Q&A: Alenka Zajić, Communications Specialist

From building RF components for cell phones to teaching signal processing and electromagnetics at Georgia Institute of Technology’s School of Electrical and Computer Engineering, Alenka Zajić has always been interested in engineering and communications. Alenka and I discussed her fascination with a variety of communication technologies including mobile-to-mobile, computer system, energy-efficient, and wireless. She also described her current research, which focuses on improving computer communication.

Alenka Zajić

Alenka Zajić

NAN: Give us some background information. Where are you located? Where and what did you study?

ALENKA: I am originally from Belgrade, Serbia, where I got my BS and MS degrees at the School of Electrical Engineering, University of Belgrade.

After graduating with a BS degree, I was offered a design engineer job at Skyworks Solutions in Fremont, CA, where my job was to create passive RF components (e.g., antennas, filters, diplexers, baluns, etc.) for cell phones.

I was very excited to move to California, but was not sure if I would like to pursue an engineering career or a research/academic career. Since it took about six months to get an H1B visa, I decided to take all the required MS courses in Belgrade while waiting for the visa and all I had to do was finish the thesis while working in California. It was a bigger challenge than I expected, but it worked out well in the end.

While I enjoyed working in the industry, I was always more drawn to research than commercialization of products/innovations. I also enjoy “trying something new,” so it became clear to me that I should go back to school to complete my doctoral studies. Hence, I moved to Atlanta, GA, and got my PhD at the School of Electrical and Computer Engineering, Georgia Institute of Technology.

After graduation, I worked as a researcher in the Naval Research Laboratory (Washington, DC) and as a visiting assistant professor in the School of Computer Science, Georgia Tech, until last year, when I became the assistant professor at the School of Electrical and Computer Engineering, Georgia Tech.

NAN: How long have you been teaching at Georgia Tech? What courses do you currently teach and what do you enjoy most about teaching?

ALENKA: This is my second year at the School of Electrical and Computer Engineering. Last year, I taught introduction to signal processing and electromagnetics for undergraduates. This year, I am teaching electromagnetics for graduate students. One of the most rewarding aspects of university teaching is the opportunity to interact with students inside and outside of the classroom.

NAN: As an engineering professor, you have some insight into what interests future engineers. What are some “hot topics” that intrigue your students?

ALENKA: Over the years, I have seen different areas of electrical and computer engineering being “hot topics.” Currently, embedded programming is definitely popular because of the cell phone applications. Optical communications and bioengineering are also very popular.

NAN: You have contributed to several publications and industry journals, written papers for symposiums, and authored a book, Mobile-to-Mobile Wireless Channels. A central theme is mobile-to-mobile applications. Tell us what fascinates you about this topic.

ALENKA: Mobile communications are rapidly becoming the communications in most people’s minds because they provide the ability to connect people anywhere and at any time, even on the move. While present-day mobile communications systems can be classified as “fixed-to-mobile” because they enable mobility only on one end (e.g., the mobile phone) while the other end (e.g., the base station) is immobile, emerging mobile-to-mobile (M-to-M) communications systems enable mobile users or vehicles to directly communicate with each other.

The driving force behind M-to-M communications is consumer demand for better coverage and quality of service (e.g., in rural areas where base stations or access points are sparse or not present or in disaster-struck areas where the fixed infrastructure is absent), as well as increased mobility support, location-based services, and energy-efficient communication (e.g., for cars moving in opposite directions on a highway that exchange information about traffic conditions ahead, or when mobile devices “gang together” to reach a far-away base station without each of them expending a lot of power).

Although M-to-M is still a relatively young technology, it is already finding its way into wireless standards (e.g., IEEE 802.22 for cognitive radio, IEEE 802.11p for intelligent transportation systems, IEEE 802.16 for WiMAX systems, etc.).

Propagation in M-to-M wireless channels is different from traditional fixed-to-mobile channels. The quality of service, energy efficiency, mobility support, and other advantages of M-to-M communication all depend on having good models of the M-to-M propagation channels.

