847 research outputs found
Wireless Network-Level Partial Relay Cooperation: A Stable Throughput Analysis
In this work, we study the benefit of partial relay cooperation. We consider
a two-node system consisting of one source and one relay node transmitting
information to a common destination. The source and the relay have external
traffic and in addition, the relay is equipped with a flow controller to
regulate the incoming traffic from the source node. The cooperation is
performed at the network level. A collision channel with erasures is
considered. We provide an exact characterization of the stability region of the
system and we also prove that the system with partial cooperation is always
better or at least equal to the system without the flow controller.Comment: Submitted for journal publication. arXiv admin note: text overlap
with arXiv:1502.0113
Opportunistic Relaying in Wireless Networks
Relay networks having source-to-destination pairs and half-duplex
relays, all operating in the same frequency band in the presence of block
fading, are analyzed. This setup has attracted significant attention and
several relaying protocols have been reported in the literature. However, most
of the proposed solutions require either centrally coordinated scheduling or
detailed channel state information (CSI) at the transmitter side. Here, an
opportunistic relaying scheme is proposed, which alleviates these limitations.
The scheme entails a two-hop communication protocol, in which sources
communicate with destinations only through half-duplex relays. The key idea is
to schedule at each hop only a subset of nodes that can benefit from
\emph{multiuser diversity}. To select the source and destination nodes for each
hop, it requires only CSI at receivers (relays for the first hop, and
destination nodes for the second hop) and an integer-value CSI feedback to the
transmitters. For the case when is large and is fixed, it is shown that
the proposed scheme achieves a system throughput of bits/s/Hz. In
contrast, the information-theoretic upper bound of bits/s/Hz
is achievable only with more demanding CSI assumptions and cooperation between
the relays. Furthermore, it is shown that, under the condition that the product
of block duration and system bandwidth scales faster than , the
achievable throughput of the proposed scheme scales as .
Notably, this is proven to be the optimal throughput scaling even if
centralized scheduling is allowed, thus proving the optimality of the proposed
scheme in the scaling law sense.Comment: 17 pages, 8 figures, To appear in IEEE Transactions on Information
Theor
Energy-Efficient Power Control for Multiple-Relay Cooperative Networks Using Q-Learning
In this paper, we investigate the power control problem in a cooperative network with multiple wireless transmitters, multiple amplify-and-forward relays, and one destination. The relay communication can be either full duplex or half-duplex, and all source nodes interfere with each other at every intermediate relay node, and all active nodes (transmitters and relay nodes) interfere with each other at the base station. A game-theory-based power control algorithm is devised to allocate the powers among all active nodes. The source nodes aim at maximizing their energy efficiency (in bits per Joule per Hertz), whereas the relays aim at maximizing the network sum rate. We show that the proposed game admits multiple pure/mixed-strategy Nash equilibrium points. A Q-learning-based algorithm is then formulated to let the active players converge to the best Nash equilibrium point that combines good performance in terms of both energy efficiency and overall data rate. Numerical results show that the full-duplex scheme outperforms half-duplex configuration, Nash bargaining solution, the max-min fairness, and the max-rate optimization schemes in terms of energy efficiency, and outperforms the half-duplex mode, Nash bargaining system, and the max-min fairness scheme in terms of network sum rate
Secure Communications for the Two-user Broadcast Channel with Random Traffic
In this work, we study the stability region of the two-user broadcast channel
(BC) with bursty data arrivals and security constraints. We consider the
scenario, where one of the receivers has a secrecy constraint and its packets
need to be kept secret from the other receiver. This is achieved by employing
full-duplexing at the receiver with the secrecy constraint, so that it
transmits a jamming signal to impede the reception of the other receiver. In
this context, the stability region of the two-user BC is characterized for the
general decoding case. Then, assuming two different decoding schemes the
respective stability regions are derived. The effect of self-interference due
to the full-duplex operation on the stability region is also investigated. The
stability region of the BC with a secrecy constraint, where the receivers do
not have full duplex capability can be obtained as a special case of the
results derived in this paper. In addition, the paper considers the problem of
maximizing the saturated throughput of the queue, whose packets does not
require to be kept secret under minimum service guarantees for the other queue.
The results provide new insights on the effect of the secrecy constraint on the
stability region of the BC. In particular, it is shown that the stability
region with secrecy constraint is sensitive to the coefficient of
self-interference cancelation under certain cases.Comment: Submitted for journal publicatio
Energy Harvesting Wireless Communications: A Review of Recent Advances
This article summarizes recent contributions in the broad area of energy
harvesting wireless communications. In particular, we provide the current state
of the art for wireless networks composed of energy harvesting nodes, starting
from the information-theoretic performance limits to transmission scheduling
policies and resource allocation, medium access and networking issues. The
emerging related area of energy transfer for self-sustaining energy harvesting
wireless networks is considered in detail covering both energy cooperation
aspects and simultaneous energy and information transfer. Various potential
models with energy harvesting nodes at different network scales are reviewed as
well as models for energy consumption at the nodes.Comment: To appear in the IEEE Journal of Selected Areas in Communications
(Special Issue: Wireless Communications Powered by Energy Harvesting and
Wireless Energy Transfer
Analysis of a Cooperative Strategy for a Large Decentralized Wireless Network
This paper investigates the benefits of cooperation and proposes a relay
activation strategy for a large wireless network with multiple transmitters. In
this framework, some nodes cooperate with a nearby node that acts as a relay,
using the decode-and-forward protocol, and others use direct transmission. The
network is modeled as an independently marked Poisson point process and the
source nodes may choose their relays from the set of inactive nodes. Although
cooperation can potentially lead to significant improvements in the performance
of a communication pair, relaying causes additional interference in the
network, increasing the average noise that other nodes see. We investigate how
source nodes should balance cooperation vs. interference to obtain reliable
transmissions, and for this purpose we study and optimize a relay activation
strategy with respect to the outage probability. Surprisingly, in the high
reliability regime, the optimized strategy consists on the activation of all
the relays or none at all, depending on network parameters. We provide a simple
closed-form expression that indicates when the relays should be active, and we
introduce closed form expressions that quantify the performance gains of this
scheme with respect to a network that only uses direct transmission.Comment: Updated version. To appear in IEEE Transactions on Networkin
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