Power-Optimal Feedback-Based Random Spectrum Access for an Energy Harvesting Cognitive User

In this paper, we study and analyze cognitive radio networks in which secondary users (SUs) are equipped with Energy Harvesting (EH) capability. We design a random spectrum sensing and access protocol for the SU that exploits the primary link's feedback and requires less average sensing time. Unlike previous works proposed earlier in literature, we do not assume perfect feedback. Instead, we take into account the more practical possibilities of overhearing unreliable feedback signals and accommodate spectrum sensing errors. Moreover, we assume an interference-based channel model where the receivers are equipped with multi-packet reception (MPR) capability. Furthermore, we perform power allocation at the SU with the objective of maximizing the secondary throughput under constraints that maintain certain quality-of-service (QoS) measures for the primary user (PU)

Principles of Physical Layer Security in Multiuser Wireless Networks: A Survey

This paper provides a comprehensive review of the domain of physical layer security in multiuser wireless networks. The essential premise of physical-layer security is to enable the exchange of confidential messages over a wireless medium in the presence of unauthorized eavesdroppers without relying on higher-layer encryption. This can be achieved primarily in two ways: without the need for a secret key by intelligently designing transmit coding strategies, or by exploiting the wireless communication medium to develop secret keys over public channels. The survey begins with an overview of the foundations dating back to the pioneering work of Shannon and Wyner on information-theoretic security. We then describe the evolution of secure transmission strategies from point-to-point channels to multiple-antenna systems, followed by generalizations to multiuser broadcast, multiple-access, interference, and relay networks. Secret-key generation and establishment protocols based on physical layer mechanisms are subsequently covered. Approaches for secrecy based on channel coding design are then examined, along with a description of inter-disciplinary approaches based on game theory and stochastic geometry. The associated problem of physical-layer message authentication is also introduced briefly. The survey concludes with observations on potential research directions in this area.Comment: 23 pages, 10 figures, 303 refs. arXiv admin note: text overlap with arXiv:1303.1609 by other authors. IEEE Communications Surveys and Tutorials, 201

Utilization of Channel State Information in Transmission Control for Wireless Communication Networks

This dissertation deals with the utilization of channel knowledge in improving the performance of wireless communication systems. The first part is about energy harvesting networks. The transmission policies in energy harvesting wireless systems need to adapt to the harvested energy availability and the channel characteristics. We start by considering the scheduling policy for a single energy harvesting source node that operates over a time varying channel. The goal of the source is to maximize the average number of successfully delivered packets per time slot. The transmission decisions depend on the available channel information and the length of the energy queue. Then, we investigate the case in which the source is helped by a relay through a network-level cooperation protocol. We investigate the case of a single relay node in which we optimize the transmission control based on channel measurements. Then, we assess the benefits of using partial relaying. We provide an exact characterization of the stability region of a network which consists of a source, a relay and a destination with random data arrivals to both the source and the relay. We derive the optimal value of the relaying parameter to maximize the stable throughput of the source for a given data arrival rate to the relay. Finally, we introduce the problem of general relaying cost minimization for cooperative energy harvesting networks with multiple relays. Then, we introduce the energy consumption as a cost criterion for the optimization problem to find an energy-efficient partial relaying protocol. In the second part, we investigate the techniques to optimally exploit channel information in transmission control for interfering sources. We discuss the scheduling problem for different levels of channel knowledge because learning instantaneous channels states may be costly or infeasible. We consider a network that consists of two transmitter-receiver pairs which operate over time varying channels. We derive the optimal scheduling policies which maximize the expected weighted sum-rate of the network per time slot. The decision depends on the information about the channels between nodes. In the third part, we investigate the effect of channel estimation on the performance of a secondary network in a cognitive radio system. We focus on estimating the sensing-channel from the primary source to the secondary source which helps in assessing the reliability of the sensing decision. The channel is estimated opportunistically when the secondary source senses the primary source to be active. We consider the performance criterion to be the energy consumed by the secondary system constrained by a required average data transmission rate for the secondary system and an allowable average failure probability for the primary system

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

Optimization of a Power Splitting Protocol for Two-Way Multiple Energy Harvesting Relay System

Energy harvesting (EH) combined with cooperative communications constitutes a promising solution for future wireless technologies. They enable additional efficiency and increased lifetime to wireless networks. This paper investigates a multiple-relay selection scheme for an EH-based two-way relaying (TWR) system. All relays are considered as EH nodes that harvest energy from renewable energy and radio frequency (RF) sources. Some of them are selected to forward data to the destinations. The power splitting (PS) protocol, by which the EH node splits the input RF signal into two components for EH and information transmission, is adopted at the relay nodes. The objective is to jointly optimize i) the set of selected relays, ii) their PS ratios, and iii) their transmit power levels in order to maximize data rate-based utilities over multiple coherent time slots. A joint-optimization solution based on geometric programming (GP) and binary particle swarm optimization is proposed to solve non-convex problems for two utility functions reflecting the level of fairness in the TWR transmission. Numerical results illustrate the system's behavior versus various parameters and show that the performance of the proposed scheme is very close to that of the optimal branch-and-bound method and that GP outperforms the dual problem-based method