful interference, yet enhances the network throughput by
100% compared to the existing standards. Extensive performance analysis
provides useful insights on the directionality level and the number of
concurrent transmissions that should be pursued. Interestingly, extremely
narrow beams are in general not optimal.Comment: 5 figures, 7 pages, accepted in ICC 201
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