Tutorials

Dr. Brian Krongold

Dept, Electrical and Electronic Engineering

The University of Melbourne

Title: Transmit Power Optimization in OFDM Systems

Abstract:

This tutorial considers two important aspects related to transmit power in OFDM systems. First, we consider the inherently large peak-to-average power ratio (PAPR) problem, which can limit performance and significantly reduce power efficiency. Various approaches, optimization problems, and algorithms to alleviate the PAPR problem will be presented, including their various tradeoffs and implementation issues. The ability to extend such approaches to multi-user and multiple antenna systems will briefly highlighted.

The second part of this tutorial looks at optimizing the transmit power spectrum based upon channel state information (CSI). This ability to allocate power and rate for each subchannel, sometimes referred to as "bit loading", can greatly enhance the throughput and performance of OFDM systems. Starting with a basic convex optimization problem, we look at optimally solving the standard bit loading problems, followed by extensions to multi-user and multiple antenna systems. Recent work in the literature, such as using quantized CSI feedback, will be highlighted.

Prof. Leandros Tassiulas

Computer Engineering and Telecommunications Dept.

University of Thessaly

Bio

Dr. Iordanis Koutsopoulos

Computer Engineering and Telecommunications Dept.

University of Thessaly

Bio

Title: Cross-layer design and optimization in wireless networks

Abstract:

Advances in wireless technologies and networking over the last few years lead to sophisticated physical layer designs that may interact with the access and network layer in multiple modes. Link quality related information can be passed from the physical layer to higher layers and can guide higher layer decisions.
At the same time several considerations belonging naturally to the physical layer, like channel coding rate, signal constellation selection, power level adjustments, frequency selection and beam steering in multiple antenna systems are to the disposal of the access layer, and may control them in various time scales.

That interaction is particularly useful for full exploitation of the volatile error-prone mobile channel and the establishment of reliable broadband wireless links amidst interference and spectrum scarcity. The design challenge of wireless systems necessitates novel models that capture the interactions described above as well as analytical tools for the design of resource allocation algorithms running at the various layers of the system. This is the focus of the current tutorial that will include more specifically the following topics:

Characterization of performance limits of cross-layer optimization in wireless networks
Max-weight and backpressure principles for max-throughput scheduling and routing in wireless networks
Network utility maximization and resource allocation
Coping with limited network state information and distributed implementation
Advanced transmission modes (OFDMA, SDMA) with emphasis on cross-layer implications
Overview of related wireless standards

Dr. João Barros

Department of Electrical and Computer Engineering

University of Porto

Bio

Title: Physical-Layer Security: Principles and Applications

Abstract:

Although much has been accomplished in terms of how to design, construct, and manage wireless networks, fundamental security issues such as privacy, integrity and authenticity both of the transported data and of the underlying sessions can still be deemed as formidable challenges. State-of-the-art wireless security typically neglects the physical properties of the communications channel, relying on cryptographic protocols that are implemented at the higher layers of the protocol stack. Inspired by recent results in information-theoretic security over noisy channels, this tutorial presents a different paradigm: a mix of physical layer security technologies capable of enhancing data and traffic protection beyond what can be achieved with cryptographic protocols alone.

First, we shall present in detail the necessary tools and basic concepts of information-theoretic security, contrasting their characteristic assumptions with those of classical cryptography. Next, we discuss some of the recent achievements in physical-layer security, including the secrecy capacity of wireless channels, the construction of codes for secrecy, the generation of secret keys, and the role of coded jamming in multi-user systems.

Prof. Wolfgang Utschick

Associate Institute for Signal Processing

Munich University of Technology

Bio

Dr. Michael Joham

Associate Institute for Signal Processing

Munich University of Technology

Bio

Title: Multiuser MIMO - Theory, Algorithms, System and Network Perspective

Abstract:

The exploitation of multiple antennas in wireless communications has become a matured subject in research. In order to comply with the information theoretic results even in practical applications there is a strong need for efficient algorithms aiming at approximate solutions. These algorithms might be considered as enabling techniques if we consider MIMO as an technological basis in layered communication systems and wireless communicaton networks.

First we will present the information theoretic fundamentals of MIMO including duality theorems and a brief introduction to the role of channel state information. A taxonomy of the related optimization problems for MIMO communications and an overview of algorithms, which have the
potential of achieving optimal bounds, conclude this part. In the second part , we discuss state-of-the-art algorithms for finding approximate solutions with low to moderate numerical complexity. The need for efficient algorithms becomes apparent in the third section of this tutorial when we study MIMO as the technological basis for the deployment of wireless communication networks, with a strong emphasis on mesh networks. In this part, the introduced algorithms play the role of enabling techniques for the solution of network utility maximization problems where a crosslayer perspective comes into question.

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