Tutorials

All tutorials will be held at the Friend Center at Princeton  University.

Linearization: Reducing Distortion in Power Amplifiers
Allen Katz
Professor of Electrical/Computer Engineering , The College of New Jersey/Linearizer Technology, Inc

Our society’s need to exchange greater and greater amounts of information has created an unprecedented demand for highly linear power amplifiers.  High linearity is required for the bandwidth efficient transmission of information.  This tutorial presentation will discuss techniques for the cancellation of distortion that are also known as linearization.  Different methods of linearization including digital approaches will be introduced and compared.  The linearization of different types of RF and microwave power amplifiers will be discussed.

Overview of new DVB-T (DVB-T2) system
Lorenzo Vangelista
Associate Professor, Department of Information Engineering (DEI)
University of Padova

A number of technical innovations have been included in DVB-T2 to boost throughput and ruggedness, enhance single frequency network coverage, and ease both transmitter and receiver implementation. In this tutorial I start from the motivations that led the DVB project to create the new standard and then I will provide a survey of the key technologies behind DVB-T2, including the LDPC/BCH forward error correction scheme, transmission scheduling, orthogonal frequency-division multiplexing with huge block size, multiple-antenna transmissions and synchronization techniques. A comparison with the current DVB-T standard is also provided, showing that DVB-T2 is able to increase the payload throughput and allows HDTV transmission with current network planning.

Biologically-inspired Communication and Networking
Ozgur B. Akan
Associate Professor, Department of Electrical and Electronics Engineering
Middle East Technical University

The developments in the communication and networking technologies have yielded many existing and envisioned information network architectures such as cognitive radio networks, sensor and actor networks, quantum communication networks, terrestrial next generation Internet, and InterPlaNetary Internet. However, there exist many common significant challenges to be addressed for the practical realization of these current and envisioned networking paradigms such as the increased complexity with large scale networks, their dynamic nature, resource constraints, heterogeneous architectures, absence or impracticality of centralized control and infrastructure, need for survivability, and unattended resolution of potential failures. These challenges have been successfully dealt with by Nature, which, as a result of millions of years of evolution, have yielded many biological systems and processes with intrinsic appealing characteristics such as adaptivity to varying environmental conditions, inherent resiliency to failures and damages, successful and collaborative operation on the basis of a limited set of rules and with global intelligence which is larger than superposition of individuals, self-organization, survivability, and evolvability.  Inspired by these characteristics, many researchers are currently engaged in developing innovative design paradigms to address the networking challenges of existing and envisioned information systems. In this paper, the current state-of-the-art in bio-inspired networking is captured. The existing bio-inspired networking and communication protocols and algorithms devised by looking at biology as a source of inspiration, and by mimicking the laws and dynamics governing these systems is presented along with open research issues for the bio-inspired networking. Furthermore, the domain of bio-inspired networking is linked to the forthcoming research domain of nanonetworks, which bring a set of unique challenges. The objective of this tutorial is to provide better understanding of the potentials for bio- inspired networking which is currently far from being fully recognized, and to motivate research community to further explore this timely and exciting topic.

Cognitive Radio Network Security
K.P. (Suba) Subbalakshmi
Associate Professor in the Dept. of E.C.E , Stevens Institute of Technology

Traditionally, radio spectrum bands have been assigned to license holders or services on a long term basis for large geographical regions. This fixed spectrum assignment policy has led to under-utilization of the available spectrum. The inefficiency in the spectrum usage and the limited availability of spectrum for wireless applications has given rise to cognitive radio (CR) enabled dynamic spectrum access (DSA) networking. DSA is also useful in interference mitigation and co-existence of heterogeneous and open spectrum networks.

The basic feature of DSA networks is that secondary (unlicensed) users in a DSA network can use the licensed spectrum bands when they are idle, under the condition that they vacate the spectrum upon the return of the primary licensed users (incumbent, primary users).  The Federal Communications Commission (FCC)'s mandated spectrum policy reform has resulted in a great deal of research activities on various aspects of cognitive radio networks including spectrum sensing and management, network architectures, capacity, codes, transmission techniques, spectrum etiquette and evacuation protocols as well as test-bed development. Standardization efforts for DSA networks include the IEEE Standards Coordinating Committee 41 (IEEE SCC41)'s sponsored projects as well as the activity under the umbrella of 802.22. Despite this body of work, there is very little done on the security aspects of dynamic spectrum access networks. Recent research shows that designing protocols for DSA networks without security in mind can lead to debilitating attacks which cannot be mitigated as an after thought.

