125 research outputs found
Energy Efficiency in MIMO Underlay and Overlay Device-to-Device Communications and Cognitive Radio Systems
This paper addresses the problem of resource allocation for systems in which
a primary and a secondary link share the available spectrum by an underlay or
overlay approach. After observing that such a scenario models both cognitive
radio and D2D communications, we formulate the problem as the maximization of
the secondary energy efficiency subject to a minimum rate requirement for the
primary user. This leads to challenging non-convex, fractional problems. In the
underlay scenario, we obtain the global solution by means of a suitable
reformulation. In the overlay scenario, two algorithms are proposed. The first
one yields a resource allocation fulfilling the first-order optimality
conditions of the resource allocation problem, by solving a sequence of easier
fractional problems. The second one enjoys a weaker optimality claim, but an
even lower computational complexity. Numerical results demonstrate the merits
of the proposed algorithms both in terms of energy-efficient performance and
complexity, also showing that the two proposed algorithms for the overlay
scenario perform very similarly, despite the different complexity.Comment: to appear in IEEE Transactions on Signal Processin
Pareto Boundary of the Rate Region for Single-Stream MIMO Interference Channels: Linear Transceiver Design
We consider a multiple-input multiple-output (MIMO) interference channel
(IC), where a single data stream per user is transmitted and each receiver
treats interference as noise. The paper focuses on the open problem of
computing the outermost boundary (so-called Pareto boundary-PB) of the
achievable rate region under linear transceiver design. The Pareto boundary
consists of the strict PB and non-strict PB. For the two user case, we compute
the non-strict PB and the two ending points of the strict PB exactly. For the
strict PB, we formulate the problem to maximize one rate while the other rate
is fixed such that a strict PB point is reached. To solve this non-convex
optimization problem which results from the hard-coupled two transmit
beamformers, we propose an alternating optimization algorithm. Furthermore, we
extend the algorithm to the multi-user scenario and show convergence. Numerical
simulations illustrate that the proposed algorithm computes a sequence of
well-distributed operating points that serve as a reasonable and complete inner
bound of the strict PB compared with existing methods.Comment: 16 pages, 9 figures. Accepted for publication in IEEE Tans. Signal
Process. June. 201
Resource Allocation for Energy-Efficient 3-Way Relay Channels
Throughput and energy efficiency in 3-way relay channels are studied in this
paper. Unlike previous contributions, we consider a circular message exchange.
First, an outer bound and achievable sum rate expressions for different
relaying protocols are derived for 3-way relay channels. The sum capacity is
characterized for certain SNR regimes. Next, leveraging the derived achievable
sum rate expressions, cooperative and competitive maximization of the energy
efficiency are considered. For the cooperative case, both low-complexity and
globally optimal algorithms for joint power allocation at the users and at the
relay are designed so as to maximize the system global energy efficiency. For
the competitive case, a game theoretic approach is taken, and it is shown that
the best response dynamics is guaranteed to converge to a Nash equilibrium. A
power consumption model for mmWave board-to-board communications is developed,
and numerical results are provided to corroborate and provide insight on the
theoretical findings.Comment: Submitted to IEEE Transactions on Wireless Communication
Energy Efficient Multiuser Scheduling: Statistical Guarantees on Bursty Packet Loss
In this paper, we consider energy efficient multiuser scheduling. Packet loss
tolerance of the applications is exploited to minimize average system energy.
There is a constraint on average packet drop rate and maximum number of packets
dropped successively (bursty loss). A finite buffer size is assumed. We propose
a scheme which schedules the users opportunistically according to the channel
conditions, packet loss constraints and buffer size parameters. We assume
imperfect channel state information at the transmitter side and analyze the
scheme in large user limit using stochastic optimization techniques. First, we
optimize system energy for a fixed buffer size which results in a corresponding
statistical guarantee on successive packet drop. Then, we determine the minimum
buffer size to achieve a target (improved) energy efficiency for the same (or
better) statistical guarantee. We show that buffer size can be traded
effectively to achieve system energy efficiency for target statistical
guarantees on packet loss parameters.Comment: Proc. Physcomnet in conjunction with WIOPT 201
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