19,840 research outputs found
Queue-Architecture and Stability Analysis in Cooperative Relay Networks
An abstraction of the physical layer coding using bit pipes that are coupled
through data-rates is insufficient to capture notions such as node cooperation
in cooperative relay networks. Consequently, network-stability analyses based
on such abstractions are valid for non-cooperative schemes alone and
meaningless for cooperative schemes. Motivated from this, this paper develops a
framework that brings the information-theoretic coding scheme together with
network-stability analysis. This framework does not constrain the system to any
particular achievable scheme, i.e., the relays can use any cooperative coding
strategy of its choice, be it amplify/compress/quantize or any
alter-and-forward scheme. The paper focuses on the scenario when coherence
duration is of the same order of the packet/codeword duration, the channel
distribution is unknown and the fading state is only known causally. The main
contributions of this paper are two-fold: first, it develops a low-complexity
queue-architecture to enable stable operation of cooperative relay networks,
and, second, it establishes the throughput optimality of a simple network
algorithm that utilizes this queue-architecture.Comment: 16 pages, 1 figur
Maximum Throughput of a Cooperative Energy Harvesting Cognitive Radio User
In this paper, we investigate the maximum throughput of a saturated
rechargeable secondary user (SU) sharing the spectrum with a primary user (PU).
The SU harvests energy packets (tokens) from the environment with a certain
harvesting rate. All transmitters are assumed to have data buffers to store the
incoming data packets. In addition to its own traffic buffer, the SU has a
buffer for storing the admitted primary packets for relaying; and a buffer for
storing the energy tokens harvested from the environment. We propose a new
cooperative cognitive relaying protocol that allows the SU to relay a fraction
of the undelivered primary packets. We consider an interference channel model
(or a multipacket reception (MPR) channel model), where concurrent
transmissions can survive from interference with certain probability
characterized by the complement of channel outages. The proposed protocol
exploits the primary queue burstiness and receivers' MPR capability. In
addition, it efficiently expends the secondary energy tokens under the
objective of secondary throughput maximization. Our numerical results show the
benefits of cooperation, receivers' MPR capability, and secondary energy queue
arrival rate on the system performance from a network layer standpoint.Comment: Part of this paper was accepted for publication in PIMRC 201
Protocol Design and Stability Analysis of Cooperative Cognitive Radio Users
A single cognitive radio transmitter--receiver pair shares the spectrum with
two primary users communicating with their respective receivers. Each primary
user has a local traffic queue, whereas the cognitive user has three queues;
one storing its own traffic while the other two are relaying queues used to
store primary relayed packets admitted from the two primary users. A new
cooperative cognitive medium access control protocol for the described network
is proposed, where the cognitive user exploits the idle periods of the primary
spectrum bands. Traffic arrival to each relaying queue is controlled using a
tuneable admittance factor, while relaying queues service scheduling is
controlled via channel access probabilities assigned to each queue based on the
band of operation. The stability region of the proposed protocol is
characterized shedding light on its maximum expected throughput. Numerical
results demonstrate the performance gains of the proposed cooperative cognitive
protocol.Comment: Accepted in WCNC 201
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