In this tutorial, we will discuss the security issues inherent in dynamic spectrum access networks. Topics that will be covered include:
•              Introduction to Cognitive Radio Networks
•              Dynamic spectrum access protocols
•              Overview of security issues in CRNs
•              Fundamentals of security as applied to DSA networks
•              Security metrics
•              Denial-of-Service attack mechansims
•              Protocol level solutions for attack mitigation
•              Cryptographic mechanisms for attack mitigation
•              Implications for CRN standards

Beyond 3G: Technical Overview of 3GPP Long Term Evolution and WiMAX
Hyung Myung
Qualcomm/Flarion Technologies

The current 3rd generation cellular wireless systems are evolving into 4th generation. As a pathway to 4G, 3GPP is currently developing Long Term Evolution (LTE) standard and IEEE 802.16-based WiMAX is also gaining attention as a 4G solution. In terms of air interface techniques, both systems use OFDMA-based multicarrier modulation, MIMO, and other advanced features to greatly improve the mobile wireless services. In this tutorial, we first survey the underlying techniques of the three beyond-3G systems such as OFDMA, SC-FDMA, MIMO, fractional frequency reuse (FFR), and fast multi-carrier resource scheduling. Then, we give technical overviews of 3GPP LTE and Mobile WiMAX. Specifically, we describe the system architecture, physical layer, and MAC layer of each system.

Primary audiences of this tutorial are research engineers, software development engineers, and systems test engineers working on wireless products as well as students and professors in wireless communications field will benefit from the proposed tutorial which gives a technical insight into the widely-anticipated beyond-3G cellular techniques and standards.

Radio over Fiber – An Optical Technique for Wireless Access
Xavier Fernando
Associate Professor and Coordinator of the Signal Processing and Communications Research Stream Ryerson University

Optical fiber based wireless (Fi-Wi) access using radio-over-fiber (ROF) concept combines the flexibility of wireless with the capacity of fiber to support bandwidth hungry services. There are several reasons why widespread interest is currently focused in Fi-Wi networks.

1.             Enables Rapid Deployment: The BriteCell® system with 500 remote antennas at the Sydney Olympics 2000 showed the rapid deployment potential of Fi-Wi networks. Three GSM operators shared this infrastructure and multi-standard radio (900/1800 MHz GSM) was supported. Dynamic allocation of network capacity was enabled and more than 500,000 wireless calls were made on the opening day using the Fi-Wi infrastructure.
2.             Enables Low-Cost Micro/Pico Cellular Networks: Micro/pico cells will not only provide better frequency reuse and coverage, but also will reduce power consumption and size of the portable units.  ROF is a viable technology to interconnect the radio access points of these micro/pico cells cost effectively.
3.             Supports Broadband Wireless: There is an inherent inverse relationship between the length of the wireless link and its bandwidth. Short air interface supports broadband access by reducing multi path delay spread and often offering strong line of sight paths. As a result, high-speed multimedia services are easily accommodated in Fi-Wi networks.
4.             Supports mm-wave Bands: Due to the crowding in the lower end of the spectrum, millimeter wave bands up to 60 GHz are explored. Since, air interface has to be very short at these ultra high frequencies Fi-Wi is a strong candidate.
5.             ROF for 4G Networks: 4G networks promise up to 1 Gbps over 100 MHz spectrum. Again the air has to be significantly short at these extremely high bit rates because the RF power requirement rapidly increases with the bit rate.
6.             Fi-Wi for MIMO Networks: ROF is a viable candidate for interconnecting MIMO antennas. Chinese Telecom envisions using ROF for its B3G MIMO wireless networks.
7.             Potential to use Existing Fiber: This is another reason for the interest in Fi-Wi networks with the widespread deployment of FTTH/FTTC networks.
8.             Fi-Wi Covers Highways and Railways: Using (existing) fiber along the railway tracks and highways, broadband access to commuters using the ‘moving cell’ concept is researched. This is another emerging Fi-Wi area.  
9.             Fi-Wi also covers special areas like tunnels, mines and subway stations that usually cannot be served by traditional wireless networks.

