Engineers have already played major roles in the development of wireless technologies and they will continue to do so. But engineers are made, and not born, requiring new integrative curricula at the undergraduate and graduate levels to foster the development of the next generation of wireless engineers. Part of this effort is already taking place at the University of South Florida, where a state-of-theart wireless-communications laboratory has been assembled to enable students to understand basic theory, software simulation, hardware test and modeling, system and component testing, and software and hardware interactions and co-simulations. The laboratory has been built in such a way that it can be used in support of wireless courses at all levels and can serve as a resource for research for both undergraduate and graduate students.

Figure 1 presents a generic wireless/microwave curriculum and the position of the proposed laboratory. The lab builds a bridge between the courses on the wireless system, wireless networks, wireless circuits/devices, and digital signal processing. The lab course is the outcome of some of the research activities developed at the electrical engineering department of University of South Florida (USF).^1-4 A variety of test beds have been developed in recent years, such as for orthogonal-frequency-division-multiplexing (OFDM) wireless-local-area-network (WLAN) and ultrawideband (UWB) measurements, with the support of industry partners including Honeywell, Conexant, Agilent, Logus broadband solutions, Anritsu Co., and Custom Manufacturing and Engineering.

The test beds integrate vector signal generators (VSGs), vector signal analyzers (VSAs), and RF hardware with computer-aided-engineering (CAE) tools such as the Advanced Design System suite of tools from Agilent and the Matlab software from The Math- Works. The flexible test beds allow generation of a wide range of waveforms, measurement and modeling of the RF and baseband circuitry under different stimulus conditions, modeling of wireless radio-channel effects and RF impairments, and optimization of the transceiver structures and baseband algorithms.

The model for using these test beds for research is integrated into the USF educational curriculum in order to help advance students in the wireless-communications area. The model is used to expose the students to real-world wireless- communication problems and prepare them for the competitive job market. It also enables students to combine theoretical knowledge with practical, hands-on experiments.

Figure 2 shows the laboratory setup integrated with various components and instruments. The three key elements, computer software and simulations, test instruments, and hardware, are shown in different rows. The top row shows simulation capabilities, to help students gain an intuitive feeling of how theoretical knowledge is related to the real world. These capabilities allow students to model and implement real-world wireless- communication systems and help them learn how different parameters impact system performance.

The second row shows the test equipment used to connect the world of simulation with hardware. Instruments include VSGs, VSAs, and spectrum analyzers. Newer spectrum analyzers, such as the Agilent PSA Series (model E4440A) instruments that can provide in-phase (I) and quadrature (Q) signal samples by means of an integral broadband digitizer, can also be used as signal analyzers for studying the broadband modulated signals found in modern wireless-communications systems.

The VSG serves as a form of "waveform playback system." It can produce custom waveforms as well as standardsbased waveforms for communicationssystems testing. The waveforms can be created and stored within the VSG's memory or generated through software (such as Matlab) on an external computer and downloaded to the VSG's memory for signal generation. Given the VSG's capabilities of generating signals from software, it can integrate seamlessly with the modeling tools in the first row of the measurement laboratory. For example, a baseband signal can be developed using Matlab (or Agilent's Signal Studio software or ADS simulator), and then downloaded to the VSG to create the physical signal. The versatile waveform- generation instrument can also create signals with noise and other impairments to evaluate a receiver's ability to demodulate desired signals in the presence of noise, interference, and other signal impairments. Similarly, signals with fading and interference can be generated to check receiver performance under different communications channel conditions. Figure 3 shows a simplified block diagram of a VSG.

A baseband, intermediate-frequency (IF), or RF signal generated by the VSG is passed through a device under test (DUT) to study the behavior of different communications components, such as RF upconverters, filters, amplifiers, and antennas. Such test signals can also be passed through real radio channels to emulate a wireless channel. Signals can also be passed through a multipath channel emulator; the emulator provides adjustable multipath channel models.

The VSG's broad frequency range and wide modulation bandwidth allows it to cover the main frequency bands used in wireless communications and generate waveforms used for high-datarate wireless communications. Important parameters for a test-signal source include amplitude accuracy, level (amplitude) repeatability, phase noise, broadband noise, output power, and frequency accuracy.

Test signals from the VSG along with interference sources from another signal generator can be received by a DUT via antenna or through direct connection by cable. Interference models can also be generated as part of baseband signals modeled for the VSG. Received signals are passed through the receiver hardware and digitized by the VSA, which can demodulate a wide range of standard signal formats. The VSA can also capture arbitrary digital I/Q samples and process these with the software components shown in the first row of the test laboratory. Using baseband receiver algorithms, the Matlab, ADS, or other simulation software tools can process the received data. This interaction between the VSA and simulation tools provides an excellent mechanism to study and analyze present and emerging wireless systems for the purposes of research and education.

Figure 4 presents a simplified diagram of a VSA. Input signals to the instrument can be RF, IF, or baseband signals. In general, important parameters for evaluating the performance of a signal analyzer include analysis or demodulation bandwidth, which is the maximum instantaneous bandwidth the instrument can analyze; the dynamic range; the I/Q memory, which determines how many signal samples can be stored and is critical for wideband system measurements; residual error vector magnitude (EVM), and measurement speed (for increased test throughput).

Based on the model presented for the communications measurement laboratory, transceiver components can be studied in a step-by-step approach throughout a semester. The bench setup allows students to study transmitted and received signals at different levels of transceiver circuitry. Students can also change noise, interference, and other impairment sources to see their effects on the component, subsystem, and overall system performance.

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