My research is focused on studying propagation and enabling communication in challenging environments (e.g., vehicle-to-vehicle wireless radio communications, underwater vehicle-to-underwater vehicle acoustic communications, and inside a processor chip). In each of these projects, my work aims not only to improve existing functionality, but also to provide highly useful functionality that has not existed before. Examples of such functionality include navigating people in a direction that will restore (or improve) their connection, voice, or even video between submerged vehicles (e.g., for underwater well-service operations), and use of on-chip transmission lines and antennas to achieve broadcast-type communication that is no longer feasible using traditional wires.

NAN: Your research interests include electromagnetics and computer system and wireless communications. How have your interests evolved?

ALENKA: My research was mostly focused on electromagnetics and its impact on wireless communications until I joined the School of Computer Science at Georgia Tech. Talking to my Computer Science colleagues, I have realized that some of the techniques developed for telecommunications can be modified to improve communication among processors, memory, racks in data centers, and so forth. Hence, I started investigating the problem of improving communication among computers.

NAN: What types of projects are you currently working on?


Two of Alenka Zajić's currrent projects are energy-efficient underwater acoustic communications and electromagnetic side channels in high-performance processors and systems.

Two of Alenka Zajićs currrent projects are energy-efficient underwater acoustic communications and electromagnetic side channels in high-performance processors and systems.

ALENKA: I have several projects and they all include theoretical and experimental work. Two of my current projects are energy-efficient underwater acoustic communications and electromagnetic side channels in high-performance processors and systems. I will provide a brief explanation of each project.

Energy-efficient underwater acoustic communications: Many scientific, defense, and safety endeavors require communications between untethered submerged devices and/or vehicles.

Examples include sensor networks for seismic monitoring, analysis of resource deposits, oceanographic and environmental studies, tactical surveillance, and so forth, as well as communications between unmanned or autonomous underwater vehicles (UUVs, AUVs) for deep-water construction, repairs, scientific or resource exploration, defense applications, and so forth. Such underwater sensing and vehicular applications will require energy-efficient underwater communications, because underwater sensor networks and AUVs are highly energy-constrained. They are typically powered by batteries that are very difficult to replace or recharge deep underwater. At the same time, existing wireless communication approaches still provide extremely low data rates, work over very limited distances, and have low energy efficiency. Radio signals and wireless optics have a very limited range underwater, so underwater wireless communications mostly rely on acoustic signals that can travel long distances in water.

Some of Alenka’s research focuses on electromagnetic side channels in high-performance processors and systems. This is a measurement setup.

Some of Alenka’s research focuses on electromagnetic side channels in high-performance processors and systems. This is a measurement setup.

Unfortunately, acoustic underwater communications have a narrow available spectrum—propagation delays that are orders-of-magnitude longer than in radio communications—and many sources of signal distortion that further reduce data rates and increase the required transmitted power when using simple modulations and coding. Hence, we are working on characterization of underwater acoustic channels and their implications for underwater-vehicle-to-underwater-vehicle communications and networking.

Electromagnetic side channels in high-performance processors and systems: Security of many computer systems relies on the basic assumption that data theft through unauthorized physical tampering with the system is difficult and easily detected, even when attackers are in physical proximity to systems (e.g., desktops in cubicles, laptops and smartphones used in public spaces, remote data centers used for cloud computing, remotely operated robotic vehicles, aircraft, etc.).

On the other hand, the motivation for attackers keeps expanding. Increasing use of electronic banking provides monetary incentives for successful attacks, while the trend toward computer-controlled everything (e.g., power plants, robotic weapons, etc.) can motivate terrorists and/or rogue states.

Although simple physical attacks (e.g., stealing the system or taking it apart to insert snooping devices) are relatively hard to carry out without significant risk of detection, more sophisticated physical attacks are likely to be explored by attackers as incentives for such attacks grow. Side-channel attacks are especially worrisome, because they circumvent traditional protection measures.