However, there are many technical challenges need to be addressed before widespread deployment of Fi-Wi networks. Some ROF issues are better addressed by wireless researchers in the electrical domain while other issues are better addressed by photonic researchers in the optical domain. However, basic knowledge of both optical and wireless communication is needed for better understanding of the issues. This tutorial will cover both optical and wireless aspects. Namely, the following problems, state of the art solutions and further research directions will be addressed. 

1.             The ROF Link
Basic link elements will be discussed in this Section including, different direct and external modulation techniques, advantages and trade-offs, impedance matching, single sideband and double sideband modulation techniques,  the fibre (multi or single mode), different dispersion mechanisms and how they affect the RF transmission, the receiver, PIN versus APD, noise/gain characteristics, various receiver RF amplifier designs for ROF links. The nonlinearity comes from the transmitter and receiver amplifier, there are device based individual linearization approaches as well as joint approaches (considering the wireless and optical channels). The latter is more promising.

2. Nonlinearity and Multipath Dispersion
Nonlinear distortion plays significant role in Fi-Wi systems because linear dispersive dynamic system (wireless channel) and static nonlinear system (optical link) are cascaded and, the uplink and downlink have different sequences. Post compensation is better for the Fi-Wi uplink while pre-distortion nonlinearity compensation is the best for Fi-Wi downlinks to provide asymmetry in complexity. There are adaptive as well as fixed techniques proposed. When multiple users share the ROF link, they will have a common static nonlinear channel in series with individual dynamic wireless channels. This is even more challenging to solve. Interestingly, OFDM performs worse in Fi-Wi networks due to large peak to average ratio while, CDMA, that is losing popularity performs better in Fi-Wi systems. 

2. Cumulating Signal to Noise Ratio
Two analog channels are cascaded in Fi-Wi systems. The signal is weak at both the optical and wireless receivers where different noise processes are added. There are two signal-to-noise ratio’s involved. The resulting SNR is a weighted sum of both electrical and optical domain SNR and will be smaller than the smallest of them.  For example, the relative intensity noise (RIN) supposed to be constant provided the mean optical power does not change. However, recently it is observed to increase with the modulating RF signal power as well. This ‘dynamic RIN’ poses additional challenge. There is a large loss (typically 20 dB) just due to E/O and O/E conversion and optical domain loss appears twice in the electrical domain. These issues pose an inherent inverse relationship between the optical and wireless channel lengths.  The SNR issue is severe in broadband and multi channel ROF systems.  Especially the PON is notorious for large power loss in each splitting stage, which will adversely affect low power subcarriers.

3. Photonic Generation and Processing of Microwave Signals
Photonic processing of microwave signals is not new; but there is increasing interest in this area with the exponential growth broadband radio networks. Inherent advantages of photonic filters such as low loss, very high bandwidth, tunability and immunity to electromagnetic interference can be used with this approach which is ideal for ROF systems.

Microwave signals can be optically generated by optical heterodyning or by optical frequency multiplying. The heterodyning is widely used and easy to implement. However, the phase noise of the two optical terms must be correlated to get narrow line width RF. Various methods have been proposed for obtaining correlated phase noise such as obtaining the two terms from a single optical source and biasing the MZI appropriately or by implementing phase locked loops. Innovative techniques yet to be devised to optically generate QAM modulated RF signal using a single stage avoiding separate generation and modulation.

Optical signal processing has many challenges in WDM ROF networks. Various Optical filters also are demonstrated to de-multiplex wavelengths as well as RF signals. Wavelength de-multiplexing is well established but poses additional challenge when wavelengths carry RF subcarriers. All optical RF filtering is an emerging are with many challenges. 

4. Single/Double Sideband Modulation
A directly modulated ROF link produces DSB spectrum with typically about 70% (unmodulated) optical carrier. This residual carrier does not carry information but increases noise and reduces receiver sensitivity. Variety of techniques has been proposed to mitigate the effect of residual carrier. These include coherent techniques; dynamic bias modulation; suppression of common mode RIN using a balanced photo detector, low bias techniques for MZI and carrier filtering techniques. DSB spectrum also has sideband cancellation affect at mm-wave bands, this can be overcome by single side band modulation. Various techniques have been proposed for this.

