Johns Hopkins University Establishes Virtual Lab for Wireless Communications with Simulink

While Dr. Edwards wanted the course to emphasize hands-on learning, he recognized several drawbacks inherent in the traditional hardware laboratory environment. In addition to the cost of purchasing, maintaining, and configuring equipment such as scopes, spectrum analyzers, and sources, a traditional lab setting was also inconvenient for students who held full-time jobs.

Dr. Edwards adds, “Often when you set up labs for demonstrations, they are canned and predictable. What we wanted is for the students to develop enough understanding and interest to explore on their own.”

The ECE Program wanted a visual software simulation environment that students could use in wireless communications as well as across all the program’s courses and ultimately in industry.

Ten years ago, Dr. Edwards standardized on MATLAB to teach wireless communications at JHU. Soon thereafter, Simulink became the primary simulation environment in the course. Today, MATLAB and Simulink are used throughout most of the program’s 40 classes each semester.

In “Introduction to Wireless Technology,” students develop a model of a wireless communications system. The course begins by covering the basics principles of all communications systems. Although many students are familiar with MathWorks tools, the course assumes no prior knowledge. Students quickly become proficient with MATLAB and Simulink by performing spectrum analysis with fast Fourier transforms.

“Students naturally assimilate Simulink,” notes Dr. Edwards “The graphical nature of Simulink made it perfect for the class because the students got the realistic simulation of a wireless environment and a block diagram description of what they were doing.”

The students then learn various analog and digital modulation schemes. Using Simulink, they model and simulate amplitude, frequency, and phase modulations to gain a deeper understanding of the waveforms and spectrums involved.

Next, the course explores channel description and modeling, again using Simulink to illustrate the underlying concepts such as Rayleigh fading and channel characteristics such as coherence bandwidth. Students also use MATLAB to plot and visualize three-dimensional field distributions.

After modeling the modulator and demodulator, the students model and simulate the wireless transceiver itself, adding capabilities such as carrier recovery, phase locked loops, and analog-to-digital conversion.

The students then use Simulink to simulate noise and channel perturbations and to visualize their effect.

By this point, the students have built up a detailed binary phase shift keying model that includes noise and channel effects as well as carrier recovery aspects. They use the model to simulate some of the direct sequence spread spectrum for the IEEE 802.11 standard.

After covering principles of Global System for Mobile Communications (GSM), the students finish the course with a complete 802.11 model in Simulink that incorporates spreading and despreading, modulation and demodulation, and channel modeling.

Roddewig and Dr. Edwards are currently considering making the course available online. “Simulink would work well in an online course because it enables students to learn independently at their own pace,” says Roddewig.