Most side-channel attacks (e.g., power analysis, timing analysis, or cache-based attacks) still require some degree of direct access (i.e., to attach probes, run processes, etc.) that exposes attackers to a significant risk of detection. However, attacks that exploit electromagnetic emanations from the system only require physical proximity. So, increasingly motivated attackers may be able to carry out numerous attacks completely undetected, and several other side channels (e.g., power, timing, memory use, etc.) can “spill over” into the electromagnetic side channel, turning electromagnetic emanations into a very information-rich side channel.

My work in this domain focuses on carrying out a systematic investigation of electromagnetic side channel data leakage, quantifying the extent of the threat, and providing useful insights for computer designers to minimize such leakage.

NAN: Is there a particular electronics engineer or academic who has inspired the type of work you do today?

ALENKA: I have been fortunate to have great mentors (Dr. Antonije Djordjević and Dr. Gordon Stüber) who taught me the importance of critical thinking, asking the right questions in problem-solving, and clearly and concisely stating my ideas and results.

ISM Basics (EE Tip #100)

The industrial, scientific, and medical (ISM) bands are radio frequency ranges freely available for industrial, scientific and medical applications, although there are also many devices aimed at private users that operate in these bands. ISM devices require only general type approval and no individual testing.

Source: Wolfgang Rudolph & Burkhard Kainka’s article, “ATM18 on the Air,” 080852, Elektor, 1/2009.

Source: Wolfgang Rudolph & Burkhard Kainka’s article, “ATM18 on the Air,” 080852, Elektor, 1/2009.

The radio communication sector of the International Telecommunication Union (ITUR) defines the ISM bands at an international level. Wi-Fi and Bluetooth operate in ISM bands, as do many radio headphones and remote cameras, although these are not usually described as ISM devices. These devices are responsible for considerable radio communications interference (especially at 433 MHz and at 2.4 GHz).

ITU-R defines the following bands, not all of which are available in every country:

  • 6.765 to 6.795 MHz
  • 13.553 to 13.567 MHz
  • 26.957 to 27.283 MHz
  • 40.66 to 40.70 MHz
  • 433.05 to 434.79 MHz
  • 902 to 928 MHz
  • 2.400 to 2.500 GHz
  • 5.725 to 5.875 GHz
  • 24 to 24.25 GHz

Some countries allocate further ISM bands in addition to those above. ISM applications have the lowest priority within any given band. Many bands available for ISM are shared with other spectrum users: for example the 433 MHz ISM band is shared with 70 cm amateur radio communications.

ISM users must not interfere with other users, but must be able to tolerate the interference to their own communications caused by higher-priority users in the same band. The band from 868 MHz to 870 MHz is often mistakenly characterized as an ISM band. It is nevertheless available to short-range radio devices, such as RFID tags, remote switches, remote alarm systems, and radio modules.

For more information, refer to Wolfgang Rudolph & Burkhard Kainka’s article, “ATM18 on the Air,” 080852, Elektor, 1/2009.

Internet of Things (IoT) Resources

Here we list several handy resources for engineers interested in the Internet of Things (IoT).IoT-WordCloud

  • The IoT Events site is an easy-to-use resource for find IoT events and meet-ups around the world.
  • The Internet of Things Conference is a resource for information relating to “IoT applications, IoT solutions, IoT example and m2m opportunities in smart cities, connected cars, smart grids, consumer electronics and mobile healthcare.”
  • The IoT Counsel website includes useful info such as bios and contact info for engineers, innovators, and thinkers working on IoT-related projects.
  • Michael Chui, Markus Loffler, and Roger Roberts present a comprehensive article on IoT in the McKinsey Quarterly. While this isn’t a design-centric document, you’ll find it’s an interesting in-depth overview of the technology and its applications.
  • The Business Leaders Network (BLN) has a page on the IoT. The most recent IoT even took place in June, but the site still has some interesting info about speakers, partners, and more.

Let us know about other good resources. Send your links via email or Twitter @circuitcellar.

New Products: July 2013



The USBee QX is a PC-based mixed-signal oscilloscope (MSO) integrated with a protocol analyzer utilizing USB 3.0 and Wi-Fi technology. The highly integrated, 600-MHz MSO features 24 digital channels and four analog channels.

