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Inject Artificial Fading Into Mobile Wireless Testing

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Micronetics WAVE3G-SIM Multipath Fading Results More Repeatable in Side-by-Side Test New Orleans, Louisiana--Micronetics, Inc. announced that it conducted a test in January, 2003, with Hollis Electronics and Wireless Test Systems to compare Micronetics' WAVE3G-SIM multipath fading simulator with the leading competitive product. The purpose was to determine which instrument was more effective for signal impairment testing. The results were very promising, and proved that the Micronetics WAVE3G-SIM outperformed the competition in several areas. Charles Freihofer, Director of Test Solutions, stated "The WAVE3G-SIM was faster at measuring and setting Signal-to-Noise-Ratio, and had better repeatability. This testing supports Micronetics' position that testing utilizing WAVE3G-SIM's all-digital implementation is superior to testing with a combination of digital/analog implementation." Mike Spitzer, President of Wireless Test Systems, said "The most important feature that we look for in an impairment test set is accuracy and repeatability. If the test set is not accurate and repeatable, then we cannot rely on the data. The Micronetics' WAVE3G-SIM was very repeatable. Based on these test results, WTS will be interested in using the WAVE3G-SIM for its own compliance testing in the future." Charles Freihofer, Director of Test Solutions, further stated "These tests by an independent lab confirm our claims that Micronetics, through its introduction of WAVE3G-SIM, offers the industry a better alternative for multipath fading and AWGN impairment testing. We are extremely pleased with the results, and thank Mike Spitzer and WTS for participating in this study." Micronetics, operating through its Defense Electronics Group, designs and manufactures microwave and radio-frequency (RF) components and integrated subassemblies used in a variety of defense, aerospace, and commercial applications. Operating through its Test Solutions and VCO Products Groups, Micronetics designs and manufactures test equipment and components that are used in, or test the strength, durability, and integrity of communication signals in military or communications equipment or systems. Micronetics serves a diverse customer base, including Aerosat, Alcatel, BAE Systems, Boeing, EADS, Ericsson, Honeywell, L-3 Communications, Lockheed Martin, Motorola, NEC, Northrop Grumman, Raytheon, Southwest Research, Teradyne, Tektronix, and Thales. Micronetics also operates through its wholly owned subsidiaries, Enon Microwave, Inc., Microwave Concepts, Inc., and Microwave & Video Systems, Inc. Contact: Richard S. Kalin, President, Micronetics Wireless Phone: (212) 239-8900 x22

You can spend a lot of time fussing with the RF section of a design and its subsequent evaluation and testing. That's where dedicated test equipment can help. Specialized test gear such as Micronetics' WAVE3G-SIM—with its ability to simulate real-world conditions—can really make life easier. Whether you're designing a portable phone or a wireless LAN (WLAN) access point, the WAVE3G-SIM is an appealing tool. It's been on the market for a while, but apparently Micronetics is marketing it aggressively these days, hence the press-release accolades from Hollis Electronics and Wireless Test Systems. Micronetics prices this equipment starting at about $50,000, and there are options that can take you from there. These options let the basic instruments be driven either as IEEE-488 systems or as RS-232 serial peripherals. You can also run them in a PC environment under Windows 98, Windows NT, or Windows 2000. If you opt for a PC system, a WAVE3G-SIM even lets you define channel models so that you can do things such as edit fading parameters. You could, for example, edit delay variations over time for a simulated path. That kind of flexibility could let you perform moving-propagation and birth-death-propagation tests that are akin to what you'd find in a real mobile-radio environment. Embedded DSP The company's press release emphasizes glowing comparisons, but never says that these generators make use of 16-bit DSPs. Nor does the press release state what the WAVE3G-SIM is compared to. A quick call to Charles Freihofer, the company's Director of Test Solutions, provided the answer. What's alluded to in Micronetics' press release is the Spirent 26 MHz bandwidth Model TAS4500 Flex Channel Emulator, priced at about $35,000. Like Micronetics' WAVE3G-SIM wares, Spirent lets you opt for a 6- or 12-path model, and can choose from various local oscillator (LO) options, attenuators, etc. For its part, the 16 MHz bandwidth WAVE3G-SIM multipath simulator can be used to test 3G (third-generation) cellular and PCS handsets and base stations. As such, it supports 3GPP, W-CDMA, and GSM systems, as well as CDMA2000, CDG, IS-95, and IMT-2000 protocols. You can order one preconfigured for channel models, too. These models are based on the aforementioned industry standards. Support Beyond Cellular The generator's applicability doesn't stop with these cellular standards, however. The WAVE3G-SIM can also be used to test and evaluate WLANs, so-called smart antennas, wireless local loop systems, cordless phones, and even CATV/HDTV system components. Moreover, it can be used effectively for making Type Approval and quality-assurance tests. Depending on the options you choose, these systems support either 6 paths/channel or 12 paths/channel. In addition to simulating multipath fading, WAVE-3G boxes can inject AWGN (Additive White Gaussian Noise) signals. These generators also include both digital and analog baseband I/Q (in-phase and quadrature) 50 W inputs and outputs that, when combined with complementary vector signal generators, make for rather complete RF test beds. According to Micronetics, if you marry a WAVE-3G SIM with a base-station emulator and a vector signal generator, you can create a 3G mobile test station. Here's what a test system would look like. click for full-size image Such configurations can create realistic environments for evaluating real-world performance, closely simulating actual channel characteristics. I/Q inputs sample at a 20 MHz rate, with 14-bit samples. Thanks to their embedded DSPs, Micronetics' modular testers also work as digital power meters and as impulse and white-noise sources. The noise sources are based on 42-bit pseudo-random generators. When used in noise-impairment evaluation, these dual-mode noise generators let you choose either random seed values or selected noise sequences that can be repeated. This can be helpful when developing noise cancellation techniques. Fading, Fading In terms of fading simulation, Rayleigh fading is accurately modeled on 6 or 12 paths, with results that can include the effects of Doppler shift, frequency offset, and a receiver's AGC (automatic gain control). In use, a WAVE3G-SIM's digital power meter can measure faded signal power and noise, and you can set a desired carrier-to-noise ratio. A final output combines a faded signal and AWGN for various test conditions. Multipath fading can be tested over a settable range extending to 72 db for digital signals, and to 60 dB for analog (with a resolution to 0.1 dB). Fading accuracy can be within 0.01 dB. Paths delays can also be set between zero and 100 ms, with a resolution to 0.05 ns and an accuracy of 0.01 ns. Similarly, the Doppler shift can be cranked-in over a range from as small as ± 0.1 Hz to ± 2 kHz. The speed range of a moving emitter can be from within ± 0.1 km/h to as high as ± 2300 km/h. A moving delay mode can set the period of oscillation at 10-3 radians/s (from one to 100 for one path). For more details, contact Freihofer at Micronetics, Inc. 26 Hampshire Dr. Hudson, NH 03051 Phone: (603) 883-2900 FAX: (603) 882-8987 Web: www.micronetics.com E-mail: cfreihofer@micronetics.com

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