Coordinated Jamming and Communications
Yu-Dong Yao
Associate Professor and Department Chair
Department of Electrical and Computer Engineering, Stevens Institute of Technology

Simultaneously jamming enemy signals and serving communications needs of friendly forces pose a  significant challenge in military and battlefield applications. While this can be a standard requirement for  such application scenarios, recent IED attacks highlight such critical needs, as jamming is one of the  effective methods to deter IED. Traditional electronic warfare or military communications research  includes the designs of LPI/LPD communications waveforms, anti-jamming signal waveforms, and  jamming techniques. Recent advances in information technologies introduce a new challenge which  requires high-capacity communications due to the networking and multimedia features of information.  The other new requirement of jamming/communications calls for integrated design or coordinated  jamming and communications (CJamCom). This tutorial lecture covers the following topics.  

1. Introduction: Current issues and trend in military communications; Advances in information networking, signal processing, radio and antenna technologies.
2. Requirements in Jamming and Communications Systems: Definitions and concepts of LPI/LPD, detection probability, false alarm rate, outage probability, sign-to-interference-plus-noise ratio, bit error rate, and network capacity.
3. Fundamental Technologies: Spread spectrum, multi-user detection, UWB antenna and communications, high-speed DSP algorithms and FPGA platform, and software defined radio (SDR).
4. Coordinated Jamming and Communications: Concept, Theory and Techniques; Modeling, analysis, and simulation results; Current research issues and topics; Current research activities CJamCom.
5. Software Radio and Implementation of Coordinated Jamming and Communications: Concepts and architectures of SDR; SDR platforms and test beds; SDR implementation strategies and examples of a CJamCom system.

High-Definition Location-Awareness
Moe Z. Win and Henk Wymeersch
Associate Professor at the Laboratory for Information & Decision Systems
Massachusetts Institute of Technology
Postdoctoral associate, Massachusetts Institute of Technology

The availability of positional information is of vital importance in many commercial and military applications, including asset tracking, search-and-rescue operations, and personal  navigation. The coming years will see the emergence of high-definition location-awareness  (HDLA) with sub-meter accuracy and minimal infrastructure requirements, operational in challenging indoor environments.   We will first cover four basic components of traditional positioning: ranging techniques  (e.g., time-of-arrival, time-difference-of-arrival); positioning algorithms (e.g., least-squares,  maximum likelihood); performance bounds (Cramer-Rao bounds); and practical positioning  systems (including GPS and WiFi positioning).   Secondly, we will discuss the limitations of traditional positioning, and move on to the key enablers for HDLA: wideband transmission and cooperative processing. In the context of HDLA, we will cover fundamental performance bounds, cooperative algorithms, and experimentation. Fundamental bounds serve as performance benchmarks, and as a tool for network design. Cooperative algorithms are a way to achieve drastic performance improvements with respect to traditional non-cooperative positioning. In order to harness these benefits, we must consider realistic operational settings. To this end, we have performed extensive measurement campaigns with UWB radios, the outcomes of which will be detailed during this tutorial.   

Tutorial Goals
This tutorial is useful for students and practicing engineers to get a high-level overview of ranging techniques, positioning algorithms, and fundamental performance bounds. It will also serve as an introduction to the state of the art in wideband transmission technologies and cooperative algorithms.

3GPP Wireless networks
H Anthony Chan
Huawei Technologies

The number of mobile subscriptions worldwide continues to grow and is reaching 4 billion by end of 2008, out of which about 85% are GSM. 3GPP has been taking advantage of this strong GSM subscription base to evolve to 3G, to Beyond 3G, and to 4G. The radio access network had evolved to ULTRA and WCDMA in 3G Wireless, to HSPA and HSPA+ in Beyond 3G Wireless, and then to Long Term Evolution (LTE). Femto cells will complement the access network. The core network had evolved to UMTS network and then to Evolved Packet Core (EPC) as it moves to all-IP network supporting different access networks with many different services and yet to reduce complexity with fatten network.

With the convergence of wireless networks, wired networks, and broadcast networks, the wireless networks are evolving fast towards 4G wireless and beyond. ITU has defined the requirements in IMT-Advanced to provide the standard for 4G Wireless. The 3GPP system of EPC, LTE+ and Femtocell is expected to be a strong player in 4G Wireless. Their architecture, requirements, challenges, and future trends will be discussed.