With its large 896-Msample buffer memory and data compression capability, the USBeeQX can capture up to 32 days of traces. It displays serial or parallel protocols in a human-readable format, enabling developers to find and resolve obscure and difficult defects. The MOS includes popular serial protocols (e.g., RS-232/UARTs, SPI, I2C, CAN, SDIO, Async, 1-Wire, and I2S), which are typically costly add-ons for benchtop oscilloscopes. The MOS utilizes APIs and Tool Builders that are integrated into the USBee QX software to support any custom protocol.

The USBee QX’s Wi-Fi capability enables you set up testing in the lab while you are at your desk. The Wi-Fi capability also creates electrical isolation of the device under test to the host computer.

The USBee QX costs $2,495.

CWAV, Inc.


DownStream Technologies FabStream


FabStream is an integrated PCB design and manufacturing solution designed for the DIY electronics market, including small businesses, start-ups, engineers, inventors, hobbyists, and other electronic enthusiasts. FabStream consists of free SoloPCB Design software customized to each manufacturing partner in the FabStream network.

The FabStream service works in three easy steps. First, you log onto the FabStream website (www.fabstream.com), select a FabStream manufacturing partner, and download the free design software. Next, you create PCB libraries, schematics, and board layouts. Finally, the software leads you through the process of ordering PCBs online with the manufacturer. You only pay for the PCBs you purchase. Because the service is mostly Internet-based, FabStream can be accessed globally and is available 24/7/365.

FabStream’s free SoloPCB Design software includes a commercial-quality schematic capture, PCB layout, and autorouting in one, easy-to-use environment. The software is customized to each manufacturing partner. All of the manufacturer’s production capabilities are built into SoloPCB, enabling you to work within the manufacturers’ constraints. Design changes can be made and then verified through an integrated analyzer that uses a quick pass/fail check to compare the modification to the manufacturer’s rules.

SoloPCB does not contain any CAM outputs. Instead, a secure, industry-standard IPC-2581 manufacturing file is automatically extracted, encrypted, and electronically routed to the manufacturer during the ordering process. The IPC-2581 file contains all the design information needed for manufacturing, which eliminates the need to create Gerber and NC drill files.

FabStream is available as a free download. More information can be found at www.fabstream.com

DownStream Technologies, LLC


Rohde Schwarz SMW200A


The R&S SMW200A high-performance vector signal generator combines flexibility, performance, and intuitive operation to quickly and easily generate complex, high-quality signals for LTE Advanced and next-generation mobile standards. The generator is designed to simpify complex 4G device testing.

With its versatile configuration options, the R&S SMW200A’s range of applications extends from single-path vector signal generation to multichannel multiple-input and multiple-output (MIMO) receiver testing. The vector signal generator provides a baseband generator, a RF generator, and a real-time MIMO fading simulator in a single instrument.

The R&S SMW200A covers the100 kHz-to-3-GHz, or 6 GHz, frequency range, and features a 160-MHz I/Q modulation bandwidth with internal baseband. The generator is well suited for verification of 3G and 4G base stations and aerospace and defense applications.

The R&S SMW200A can be equipped with an optional second RF path for frequencies up to 6 GHz. It can have a a maximum of two baseband and four fading simulator modules, providing users with two full-featured vector signal generators in a single unit. Fading scenarios, such as 2 × 2 MIMO, 8 × 2 MIMO for TD-LTE, and 2 × 2 MIMO for LTE Advanced carrier aggregation, can be easily simulated.

Higher-order MIMO applications (e.g., 3 × 3 MIMO for WLAN or 4 × 4 MIMO for LTE-FDD) are easily supported by connecting a third and fourth source to the R&S SMW200A. The R&S SGS100A are highly compact RF sources that are controlled directly from the front panel of the R&S SMW200A.

The R&S SMW200A ensures high accuracy in spectral and modulation measurements. The SSB phase noise is –139 dBc (typical) at 1 GHz (20 kHz offset). Help functions are provided for additional ease-of-use, and presets are provided for all important digital standards and fading scenarios. LTE and UMTS test case wizards simplify complex base station conformance testing in line with the 3GPP specification.

Contact Rohde & Schwarz for pricing.

Rohde & Schwarz


Texas Instruments CC2538


The Texas Instruments (TI) CC2538 system-on-chip (SoC) is designed to simplify the development of ZigBee wireless connectivity-enabled smart energy infrastructure, home and building automation, and intelligent lighting gateways. The cost-efficient SoC features an ARM Cortex-M3 microcontroller, memory, and hardware accelerators on one piece of silicon. The CC2538 supports ZigBee PRO, ZigBee Smart Energy and ZigBee Home Automation and lighting standards to deliver interoperability with existing and future ZigBee products. The SoC also uses IEEE 802.15.4 and 6LoWPAN IPv6 networks to support IP standards-based development.

The CC2538 is capable of supporting fast digital management and features scalable memory options from 128 to 512 KB flash to support smart energy infrastructure applications. The SoC sustains a mesh network with hundreds of end nodes using integrated 8-to-32-KB RAM options that are pin-for-pin compatible for maximum flexibility.

The CC2538’s additional benefits include temperature operation up to 125°C, optimization for battery-powered applications using only 1.3 uA in Sleep mode, and efficient processing for centralized networks and reduced bill of materials cost through integrated ARM Cortex-M3 core.

The CC2538 development kit (CC2538DK) provides a complete development platform for the CC2538, enabling users to see all functionality without additional layout. It comes with high-performance CC2538 evaluation modules (CC2538EMK) and motherboards with an integrated ARM Cortex-M3 debug probe for software development and peripherals including an LCD, buttons, LEDs, light sensor and accelerometer for creating demo software. The boards are also compatible with TI’s SmartRF Studio for running RF performance tests. The CC2538 supports current and future Z-Stack releases from TI and over-the-air software downloads for easier upgrades in the field.

The CC2538 is available in an 8-mm x 8-mm QFN56 package and costs $3 in high volumes. The CC2538 is also available through TI’s free sample program. The CC2538DK costs $299.

Texas Instruments, Inc.

Embedded Sensor Innovation at MIT

During his June 5 keynote address at they 2013 Sensors Expo in Chicago, Joseph Paradiso presented details about some of the innovative embedded sensor-related projects at the MIT Media Lab, where he is the  Director of the Responsive Environments Group. The projects he described ranged from innovative ubiquitous computing installations for monitoring building utilities to a small sensor network that transmits real-time data from a peat bog in rural Massachusetts. Below I detail a few of the projects Paradiso covered in his speech.


Managed by the Responsive Enviroments group, the DoppelLab is a virtual environment that uses Unity 3D to present real-time data from numerous sensors in MIT Media Lab complex.

The MIT Responsive Environments Group’s DoppleLab

Paradiso explained that the system gathers real-time information and presents it via an interactive browser. Users can monitor room temperature, humidity data, RFID badge movement, and even someone’s Tweets has he moves throughout the complex.

Living Observatory

Paradiso demoed the Living Observatory project, which comprises numerous sensor nodes installed in a peat bog near Plymouth, MA. In addition to transmitting audio from the bog, the installation also logs data such as temperature, humidity, light, barometric pressure, and radio signal strength. The data logs are posted on the project site, where you can also listen to the audio transmission.

The Living Observatory (Source: http://tidmarsh.media.mit.edu/)


The GesturesEverywhere project provides a real-time data stream about human activity levels within the MIT Media Lab. It provides the following data and more:

  • Activity Level: you can see the Media Labs activity level over a seven-day period.
  • Presence Data: you can see the location of ID tags as people move in the building

The following video is a tracking demo posted on the project site.

The aforementioned projects are just a few of the many cutting-edge developments at the MIT Media Lab. Paradiso said the projects show how far ubiquitous computing technology has come. And they provide a glimpse into the future. For instance, these technologies lend themselves to a variety of building-, environment-, and comfort-related applications.

“In the early days of ubiquitous computing, it was all healthcare,” Paradiso said. “The next frontier is obviously energy.”